Floriculture Greenhouse Update

Greenhouse tomatoes are usually scheduled to come into production when field tomatoes are not available. In Northern sections of the country, such as New England, the field production season occurs late in the summer and is short in duration. As a result, greenhouse tomato growers in New England, find they can market greenhouse tomatoes through most of the summer and still get a good price. The time interval between sowing a crop and harvesting ripe fruit will vary with the season since the rate of seedling and fruit development are affected by temperature. Light during seedling development will also affect the timing of initial flowering. Under ideal conditions, high light and warm temperatures, it will take about eight (8) weeks from seeding until the first flowers open and another eight (8) weeks from flowering until first harvest. Seedlings are generally transplanted into the production greenhouse 2-3 weeks before flowering. During less than ideal conditions the period from seed to harvest will be longer than 16 weeks. Use the schedules listed below as a general guide. Remember the actual time required will vary between cultivars and with the light and temperature conditions in your greenhouse.

Crop season, Development stage, Time interval, Weeks from seed

Early Spring Seed: Oct 25-Nov 25 Transplant: Jan 1-Jan 15, Weeks from seed: 9-10 Harvest: April 1-July, Weeks from seed: 22-23Late spring Seed: Dec 15-Jan 15 Transplant: Feb 1-March 1, Weeks from seed: 6-7 Harvest: May 1-July, Weeks from seed: 19-20Fall Seed: June: 15-July 15Transplant: July 20-Aug 15, Weeks from seed: 5 Harvest: Oct 1-Dec, Weeks from seed: 16

Richard McAvoyPlant Science Department, University of Connecticut

Links to presentations and handouts from Greenhouse and High Tunnel Tomato Conference held November 2009.

High night temperatures can cause mum flowering to be delayed.

Chrysanthemums are short-day plants. Both flower initiation and development of the flower buds occur more rapidly under short days than under long days. However, temperature has a greater influence than daylength on flowering of garden mums.Delay of flowering and in more extreme cases, failure of buds to develop properly (crown buds) are often associated with heat delay. Heat delay occurs when night temperatures are greater than 73F. Garden mum cultivars vary in their sensitivity to heat delay.  Also research at Kansas State University has shown that plants are more sensitive to heat delay when plants are subjected to high night temperatures during the first 2 weeks of short days, during flower bud initiation. Plants subjected to high night temperatures after 3 weeks of short days showed no permanent damage and only exhibited delayed flowering. Dr. Kimberly Williams, Kansas State University explains heat delay in this short video.

Tina Smith, UMass Extension and Leanne Pundt, UConn Cooperative Extension

Nature seems to be getting more violent in recent years with frequent earthquakes, increased numbers of hurricanes and record breaking snowstorms.  Insurance damage claims have increased considerably.  The International Building Code has revised upward its wind and snow loading requirements for some areas of the U.S.  Each year there are reports of greenhouses that have been damaged by weather and natural events.  Greenhouse design is different than conventional farm buildings in that the structural profile has to be small to allow maximum light to reach the plants. Most farm buildings are over designed to handle severe weather conditions.Storm damage to greenhouses can include racking of the frame, bending of the hoops, broken glass or torn plastic and uplifted foundation posts.  Preparation ahead of time can minimize the damage.Wind loadingWind forces that act on a greenhouse are influenced by numerous factors including the basics wind speed, building orientation, exposure, height and shape of doors or vents that may be open.  The wind passing over a greenhouse creates a positive pressure on the windward side and a negative pressure on the leeward side.  These can combine to create a force that wants to collapse or overturn the building.  An 80 mph wind can produce a pressure of 16 pounds per square foot (psf).  For example, the 10' by 100' sidewall of a gutter-connected greenhouse would have to resist a 16,000 pound force.Wind can also create a force similar to an aircraft wing that wants to lift the greenhouse off the ground.  An 80 mph wind blowing perpendicular to the side of a 28' x 100' hoophouse can create a lifting force of 220 pounds per foot of length or 22,000 pounds of uplift on the whole structure.  When you consider the total weight of materials and equipment in the greenhouse is about 6000 pounds, the foundation must have a withdrawl resistance of about 300 pounds each.  This is why building inspectors frequently require that the posts be surrounded by concrete.Although you have no control over the force or direction of severe winds, here are a few tips to help minimize storm damage:

• Check the area for loose objects.  Anything that can be picked up and hurled through the glazing should be secured or moved indoors.  Metal chimney (stove pipe) sections should be secured with sheet metal screws.
•  Inspect for dry or weak tree limbs that could fall on the greenhouse.
•  Close all openings including vents, louvers and doors.  The effective force of the wind is doubled when it is allowed inside the building.  The wind on the outside puts a pressure or lifting force on the structure.  The wind inside tries to force the walls and roof off.
•  On air inflated greenhouses, increase the inflation pressure slightly by opening the blower’s intake valve.  This will reduce the rippling effect.  Check to see that the plastic is attached securely and that any holes are taped.
•  Disconnect the arm to the motor on all ventilation – intake shutters and tape the shutters closed.  Then turn on enough exhaust fans to create a vacuum in the greenhouse.  This will suck the plastic tight against the frame.
•  Windbreaks can reduce the wind speed and deflect it over the greenhouse.  Conifer trees (hemlock, spruce, pine, etc.) in a double row located at least 50' upwind from the greenhouse can reduce the damaging effects of the wind.  Wood or plastic storm fencing can be used as a temporary measure.

John Bartok, Extension Professor Emeritus and Ag Engineer, UConn

Fact Sheet: Reducing Storm Damage to Your Greenhouses (includes snow loading also)

Note: With wind, rain and cooler temperatures, growers are advised to continue inspecting plants and use preventative sprays for diseases such as Downy mildew on basil and Chrysanthemum white rust on garden mums.  Leanne Pundt, UConn

This information was summarized from a recent article by Rob Wick and M. Bess Dicklow, Plant, Soil and Insect Sciences, UMass Extension published in Floral Notes, 23(1), July-August 2010

During 2008 and 2009, Downy mildew (Peronospora species) of basil occurred throughout the east coast in epidemic proportions both in the field and in greenhouses. Although the downy mildew pathogen has been detected in basil seed; seed transmission is probably a rare event. Air-borne dissemination from infected plants is more likely.

Symptoms on the top of the foliage occur as yellowing as if the plants are nitrogen or nutrient deficient. When spores are produced, a characteristic gray, fuzzy growth on the underside of the leaves is evident. Symptoms of downy mildew on basil can easily be mistaken for nutritional deficiency.

The most important environmental factors favoring disease development are high humidity and extended leaf wetness. Cultural controls are directed at reducing the amount of time leaves remain wet by reducing plant density and watering early in the day. In the greenhouse, horizontal air flow can be increased and condensation reduced by fans. Removing and destroying severely infected plants can slow disease development.Field trials conducted in southern New Jersey in 2009 determined that commonly-grown sweet basil (Ocimum basilicum) cultivars such as ‘Poppy Joe’ and ‘Nufar’ were the most susceptible to downy mildew. The least susceptible basils include the lemon and spice types such as O.x citriodorum and O. americanum  cultivars, “Lemon Std’, ‘Lemon’, ‘Lime’, ‘Spice’, ‘Blue Spice’ and ‘Blue Spice Fil’.

