Floriculture Greenhouse Update

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

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

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

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

 

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

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

Nematodes are small, colorless, cylindrical round worms that occur naturally in soils throughout the world. Different species work best against different target pests. Steinernema feltiae is primarily used against fungus gnat larvae and thrips pupae in the soil. Fungus gnat larvae may be parasitized in any larval stage.  Nematodes have traditionally been used against soil dwelling pests because they are sensitive to ultra violet light.

The nematodes enter the insect host through body openings. They multiply within the host and release a symbiotic bacterium whose toxin kills the fungus gnats. The larvae are killed in one to two days by blood poisoning.  More than one generation of nematodes may develop in dead host insect in the media. The infective juveniles then exit the dead body and search for new hosts to infect

The nematode S. feltiae is sold under the trade names of NemaShield and Nemasys. Both of these products are labeled as a soil drench treatment against fungus gnat larvae. Preventative applications to moist soils work best.  Apply nematodes with a sprayer (remove screens and filters), injector, hose end sprayer or even a watering can. If using an injector, set the dilution to 1:100. Remove all filters or screens on the intake tube. Remove pump filters. Use a small battery powered submersible pump to keep the solution agitated.

Unlike many traditional pesticides there is no REI (an added bonus in propagation houses), nor possibility that the target pest will develop resistance. No adverse effects have been shown against non-target organisms in many different field studies. But, beneficial nematodes are living organisms, so there are a number of precautions you need to follow for their successful use.

Check viability before application. To do this, place a small amount of the product in a small container or petri dish. Add 1 or 2 drops of room temperature water; wait a few minutes and look for actively moving or swimming nematodes. Use a dark black background and a hand lens or field microscope to see the small (0.6 mm or 0.02 inches in length) nematodes. Apply in the evening or at dusk or on a cloudy, overcast day. (Nematodes are very sensitive to UV light and desiccation).

Nematodes are compatible with a number of different pesticides. However, they are generally not compatible with organophosphates, carbamates, and nematicides.   However, do not mix nematodes with your fertilizer solution!  

For more detailed information on pesticide compatibility: consult with your supplier or with the following resources on the Internet:

- Pesticide Side Effects Database – www.koppert.com

- Pesticide Side Effects Database - www.biobest.be/

Apply immediately after receiving them, if possible.  If you must store the nematodes, store in a refrigerator (38-42°F). Avoid placing in a small refrigerator where they may freeze. Check expiration date on the package for how long you can store them.

Specific Tips for Use Against Fungus Gnat Larvae. 

• Treat as soon as possible (2 to 3 days) after sticking cuttings, planting plugs or starting seeds. 
• Apply as a media drench to target the fungus gnat larvae.
• Media temperatures should be above 50° F but avoid applying when soil temperatures are above 80°F. Optimum media temperatures are between 60-70°F. (Use a soil thermometer to monitor temperatures).
• Water the growing media before and after application. (Nematodes need moisture for movement). But, avoid over watering, so they aren’t washed out of the container.
• Apply in the evening or at dusk or on a cloudy, overcast day. (Nematodes are very sensitive to UV light and desiccation).
• Repeated applications are often needed. Reapply in 2 to 4 weeks under moderate to heavy infestations. For longer term crops, apply at the beginning and at mid crop.

The symbiotic bacteria breaks down the host insect’s cuticle. The infected larvae rapidly disappears, so may be difficult to locate. Infected fungus gnat larvae are often opaque-white to light yellow in color.

In addition, the product Nemasys is also labeled for use against western flower thrips. Specific tips for use against western flower thrips (from the Nemasys label).

• Nematodes require moist conditions to enhance effectiveness.
• If plants are dry, provide light overhead irrigation prior to nematode application.
• Ensure good foliar coverage of spray mix to enhance contact with the target pest.
• Use of a wetting agent or surfactant will enhance wettability of the spray mix and encourage nematode movement.
• Following application, ensure that the crop remains wet for at least two hours.
• Do not apply in direct sunlight.

Note: the nematodes will dessicate after about one day.  Growers who have had success with this application method, apply the nematodes on a weekly basis, and target the young growing point where thrips tend to hide.

