David Owens, Extension Entomologist, owensd@udel.edu
Sorghum
A report of sugarcane aphid activity came in from Kent County this week. This aphid has the potential to cause significant yield loss as late as the soft dough stage. Thresholds range anywhere from 40 to 140 per leaf, depending on soil moisture conditions. Thresholds are also quite a bit higher for tolerant sorghum varieties.
Earworm moths are also in pollinating sorghum heads. Begin checking heads for earworm next week. There is a sorghum headworm threshold calculator available on Texas A&M’s website: https://extensionentomology.tamu.edu/sorghum-headworm-calculator/.
Hemp
Be prepared to treat hemp in the next week or so for earworm. Our best labeled materials are viruses such as Gemstar or the Bt formulations that are labeled. In tests by Virginia Tech, Gemstar performed a bit better than Bt.
Soybean
Green cloverworm populations have increased a bit this week. Keep an eye on defoliation, and if defoliation reaches 20% and defoliators are present, a treatment is advisable. Small, below threshold populations of corn earworm are widely present in soybean, and in double crops in particular. We flushed several moths out of fields while sweeping earlier this week. Moths are attracted to the flowers as a food source. Earworm control with pyrethroids alone is not a guarantee. In small plot spray trials on Delmarva conducted by Virginia Tech and University of Delaware in various crops over the last two years, Hero and Baythroid have outperformed other pyrethroids. Premix options include Besiege and Elevest. Other options include Radiant, Blackhawk, Intrepid Edge, Steward, and Vantacor (also Prevathon). A few soybean looper are showing up in fields as well. Last year we were able to put a soybean looper trial out in a field treated with Lorsban for corn earworm. Diamide treated plots had reduced looper pressure while pyrethroid treated plots had more looper pressure than the untreated check. Steward and Hero performed well in the trial, although I will caution against pyrethroids for loopers; other researchers have used Hero in the past to flare loopers. If stink bugs are present, Lorsban and Elevest are probably the best worm/bug materials.