Few fungicides are labeled for herb plants. Copper products and phosphites are labeled for use on basil. It is the grower’s responsibility to read and follow label directions. The label is the law and any recommendations made here are superseded by the label.

At the University of Massachusetts, we are investigating methods to control this disease with biological control agents. We are interested in collecting live, infected plants.

If you think your basil plants are infected, please call or email Rob Wick, Dept. of Plant Soil and Insect Sciences; 413-545-1045, rwick@pltpath.umass.edu.

Photos: DM symptoms on top of Basil foliage, DM symptoms on underside of leaf

Robert Wick and Bess Dicklow, UMass Extension

Note: Downy mildew has also been observed recently on ornamentals in the Lamiaceae family, which includes basils (Ocimum spp), mints (Menta spp.), sages (Salvia spp) and other aromatics. According to Margaret McGrath, Cornell University, the coleus and basil downy mildew pathogens have now been demonstrated to be genetically different; therefore, these ornamental plants are not considered potential alternative host. However, there are many ornamental basils that are also hosts to pathogen affecting basil grown for use as an herb. Tina Smith, UMass Extension and Leanne Pundt, UConn Extension

Fact Sheet with photos and more details: Basil Downy Mildew (Cornell University)

The hot, dry summer has resulted in outbreaks of western flower thrips, spider mites, potato leafhoppers,  and tarnished plant bugs have also been troublesome.  Smaller, black melon aphids also tend to be more prevalent in the summer and fall months.

ThripsThrips are pollen feeders, so as more plants are flowering, their populations tend to increase.  In the summer months, as grasses or nearby hay fields are mowed, thrips often enter greenhouses thru vents and open roofs. (It is often helpful to close the roofs if nearby areas are being mowed in the evening.)  They also may migrate to yellow flowering weeds such as galinsoga, so good weed control always helps.  

Here’s an example of how temperature speeds up their development:

Temperature:         Egg to Adult Development Times for Western Flower Thrips  (On chrysanthemum leaves, 45-55% Relative humidity, Robb 1989)59F            39 days 69F            26 days 77F            12.9 days 81F            10.2 days 80F            9.3 days 90F            10.7 days

With the increased development time, and emigration of thrips, it is very difficult to keep thrips levels at those maintained in the spring before plants bloom.  Sticky card counts vary depending upon the how attractive the plants are in the greenhouse to thrips, whether the plants are flowering, placement of cards, what stage of thrips is present, and migration of thrips into greenhouses.  Growers also need to relate sticky card counts to crop damage.  For example, high numbers of thrips may be present on the sticky cards in open roof greenhouses, but limited plant damage to garden mums may be observed.

Working grower action thresholds of 10 per card may be appropriate only during spring production.  Higher action thresholds may be more appropriate in the summer months for garden mum and poinsettias. (Woody plants such as roses and poinsettias are not hosts of impatiens necrotic spot virus).

If using chemical sprays, spray intervals need to be shortened to every 3-4 days.  For more information see, Thrips Management Plan andWestern Flower Thrips- Management on Greenhouse Grown Crops Nematode application frequency needs to be increased in hot summer weather conditions. It's also important to apply enough moisture with the nematodes.  Sprays may dry out too rapidly in the high, dry environment.  One grower says he is now applying 500 gallons instead of 200 gallons of spray solution  to the same sq footage.  As with any biological control measure, they are most effectively used preventively in conjunction with good cultural practices for thrips control (sanitation, rigorous weed controls, etc). For more information see the article:  Nematodes in Pest Management.

Fact Sheet: Field Grown Cut Flowers: Tarnished Plant Bugs

Leanne Pundt, University of Connecticut

Chrysanthemum white rust (Puccinia horiana) is a serious fungal disease of chrysanthemum. White rust can spread quickly in greenhouse and nursery environments causing severe crop losses.Chrysanthemum white rust (CWR) is a quarantine significant pest in the United States; therefore, occurrence of this disease leads to state and federal regulatory action. In the last few years chrysanthemum white rust is occurring with more frequency in New England.  The federal management plan for CWR includes the following measures destroying symptomatic plants, fungicide treatments on remaining asymptomatic plants, surveys of the surrounding area, and trace backs of infected stock. The full management plan can be viewed on the web on the USDA, APHIS website. The symptoms of chrysanthemum white rust are very distinct. Light green to yellow spots up to 5mm in diameter appear on the upper surface of the leaf. These spots become brown and necrotic with age. Raised beige to pink pustules form on the underside of leaves beneath the spots. Pustules become white with age. Pustules are most common on young leaves and flower bracts but may form on any green tissue or the petals. Symptoms usually occur during cool, wet weather.Infected plants may show no symptoms until environmental conditions encourage symptom development. If the warm, dry weather pattern this season in southern New England continues, symptoms may be delayed. Preventative fungicide applications, being used by some growers, will suppress disease development. For a list of treatment options see the floricast by Margery Daughtrey, Cornell University . Syngenta has a bulletin on chrysanthemum white rust that can also be downloaded.Note: Growers finding CWR are required to report the finding to their State regulator agency. There are on-going discussions concerning Chrysanthemum White Rust regulations. As a result, APHIS has established a Stakeholder Registry for those interested in receiving updated information related to these discussions. When registering, check Chrysanthemum White Rust  in Topics of Interest.

Paul Lopes, UMass ExtensionWith input from Margery Daughtrey, Cornell University

Carefully inspect incoming poinsettia cuttings (by each batch, and variety) to insure that they are free of insects and diseases and are of the quality you expect.

Look for whitefly egg, nymphs and pupae on the underside of the leaves, especially the oldest bottom three leaves where most of the whitefly may be found. If possible, randomly inspect from 10 to 30% of the cuttings.  Inspect each shipment and cultivar separately.  Record which shipment or cultivar has whitefly and which stage is present.

Whitefly eggs and nymphs are very small, so a 10x  handlens or hands free optivisor is helpful. Patches of dried spray residue or dried latex might be confused with dusty appearance once sees near the whitefly eggs.

Don’t assume that if you don’t see whitefly adults emerging from the shipping containers, that you are free of whitefly. Adults are less likely to be observed compared to the more sedentary stages.

Record which shipments and varieties may need follow-up treatments.  For information on chemical control of whiteflies, including the highly resistant Q Biotype of the siverleaf whitefly see "The Best Guess" pesticide program for the Q whitefly on poinsettia. Scroll down to get to the recommendations and for links to more information.

If you are using biological control of whiteflies, see the pest message posted on Friday, June 25th.

In addition to whitefly, look for fungus gnat larvae and signs of their feeding damage (blunt root tips). Roots should be white and healthy with no signs of root rot disease.

Look for any angular leaf spots with a yellow halo, that may be indicate of a bacterial leaf disease. Bacterial leaf diseases spread rapidly under warm, wet conditions. See an example of a bacterial leaf spot disease on poinsettia.