For more information on Steinernema feltiae:

NemaShield- BioWorks Nemasys - BeckerUnderwood Searchable Database on Insect Parasitic Nematodes: Ohio State University

Leanne Pundt, University of Connecticut

It is time to plan aphid management if you will be using biological control agents. See the message posted January 29, 2009 for more details. Ornamental plants are susceptible to many aphid species such as green peach, melon, potato and foxglove. Managing aphids using biological control agents is a bit complicated because parasitic wasps are not general feeders and they parasitize specific aphid species. Some suppliers primarily recommend several parasitic wasps, banker plants and a predatory midge to manage the various aphid species. Other suppliers also recommend using predatory lacewings. Place orders for banker plants about 6 weeks prior to expected aphid infestations. Banker plants with Aphidius colemanii should be started 3 weeks prior to seeding or sticking cuttings in propagation houses as a preventative measure for green peach and black melon aphids. Since cereal aphids used in this banker-system attack monocots, they should not be used in greenhouses containing lilies or grasses. The first Aphidius colemanii banker plants containing the grass feeding aphid species need to be transplanted into larger pots (10”) upon arrival. A week later, the parasitic wasps, Aphidius colemani should be ordered and immediately released on the banker plants. If aphids are observed in the crops, they should be identified and additional biological control agents selected for that species. If aphid populations increase and more control is needed, Aphidoletes aphidimyza can be introduced weekly for 3 weeks in hot spots to supplement the parasites. Aphidoletes aphidimyza is a generalist predator that feeds on many different species of aphids. They arrive as midges and adults and adults fly out of the tubes upon opening. The midges and other stages are evenly sprinkled upon the leaves of the crop. If using predatory midges, placing the pots in trays with moist sand will help provide pupation sites for them. (The predatory midges pupate in the soil).The parasitic wasps Aphelinus abdominalis and Aphidus ervi are used for potato and foxglove aphids They are released weekly for at least 3 weeks or until aphids are controlled. Yellow sticky cards should continue to be used to monitor aphid predators and new growth should be inspected for aphid populations.

Work with your supplier for rates. Guidelines are available in the 2009-2010 New England Greenhouse Floriculture Guide (ordering info)

Photos: Banker plants with aphids, Close up, Starter cage 

More information: Biobest - biological control, Propagation of ornamental crops

Two good articles in "Greenhouse IPM Bi-Weekly Report" by Stanton Gill, University of Maryland on experiences using banker plants:  Aphid Control -Results in Maryland and Banking and Investing on Aphid Control in Greenhouses 

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

Planning ahead is essential for success if you are considering using biological control for pest management. Growers that successfully use biological control for spring crops start in propagation greenhouses at the very beginning of the crop cycle. Biological control should never be started in the middle of a crop cycle. For growers purchasing plant material from other growers, request information on what specific pesticides were applied to the plant material to ensure that no long lasting pesticide residues adversely impact the biological control agents. For example, many organophosphate and pyrethroid pesticide residues may impact biological control agents for 3 to 4 months. See message posted October 9th for more details on preparing your greenhouse.   Growers starting their own seeds or cuttings, begin by using beneficial nematodes (Steinernema feltiae) as a preventative measure for fungus gnats, but also thrips larvae suppression. The nematodes are mixed with water and applied during the first or second watering as a soil drench with a repeat application when repotting or transplanting. As a guide, 2 applications spaced 2 weeks apart usually provide 6 weeks of protection. Nematodes do not control shore flies.  Beneficial nematodes can also be applied with Trichoderma (RootShield) which also needs to be applied preventatively. Hydrogen dioxide (XeroTol) and fertilizer solutions are not compatible with the beneficial nematodes and need to be applied separately.   For shore flies (and also fungus gnats), Atheta coriaria (Rove Beetle) is commonly used, applied one time during seeding or sticking cuttings. Atheta are nocturnal and are easily established in greenhouses. They come in a tube of peat-vermiculite mix with all three stages of the insect present (egg, larva and adult). Open the container where you will release them and sprinkle them evenly across the area to be treated. Reapply when transplanting or repotting. The predatory mite, Stratiolaelaps scimitus  (formerly known as Hypoaspis miles) is also included for fungus gnats during propagation. It is applied once during seeding or sticking. Hypoaspis are very mobile and will colonize the surface of the growing media. They also come in a tube of vermiculite/peat which should be evenly distributed by sprinkling across the area to be treated and should be reapplied when transplanting or repotting. Growers are also including the predatory mite Amblyseius cucumeris as a preventative for thrips in their propagation areas. Amblyseius come in a tube of bran. A small pile of bran is placed on each seedling tray which acts a breeder pile for mites. Adult mites emerge from the pile and attack early larval stages of thrips development and sometimes eat spider mites and their eggs. The pile needs to be kept intact for breeding to continue and mites to emerge. Amblyseius should be reapplied when transplanting or repotting. Use yellow sticky cards to monitor for shore flies and fungus gnat adults and use potato wedges to monitor fungus gnat larvae. For information on rates, contact your supplier. Also see: 2009-2010 New England Greenhouse Floriculture Guide (ordering info)

