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Weeds
Volume 57 Number 10 Date 06/14/2012 GIANT RAGWEED - Soybeans are particularly susceptible to giant ragweed competition and require a prolonged ragweed-free period to avoid yield reductions. In Dane and Grant counties, many ragweed plants now average two feet tall and are almost certainly reducing yields. Early-planted soybean fields subjected to ragweed pressure during the last 3-4 weeks could incur losses of 25% or more. Herbicide treatments should be applied before ragweed plants are 6-10 inches tall to avoid losses. VOLUNTEER CORN - Planting continuous corn or rotating soybeans and corn with the same herbicide traits allows volunteer corn plants to persist in fields, unless cultivation is incorporated into the management scheme. Management strategies should account for volunteer corn control since this weed can substantially reduce crop yield and quality, and its widespread occurrence is thought to contribute to development of Bt resistance among corn rootworm populations. Post-emergence grass herbicides are an option for control of volunteer corn in soybeans. --Clarissa Hammond, DATCP Weed Scientist 
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