Fact Sheets: Managing Whiteflies in Greenhouses University of ConnecticutManaging Fungus Gnats and Shoreflies in the Greenhouse University of Connecticut

Photo: Fungus gnat vs Shorefly adults on sticky card

Leanne Pundt, University of Connecticut and Tina Smith, University of Massachusetts

Damage from broad mites has been reported on peppers and New Guinea impatiens. Tarsononemid mites including cyclamen mite and broad mite can cause serious damage to a wide range of greenhouse crops such as New Guinea impatiens, garden impatiens, dahlias, gerbera, ivy, lantana, snapdragon, verbena, zinnia, peppers and other vegetable plants. Broad mites inject a toxin from their saliva as they feed. Their feeding causes twisted, hardened and distorted growth in the terminal of the plant and bronzed, rough, lower surfaces. Young terminal buds can be killed and leaves turn downward. Broad and cyclamen mites are too small to see without the aid of a microscope. Regular inspection of crops for their feeding damage is the best way to detect infestations. If characteristic symptoms are seen, send samples to the diagnostic laboratory where they can be inspected under a microscope.

Mites can be easily spread to healthy plants by workers' and infested hanging plants can infest plants below. During scouting and other tasks, enter mite-infested areas last. Clean the greenhouse thoroughly.

Damage caused by cyclamen mites has been observed on Delphinium. Symptoms are very characteristic and are sometimes mistaken for disease. Leaves cup or curl and are often blackened. Flower spikes are stunted and blackened. Aconitum, dahlia, chrysanthemum, verbena and viola are also hosts, although they do not exhibit so serious a reaction to the feeding.

Miticides labeled for broad mites and cyclamen mites on ornamentals include: products containing abamectin (Avid, Lucid, Minx and others), chlorfenapyr (Pylon), dicofol (Kelthane), fenpyroximate (Akari) and spiromesifen (Judo). Note that the effects of their feeding may persist long after the mites have been eradicated. The Judo (spiromesifen) label recommends not spraying impatiens spp. (including New Guineas). Follow label precautions for crop safety. It is an very effective spray against broad mites. For vegetable plants see labels of Pylon and Minx.

Fact Sheet: Managing Cyclamen Mites and Broad Mites in Greenhouses

Tina Smith, University of Massachusetts and Leanne Pundt, University of Connecticut

Fall mums will exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation.Fall mums wilt when the soil is dry, but wilting will also occur in hot weather which may cause plants to be stressed, or if the roots are damage from a root disease such as Pythium, even if the soil is saturated with water. When the roots stop functioning normally the plants will show signs of stress by wilting.

Keep in mind fall mums can survive excess amounts of fertilizer and resulting soluble salts when temperatures are normal and soil moisture is maintained. Problems occur when the growing medium is dry and the salts become more concentrated, resulting in root damage. The plants will react first by wilting and than collapsing.

Take precautions to avoid overwater garden mums especially during periods of hot weather like this week.  Lift the pots and check the roots periodically. If the pots feel heavy and the soil is saturated, do not irrigate, even if it is hot. However, do not allow plants to dry to wilt prior to watering.

If plants are wilting on a regular basis and excess amounts of fertilizer have been used, the roots maybe damaged and root disease will occur. Check the plant roots, especially with slower growing varieties. The roots tell a lot about a plants health, often before the top growth shows symptoms.

Paul Lopes, Tina SmithUniversity of Massachusetts Extension

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Fall mums will exhibit signs of wilting during extended periods of 90 plus degree temperatures. The solution may not be as easy as turning on the irrigation.

Fall mums wilt when the soil is dry, but wilting will also occur in hot weather when the soil is saturated with water, and/or if the roots are damage from a root disease such as pythium. When the roots stop functioning normally the plants will show signs of stress.

Keep in mind fall mums can survive excess amounts of fertilizer and resulting soluble salts when temperatures are normal and soil moisture is maintained. Problems occur when the growing medium is dry and the salts become more concentrated, resulting in root damage. The plants will react first by wilting and than collapsing.

Take precautions to avoid overwater garden mums especially during periods of hot weather like this week.  Lift the pots and check the roots periodically. If the pots feel heavy and the soil is saturated, do not irrigate, even if it is hot. However, do not allow plants to dry to wilt prior to watering. If plants are allowed to wilt on a regular basis when controlled release fertilizer is used, the roots may burn and root disease will occur. Check the plant roots, especially slower growing varieties. The roots tell a lot about plant health, many times before the top growth shows symptoms.

Watch for potato leafhoppers. Leafhoppers are found on many different out-door grown perennials, vegetables and sometimes garden mums. Of the many species of leafhoppers, the potato leafhopper and aster leafhopper are most likely pests on ornamentals in New England. Both adult species have slender bodies and wings that are held roof-like over their body. Leafhoppers jump or fly when disturbed and can quickly move sideways, backwards or forwards. The nymphs resemble adults but lack wings. They have piercing-sucking mouthparts and feed on plant sap, causing yellowing, stunting and loss of vigor.

The potato leafhopper feeds by inserting a needle-like beak into the plant and sucking out the sap. It also injects a toxin as it feeds so leaves may develop a v-shaped brown, edge burn at the tip known as "hopperburn". Photo: hopperburn on Astilbe. This injury may be confused with leaf scorch especially on drought-sensitive Astilbe. Plants may also be stunted with distorted new growth. Growers with retail customers should be aware that potato leafhoppers are building up in beans, potatoes and eggplants now. Damage is worse under drought conditions.

The aster leafhopper transmits the pathogen that causes aster yellows. Other species of leafhoppers may not inject a toxin or transmit diseases as they feed so control may not always be necessary.

Scouting: Brush the leaves of plants with your hand. Small light yellow-green potato leafhoppers dart around and fly up from foliage when disturbed. Tap the foliage over a yellow sticky card or briefly place a sticky card among the plants to catch adults. Potato leafhoppers (Empoasca fabae) adults are approximately 1/8 inch long, and light green with characteristic 6 white spots just behind their head. Once you see adults, look closely at several leaves for nymphs. Nymphs are small, narrow light green wedge shaped insects that move very fast sideways, front and back. Look on the underside of leaves along the leaf vein for the young nymphs especially on Alcea, Astilbe and Dahlia.

Management: The potato leafhopper does not overwinter in New England. It migrates into New England in late April or early May from the south. There may be from 3 to 4 generations per year. Potato leafhoppers also feed on woody plants such as birches, maples and apples. Field crops such as alfalfa, clover and sunflower are also hosts.

Systemic insecticides such as neonicotinoids may be applied to prevent feeding damage when leafhoppers first appear. There are many other pesticides labeled for leafhoppers including azadirachtin, (MOA Group 18) pyrethroids (MOA Group 3), and Beauvaria bassiana(MOA Group M). Pesticides with limited residual will need to be reapplied with good coverage on the undersides of leaves. See the New England Guide for specific pesticides.

Fact Sheet: Leafhopper Pests of Connecticut Nurseries and Landscapes

Leanne Pundt, University of ConnecticutTina Smith, University of Massachusetts

Update on Late Blight of Tomato and Potato for Retailers--

On 6/19 late blight was confirmed on tomato from a community garden on Long Island. The gardeners are taking out all their tomato and potato plants. On June 17 a plant pathologist confirmed late blight on tomato from a home garden in New Haven county, CT. The plants had been grown from seed by the gardener. Thus, late blight ha been confirmed in one location in New England. LB has been confirmed in NY, CT, PA, MD, KY, LA, FL and Manitoba to date this year on either tomatoes or potatoes.