Becker Underwood: Chemical Compatibility Chart for Beneficial Nematodes

Biobest, Crop Info-Sheet: Propagation of Ornamental Crops  (Biocontrol)

Biobest, Crop Info-Sheet: (Biocontrol) Spring Crops (Bedding Plants and Hanging Baskets)

Technical Bulletin: Propagation of Ornamental Crops Using Biological Control Agents for Pest Protection

Sometimes rates are in metric. For metric conversion see: www.metric-conversions.org 

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

To prepare for thrips management in spring crops, it’s time to begin growing ornamental pepper plants ‘Black Pearl’ as banker and indicator plants. The plants need to be growing for about 2 months before spring bedding plants are started and planted in 6” pots in early December.

The following information was adapted from Greenhouse TPM/IPM Weekly Report, Oct. 10, 2008, Maryland Cooperative Extension,Central Maryland Research and Education Center.

The predaceous minute pirate bug, Orius insidious is expensive to purchase. Orius is a beneficial generalist predator that feeds upon adult and larval thrips. It will also feed on other small insects such as aphids, and spider mites. Orius is not effective under short days.  A pollen food source helps them establish in the greenhouse. 

So, the idea is to rear them on pollen producing pepper plants and place plants throughout the greenhouse to distribute the minute pirate bugs throughout the greenhouse. Pepper plants are magnets for thrips and serve as banker plants and indicator plants for early detection. Minute pirate bugs are released at a rate of 60-80 per pepper plant. The minute pirate bugs will lay eggs on the pepper plants in the same area where thrips lay eggs, usually in or near flowers. One pepper plant covers around 1,000 sq. ft. of growing area. As long as the pepper plants are in flower and producing pollen, the minute pirate bugs will reproduce on them. The adults will fan out across the greenhouse and kill 1st and 2nd instar thrips larvae and adult thrips. Only one release of minute pirate bugs onto the banker plants is necessary. Peppers need to be removed about once a month from the pepper plants to keep them flowering, in order for the process to work. Some growers have mentioned that keeping peppers picked off the plants is tedious and time consuming. For information on growing ‘Black Pearl’ ornamental pepper from seed see  Grower Facts from PanAmerican Seed. 

Leanne Pundt, UConn and Tina Smith, UMass Extension

 

If you are planning to use biocontrol for pest management in your greenhouse for spring crops, then it is time to prepare now.  Management, growers and staff all need to be on-board and involved. A biological control program should never be started in the middle of a growing season. Begin a biocontrol program that will be at the start of a new crop cycle. Biocontrol prevents problems, it does not fix problems, which is why planning needs to be done now. Begin by reviewing pest problems from this past year and VERY IMPORTANT, avoid pesticide use 3-4 months prior to using biological control. When crops are in the greenhouse, develop and start a consistent monitoring procedure. Set a start date for using biological control. Develop a strategy based on your production planning, that is right for your particular situation. Start using biological control agents in your propagation area, right from the start. If you are buying in rooted or unrooted cuttings ask your supplier/broker to supply specific information on what pesticides may have been used on the cuttings.  Toxic pesticide residues either on, in or around the greenhouse or on plant material is one of the main reasons for failure using biocontrol control agents.  It is important to phase out the use of pest control materials in the organophosphate, carbamate, and pyrethroid chemical classes prior to releasing natural enemies since many materials in these chemical classes can persist for four months or longer in the greenhouse. 

