Floriculture Greenhouse Update

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

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

Growers have expressed interest in growing herbs organically. The US Department of Agriculture has developed a set of standards that food and plants labeled "organic" must meet. To become organically certified, a government approved certifer inspects the farm to make sure the farmer is following all the rules necessary to meet USDA organic standards. The USDA National Organic Program web site provides a listing of certifying agencies.

Here are a few general guidelines to consider:

• Use organic seed or if organic seed is not available, untreated seed.

• Use approved materials  - i.e. potting soil, fertilizer and pest and disease control substances.

Herbs are light feeders compared to traditional bedding plants. Lower rates of 100- 150 ppm constant liquid feed are preferred. In addition, routine clear watering is helpful to leach excess salts from the media, especially as herbs prefer to be kept on the dry side. Over fertilizing herbs results in lush growth that is more prone to foliar diseases such as Botrytis blight and web blight, and makes the plants more attractive to sucking insects. Excess levels can result in root tip damage.

If using organic fertilizers, no more than 50% of the nitrogen should be in the ammonium form. As with any fertilizer, your choice should be based upon the pH and alkalinity of the greenhouse irrigation water as well as the pH and nutrient supplying ability of the potting soil.

The Organic Materials Review Institute (www.ormi.org) is a non-profit organization that specializes in the review of pesticides and fertilizers for use in organic production. See their web site for a listing of approved insecticides and fungicides. (Some products may be regulated and subject to restrictions.)

For a listing of selected insecticides and fungicides labeled for use on herb bedding plants, (updated in 12/06), go to the UConn IPM Web site and see the tables listed for the Publication, Pest Management for Herb Bedding Plants Grown in the Greenhouse.

If you are also growing crops conventionally,

• Keep production areas separate and plan on keeping good records to document this separation.

•  Plants must not be contaminated or commingled with non-organic plants or prohibited substances.

Additional sites for information on organics, include: Northeast Organic Farming Association Sustainable Agriculture Research and Education Northeast Organic Network

There are also a number of fact sheets and publications on growing herbs organically from the National Sustainable Agriculture Information Service.

Leanne Pundt University of Connecticut