David Owens, Extension Entomologist, owensd@udel.edu
Sorghum
Any sorghum that was shedding pollen in the last 7-10 days or is currently shedding pollen should be scouted for corn earworm. Beat 50 heads into a bucket and count the number of small, medium, and large worms. Compare your findings to the Texas A&M headworm threshold calculator: https://extensionentomology.tamu.edu/sorghum-headworm-calculator/. A good rule of thumb is 1 earworm per head on average can result in about a 5% yield reduction. Also as mentioned last week, FMC now has a 2ee recommendation for using Vantacor at its low rate of 0.9 fl oz/a.
Soybean
Widely scattered reports of near threshold to over threshold corn earworm have been received from southern Kent County, DE and throughout Sussex County in double crop soybean at R2-R3. Full season bean fields are generally at considerably lower risk for a sizeable podworm infestation. Corn earworms like open canopies. The moths look for flowers to fuel up on and lay eggs. We still have a bit of time for moths to continue laying eggs, and thus products with long residual would be best. I use a ballpark of 3 earworms per 15 sweeps field average as a threshold. We have been in many fields where we are near that in some samples but then take many samples with 0-2 in 15 sweeps which puts the field squarely in the ‘watch and resample early next week’ category. Last week I wrote an update to an article on CEW treatment considerations originally written in 2023. Take a moment to read it: https://sites.udel.edu/weeklycropupdate/?p=25130. When sweeping double crop fields, the sweep net should pass through a full half pendulum arc. For 15” beans, the net should pass through 3 rows.
Soybean looper are also widespread in fairly low numbers, although we ran into pockets of fields where the numbers were 1 per 2-3 sweeps. Field canopy was in excellent shape. If using a broad spectrum material like a pyrethroid or if you are clearing out some old chlorpyrifos, scout to ensure that this pest isn’t flared up. If a treatable number of loopers are present in a field (near 1 per sweep).