For more information on the compatibility of pest control materials with natural enemies refer to on-line databases under side effects, such as Koppert, Inc., or Biobest .  Talk with your supplier of natural enemies, too. Research is continuing on the compatibility of pest control materials with natural enemies.  During the transition period, before using biocontrol, growers might use products that are not necessarily compatible with natural enemies, but have a short residual effect of less than 2 weeks. Examples of these pesticides are abamectin (Avid), imidacloprid (Marathon, Tristar), dinotefuran (Safari) and pyriproxyfen (Sanmite). Products that are compatible and have short residual include  bifenazate(Floramite) and pymetrozine (Endeavor).

Tina Smith, UMass Extension and Leanne Pundt, UConn

 

Most insects are not pests, which is easy to lose sight of,when your spring hanging baskets are ready to ship and suddenly there is an outbreak of aphids. However, now that you are scouting your outdoor field mums or herbaceous perennials, it’s important to keep an eye out for naturally occurring beneficial insects and mites. If they are present in sufficient numbers, they can do your work for you! These good guys may be either generalist predators that feed on many pests during their lifetime or more specialized host specific parasitic wasps that may parasitize aphids or tomato hornworms.  

To help conserve beneficials, select more environmentally friendly “softer” materials such as oils, soaps, and certain insect growth regulators that tend to be more compatible with natural enemies, if you do need to spray. If advising home gardeners, correct insect identification is important, for many home gardeners do not recognize beneficial insects and think if it’s crawling, it must be a pest. (For example, although homeowners recognize adult lady bird beetles, they don’t recognize the larvae stages!)

Many aphid predators have been noted, such as hover flies or syphrid flies, in the field. These non stinging flies closely resemble small bees or wasps. However, unlike bees or wasps they only have two wings. Adults are usually about ½ to ¾ of an inch long. These pollen feeders are often seen near perennials in flower. Adults lay eggs that resemble a small grain of rice.The eggs hatch into small legless larvae that feed upon aphids as well as thrips and small caterpillars. Other aphid predators that may help control aphids include lacewing larvae, lady bird beetles or ladybugs, parasitic wasps, as well as naturally occurring fungi.

Photos: Hover flies and Lady beetle larvae

Here are some links to more information on recognizing beneficial insects and mites:  

Flash Cards: Good Guys: Natural Enemies of Insects 

Biological Control: A Guide to Natural Enemies in North America 

Beneficial Insect and Mites

Reference books (with excellent color photos)  

Flint,M.L. and S. H. Dreistadt. 1998. Natural Enemies Handbook: The illustrated guideto Biological Pest Control. Universityof California. 154 pp.800-994-8849. Publication #3386

Cranshaw. W. 2004. Garden Insects of NorthAmerica: The Ultimate Guide to Backyard Bugs: 656 pp.  

On the effect of plant diversity on beneficial insects andoverall diversity:

Bringing Nature Home – on the role native plants play tosupport native insect herbivores and overall diversity

Attracting Beneficial Insects with Native Flowering Plants 

Leanne Pundt, University of Connecticut

Watch for two-spotted spider mites on ipomoea, New Guinea impatiens and other crops. Mites may come in on incoming plants or have over-wintered in your greenhouse. Look for dull stippled foliage on plants particularly in warm, dry locations in your greenhouses such as near steam pipes, furnaces, heaters or overhead hangers. Use a 10x handlens and look on the underside of mature leaves, especially along the midvein for eggs, immature stages and adults. Note that young nymphs do not have the dark two spots.

