Given the late growing season, many soybeans have not yet been treated with planned postemergence herbicides. Soil-applied herbicides are beginning to fail and weeds are emerging in these fields.

If weed escapes are the major concern, we suggest mechanical strategies be used rather than a postemergence herbicide. If you had planned to apply a postemergence herbicide, carefully consider the stage of soybean development, condition of the crop, and level of weed infestation. Again, mechanical control strategies may be your best option.

The relative risk of herbicide injury to the soybean plant also is affected by the choice of adjuvant. This risk, from greatest potential for injury to least, is COC > MSO > NIS > UAN > AMS. It is important to remember that the adjuvant alone does not typically cause injury, but affects the efficacy of the herbicide. Refer to the herbicide label to determine which adjuvants are labeled and if there is concern for injury, select the adjuvant with the least potential to enhance herbicide injury. Information concerning adjuvant selection is included in the table that accompanies this article.

Another consideration is the legal delay between herbicide application and harvest. Although planting was significantly late this year, harvest could occur around the first or second week in October in "normal" conditions. This is approximately 70 days. However, if an early frost occurs, this number could change considerably. The maximum stage of soybean development allowed for postemergence application is listed in the table below.

Notes: 1) N refers to both AMS and liquid nitrogen solutions. Refer to the label to determine which is recommended. 2) DBH = days before harvest. 3) Do not apply after pod set.