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Greenhouse Updates: Nov 21, 2016

A few take -home Biocontrol tips from the Northeast Greenhouse Conference and Expo
Nov 21, 2016

Here are a few take-home tips from the “Advanced Biocontrol Panel” with Suzanne Wainwright-Evans, Buglady Consulting; Ron Valentin, Bioline Agroscience and Jeff Marstaller, Cozy Acres Greenhouses.

Sachets are very popular for distributing the predatory mites Amblyseius cucumeris or A. swirskii for managing thrips.  These mini-rearing systems or sachets are a complex eco-system that contain either A. cucumeris or A. swirskii; with “food mites” that the cucumeris/swirskii prey upon while in the sachet; plus yeasts and fungi on the bran for the food mites.  Low humidity (around 40-50% RH) will kill the yeasts/molds and starve the food mites. When this happens, the mites in the sachets stop reproducing.

Storing Predatory Mite Sachets.  It is best to distribute the sachets containing predatory mites the same day as you receive them. However, if predatory mites need to be stored, then store your mite shipments in the greenhouse where the relative humidity is higher than in your office. Place the boxes under a bench (in a shaded area) to protect them from sun.  Also, open the box to prevent the buildup of carbon dioxide. The predatory mites in the sachets are more adversely affected by low relative humidity than temperature. Do not store in an office or in a refrigerator or in an area below 60% RH.

Do not tear or enlarge the tiny hole in predatory mite sachets.  The tiny hole has been specially designed to be just large enough for predatory mites to emerge, while maintaining the proper humidity inside the sachet.

Proper placement of sachets on plants is important.  It is best to place the mite sachets within the plant canopy, where they will be shaded from the sun and relative humidity is the highest.  More mites will emerge and they will last longer (6 weeks compared to 1 to 2 weeks) when sachets are protected from sunlight than when they are exposed to direct sunlight.  Both beneficial and prey mites need high humidity levels for their eggs to hatch.

Phytoseiulus persimilis is a predatory mite used specifically for managing two-spotted spider mites that will starve to death without two spotted spider mites to feed upon.  P. persimilis cannot feed on alterative food sources so is not available in sachets.  It is only available in tubes containing loose vermiculite.  Tubes or vials can vary in size depending upon the amount of carrier used.  

Hot spot vials (30 ml or 1 oz.) with a funnel applicator cap on the tip of the vial are designed for dosing specific areas of the crop and may be especially useful in hanging basket crops. The mites congregate near the opening and can be distributed by touching the foliage with the applicator tip. The smaller size of the vial helps reduce your shipping costs, too.

Biopesticide dips as a first line approach against incoming pests on plant material.
There was significant discussion about using dips on incoming cutting or plug trays.  Bundles of cuttings or plug trays are briefly submerged in a solution of biopesticides such as Botanigard (Beauveria bassiania) (WP formulation only, not ES) plus Steinernema feltiae (beneficial nematodes) and Root Shield or Rootshield plus WP (Trichoderma spp.) and thoroughly wetted according to label directions. Plant material is then stuck or planted. The panel recommended mixing and using very small batches of this dip rather than large quantities to prevent disease spread during the dipping process.

Unbiased, detailed information on using biological control is available in the 2017-2018 New England Greenhouse Floriculture Guide. The Guide is updated every two years by floriculture faculty and staff from the six New England State Universities, and is published by New England Floriculture, Inc. The 2017-18 edition of the Guide is available for $40 per copy via the Northeast Greenhouse Conference website (, and from the Extension publication offices of the Universities of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont.

Tina Smith, UMass Extension and Leanne Pundt UConn Extension


Buitenhus R., M. Brownbridge, A. Brommit, T. Saito and G. Murphy. 2016. How to Start with a Clean Crop: Biopesticide Dips Reduce Populations of Bemisia tabaci (Hemiptera: Aleyrodidae) on Greenhouse Poinsettia Propagative Cuttings. Insects 7(4).

Jandricic S. 4 Ways Your Accidentally Killing Your Predatory Mites. ONfloriculture.

Valentin R. Biological Control Starting in Propagation. Bioline North America.

Clean Up Incoming Plant Material By Utilizing Dips, BioWorks Fact Sheet.