Contact or translaminar miticides can be used to manage two-spotted mites. Translaminar means that the material penetrates leaf tissues and forms a reservoir of active ingredient within the leaf which provides extended residual activity. Miticides with translaminar activity include abamectin (Avid), etoxazole (TetraSan), chlorfenapyr (Pylon) and spiromesifen (Judo). After treatment, mark several plants and use a 10X hand lens to look for live and dead mites and eggs. Most miticides are not effective against the egg stage, so repeat applications may be needed in 5-7 days. Thorough coverage is important for contact activity. Insecticidal soaps and horticultural oils are also effective. Consult label for plant safety.  Go back and check plants within a few days to see how effective the treatment worked. You will hopefully see dead and dying mites, but you may also see eggs. Continue to monitor and repeat treatments as needed.

Biological Control

A fast acting predatory mite that is commercially available is Phytoseiulus persimilis. This predatory mite only feeds upon spider mites, and will disperse or starve with no prey. The adult P. persimilis is bright red in color, pear shaped, long-legged and slightly larger and more active than spider mites.

P. persimilis is best released when mite populations are first noticed, in hot spots of mite activity and adjacent areas. Relative humidity should be greater than 75% and temperatures above 68F for some hours of the day. (At low relative humidity, less than 60%, eggs shrivel and do not hatch.). According to Raymond Cloyd, University of Kansas, P.persimilis is suitable for short-term crops such as bedding plants at release rates of 1-4 mites per ft² per week. Two applications, one week apart may be required. Spider mite colonies should be reduced in two to three weeks. To scout, shake plants over white paper and observe mites. Pest control materials that have been shown to be compatible with P. persimilus include spinosad (Conserve), pymetrozine (Endeavor) and clofentezine (Ovation). Bifenazate (Floramite), spromesifen (Judo) and chlorfenapyr (Pylon) may be harmful.

The spider mite predator Neoseilus californicus is slower acting than P. persimilis, but can survive longer in the absence of prey. It is useful for keeping low spider mite populations under control. In certain situations where high temperature or relative humidity variations can occur, N. californicus may be an option. N. californicus is active at temperatures between 46°F to 95°F, 40-80% relative humidity. At low pest densities, it declines less than P. persmilis, for N. californicus can survive on other mites, thrips, molds and nectar. N. californicus can also be introduced preventively and is compatible with P. persimilis.

Some suppliers offer a mix of different species of predatory mites.

Photo Gallery: Mites and Damage Mite injury on moonflower (Ipomoea)

Fact Sheet: Managing Two-Spotted Spider Mites in the Greenhouse

Raymond Cloyd, Kansas State University authored the newly explanded section on biological control in the 2009-2010 New England Greenhouse Floriculture Guide. The guide can be ordered from the University of Connecticut or University of Massachusetts or New England Greenhouse Conference .

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

Using Biocontrol If you plan to use biological control such as the predatory mite, Neoseilus cucumeris to manage thrips, then review the message posted February 4, 2008. It is important to begin prophylactic introductions of natural enemies on young plants or in propagation areas before thrips are detected. (It is also helpful to check with your supplier to determine if they have applied any long residual pesticides to the incoming plant material that may adversely affect the biological control agents.)

N. cucumeris is a small, predatory mite that feeds upon young 1st instar thrips larvae. Apply N. cucumeris in bulk to flats and bench top crops. For bedding plants, apply in weeks 1-3, 5, 7 and 9. In week 2 or 3, apply nurse sachets to hanging baskets that cannot be easily reached or apply breeder mix to the hanging baskets as they are planted. Hypoaspis miles or H. aculifer are soil dwelling predatory mites that feed upon pupal stages of thrips in the soil as well as fungus gnat larvae. A single preventive release to the media at planting is generally recommended to supplement control with N. cucumeris.  

Using Pesticides For growers using pesticides to manage thrips, plan to treat in the early evening. Thrips have two mass flights per day, so sprays in the early evening may contact more thrips. Small droplet sprays, repeated applications (two to three sprays about 5 days apart) and treating before you see a peak in adult numbers on yellow sticky cards are 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.  A mass aggregretion pheromone or thrips lure is also available to be placed into sticky cards to aid in early detection of thrips.

