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Greenhouse Updates: Jan 22, 2015

Getting Started with Biocontrol for Spring Crops
January 22, 2015

It is important to plan ahead if you will be using biological controls for pest management on your spring crops. Growers that successfully use biological controls 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. When purchasing plant material or liners, request information on what specific pesticides were applied to the plants to ensure that no long lasting pesticide residues adversely impact the biological control agents you plan to release. For example, some pesticide residues may impact biological control agents for 3 to 4 months.

With the exception of banker plants, plan to order your beneficials  one week before beginning propagation or the expected arrival of plant material for production so they can be used right from the start. Growers often order Steinernema feltiae (beneficial nematodes), Atheta = Dalotia (Rove beetle), Hypoaspis miles = Stratiolaelaps scimitus (predatory mites), and Neoseiulus (Amblyseius) cucumeris (predatory mites) to be released in propagation areas and production houses as soon as crops arrive and/or seedlings started.

Aphid banker plants are usually ordered 4 or more weeks before greenhouses are opened up to have time to produce adult parasites on them. Most growers put aphid banker plants into greenhouses as soon as greenhouses are opened up and plants arrive. Banker plants are used to rear, release and sustain aphid parasites before aphids appear in the crop. Barley or wheat plants with bird cherry oat aphids (which attack only monocotyledons) are planted in hanging baskets. Banker plants plugs that contain bird cherry oat aphids are commercially available. Once the bird cherry oat aphids are established, Aphidius colemani  (parasite wasp) are sprinkled on the bird cherry oat aphids. Aphidius parasitizes and emerges from the bird cherry oat aphids. Once parasitized mummies are observed, the banker plants are then placed throughout the greenhouse where emerging Aphidius will parasitize green peach and melon aphids.

When starting your own seeds or cuttings, begin by using beneficial nematodes (Steinernema feltiae) as a preventative drench against fungus gnats, and thrips pupae in the growing media. As a general guideline, 2 applications spaced 2 weeks apart usually provide 6 weeks of protection. Steinernema feltiae does not control shore flies, however, the beneficial nematode Steinernema carpocapsae (Millenium) is being sold for shore fly larvae. Often, growers apply beneficial nematodes with Trichoderma (RootShield or RootShield Plus ) 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.

In addition to beneficial nematodes, the predator Atheta = Dalotia coriaria (rove beetle) is applied for fungus gnats and shoreflies, once during seeding or sticking cuttings. Atheta are nocturnal and are best applied in the evening. These strong fliers are easily established in greenhouses.  Rove beetles are packaged in a tube of peat-vermiculite mix with all three stages 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, Hypoaspis miles is also applied for fungus gnats during propagation. They are applied once during seeding or sticking. Hypoaspis are very mobile and will colonize the surface of the growing media. Hypoaspis miles = Stratiolaelaps scimitus are packaged 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 also release the predatory mite Neoseiulus (Amblyseius) cucumeris as a preventative for thrips larvae. This predatory mite is sold in bulk or in slow release sachets and also mini sachets.

In bulk, they arrive mixed with a bran carrier for broadcast release or for use in breeder piles. A small pile (about a teaspoon) 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 and sometimes eat spider mites and their eggs. The pile needs to be kept intact, so care needs to be taken when watering. Amblyseius should be reapplied when transplanting or repotting.

Slow release sachets consist of bran, whitish storage mites (that feed upon the bran), and N. cucumeris which prey upon the storage mites. Predatory mites should emerge from the sachets for 4 to 6 weeks unto the crop.  If using sachets in bench crops, the foliage should be touching, forming a bridge so that the mites can move from plant to plant.  These small predatory mites do not disperse well between isolated plants.

Sachets are also now available in smaller sizes as “mini-sachets” which are less expensive with fewer predatory mites so they can be placed onto individual hanging baskets. (Leaves would not be touching so the predators cannot move from hanging basket to hanging basket). Recent research has shown that these mini-sachets are best placed in the plant canopy where they are protected from bright sunlight.  If the mini-sachets are placed in bright sunlight, high temperatures and low relative humidity in the sachets adversely affects the reproduction and egg hatch of the predatory mites. (Eggs will shrivel and die at low relative humidity).  If mini sachets are placed within the plant canopy, the temperature peaks less, with higher relative humidity needed for the reproduction of these predatory mites

For information on rates, contact your supplier.

Leanne Pundt, UConn Extension and Tina Smith, UMass Extension

To help get you started, also see:

New England Greenhouse Floriculture Guide (ordering info)
Selecting a Supplier of Beneficial Insects and Mites, UConn Extension
Beneficial Nematodes: An Easy Way to Begin Using Biological Control in the Greenhouse, UConn Extension
Biological Control of Western Flower Thrips, UConn Extension
Biological Control of Fungus Gnats, UConn Extension
Biological Controls for Greenhouse Pests, UConn Extension

Grower Guide: Quality Assurance of Biocontrol Products: Vineland Research and Innovation Center (2014)

 

Biological Control in Greenhouses: Preparing for Spring Crops, UMass Extension
Using Beneficial Nematodes, UMass Extension

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