Greenhouse insect management

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 1/2-full with moist soil. If fungus gnat adults emerge within three 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 with as clean a crop 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: Avid, Mesurol, NemaShield, Orthene 97, Overture, Pedestal, Pylon, Safari, 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.

New products

Benefit. A new imidacloprid product formulated as a 60 WP from Scotts. Benefit can be used in the greenhouse, and on all indoor and outdoor ornamentals. Listed crop uses include trees, fruit trees, shrubs, evergreens, flowers, foliage plants, ground covers, interior plantscapes, and vegetable plants. Pests listed on the label include adelgids, aphids, armored scales (suppression) fungus gnat larvae, lacebugs, leaf beetles, leafhoppers, leafminers, mealybugs, psyllids, root mealybugs, root weevils, soft scale, thrips (suppression), white grubs, and whiteflies.

Overture. Overture is a 35 WP formulation of pyridalyl, a new insecticide active ingredient from a new class of insecticides. Overture can be used on greenhouse-grown ornamentals including flowering and foliage crops, ground covers, shrugs, and ornamental trees. The product label lists treatment rates for thrips and lepidoptera larvae (caterpillars).

Suffoil-X. A new horticultural spray oil from Bioworks. Bioworks lists soft-bodied insects and mites on the label. Traditionally, oil sprays have been effective on whiteflies and mites. The label gives a range of application rates from one to two percent, but testing of other horticultural oils resulted in some damage to flowers and sensitive leaves at a two percent concentration. Caution is suggested for any rate above one percent.

. NemaShield is a new biological control product consisting of live Steinernema feltiae nematodes. The nematodes should be checked for activity after a shipment is received by placing a small amount in a glass of water and observing after 30 minutes for movement. The NemaShield product label lists fungus gnats and thrips pupae as target pests. Nematodes work best when applied as a soil drench to moist soil that will remain moist for at least 24 hours.

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

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