To manage thrips, shorten spray intervals to 4-5 days and rotate pesticides with different modes of action. Some options for management (based upon grower feedback) include Avid (abamectin-group 6) tank mixed with Azatin (azadirachtin- Group 18B), Mesurol (methiocarb-group 1A), Pedestal (novaluron-group 15) tank mix with Pylon (chlorfenaphyr- group 13), Safari (dinotefuran Group 4A) and Conserve (spinosad-group 5).  Overture (pyridalyl) (unknown mode of action) has contact, translaminar and some ingestion activity and can be added into your rotation program. It is labeled for thrips and caterpillars but may take from 7 to 14 days before you see control.  

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 and Pedestal is an IGR labeled for immature stages. In addition, TriStar (acetamiprid - group 4A) or Aria (flonicamid - Group 9C) may help suppress thrips.

Growers often ask about adding sugar to their spray for thrips management. Recent research by Raymond Cloyd, Kansas State University showed that the addition of brown sugar and other sweeteners to lure thrips from hiding does not work and in some cases can cause the growth of black sooty mold.

For a complete list of insecticides labeled for use against thrips, see the New England Greenhouse Floriculture Guide.

Sources of thrips pheromone lures ThriPher Thripline

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

Many different species of entomopathogenic (insect-killing) nematodes are available for soil dwelling pests. (Insect killing nematodes are very sensitive to ultra-violet light and desiccation). Growers have been successfully using Steinernema feltiae (Nemasys, Nemashield, ScanMask) as a drench against fungus gnat larvae, especially in propagation areas. S. feltiae also attacks the pupal and prepupal stages of western flower thrips that are primarily found in the growing media. (However, some thrips may also pupate in chrysanthemum flowers).

In the past few seasons, nematodes have been promoted for controlling the above ground stages of thrips.  Cut chrysanthemum growers in Canada and the UK have successfully used S. feltiae against thrips with weekly sprays.  Special precautions are taken to help reduce potential desiccation: use of a non-ionic wetting agent, spraying in the late afternoon or evening, and the use of black cloth.  

Although all stages were susceptible to infection, Buitenhuis and Shipp (2005) (see links below) found that the prepupae and pupae stages were most susceptible to infection by S. feltiae.   During the weekly sprays, a significant number of nematodes reached the growing media via runoff from the foliar sprays. Nematodes are very short lived on the foliage (significant reduction after one hour) but may persist for several weeks in the media.

In this study, significant kill of the 1st and 2nd instar larvae, was only obtained at very high rates of application (~13 to 26x the recommended rate used for ornamentals in greenhouses), which may not be cost effective. The mobile adults and larvae may escape infection. Immobile adults were killed.

Grower feedback has been variable, with some observing very good results and others less so.  Efficacy will be variable depending upon the relative humidity, and temperature in your greenhouse, dose applied, frequency of application, and life stage of the thrips.  Applying the nematodes as a heavy surface spray or "sprench" to young, incoming plant material will have an added benefit of targeting any incoming fungus gnats in the media as well as thrips pupae.   

Nematodes also need to be alive in order to be effective. Place a small quantity of the nematodes into a shallow container, add a few drops of water, and look for the actively moving nematodes, which will have a slight "J" curvature. Place the container against a black background, so it is easier to see the nematodes.  

University of Guelph researchers just started a project investigating the use of softer options, such as oils, soaps or beneficial nematodes to disinfest vegetative cuttings against thrips and whiteflies before they are planted into the greenhouse.

For more information: (this is a PowerPoint file that may take time to download).

http://www.cost850.ch/publications/20050423_hannover/COST850-4-Hannover-Bennison.pdf

Leanne Pundt, University of Connecticut

Aphid banker plants are containers with winter barley or common rye or oats on which colonies of grass-feeding aphid species such as the corn-leaf aphid (Rhopalosiphum maidis), greenbug (Schizaphis graminum), and/or bird-cherry aphid (Rhopalosiphum padi) are established. Banker plants are primarily used to rear prey or hosts, in order to attempt to have a sufficient population of continually reproducing natural enemies.

