Managing spider mites in nurseries
While predator mites usually control spider mites in the landscape, a miticide may be needed in nurseries where insecticides have previously been used.
In the landscape, predator mites and other predators provide excellent natural control of spider mites. But in nursery fields where insecticides are often used, the predator mites are more harmed by pesticides than are the spider mites. This may lead to outbreaks that require a miticide to get the spider mites under control. Most miticides are also more toxic to predator mites than spider mites, thus creating the “pesticide tread-mill.”
Unfortunately, once an outbreak of spider mites is observed, it may take six months to a year before pesticide residues decrease to the point where predator mites can survive. If your goal is to re-establish natural control, then use a selective miticide like Hexygon (hexythiazox) to maintain control of spider mites. Also, no insecticides can be used when trying to re-establish natural control.
Fortunately, we have quite a few miticides available to nursery growers to control spider mites. Below is a list of miticides, the active ingredient, and a N or L to indicate a label for Nursery or Landscape use. The only highly selective miticide in the list below is Hexygon. A low concentration of horticultural oil (0.5 percent) can also be effective against spider mites without harming plants if applied once per week.
Miticides for nursery and landscape use.
|Miticide active ingredient||Product name||For Nursery or Landscape use|
|Horticultural oil||Many products||N/L|
For a complete list of products, see Cornell University’s Pest Management Guidelines/Trees and Shrubs.
Dr. Smitley's work is funded in part by MSU's AgBioResearch.