Originally published July 16, 2013
Recently, I have been receiving quite a few phone calls regarding corn earworms (CEW) moving into soybeans. Many of these populations were below the action threshold of 8 larvae (>1/2 in) per 25 sweeps and sporadically located across the northern half of the state.
Corn earworms are typically more attracted to soybeans from R2-R5 because adults are attracted to flowering beans to oviposit their eggs. Fields further along in maturity are less desirable for colonization by ear worms; however, fields should be scouted routinely so populations are not missed. Pheromone trap catches confirmed a relatively small flight, less than 50 adults, in traps at the Northeast and Macon Ridge Research Stations in the past week. Although this is not a large outbreak of corn earworms, larvae will consume flowers and small pods if populations are not kept in check. Fields that have had a previous application of a pyrethroid for stink bugs or three-cornered alfalfa hoppers will typically have greater numbers of earworms because of the elimination of natural enemies.
Pyrethroid susceptibility monitoring has indicated high levels of resistance, and pyrethroid applications may not provide effective control of these pests. However, new diamide chemistries – including Besiege, Prevathon and Belt – have demonstrated satisfactory control of these and other worm pests in soybeans.
Belt (AI: Flubendiamide) and Prevathon (AI: Chlorantraniliprole) only provide control of lepidopteran pests; Besiege (AI: Chlorantraniliprole + Lambda-cyhalothrin ) will control a broader spectrum of pests because of the inclusion of lambda-cyhalothrin. A tank mix of a pyrethroid and 0.5lbs of acephate may provide effective control on low numbers of CEW. Beware, only 1.5 lbs of acephate can be applied per acre per season in soybeans, and producers may want to save acephate for stink bug applications.
For more information or if you have any questions or concerns, please contact:
Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)
Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)
Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)
Dr. Jeff Davis at 225-747-0351 (cell) or 225-578-5618 (office)
The LSU AgCenter and the LSU College of Agriculture