Banker plants need to be placed along walkways and at the end of benches. It is essential to evenly distribute them throughout a greenhouse. General recommendations suggest that banker plants should be placed approximately 131 feet apart, using 4-5 banker plants per 10,000 ft2, in order to increase parasitization. Some growers will place the banker plants at the hanging basket levels with drip irrigation that also insures that the banker plants will remain irrigated without inadvertently washing the aphid natural enemies off of the plant.

It has also been recommended to distribute containers of rye or barley, with the grass-feeding aphid, among the main crop at a rate of one banker plant per 1,000 ft2 even before aphids are detected. It should be noted that existing recommended rates may vary since limited research has been conducted; start with these rates and adjust in succeeding years based on your experience. In research with aphid banker plants in greenhouse pepper production in the Netherlands, 4 banker plants per acre were introduced every two weeks and were able to keep the aphids below threshold. With this rate and frequency of introduction of banker plants, the average number of Aphidius caught per sticky card (3.9" by 9.75") per week was 10 per card per week.

Banker plants may have to be placed closer together or placed in greater frequency within a given area in order to allow parasitoids such as Aphidius colemani to find prey on plants, since research has found that this parasitoid migrates just 3.2 - 6.5 feet from the point of release.

Starter aphid banker plants are available from several biological control suppliers.  

• Place orders for banker plants up to 6 weeks before aphids are expected in your greenhouse.
• Transplant the plugs into larger sized pots (10 inch) so that the grass plants have plenty of room to grow.
• Wait one or two weeks for grass feeding aphid populations to grow.
• Lightly release the "aphid mummies" or Aphidius colemani adults onto the starter banker plants. For example, 100 hundred Aphidius per banker plant before it is divided and repotted. Aphidius colemani attacks the grass-feeding aphid, which is not an aphid pest of most greenhouse-grown crops except monocots such as ornamental grasses.
• Check banker plants weekly and look for newly parasitized aphids ("aphid mummies"), which indicate that the parasitoids are establishing on the banker plants.
• Start new banker plants on a regular basis because they will decline and die within a few weeks.
• Inoculate new banker plants by physically transferring aphids from old banker plants onto new ones every 2 weeks.
• It may be necessary to "protect" or isolate your replacement banker plants from natural enemies (either established in your greenhouse or naturally occurring natural enemies that may enter the greenhouse from outdoors during warmer weather). If so, place banker plants in "starter cages" so you can build up your population of grass feeding aphids before releasing A. colemanii. (see photo).   

Keep in mind that the bird-cherry aphid is too small for the parasitoid, A. ervi, to develop.  A. ervi parasitizes larger aphids such as the foxglove or potato aphid.  If foxglove or potato aphids are your predominant species, one option is to use the predatory midge, Aphidoletes aphidimyza for release onto your banker plants. If using predatory midges, placing the pots in trays with moist sand will help provide pupation sites for the predatory midges. (The predatory midges pupate in the soil).

Adapted from: Cloyd, R. Pest Management in Greenhouses. Biological control. From 2009-2010 New England Greenhouse Floriculture Guide.

Thanks to Carol Glenister, IPM Laboratories and Ron Valentin, BioBest for there suggestions. 

Photos: Banker Plants,  Banker Plants with aphids,  Starter Cage

Leanne Pundt, University of Connecticut

Updated 7/09

If you are planning to use biological control for spring crops, then take some important steps now. The success of any biological control program relies on patience and a commitment to detail such as sanitation, scouting and record-keeping.

Clean as early as possible to eliminate over-wintering sites for pests to reduce their populations prior to the growing season. Greenhouse pests will over-winter in weeds and protected areas in unheated greenhouses and especially during years with unseasonably warm temperatures. Pests are much easier to prevent than to cure.

To learn about cleaning and disinfecting see the fact sheet: Cleaning and Disinfecting the Greenhouse

It is important to phase out the use of pest control materials in the organophosphate, carbamate, and pyrethroid chemical classes prior to releasing natural enemies since many materials in these chemical classes can persist for up to four months in the greenhouse. For more information on the compatibility of pest control materials with natural enemies refer to on-line databases, such as Koppert, Inc., (www.koppert.com) or Biobest (www.biobest.be). Check under "Side Effects." Research is continuing on the compatibility of pest control materials with natural enemies.  

