IPM Crop Survey - Insect Update (07/21/21)
Soybean aphid numbers continue to be low and aphids were observed in only 22% of the soybean fields scouted last week, mainly in MN. The percent of plants infested ranged from 3-39% with an average of only 1-4 aphids per plant among the positive observations. Growth stages of soybeans ranged from late vegetative to R4 (full pod). Continue to scout soybean fields at least weekly for soybean aphids and spider mites through R6 (full seed).
Grasshoppers are increasing and in mixed nymph-adult stages. The hot and dry weather will quickly push insect development into mainly adult grasshoppers, as well as increase grasshopper movements into greener crops as cereal crops mature and are harvested.
Adult grasshoppers cause more crop damage because adults feed more, are more mobile (adults have wings) and attack many crops where they defoliate leaves and chew on seed / pods. Adult grasshopper feeding activity usually peaks in August.
One of the reasons that we are seeing high densities of grasshopper populations, besides the favorable weather conditions in 2021, is that densities have been slowly building over the past years. The percentage of fields infested with grasshoppers increased from 28% in 2017 to 57% in 2020 and 65% in 2021. The total number of grasshoppers collected with sweep nets also was higher the last two years, 2020 and 2021 (Table 1). [Source: NDSU Extension IPM Crop Survey Program]
Continue to scout all crops frequently.
Banded sunflower moth trap update
Trap captures for banded sunflower moth and Arthuri sunflower moth increased this last week. The highest trap numbers for banded sunflower moth were in Cass and Golden Valley counties, both counties in the southern half of ND. Sunflower crop stages were in the late vegetative to R2 (bud <1 inch from leaf) stages.
See last week’s article on scouting and thresholds for banded sunflower moth eggs in NDSU Extension Crop & Pest Report 12, July 15.
IPM maps of insect pests and diseases are posted on the IPM website: https://www.ag.ndsu.edu/ndipm