Field pennycress is a winter annual weed that has generated interest as a potential oilseed crop. Reports of issues with pennycress have increased in recent weeks in various crops, including forages and wheat. This plant emerges in the fall, interferes with establishment and early growth of wheat, and sets seed early in the spring. The difficultly with managing fall emerging plants is that yield potential and control efficacy are typically already reduced by the time plants bolt and are more noticeable in the spring.
The best strategy for control of winter annuals such as field pennycress is to plan for treatment during the seedling stage in fall when plants are small. An application of glyphosate prior to wheat emergence can be beneficial for reducing populations of field pennycress and other winter annuals like chickweed and purple deadnettle, two other species for which populations become very apparent this time of year. If pennycress populations are dense in the spring and justify an herbicide treatment, applications of 2,4-D after full tiller can be made in wheat and other labeled small grains. Be sure to check labels for specific growth stage cutoffs, which can vary depending on the product. Dicamba is less effective than 2,4-D for field pennycress control in wheat. Other options include Huskie, Harmony Extra, or tribenuron products (Express, Victory), and may be beneficial for situations where chickweed, deadnettle and other winter annuals less sensitive to 2,4-D are present. Herbicide options become limited as wheat matures in the spring, and there is a narrow window for effective applications. Infestation level of a given weed and wheat growth stage are critical factors to consider when planning herbicide applications. See Table 19 of the Weed Control Guide for other herbicide options in small grains.
In forage situations and pastures where grazing takes place, it is important to confirm correct identification and monitor the presence of field pennycress. Though livestock tend to avoid the plant, consumption of large amounts can cause off-tasting meat and milk, and risk toxicity to the animals. Butyrac 200 is an option for control of small field pennycress plants in seedling or established alfalfa, and is more effective when applied in late fall than spring. See Table 20 and Table 21 of the Weed Control Guide for other options in alfalfa and grass pastures, respectively.