In addition to sanitation and phasing out the use of residual pesticides, a good weekly monitoring program should be in place. Detecting problems early is essential, since beneficials are introduced at the first sign of an infestation. A 10X hand lens will help to identify pests and beneficials. Knowing the major insects, mites and diseases prone to the crop and how to recognize beneficials is essential.

Other considerations include establishing a supplier in advance, having someone available when shipments arrive and checking shipments for viability (remember they are living organisms).

If this will be the first time using biological control, it is recommended to try it in a small isolated greenhouse, in propagation houses, or in a greenhouse where edible crops such as herbs are being grown. This will allow you to obtain experience and then have the opportunity to expand into other production areas.

More Information: Starting A Biological Control Program for Greenhouse Insect and Mite Pests Links to suppliers

2009-2010 New England Greenhouse Floriculture Guide, A Management Guide for Insects, Diseases, Weeds and Growth Regulators - $25 (Includes shipping and Handling)

Excellent  source of information on using biological control written by Raymond Cloyd, Kansas State University. For Ordering Information and sample sections.

Tina Smith, University of Massachusetts

Mealybugs are typically a problem on long-term crops such as orchids, foliage plants that are often found in retail greenhouses, conservatories, and interiorscapes. Common species include the citrus mealybug (Planococcus citri), longtailed mealybug (Pseudococcus longispinus), and obscure mealybug (Pseudococcus viburni). Other mealybugs that have been introduced into the USA, which may be present in greenhouses, include the pink hibiscus mealybug (Maconellicoccus hirsutus), maderia mealybug (Phenacoccus madeirensi), and the Mexican mealybug (Phenacoccus gossypii).

Mealybugs usually enter a greenhouse on already infested plant material.  Now is a good time to inspect any tropical plants that you are thinking of overwintering in your greenhouses.         

Look on leaf undersides, petiole and leaf junctions, and near the base of plants. Mealybugs can also be found on the inside of container lips and in the drainage holes of containers.  On standard plants, they may hide under the tape on the garden stakes. Mealybugs can live for 2 to 3 weeks without hosts.  Power washing the greenhouse between crops is helpful to remove mealybugs hiding in cracks and crevices. Young, immature mealybugs prefer to move to tip growth to feed, so inspect stock plants before taking cuttings. Susceptible plants, should be monitored closely and include coleus, rosemary, sage, Swedish ivy, artemesia, Ipomoea, and gardenia.

Chemical control is difficult because the mealybug's waxy covering reduces its contact with spray materials. Crawlers, with the least wax, are most susceptible to chemical treatments. The systemic insecticide, Safari, is very water soluble and effective against mealybugs  as a drench treatment. Recent research has also shown that Celero, Aria & Talus or Talus also work well.  Repeated applications may be needed as eggs hatch throughout the growing season.

Stanton Gill, University of Maryland reports that growers of edible herb crops may apply insecticidal soap (containing fatty acid and alcohol) to dissolve some of the waxy coating, then follow-up with an application of horticultural oil a day later.

Biological Control of Mealybug

To choose the best natural enemy, it is important to have the mealybug identified to species. For example, the commercially available parasitoid, Leptomastix dactylopii only attacks the citrus mealybug.  In general, predators are less efficacious against mealybugs than parasitoids.

The mealybug destroyer, (Cryptolaemus montrouzieri) feeds on citrus and longtailed mealybugs as adults and larvae. .The wax-covered larvae resemble mealybugs, except they are twice as large and feed on mealybug eggs, crawlers, and honeydew. Adults and young larvae prefer to feed on mealybug eggs, however older larvae will attack any stage. The mealybug destroyer is also most effective during spring through fall; less so during winter.

For more information see: Managing Mealybugs in the Greenhouse, University of Connecticut

Mealybugs Web Page by Lance Osborne http://mrec.ifas.ufl.edu/LSO/Mealybugs.htm

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