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Greenhouse Pest Management with Insecticides

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February 10, 2022 - Author:

Starting clean:  Do not carry-over insects from one crop to another.  Keep thrips numbers down to less than 10/card/week in the fall and winter on poinsettias and cordyline (Dracaena). Avoid keeping houseplants or allowing weeds to grow in the greenhouse.  When each batch of growing media arrives for a new crop, check it for fungus gnats by filling a 1 gal Zip-lock bag 1/2-full with moist soil.   If fungus gnat adults emerge within 3 weeks, consider applying a fungus gnat treatment at planting time. Check incoming plant material carefully. If insects are found treat them with an appropriate product listed below to start as clean as possible.

Scouting: Monitor thrips and whiteflies with yellow sticky cards.  Change cards once per week.  Use at least one card per house or one per 2,000 ft2. Check the first plants to flower for thrips. For spider mites and aphids, check susceptible plants like marigold (mites) and pepper (aphids), weekly. Potato wedges can be stuck in soil and checked 24 hours later for fungus gnat larvae. Frequent scouting is critical for early detection and control of greenhouse pests, and for evaluating efficacy of products being used.

Systemic insecticides: Kontos, Mainspring, Imidacloprid, Flagship, and Safari can all be applied to the soil surface as a drench for uptake by plant roots and systemic movement throughout the plant. Gaucho can be used as a soil systemic on cucumbers, tomatoes, eggplant, and peppers. All neonicotinoid insecticides are soil systemics, with the exception of Tristar, and are listed below in italics. The only soil systemic insecticides available at this time that are NOT neonicotinoids are Kontos and Mainspring. Kontos1 is labeled for spider mites, aphids, mealybugs, and whitefly. Mainspring is labeled for thrips, aphids, whiteflies and mealybugs.

Which products are neonicotinoids? In this bulletin all neonicotinoid active ingredients and product names appear in italics.  Technically, according The IRAC classification system based on mode of action, neonicotinoids are all insecticides in category 4A. This includes acetamaprid (Tristar), dinotefuran (Safari, Dinotefuran, Sagacity), thiomethoxam (Flagship) and imidacloprid (Marathon, Benefit, Discus, Imigold, Bounty).  Flonicamid (Aria) has a related chemical structure but a different mode of action (category 9C). However, I have seen some news articles that incorrectly include flonicamid with the neonicotinoids. Neonicotinoid products are listed in italics.

Pyrethroid insecticide products: Pyrethroids have been excluded from this list because of documented resistance problems in the greenhouse populations of mites, thrips, whiteflies and aphids. However, they may work for control of susceptible populations of many greenhouse pests. Some pyrethroid insecticide products available for greenhouse use are: Astro, Attain, Bifenthhrin, Talstar, Decathlon, Decathlon, Tame, Scimitar, and Mavrick.

Preventing outbreaks: If yellow sticky cards or scouting indicates an increase in aphids, mites, thrips, fungus gnats or whiteflies, apply one of the following insecticide products once per week as a foliar spray, unless a soil drench application is mentioned:

Thrips: Aria, BotaniGard ES, Mainspring, Mesurol, Orthene 97, Overture, Pedestal, Pradia, Pylon, Safari, Sarisa and Tristar. Also, if Distance is applied as a soil drench it will reduce the number of thrips adults emerging from pupae in the soil.

Aphids: Acephate 97, Altus, Aria, azadarachtin + M-Pede1 (Aza-Direct, AzaGuard, Azatin), BotaniGard, Distance, Endeavor, Enstar II, Gaucho2, Kontos3, Mainspring, Ornazin, Pradia, Talstar (but resistance is possible), Tristar (residue not toxic to bees) and Ventigra4.

Neonicotinoids: Imidacloprid, Safari, or Flagship applied as a soil drench or as a spray. Tristar as a spray.

Whiteflies: Acephate 97, Altus, azadarachtin (Aza-Direct, AzaGuard, Azatin-O, Azatin XL, Molt-X), Beauveria bassiana spores (BotaniGard ES or 22WP, Mycotrol ES), Distance (not for Q biotype), Endeavor, Enstar (not for Q biotype), Gaucho2, Kontos3 (see phytotox footnote), Mainspring, Ornazin, Pedestal (do not use on poinsettias), Pradia, pyriproxyfen (Distance, Pyranica or Engulf), Sanmite, Sarisa, Savate, Talus (not for Q biotype), Velifer, Ventigra4 and Xxpire. Insecticidal soap5 (M-pede) and horticultural oils5 (SuffOil-X, Ultra- Pure Oil, SunSpray Ultra-Fine Oil, Triact70, Saf-T-Side) can be used if care is taken not to exceed label rates and not to spray open flowers, to avoid phytotoxicity.

Neonicotinoids:  Imidacloprid, Safari, or Flagship applied as a soil drench or as a spray.

Tristar as a spray.

Spider mites: Akari, Applause, Avid, Floramite, Hexygon, Kontos, Magus, Novato, Ovation, ProMite, Pylon, Sanmite, Savate, Shuttle-O, Sultan, Tetrasan, Ultiflora

Broad mites and cyclamen mites: Avid, Akari, Pylon, SanMite, 2 % horticultural oil (oils may be phytotoxic, test first).  Reduce humidity to below 80% if possible.

Fungus gnats: Azadarachtin (Aza-Direct, AzaGuard, Azatin O), Adept (not on poinsettias), Citation, or pyriproxyfen (Distance Pyranica or Engulf) as a soil drench. Allow growing media to dry between waterings, as soon as is possible.

Neonicotinoids: Imidacloprid, Safari or Flagship applied as a soil drench.

Mealybugs: Altus, Aria, Kontos, Orthene 97, Pradia, Sarisa, Talus and Ventigra4. Neonicotinoids: Imidacloprid, Safari, or Flagship applied as a soil drench or as a spray. Tristar applied as a spray.

Florida fern caterpillar: Because these caterpillars are usually resistant to pyrethroid insecticides try using Adept, Bt, Pedestal, Orthene, Pradia, Mesurol, Sarisa or Duraguard ME.

1AzaDirect at 24 oz and M-Pede at 128 oz per 100 gallons.

2Gaucho is labeled for use as soil systemic only on greenhouse-grown vegetables. Bemesia (silverleaf whitefly) resistance to imidacloprid is common.

3On the Kontos label: Not recommended for use on geraniums, orchids, hoya, Dracaena, Cordyline, Schefflera, neanthebella palm, and ferns. Do not make more than one application per season to Hydrangea, Impatens spp., crotons, Fuschia hybrids, Petunia, Peperomia, stock, or cyclamens.

4On the Ventigra label: Plants sensitive to Ventigra include coleus, poinsettia (in bract), impatiens and petunias (in flower).

5In phytotoxicity testing, insecticidal soap and horticultural oil products have been at the top of the list for being the most phytotoxic to greenhouse plants (assuming that plants listed on the label as being sensitive are not included in the test). Do not exceed labeled rates which are usually a 1% concentration of oil or a 2% concentration soap.

IR-4 Efficacy summaries:

For summaries of research evaluations of insecticides used on ornamentals for thrips management, go to the IR4 Ornamental Horticulture website:

  • Environmental Horticulture Research Summaries – IR-4 Project (ir4project.org)
  • Scroll down to ‘Efficacy’ then click on ‘Entomology’
  • Click on ‘Thrips’, on the right side

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Authors

David Smitley

David Smitley
smitley@msu.edu

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