Wednesday, April 29, 2009

Greenhouse - Thrips

In recent greenhouse visits, one pest that was found in many greenhouses was thrips. The following is a review of how to manage thrips using insecticides.

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.

Information from the New England Greenhouse Update:

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