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Soybeans
Volume 61 Number 18 Date 09/01/2016


SOYBEAN APHID - The annual survey conducted in late July and August found a statewide aphid average count of eight per plant. This average compares to 35 aphids per plant last year and is only marginally higher than the record-low count of seven aphids per plant documented in 2012. One hundred and seventy soybean fields in the R2-R5 growth stages were sampled during a three-week period from July 25-August 15. Aphid densities were below 151 per plant in all fields, and the majority of sites had counts of less than 25 aphids per plant. Results of the survey confirm that aphid populations remained low or moderate in most fields this season and widespread treatment for aphid control was not required.

NORTHERN CORN ROOTWORM - This rootworm species was abundant in Richland County soybean fields surveyed earlier this week, where 10-40% of plants showed minor defoliation. NCRW beetles occasionally appear in large numbers on soybeans at this time of year to feed on the leaves, and their presence does not mean that egg deposition is occurring. An Iowa State study from 2005-2007 confirmed that the NCRW is capable of laying very low numbers of eggs in soybeans, but the behavior is probably rare and does not pose a threat to rotated corn. Insecticide use is not recommended.

WHITE MOLD - Environmental conditions have been conducive for development of this disease this season, especially in central and northern Wisconsin. Management of white mold requires basic cultural controls such as harvesting infected fields last, and thoroughly cleaning harvesting equipment. Rotations of 2-3 years between soybean crops with corn or small grains can also reduce levels of the fungal pathogen in the soil.

-- Krista Hamilton, DATCP Entomologist