Once late blight is detected, it is important to pull and destroy infected plants as soon possible. Any infected plants left in the ground have the potential to provide inoculum that can spread to other gardens and farms many miles away.

Protection with Fungicides. All potato and tomato crops should be protected with fungicides on a regu­lar basis.  Products containing chlorothalonil or copper can be suggested for home gardeners.

New Fact Sheets:

More information and photos can be found in the updated fact sheet by Dr. Sharon M. Douglas titled Late Blight of Tomato and Potato in Connecticut--2010.

And to help distinguish LB from other leaf spots on tomatoes see this new fact sheet: Recognizing Tomato Blights (University of Massachusetts)

Tina Smith, University of Massachusetts and Leanne Pundt, University of Connecticut

If you are a wholesale propagator of poinsettias, be sure to use IPM practices and pesticides that are compatible with biological control agents (BCA) or use BCA’s  during propagation. This will help customers who are planning to use BCA’s  during production. It would also be helpful to provide a list of pesticides used on the crop. To find out if a pesticide is compatible, use one of the on-line searchable side effect data bases available from suppliers. Click on "Side Effects" Enter product and natural enemy to search. BiobestKoppert

If you are buying in cuttings and plan to grow poinsettias using biological control for pest management, know the pesticide history of your cuttings. Last year, some growers had problems with biocontrol for whitefly due to pesticide residue on their cuttings. Pesticide residues negatively affect BCA's for the first 3-4 weeks of the crop after arrival at the finishing growers operations. BCA’s are then not able to establish on the first generation of whitefly.

For the past few years, Sanmite (pyridaben) IRAC Group 21 has worked well for whiteflies on poinsettia, without causing phytotoxicity. It was being used by breeders, rooting stations and growers. As a result of overuse, reports are coming in that resistance seems to be occurring.

Tina Smith, University of Massachusetts and Leanne Pundt, University of Connecticut

Bacterial leaf spot on pepper transplants was identified at a retail garden center.

Bacterial leaf spot of pepper caused by Xanthomonas campestris pv. vesicatoria is the most common and destructive disease of peppers in the Northeast. Different strains or races of the bacterium are cultivar specific, causing disease symptoms in certain varieties only.

The bacterium is carried within seed, or in solanaceous weeds and crop debris. Tomatoes are also susceptible. Disease development is favored by high nighttime temperatures and high moisture and may be arrested during prolonged dry spells. Bacteria spread from plant to plant by splashing water, blown by high-pressure sprayers, or on workers hands and equipment.

Resistant varieties offer the best protection against this disease. Start with certified disease free seed or treat seed with hot water or dilute solutions of bleach. Grow transplants in a clean, disinfected greenhouse, rotate crops, control solanaceous weeds, rogue infected plants, and minimize leaf wetness periods by proper irrigation practices and plant spacing.

Streptomycin can be applied before transplant. Maintain adequate fertility, especially nitrogen in the field and apply copper bactericides at a 7-10 day schedule as soon as disease is detected. Sprays can be stopped with the arrival of cooler and drier weather. Bactericides are only marginally effective when environmental conditions are conducive for disease development; sanitation and environmental control are important disease management principles.

M.Bess Dicklow, UMass Extension Plant Diagnostic Clinic and Paul Lopes, UMass Extension

Lily leaf beetle adults and larvae are active, feeding on foliage of Asiatic lilies and Fritillaria in many areas. In other areas Eggs have been laid and are hatching.  Monitor for the bright red beetles and also for the eggs on the undersides of the foliage.  Inspect the leaves for fine tan-colored, irregular-shaped lines about one inch long.  On closer examination, these tan lines will be a row of eggs.  Just before hatching, these eggs turn a bright red color.  When eggs are found, they can be removed and destroyed.

Lily leaf beetle (Lilioceris lilii) is known to lay its eggs and develop only on true lilies, Lilium species (Turk's cap lilies, tiger lilies, Easter lilies, Asiatic and Oriental lilies) (not daylilies), and fritillaria (Fritillaria sp). Although lilies and fritillaria are the primary hosts, lily leaf beetle also feeds, sometimes just lightly, on a number of other plants, including lily of the valley (Convallaria majalis), soloman's seal (Polygonatum sp.), bittersweet (Solanum sp.), potato (Solanum tuberosum), hollyhock (Alcea) and various hosta species. It is however, a devastating pest to true lilies.

If your customers only have a few plants in their garden, hand-picking adults and eggs can be effective. Products containing neem (Bon-Neem, Azatin), a botanical insecticide, have been shown to kill very young larvae but must be applied every five to seven days after egg hatch. Products containing the systemic imidacloprid are providing effective control applied either as a foliage spray or soil drench depending on label instructions. Imidacloprid is the active ingredient in Marathon and Merit and one of the active ingredients in Bayer Advanced Rose and Flower Insect Killer for home gardeners. Products containing spinosad a microbial insecticide, are effective on larvae. Spinosad is sold as Conserve and Entrust for commercial growers and Monterey Garden Insect Spray, BULL’S-EYETM and others for home gardeners.

The University of Rhode Island (URI) Biological Control Lab is researching natural enemies of the lily leaf beetle. Small parasitic insects have been released throughout NewEngland and URI researchers hope that the insects will disperse naturally from these release sites, eventually reducing problems with the lily leaf beetle.

Lisa Tewksbury, URI is continuing to track these parasitic insects by collecting the large larvae covered with excrement (brown blobs) that are found on lilies. They will dissect the larvae to look for the parasitic insects. If you or customers you know have larvae, and wouldn’t mind sending them to URI please use the following instructions to send them to Lisa at the URI Department of Plant Sciences or contact her for more information. Instructions and more information

More information on LLB

Photos: Larvae Eggs Adult Beetle

Lily Leaf Beetle Fact Sheet, UMass

University of Rhode Island Bio Control Lab (includes photos of parasitic wasp) Evaluation of resistance to Lily Leaf Beetle in Lilium spp. Cultivars

Tina Smith, University of MassachusettsLeanne Pundt, University of Connecticut

Viburnum leaf beetles are becoming active in nurseries and retail garden centers. See information and photos: Viburnum Leaf Beetle UMass and Cornell

High temperature is one of the most important factors to control in the retail yard. Shading and air movement are ways to help keep temperatures cooler for plants in the retail setting. The use of 50% shade of the midday sunlight will reduce light to appropriate levels. See the fact sheet Caring for plants in retail settings: 

Two-spotted spider mites are showing up on Ipomoea. See message and photos on managing mites.

Spittlebugs: The white foam from spittlebugs can be seen now on many perennials as the spittlebugs move in from grassy areas. Most of the damage is cosmetic only and does not harm the plant. If the infestation is small, either handpick the spittle masses with a gloved hand or use a forceful jet of water to dislodge the nymphs. For more information and photo see this previous message.

