NDSU Crop/Pest: Soy aphids, spider mites

North Dakota State University’s  Crop&Pest Report came out Aug 12, after skipping a week.  Among this week’s topics:

  • Soy aphids, spider mites – While soybean aphids have remained largely below economic threshold of 250 aphids per plant in 80 percent of a field’s plants, there has been some isolated spraying in the state, says Janet Knodel, NDSU Extension entomologist. Winged and wingless aphids were “starting to increase” in Cass, Richland, Steel and Traill counties. Winged aphids move quickly between fields and farmers need to scout through the R6 or “full seed” stage. Also watch for spider mites, although rains/thunderstorms may have cut their numbers.

By the way, “no research” in the region shows that adjuvants will improve soy aphid control or increase residual levels.

The Optimal application includes: 1) apply when fields are at economic thresholds; 2) set spray nozzles for fine droplet sizes; 3) use 40 psi or more to penetrate canopies; use more than 18 gallons per acre to ensure coverage in dense canopies, and 5) calibrate tractor sprayers carefully.

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