It is not unusual to discover outbreaks of pests such as spider mites, thrips, whiteflies and aphids in greenhouses full of flowering bedding plants scheduled to be sold within a week or two. If you discover an insect or mite problem within a couple of weeks of sale, we suggest using a safe, effective contact spray that will knock down the infestation to provide good protection for a couple weeks. If infestations are localized, spot treating may be best. Once plants are planted outdoors in a garden, aphids, mites, whiteflies and thrips are not usually a problem. Some good examples for out-the-door treatments are:
- For thrips, aphids, whiteflies: abamectin (Avid), pyridaben (Sanmite), and bifenthrin (Talstar).
Note that previously used products such as imidacloprid (Marathon II), dinotefuran (Safari), thiamethoxam (Flagship) and acetamiprid (Tristar) are neonicotinoids and should not be used on plants going out the door and especially bee-friendly plants. These include many perennial and native plants and also annual bedding plants. Many retailers now market plants as “Bee Friendly”. These plants should never be treated with neonicotinoids.
- For aphids and whiteflies: pymetrozine (Endeavor).
- For mites: abamectin (Avid), bifenazate (Floramite), hexythiazox (Hexygon), pyridaben (Sanmite).
- For Botrytis on petunia blooms: fludioxinil (Medallion), cyprodinil & fludioxinil (Palladium), Polyoxin D zinc salt (Affirm, Veranda O), fenhexamid (Decree), and biofungicides Bacillus subtilis QST713 (Cease), Streptomyces lydicus (Actinovate SP).
You will want to use the safest products available with everything in bloom and follow label directions. None of the products listed above are known to cause a phytotoxicity problem when used at the rate on the label. Usually wettable powder and flowable formulations are the least likely to be phytotoxic. However, wettable powders may cause visible residue. Make sure wettable powders are completely dissolved in the spray tank and the tank is agitated. This will prevent slurry from forming at the bottom of the spray tank, which could be phytotoxic if sprayed on plants. The re-entry time-period following application of the products listed above is 4-12 hours except for Actinovate SP, 1 hour REI. Note that Endeavor works by interfering with the insects ability to feed and may take 5 - 10 days or longer to see results.
Tina Smith, University of Massachusetts and Leanne Pundt, University of Connecticut