Source: Mississippi State University Extension Service

Weeds grow on every acre used for crop and timber production. Weeds also grow in those areas not used for crop and timber production. Weeds can be found just about everywhere and all times of the year.

Soybean is the largest acreage row crop grown in Mississippi. Weeds are a significant pest problem in most soybean fields. Producers typically rely on preplant, preemergence and postemergence herbicide applications, often combined with cultivation to manage weeds. There are numerous herbicides available to control weeds in soybean.

The 10 most common weeds in soybeans in Mississippi are johnsongrass, prickly sida, entireleaf morningglory, common cocklebur, pitted morningglory, spotted spurge, sicklepod, hemp sesbania, barnyardgrass, trumpetcreeper.

The 10 most troublesome weeds in soybean in Mississippi are sicklepod, eclipta, redvine, spotted spurge, johnsongrass, prickly sida, horsenettle, Pennsylvania smartweed, common bermudagrass, and trumpetcreeper.

One of the newest methods of weed management, in soybeans, involves transgenic cultivars that can tolerate nonselective herbicides, such as Roundup Ultra and Liberty. These cultivars are genetically modified to tolerate herbicides that will kill conventional soybean cultivars. The traditional approach to herbicide development was to synthesize a new herbicide, then simultaneously evaluate soybean tolerance and activity on several key weeds. Genetic engineering allows the company to develop crop tolerance to a herbicide that has already been examined by EPA and determined safe to use, and that provides good control of many weeds in soybean.