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Soybeans
Volume 61 Number 9 Date 06/23/2016 SOYBEAN APHID - Colonies are appearing gradually in soybean fields this season and have been found thus far in Adams, Columbia, Dane, Green, Iowa, La Crosse, Monroe, Richland, Rock and Trempealeau counties. Only 11 of the 69 (16%) fields surveyed in the last two weeks have had detectable populations. Densities were below two aphids per plant and 10 per infested plant based on examination of 100 plants per field, with the week's highest total count of 35 aphids per 100 plants found in Adams County. SOYBEAN DEFOLIATORS - An assortment of minor defoliators can be found at very low levels in many soybean fields. Included in this category are bean leaf beetles, green fruitworm larvae, grasshopper nymphs and rose chafers, all of which were noted on fewer than 4% of plants examined in fields surveyed from June 16-22. Prebloom soybean fields with combined defoliation rates of 30% or more may qualify for treatment, though defoliation in the vegetative stages seldom results in yield loss, especially when soil moisture, temperatures and other growing conditions are favorable. The economic threshold is lowered to 20% defoliation once soybeans reach the bloom and post-bloom stages. -- Krista Hamilton, DATCP Entomologist 
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