Plant nutrition: Bedding plants in retail yards may be showing signs of lack of feed. With the recent prolonged high temperatures and frequent watering, fertilizer may have leached out. If new growth is yellowing and roots are healthy, fertilize with 200 ppm of a complete fertilizer such as 20-10-20 at every watering. Bedding plants usually recover easily because they are quickly purchased, and are planted out in the garden, fertilized and have room to grow.

Hanging baskets and patio pots are a different story. Plants in hanging baskets and planters will stay in those containers throughout the summer. The small volume of soil in a container is the only available source of nutrients for the plant compared to the much larger volume of soil available to the plants in a garden. Frequent watering causes much of the fertilizer to be leached out. If hanging baskets and planters are not fertilized in the retail sales area, or if controlled-release fertilizer was not used, all the fertilizer will leach out by the time the consumer buys the plants. The plants will quickly decline in quality once the customer takes the basket home. There are solutions. One is to fertilize baskets and planters in the retail sales area, on a weekly basis, using 400 ppm N, or using 200 ppm N at every watering. Another solution is to top-dress the basket or planter with a controlled- release fertilizer using 3-5 grams of N of a shorter term, 4-6 month material or use tablets according to directions. Retailers should communicate with their wholesale growers to make sure controlled-release fertilizer has not already been applied prior to shipping before fertilizing plants.

Tomato plants: Monitor for late blight and bacterial canker. See message.

Garden Mums should be planted as soon as possible upon arrival. See the message  about early season care including fertilizing and crown buds.

Tina Smith, University of MassachusettsLeanne Pundt, University of ConnecticutPaul Lopes, University of Massachusetts

Be on the watch for Bacterial Canker Clavibacter michiganensis pv michiganensis and Late Blight caused by Phytophthora infestans. These two diseases can be very destructive to tomatoes in Massachusetts.

Initial symptoms of Bacterial Canker are the result of primary, systemic infection that first affect the lower leaves causing leaf curling, wilting, chlorosis, and shriveling. In advanced stages, the pathogen spreads throughout the plant and causes poor growth, wilt, and plant death. Foliage throughout the canopy wilts, yellows, turns brown, and collapses. Stems can split resulting in open breaks or cankers and stems break easily. Secondary infections occur from water splash onto foliage, stems, and fruit. Spots occur on green fruit and are very characteristic: white to yellow spots, 3-4 mm with raised brown centers (“bird’s eye spots”).

Late blight appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire vines may be killed in a short time when moist weather persists.

 Note: The symptoms for Bacterial Canker and Late Blight most often do not appear early in the growing season, but can be introduced and symptoms noticed on plants grown and shipped to New England from the south.

Photo: Cut stem of a potted tomato plant with Bacterial canker

Late Blight information and photos (scroll down for photos)

Paul Lopes, University of Massachusetts

Mum cuttings are arriving at some growers. Begin the season by reviewing your fertilizer program and teaching new employees to recognize Chrysanthemum white rust symptoms.

Mums are heavy feeders during the first few weeks. Growers use a variety of ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. Regardless of the program you use, start plants off right and prevent premature buds by:

Using moistened soil when potting up plants, then water-in freshly planted cuttings with a fertilizer solution. Many growers are successfully using 200 to 300 ppm of 20-20-20 immediately after planting. The cuttings establish faster and grow more rapidly.

Do not stress the young plants during their first 4 to 5 weeks of growth, and especially during the first 10 days of the crop or plants will develop buds prematurely and plants will be short. Keep plants moist, well fertilized and properly spaced.

Also check plant roots regularly to monitor plant health.

To encourage soft growth that branches freely, many growers use 250-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks for all fertilizer programs. Then, growers using 100% water soluble fertilizer throughout the season, switch to 200-250 ppm 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. The 20-10-20 contains less ammonical nitrogen. Once plants start to show color, fertilizer is reduced to 100 ppm constant feed.

If using controlled-release fertilizer, keep in mind that the rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cool temperatures, fertilizer is going to be slow to release. We often have cool temperatures in June when plants need the most fertilizer. This is the reason liquid feed becomes important, to get plants growing and create vegetative growth.

Garden mums initiate flower buds easily and develop rapidly if plants are stressed in any way. If terminal flower buds are observed when cuttings arrive, plants should still perform satisfactorily. When cuttings with terminal flower buds are planted, they should be pinched hard (allow 4-5 leaves to remain) when they are turgid (4-5 days after planting). This will force out lower breaks which tend to be more vegetative. If both terminal and lateral buds have developed when cuttings arrive, it is best not to plant them, as they most likely will not perform satisfactorily.

Tina Smith, University of Massachusetts

For more information see:

Fact Sheet: Garden Mums for Fall Sales. University of MassachusettsFact Sheet 2008: Chrysanthemum White Rust. University of Massachusetts.Grolink: Belgian Mum Cultural Information Fact Sheet. Garden Mums from Cell Paks. Griffin Greenhouse Supply Company.

Weather related problems were observed over this past week. Paper thin brown spots - sunscald (many crops) caused by sun and wind, wilted new growth (basil) caused by chilling injury and silver color foliage (bacopa) were just a few of the symptoms observed. Shade perennials placed in full sun in both retail and grower locations resulted in sunburned foliage. Continue to watch weather reports over the next week. Cover plants at night, protect plants from the wind. Gradually expose plants grown in the greenhouse to cool temperatures.

Late season thrips and Impatiens necrotic spot virus were observed on plants this week.

Many growers used biological control for aphids and other pests this season. There has been confusion over identification of aphid mummies versus healthy aphids at retail locations. See photos of black aphid mummies and brown aphid mummies, many on a leaf.

Monitor for Rhizoctonia web blight on impatiens, herbs and other plants encouraged by dense canopies, closely spaced plants and humid conditions. Rhizoctonia is more commonly known as a fungus that causes root rot diseases.  It may grow up from the media causing web blight during favorable environmental conditions. Stems and leaves collapse, with fine, web-like mycelium present. If you look closely, you can see the fine strands of the fungus.  If there are certain houses or locations where you have seen outbreaks of Rhizoctonia web blight, consider growing crops that form a less dense canopy in those locations.  Web blight can occur in the some locations and on the same crops year after year.   Many of the fungicides labeled for Rhizoctonia root rot may also be helpful in limiting web blight. Rhizoctonia is a natural inhabitant of the soil and can survive there indefinitely.

Leanne Pundt, University of ConnecticutTina Smith, University of Massachusetts

It is not unusual to discover outbreaks of pests such as spider mites, thrips, whiteflies and aphids in greenhouses full of flowering bedding plants scheduled to be sold in the next week or two. If you discover an insect problem now, we suggest using a safe, effective contact spray that will knock down the infestation to provide good protection for a couple weeks. If infestations are localized, spot treating may be best. Once plants are planted outdoors in a garden, aphids, mites, whiteflies and thrips are not usually a problem. Some good choices for out-the-door treatments are:

• Thrips, aphids, whiteflies: abamectin (Avid), imadacloprid (Marathon II), dinotefuran (Safari), pyridaben (Sanmite), acetamiprid (Tristar), thiamethoxam (Flagship), and bifenthrin (Talstar).
• Aphids and whiteflies: pymetrozine (Endeavor)
• Mites: abamectin (Avid), bifenazate (Floramite), hexythiazox (Hexygon), pyridaben (Sanmite).

