Agronomic Crop Scouting Report

David Owens, Extension Entomologist, owensd@udel.edu

Soybean
Continue scouting for stink bugs and bean leaf beetles. If during the next several weeks you encounter more than 4 beetles per sweep, collect pods to determine how many are being fed upon. Depending on the number of beetles and extent of pod scarring, a pyrethroid treatment may be necessary. Corn earworm moth activity is light right now but be sure to scout double crop soybean. Soybean looper has been observed in Delaware in low numbers.

Sorghum
Scout sorghum that has already shed pollen for earworm and armyworm. This is best done by taking a bucket to the field and beating heads against the inner bucket wall. Count the number of worms per 50 heads. If you see sorghum webworm (small, fuzzy brown with white stripes), it is ‘worth a half’ of an earworm. Texas A&M has a useful earworm threshold calculator for sorghum: https://extensionentomology.tamu.edu/sorghum-headworm-calculator/.

In late maturing sorghum, begin scouting for sugarcane aphid (also now being called sorghum aphid). They will appear as light yellow and form dense colonies under leaves. Look for leaves that are shining with honeydew. Thresholds and recommendations for sugarcane aphid control can be found here: https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/InsectControlinSorghum-2020-updated.pdf.

Look at emerging heads for signs of heavy corn leaf aphid pressure as well. In years past I considered this species to be beneficial because natural enemies usually take it out but last year, I visited fields in which I suspect corn leaf aphids successfully colonized the head and lead to yield loss.

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