Foliar Health Basics: Soybean White Mold Control
Soybean white mold (Sclerotinia stem rot) threatens soybean acres in the northern United States, from Nebraska to the Atlantic Coast. Spores can remain dormant in soil for 10 years.
Severe soybean white mold infection can reduce yield by more than 50 percent. Yield losses of 2 to 5 bushels per acre can occur for every 10 percent increment of infected plants at R7. Under ideal conditions, white mold infection can spread from 5 to 10 percent of soybean plants in an area one year to 50 percent the following season if not controlled.
Cool, wet, humid conditions during spring flowering favor soybean white mold growth. Planting practices that promote fast canopy development, such as early seeding, narrow rows, high seeding rates and high soil fertility, also increase infection risk. Moist conditions beneath the plant canopy due to poor drainage and airflow promote mold growth.
Begin scouting for soybean white mold at canopy closure, examining soil near rows for apothecia – ¼- to ½-inch-high, tan, mushroom-like structures that grow from sclerotia and release millions of microscopic spores, which are carried by wind to surrounding plants. Soybean plants are most vulnerable to infection at bloom.
Signs of Infection
Soybean white mold signs include rapid stem and leaf wilt; grey or white lesions at stem nodes; leaf flagging; fluffy, white growth; and patches of dead plants.
Soybean white mold infection starts weeks before physical signs appear. An initial preventive application of DuPont™ Aproach® fungicide made at 100 percent bloom, followed with a second application 7 to 10 days later, if needed, helps preserve yield potential. For best results, make sure the fungicide solution penetrates deep into the crop canopy to adequately cover flowers and areas where the mold spores could lodge. To prevent disease spread, harvest infected fields last and thoroughly clean equipment before leaving those fields.
DuPont™ Aproach® fungicide is not registered in all states. See your DuPont retailer or representative for availability in your state.
Endura® (BASF); Proline®, Stratego® (Bayer); Topsin® (Nippon).
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