Two Spotted Spider Mites in Soybeans

Growers should be inspecting the edges of the soybean fields now.  Here is what you are looking for:
Plant Symptoms; stippling on the leaves

Mite Presence

Observe under the leaves. you will note very small spider like insects in small colonies with some webbing. There are two variations of the two spotted spider mites. Only a trained entomologist can tell the difference. One variant is susceptible to insecticides and the other is resistant. This may have changed since Dr. Ron Ochloa USDA first identified the differences in 2008.

Thresholds for treatment:

Insecticide Treatment Options:

1. Edge treatment does not always work since many times the mites are already within the field.
2. The use of pyrethroids other than Bifenthrin prior to a drought and this application can spike the two spotted spider mites. Check fields within 14 days of treatment to see if mite populations have exploded.
3. Mites are on the underside of leaf be sure to apply in excess water more than 20 gallons per acre to ensure coverage.
4. None of the insecticides control eggs so repeat applications may be necessary. In 2009 near Hershey three applications were made with little success due to egg hatch as well as low carrier rates.
5. If rains return this does not translate into mite control. They build in droughts due to the absence of a disease and it takes time for hte disease to build after rains to assist in managing the populations.  Heavy rains may wash some off but rarely lead to control of the pest.