You will want to use the safest products available with everything in bloom. None of the products listed above are known to cause a phytotoxicity problem when used at the rate on the label. Usually wettable powder and flowable formulations are the least likely to be phytotoxic. However, wettable powders may cause visible residue. Make sure wettable powders are completely dissolved in the spray tank and the tank is agitated. This will prevent slurry from forming at the bottom of the spray tank, which could be phytotoxic if sprayed on plants. The re-entry time-period following application of the products listed above is 12 hours with the exceptions of Tristar (24 hours). Note that Endeavor works by interfering with the insect’s ability to feed and may take 5 – 10 days or longer to see results.

Tina Smith, University of MassachusettsLeanne Pundt, University of Connecticut

Monitor for Downy Mildew. See previously posted message on Downy Mildew.

Thrips populations are increasing with the warmer temperatures. Monitor for thrips using yellow sticky cards and monitor plants for Impatiens necrotic spot virus. See the message Thrips and Tospoviruses

Iron deficiency symptoms are showing up on crops. Symptoms appear as an interveinal chlorosis, normally starting at the shoot tips, but often they occur throughout the entire plant. Sometimes the leaves of iron deficient plants turn almost white. Bacopa, calibrachoa, scaevola, snapdragons, and petunia are crops susceptible to iron deficiency. Preventing iron deficiency can be accomplished by controlling pH and using an iron chelate fertilizer. Before applying iron, check the plants roots to be sure they are healthy. Unhealthy roots will result in yellow, stunted plants that may be confused with iron deficiency. See Preventing Iron Deficiency and Selecting which iron chelate to use.

Late Blight reminder to retailers: Buy and sell only tomato plants that have been started and grown here in the northeast. Tomato growers and home gardeners will be very appreciative if you do not bring late blight into New England. Late blight is a very destructive and very infectious disease that killed tomato and potato plants in gardens and on commercial farms throughout the eastern U.S. during 2009. Please do your part to prevent this disease! For information and photos on late blight, see the message: Garden Retailers and Late Blight

Tina Smith, University of MassachusettsLeanne Pundt, University of Connecticut

Plants at many greenhouses appear to be a little ahead. If you are thinking about holding plants using growth regulators, review the message: Using Plant Growth Regulators to Hold Finished Plants. A proper hold rate using growth regulators should give enough control to hold a mature plant under hot weather for 2-3 weeks but low enough that the plant will recover and grow for the consumer. Spray treatments carry less of a risk of overdose than drench treatment, especially when the root-active PGRs are used.Monitor for powdery mildew on gerberas. A good short video on the subject is available from Floricast by Margery Daughtery, Cornell University.Spider mites continue to be a problem on crops such as ivy geraniums and mandevilla and on perennials such as salvia, monarda, nepeta and perovskia. Spider mite injury on ivy geraniums looks like oedema, so be sure to monitor carefully with a hand-lens. See photos of oedema vs spider mite damage.

See message: Managing Two-spotted spider mites  Spider mites are very successful at surviving over the winter in their resting stage. The can hibernate in any crevices in the greenhouse so growers having problems last year are likely to have problems this year.Finally, when sunshine turns to clouds and rain, avoid wet foliage, reduce humidity by heating and venting and monitor for Botrytis. See messages: Heating and Venting and Botrytis

Leanne Pundt, University of ConnecticutTina Smith, University of Massachusetts

‘Tis the season for extreme temperatures. Monitor the weather forecast and avoid moving cold tolerant annuals and herbaceous perennials outdoors if a hard frost (colder than 28°F) is predicted at any point within at least three nights of when plants would be put outside. Avoid placing plants in low-lying areas because frost will more likely settle in these areas. Be prepared to cover plants if temperatures go below 28°F.

While herbaceous perennials and cool tolerant annuals, can be displayed or grown outdoors, they need to be acclimated or hardened off first. Cool tolerant crops include pansy, annual phlox, alyssum, osteospermum, nemesia, calibrachoa, verbena, diascia, bidens, antirrhinum (snapdragon), mimulus, lobelia and petunias.

Begin with just a few plants and experiment with cultivars, making adjustments as needed. Some varieties of the same type of plant have varying degrees of cold hardiness. Learning which plants perform best will take some experimenting.

Plants will adapt best to cooler temperatures when they have been started at optimum growing temperatures and have a well-established root system. Once plants get to their desired size, lower the greenhouse temperatures to 45° - 55°F for at least a week to acclimate them for outdoors.

Botryis blight and lack of fertilizer are two common problems which occur with outdoor growing. To prevent Botrytis, water plants in the morning and let the foliage dry before night. Plants growing outdoors may require less water and less frequent irrigation and this means that plants are fertilized less often. Although plants are being grown cool, it is important to continue to fertilize plants and maintain proper fertility. Pay particular attention during rainy periods, (like this weekend) and monitor plants for both Botrytis and nutrient leaching.

Cool media temperatures also increase the risk of root rots caused by Pythium, Rhizoctonia and Thielaviopsis. Regularly monitor roots for disease and apply fungicides early. Fungicides work more slowly in cool media. It may take longer to see results of an application or an application may be less effective.

Without some sort of protection, you are always taking a chance when growing outdoors in early spring and occasionally plants will get damaged. By choosing cool tolerant plants, acclimating plants, closely watching weather forecasts and providing extra protection when needed, you will minimize the risk, grow higher quality plants and provide an extra turn in production.

Fact Sheet: Moving Cool Tolerant Plants Outdoors: Risks and Benefits Link to: Proven Winner outdoor growing guidelines

Tina Smith, UMass ExtensionLeanne Pundt, UConn Extension

When scouting, it’s important to be able to tell the difference between pest mite species and beneficial mite species.  In general, beneficial predatory mites are very active, fast moving pear-shaped mites. One of the most commonly released predatory mites in greenhouse production is Phytoseiulus persimilis.  This beneficial, predatory mite is bright orangish-red, pear-shaped mite is very fast moving compared to the more sedentary, pest species, two-spotted spider mite. The female P. persimilis is about 0.6 mm in length and the male is slightly smaller.   

With decreasing day length in the fall, as well as falling temperatures and less available food, female spider mites enter diapause.  Females entering diapause become an orange-red color within a few days of becoming an adult. They may overwinter in hoop houses and cooler greenhouses in a dormant stage. During this time, they do not eat, or lay eggs and are less susceptible to pesticides.  They are also more difficult for predatory mites to find.  By looking at the body shape (which is NOT pear shaped), you can tell the difference between diapausing spider mites compared to P. persimilis mites.

To evaluate whether predatory mites are working, look for shriveled, dried up spider mites plus the presence of predatory mites and their eggs. P. persimilis eggs are oval or “football shaped” and roughly twice the size of spider mite eggs.  Eggs are laid close to a food source. When first laid, they are a transparent light pink shade and later turn darker.  You may start to see the eggs about two weeks after releasing the beneficial (depending upon temperature).

