Biological Control - Propagation Greenhouses
Friday, 04 December 2009 15:03
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:
2011-2012 New England Greenhouse Floriculture Guide (ordering info)
UMass Fact Sheet: Biological Control in Greenhouses: Preparing for Spring Crops
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
Updated 11/10
