By Hayden Schug
As we move into July and August, insect pressure tends to ramp up across Maryland row crops, particularly in soybeans and corn. These months are critical for monitoring pest activity and making timely, threshold-based decisions. Several pests are commonly active during this period, including corn earworm, stink bugs, Japanese beetles, other defoliators, and spider mites.
Corn earworm moths typically migrate into Maryland in larger numbers in mid to late July, although some can overwinter here, and early flights have already been reported moving up the coast. In soybeans, larvae can cause significant injury during the R1 to R5 growth stages by feeding on pods and developing seeds. When I ran the numbers, the threshold was approximately 2.5 larvae per 15 sweeps, but thresholds can vary depending on market value and treatment cost. You can use the NCSU dynamic threshold calculator to run your own field-specific estimates: https://go.umd.edu/CEW. It’s important to sample evenly across the field, as female moths may lay eggs in clusters, leading to localized infestations. Many corn earworm populations show resistance to pyrethroids, so growers should consider using alternative insecticide chemistries when treatment is needed.
Source : umd.edu