Outlook for Stewart’s disease for 2007

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.

Warmer temperatures and longer periods of daylight always give insects a big boost in April and May. Consequently, it is not unusual to discover yellow sticky cards covered with thrips or whiteflies, or outbreaks of spider mites and aphids in greenhouses full of flats scheduled to be shipped in the next week. If you discover an insect problem now, I suggest using a safe, effective contact spray that will knock down the infestation enough to provide good protection for two weeks. This will get your bedding plants through the shipping and retail phase. Once they have been planted outdoors, the aphids, mites, whiteflies and thrips will disappear naturally. Some good choices for out-the-door treatments are:

  • Thrips, aphids, whiteflies: Avid, Marathon II, Orthene 97, Safari, Sanmite, Tristar, Flagship, and Talstar.
  • Mites: Avid, Floramite, Hexygon, Sanmite.

With everything in bloom, you want to use the safest products available. 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. With wettable powders, make sure the pesticide is completely dissolved in the spray tank and the tank is agitated. This will prevent sludge 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 12 hours with the exceptions of Floramite (4 hours), Orthene (24 hours) and Tristar (24 hours).

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