Greenhouse Insect Management for 2011

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Starting clean

Do not carry-over insects from one crop to another. Keep thrips numbers down to less than 10 per card per week in the fall and winter on poinsettias and Dracaena. Avoid keeping houseplants or allowing weeds to grow in the greenhouse. When each batch of media arrives for a new crop, check it for fungus gnats by filling a 1 gallon zip-lock bag half-full with moist soil. If fungus gnat adults emerge within 3 weeks, consider applying a fungus gnat soil-drench 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.


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.

Systemic insecticides

Use Marathon, Tristar, Flagship, Safari, or Aria in poinsettia pots, lily pots, or in hanging baskets prone to problems with whiteflies, aphids, mealybugs or soft scales. Note: Aria does not work on silverleaf whitefly. Tristar and Safari also control thrips.

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:

  • Thrips - Aria(spray or drench), Avid, Mesurol, NemaShield, Orthene 97, Overture, Pedestal, Pylon, Safari(spray or soil drench), Sanmite, Tristar, and Conserve. Note: thrips may be resistant to Conserve.
  • Aphids - Aria, Azatin, Benefit, BotaniGard, Decathlon, Discus, Distance, Endeavor, Enstar II, Flagship, Kontos, Marathon, Ornazin, Orthene 97, Precision, Safari, Tame, Talstar, Tristar.
  • Whiteflies - Aria, Azatin, Benefit, BotaniGard, , Decathlon, Distance, Endeavor, Enstar, Flagship, Kontos, Marathon, Ornazin, Orthene 97, Pedestal(do not use on poinsettias), Precision, Safari, Sanmite, Talus, Judo, Tame, Tristar (Note: many populations of silverleaf whitefly are resistant to Marathon. Other nicotinoids, like Aria, Flagship, Tristar, and Safari may still be effective).
  • Mites - Akari, Avid, Floramite, Hexygon, Judo, Kontos, Ovation, ProMite, Pylon, Sanmite, Shuttle-O, Suffoil-X (> 1% may be phytotoxic), Tetrasan, Kanemite.
  • Broad mites - Avid, Akari, Judo, Pylon, SanMite.
  • Fungus gnats - Azatin XL, Adept (not on poinsettias), Benefit, Distance, Marathon and perhaps other nicotinoids (drenches), Mesurol, NemaShield.
  • Mealybugs - Aria, Flagship, Orthene 97, Safari, Talus and Tristar.

Dr. Smitley's work is funded in part by MSU's AgBioResearch.

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