Spider mite eggs are round or barrel shaped and are often found along the midvein on the underside of leaves. When spider mite eggs are first laid, they are transparent.  They turn straw colored near the time of hatching.  Eggs hatch into larvae and then two nymphal stages before becoming adults. Larvae are at first colorless and develop color as they feed. Their characteristic body spots are more distinct in the nymphal stage.  Spider mite adults are easily recognized by their two dark spots on either side of their body.  Eggs, nymphs and adults can be found on the underside of the leaves.

Leanne Pundt, University of Connecticut

Just like you need to inspect incoming plants to assess their quality, it’s also important to inspect biological control agents as you receive them.  Here are some tips for assessing the quality of the various types of natural enemies.  Also, ask your biological control supplier on how to best evaluate any incoming shipments.

* Check number of shipment days and how cold or warm the ice packs are. * Keep the package out of extremes of sun, heat or cold. Release as soon as possible. * Predators and parasitoids that are shipped as mobile stages (predatory mites, some wasps) should be inspected upon arrival to determine if they are actively moving.

As an example, to assess the quality of predatory Mites such as Neoseiulus cucumeris or P. persimilis, spread a small sample of the mites on a white sheet of paper. Check with a 10 to 16x hand lens to make sure the predatory mites are active and moving rapidly. You should also check the rim of the container in which the predatory mites are shipped for the presence of live individuals.  Shipments of N. cucumeris may also contain grain mites which serve as a food source. Grain mites are white, have long protruding hairs on their back and are generally less mobile than the tan-colored N. cucumeris.

Biological control agents shipped as eggs or pupae should be checked for viability by placing a small sample in a clear, airtight, dry container. Keep the container in a shaded, unsprayed area for two or three days, and carefully looking for the active larvae or adults.

Storage Most natural enemies have a very short shelf-life, especially those that are shipped without a food source, and thus should be applied immediately. Natural enemies that are supplied with a food source can be stored for a few days before use; however, it is strongly recommended to use natural enemies immediately upon arrival. Storage time depends on the particular natural enemy and environmental conditions. If natural enemies must be stored, maintain them at 50-60ºF  and 50-70% relative humidity. Do not place parasitoids or predators into refrigerators or in direct sunlight since refrigerator temperatures (35-45ºF) and exposure to sunlight are detrimental to both natural enemy types. In general, the longer that natural enemies are stored, the lower the survivability of the individuals. One common cause of natural enemy mortality during storage is desiccation, which may be avoided by placing containers of natural enemies in a plastic bag along with a moist sponge, and then securely sealing the bag. From: New England Greenhouse Floriculture Recommendation Guide For more information:  Greenhouse IPM with an Emphasis on Biocontrol by Penn State University - Appendix D: Quick Methods for Evaluation Biocontrol Shipments. This is a overview chart of how to determine viability, and to determine establishment and reproductive success in the greenhouse for a number of biological control agents.   Also, check with your supplier for additional information.

Leanne Pundt, University of Connecticut

Thrips are active in many greenhouses now. If you use pesticides to manage thrips then plan to treat in the early evening. Thrips have two mass flights per day, so sprays in the early evening may contact more thrips.  Treating before you see a peak in adult numbers on yellow sticky cards is critical. Adult thrips numbers on cards tend to peak every two to three weeks. Apply insecticides before this peak, so adults will be killed before they lay eggs. Small droplets of pesticide sprays are most effective for coverage.

To manage thrips, make two to three pesticide applications about 5 days apart and rotate pesticides with different modes of action. Two materials that some growers are successfully using are pyridalyl (Overture) and chlorfenapyr (Pylon).  It appears that pyridalyl (Overture) is more toxic to second instar nymphs than adults. Also, Overture takes at least seven days to kill a majority of WFT, so don’t expect an immediate reduction in populations when using this insecticide. Read the label for plant safety. Both products have precautions. Both of these products also have translaminar activity. Remember that translaminar insecticides penetrate leaf tissues and form a reservoir of active ingredient within the leaf, providing residual activity. Insecticides with contact or translaminar activity are generally better than pesticides that are systemic because systemic insecticides typically don’t move into flower parts (petals and sepals) where WFT adults normally feed. Azadirachtin (Molt X, Aza-Direct, Azatin, Ornazin, Neemix) is an insect growth regulator (IGR) and "stressor" so may be helpful in some tank mixes. For example, if thrips populations are low and plants are not yet in flower, Beauveria bassiana (Botanigard, Mycotrol) and azadirachtin may be an option. Abamectin (Avid) (translaminar activity) with azadirachtin has also been working well for some growers.

Pesticide rotation options for management suggested by Dr. Raymond Cloyd, Kansas State University are: * Spinosad (Conserve), Chlorfenapyr (Pylon), Abamectin (Avid), Methiocarb (Mesurol) * Novaluron (Pedestal), Pyridalyl (Overture), Chlorfenapyr (Pylon), Spinosad (Conserve) * Beauveria bassiana (BotaniGard/Naturalis), Acephate (Orthene), Spinosad (Conserve) * Abamectin (Avid), Pyridalyl (Overture), Chlorfenapyr (Pylon), Spinosad (Conserve) * Chlorpyrifos (DuraGuard), Novaluron (Pedestal), Abamectin (Avid), Bifenthrin (Talstar)

Horticultural oil (Pure Spray Green, Saf-T-Side, or Ultra fine oil) may also be an option provided label cautions regarding plant safety are followed. Note that Mesurol has a 24 hour REI plus it may leave an unsightly residue, so it may be best early in the growing season. Pedestal is an insect growth regulator (IGR) labeled for immature stages. TriStar (acetamiprid - group 4A) or Aria (flonicamid - Group 9C) may also help suppress thrips.

Articles: Western Flower Thrips Management: Have We Reached an Impasse?by Raymond Cloyd

2010 Thrips Management Plan

Tina Smith, University of Massachusetts Leanne Pundt, University of Connecticut 

Questions have been asked about using pheromone lures to detect Western flower thrips and the effectiveness of using sugar in the spray mix to enhance spray efficacy.

Phermone Lures

A new item for WFT is a sex aggregation pheromone lure for early detection of low level populations. It is reportedly best used very early in the crop cycle. A number of companies sell or distribute lures that are suppose to increase the number of WFT thrips adults captured on sticky cards or attract WFT out of hiding places such as flowers or buds, increasing their exposure to insecticide spray applications and achieving higher mortality. Note that a pheromone lure is not a “control” device. Some growers are concerned about attracting WFT to un-infested areas, especially if used this late in the growing season with active thrips infestations. Also there are questions about the longevity of the scent within a greenhouse and how effective the pheromone lure is when many different plant types are in flower.

Using Sugar in Spray Solution

Growers for years have suggested that mixing white or brown sugar with a contact insecticide in the spray solution enhances efficacy of the spray application against western flower thrips. Research by Dr. Raymond Cloyd, Kansas State University showed that the addition of sugar and other sweeteners to lure thrips from hiding does not work and in some cases can cause the growth of black sooty mold.

Information on thrips management by Dr. Raymond Cloyd: Western Flower Thrips Management: Have We Reached and Impasse?

