Weed ID

Lately, I have seen several fields with Palmer amaranth flowers (Figure 1). It is imperative that these plants be managed before harvest (Palmer amaranth is listed as a noxious weed in Maryland and Delaware). At this point, mowing or herbicides will not improve yield nor prevent Palmer from germinating next year. Plants need to be physically removed from fields. Palmer amaranth has both male and female flowers on separate plants (Figure 2), and focus should be placed on removing the seed-producing females first. A single female can produce approximately 600,000 seeds per plant, and these seeds can remain viable for six years. Palmer seed matures within 2 weeks of flowering and if left unchecked, a single plant can infest an entire field within a few years (Figure 3). 

Japanese stiltgrass is an invasive grass that is typically seen in wooded areas. It likes shaded, wet areas and can easily take over the forest understory. Unfortunately, it can also creep into pastures and hay fields. The leaves of Japanese stiltgrass are wider and shorter than most of our common pasture grasses. There is also a distinctive silvery midvein that is slightly off-center from the middle of the leaf (Figure 1).

Agronomy News is a statewide newsletter for farmers, consultants, researchers, and educators interested in grain and row crop forage production systems. The topic for this edition is Double Crop Beans, Not So Fast, Herbicide Field Day, July IPM Insect Scouting Tips, Hemp Twilight Tour, Corn Disease Update, 4R Field Day, Poison Hemlock Identification and Management, Tar Spot: New Disease of Corn, Soybean Board Field Day, 2021-2022 Cover Crop Sign-Up, LEAD Maryland Fellowship Applications, Maryland Commodity Classic, MDA Pesticide Exams, MDA Pesticide Disposal Program, Weather Outlook, and Regional Crop Reports.

Marestail (Conyza canadensis), also known as horseweed or Canada fleabane, is a common winter or summer annual broadleaf weed found in nurseries, greenhouses, landscapes, roadways, meadows, turfgrass, and crops. It is problematic due to vast seed reproduction in two cycles, wind dissemination, lack of seed dormancy, and adaptability to both moist and dry soils.