Nothing adds insult to injury like spider mites when you ‘re waiting for a drought to end. Mites are naturally controlled by fungi and flourish when conditions aren’t favorable for fungal growth.
For the past several weeks southeastern Virginia has been locked in one of the worst heat/drought situations on record. In Suffolk, triple digit heat and heat indexes in the 110 range broke a number of long-standing records.
The corn crop, in particular, has been decimated in some areas of Virginia and northeast North Carolina. Losing a crop to drought is something that cannot be prevented without irrigation. Losing a drought-weakened crop to spider mites is something that can be prevented.
Spider mites defy attempts to define thresholds, particularly in cotton. Many cotton fields harbor mites all summer long with no apparent yield loss. Other fields have population explosions soon after an insecticide spray kills too many beneficial insects. Even then growers are often slow to treat because it’s hard to define just how bad the infestation is.
Ames Herbert, Virginia Tech entomologist and Virginia IPM coordinator, advises that when spider mites shed leaves, or stunt plants, it’s time to take them out.
Controlling spider mites in cotton or peanuts depends on catching infestations early. Knowing where they are most likely to strike is helpful.
Mites are often spread by mowing operations, so field edges near highways should be checked thoroughly. Weeds around utility poles are also frequent hotspots. Fields treated more than once for thrips are extremely vulnerable to mites and should be scouted at least weekly during dry weather.
Identifying and controlling mites should be done before leaves shed or change color from intense feeding in peanuts and cotton. In peanuts this is rapidly followed by bright yellow spots in the field, and in cotton leaves turn orange or red.
Since many peanut farmers are also cotton farmers it’s important to remember that mites often move from cotton to peanuts. Spider mites are easier to control in cotton. There are more chemicals labeled for spider mite control in cotton and cotton is more tolerant to mites. Sometimes it’s best to pick your battles and kill them in the cotton before they find your peanuts!