Does Dew Do It?

Tina Smith, University of Massachusetts

 

Inspect incoming plants carefully for signs of insects, diseases, weeds and cultural problems. Inspect the entire plant - leaves, stems and roots for signs of pest activity and for general health. Look for any distorted new growth on incoming plugs and transplants that might be caused by thrips. Blackened, firm stems and leaf spots on garden impatiens and New Guinea impatiens are signs of Impatiens necrotic spot virus (INSV). INSV test kits are useful for quick tests of suspicious looking plants.

Look on the undersides of leaves for spider mites. They are often found along the mid-vein of ivy geraniums, ipomea, thunbergia and other susceptible plants. On ivy geraniums, spider mite damage is similar to damage caused by thrips and oedema. Inspect root health also. Roots should be white with vigorous growth. Roots that are brown or decayed are evidence of root rot disease or may be caused by overwatering or high soluble salts.

When handling and cleaning incoming plants, work in blocks and wash hands thoroughly between blocks of plants. If disposable gloves are worn, change or clean them between blocks. This will prevent spreading infectious diseases that are transmitted mechanically, such Bacterial leaf spot on geraniums and Tobacco Mosaic Virus on petunias and related crops.   If at all possible, do not accept plant shipments with serious insects or diseases with wide host ranges, and are difficult to treat. Do not accept plant material infected with incurable diseases, such as root rots, viruses, bacterial leaf spot diseases, or foliar nematodes. If you need confirmation, isolate a few plants showing symptoms and send them to a diagnostic laboratory. If you find isolated evidence of some insect activity, for example, aphids, and decide to keep the shipment, identify an isolated, quarantine area in which to keep the plants. Treat immediately and hold the plants in this area until you are sure that they are healthy, salable and free of pest problems. Only enter this quarantine area at the end of the day to avoid moving pest problems throughout your operation.

Tina Smith, University of Massachusetts

Late Blight caused by Phytophthora infestans – a very destructive and very infectious disease killed tomato and potato plants in gardens and on commercial farms throughout the eastern U.S. during 2009. Late blight occurs at some locations in the Northeast each year, however in 2009 infected plants were distributed through large local retail stores throughout the region (Ohio to Maine) during June, and outbreaks were reported over this entire region by early July. Never before had such an extensive distribution of infected plants occurred, especially so early in the season. This, combined with the cool, wet growing season and the exceptionally contagious nature of the disease during cool, rainy, windy weather all contributed to a disastrous year for farmers. Garden retailers can help prevent the spread of late blight in gardens and on farms this growing season and provide customers with the facts about this disease. Grow your own transplants from seed or purchase locally grown plants Late blight is not seedborne in tomatoes (however, it is tuber-borne in potato), so tomato plants started from seed locally would be free of the disease. Growing your own transplants from seed or purchasing from a reputable local grower will ensure a healthy start to the season for your customers and local farms. Provide disease-resistant or tolerant varieties       Tomatoes: Disease-resistant or tolerant varieties of tomatoes exist, however seed is in limited supply this year. ‘Mountain Magic’, ‘Plum Regal’, and ‘Legend’ are three varieties with resistance or tolerance to late blight. Note that the variety ‘Legend’ is the only late-blight resistant variety for which seed is readily available this year. In addition to late blight, each year tomatoes become infected with early blight and Septoria leaf spot, which look very similar. If possible, also provide tomato plant varieties that are resistant or tolerant to early blight for your customers, such as the varieties ‘Mountain Fresh’, ‘Mountain Supreme’, and ‘Plum Dandy’ and others.       Potatoes: Purchase certified, disease-free seed potato from a reputable source, and ask your supplier about their source of seed and if it was inspected in the field for late blight. Seed potato from the northeast are less likely to carry the disease. Inspect transplants for signs of disease If you purchase plants to sell, inspect all transplants for stem, petiole cankers or leaf blight as long as plants are on the shelf. Teach your staff what to look for, using the web-links below. If you suspect a late blight infection, use your Plant Diagnostic Lab to confirm if late blight is present. Know the FACTS for Staff and Customers Train employees and provide information to your home gardening customers. * Potatoes that freeze or fully decompose will not carry the pathogen over winter. * Tomatoes will not carry late blight over the winter, because freezing kills the whole plant. *  Tomato seed, even from fruit that was infected with late blight, will not carry the pathogen, so no need to worry about the tomatoes left behind in the garden or compost pile. Certain perennial weeds can become infected with late blight, but none of their above-ground tissues live through the winter. *  Late blight will not survive on tomato stakes and cages. * The biggest threat for overwintered disease in New England is on potatoes. In the spring, advise home gardeners to inspect last year’s potato plot and any compost or cull piles for volunteer potato plants that might come up. If they find potato plants, pull them out and put them in the trash or destroy them. If tubers were infected and survive, then the late blight could grow upward from the tuber, infecting the stem and producing spores when weather conditions are favorable. These spores could then disperse to other tomato and potato plants. * During the growing season, pay attention to pest alerts to learn about whether late blight has been observed in New England, and what actions you need to advise to customers. Pest alerts will be updated on the UMass Extension Vegetable Program Website, www.umassvegetable.org   

Photos: Symptoms on stems, leaves and fruit (Cornell) Photos, FAQ, Fact Sheets (Cornell)

Tina Smith, University of Massachusetts

Hunter flies are becoming more common on sticky cards in greenhouses. The Hunter fly (Coenosia attenuata) is a greyish, predatory fly in the same family as the housefly and similar in appearance, but smaller than the common housefly. Some growers confuse them with shore flies. Adult shoreflies also resemble small houseflies, with their short robust bodies, short legs and short antennae, but are smaller than the hunter fly, darker in color and have characteristic five clear spots on the wings.

The adult hunter fly preys on other flying insects, catching them in flight. It feeds on fungus gnats and shoreflies, but also on other flying insects such as leafminer and, to a lesser extent, whiteflies. The larvae live in the soil and are generalist predators on soil-dwelling organisms such as fungus gnat and shorefly larvae.

Hunter flies are originally from Europe. They were first found in the United States in October of 1999 at a commercial greenhouse in upstate New York. Adult females lay eggs in the soil that hatch in about 5 days. The hunter fly larvae seek other soil dwelling insects such as fungus gnat larvae as prey. Larvae grow for about two weeks and then pupate in the soil for two weeks.

Photos: Hunter fly adult, Hunter flies on sticky cards, Fungus gnat and shorefly on sticky card, Shoreflies and others on sticky cards

More Photos: Fact sheet on fungus gnats and shoreflies including photos of hunter flies, shore flies, fungus gnats and common parasitic wasps found on sticky cards.   Need to scroll to figures 11-14

Leanne Pundt, University of Connecticut Tina Smith, University of Massachusetts

We came across this short video (15 minutes long) that might interest some growers. A Minnesota farmer, Steven Schwen explains how his thermal-storage greenhouse works. He uses diagrams and talks a little about costs. This project was funded in part by SARE.

http://cookingupastory.com/sustainable-energy-thermal-banking-greenhouse-design 

Paul Lopes and Tina Smith University of Massachusetts