Weed Management

Agronomy News-August 2022, Volume 13, Issue 4. Topics in this issue are Small Grain Variety Trials, Palmer Amaranth Control in Organic Systems, Possible Changes to Atrazine Use, Japanese Stiltgrass Identification and Control, Sampling for Nematodes in Soybeans, Sprayer and Pesticide Twilight Meeting, Broiler Grower Settlements, New Rules for Processing Food Wastes and Residuals, Webinar: Solar On The Farm, Pasture and Grazing Workshops, Grain Market Report, Weather Outlook, and Regional Crop Reports.

Now is the time to scout pasture and hay fields for Japanese stiltgrass and take note of its locations. This invasive grass is typically seen in wooded areas, but unfortunately has been creeping into fields. Once the seed heads start to form in another month or two, you’ll want to have the mower ready.

Starting clean, or weed-free, is a critical component of any weed management program. In 2022, growers experienced either a lack of or higher cost of glyphosate-based herbicides that are typically used to control weeds prior to planting soybean. In a study sponsored by the Maryland Soybean board and conducted at the University of Maryland’s Central Maryland and Wye Research and Education Centers, different glyphosate-based and non-glyphosate based herbicide treatments were evaluated for their ability to provide effective preplant weed control (Table 1). These treatments included both single and sequential herbicide applications.

A common question asked by farmers dealing with herbicide resistant Palmer amaranth is, “What are the most effective burndown options in situations where Palmer amaranth is larger then the ideal 3-4 inch control range?”

Italian ryegrass is a winter annual weed that often needs to be managed prior to soybean planting. In Maryland, populations of Italian ryegrass have been confirmed to be resistant to group 1 (Axial, Select) and group 2 (Harmony, PowerFlex) herbicides, but recent populations have appeared to develop resistance to glyphosate (Figure 1). With limited herbicide options, preplant control of Italian ryegrass will be challenging for growers.

It’s that time of year when growers are considering which herbicides to include in their burndown programs. Utilizing effective herbicides will help to ensure less weed competition at planting. However, growers should consider not only what herbicides they plan to use in their burndown programs, but also the weed species present in the field.

This is a poster that provides the relative effectiveness of various integrated weed management tactics for summer annual crops. The chart helps identify the most effective tactics to manage weeds.

Canada Thistle is also known as creeping thistle, as well as green or perennial thistle, depending on the source. Others express their opinion about it by calling it hard thistle and cursed thistle. Canada thistle is an aggressive and colonial perennial, with both male and female plants. It is considered a noxious weed in Maryland and many other areas across the U.S.

New Ecological Mitigation Menus to Reduce Pesticide Runoff

Over the past few years there have been quite few cases in Maryland of injury to grapevines from herbicides that were sprayed to control weeds before planting crops on adjacent or nearby fields. Damage has ranged from some minimal leaf distortion through severe damage, crop loss, and vine death.