Weed Management

Weeds in forage crops have an impact on your profit margins because they affect the quality of your forage, reduce yield, palatability, and your grazing area. Make use of Penn State Extension’s vast resources covering weed control and management of forage crops, common toxic and noxious weeds, and find tips on herbicide application.

Weed Control and Management in Forages

Weed control plays a key role in forage production. Without it, you run the risk of reduced forage yield, lower forage quality, increased incidences of disease and insect problems, premature stand loss, and problems when harvesting.

Understanding the characteristics of weeds, their life cycles, and keeping up to date with the latest weed control methods means you can choose the best methods for your own forage crop production.

There are many forage weed management strategies, but your focus should be on cultural practices, before chemical weed control. Forage stands that are vigorous and dense-growing, for example, have fewer weed problems. Other cultural and weed management practices that promote a highly competitive forage stand include seeding vigorous, well-adapted, and long-lived varieties, buying weed-free seed, cutting forage at the right time and growth stage, timely control of insect and disease problems, and rotating crops.

Timing plays an important role in a forage weed management system. Annual and perennial weeds are best controlled after silage harvest or in fallow areas. Fall is an excellent time for the control of biennial weeds. However, it’s still possible to effectively kill perennial and biennial weeds after a few hard frosts.

Herbicides provide a very convenient, economical, and effective way to control weeds. However, you should only use them when necessary, at recommended rates and times of application, and only for crops and uses listed in the label. Penn State Extension holds a Soybean Management Workshop and Herbicide Demonstration on-site, where producers are given the opportunity to discuss herbicide usage. Recommended herbicides do not generally injure people, wildlife, livestock, crops, or pasture.

Common Toxic and Noxious Weeds

If you want to control or eradicate weeds in your forage crops you have to be able to identify the different species. This is especially important for species that are toxic. Grazing animals will rarely eat poisonous weeds, but you should still aim to minimize the risk with careful control.

• Jimsonweed: This is an annual plant that is poisonous to animals and humans. One distinguishing characteristic is its spiky egg-shaped pod.
• Multiflora rose: It was originally introduced from Asia and promoted as a “living fence” but it is now a noxious weed in Pennsylvania and surrounding states. You can control it, but it takes considerable effort.
• Noxious pigweeds: Palmer amaranth and waterhemp are two species of pigweed recently introduced into Pennsylvania. It requires an integrated management approach and aggressive weed management strategies to prevent seed production and the spread of these weeds.
• Milkweed: Milkweed is a native perennial that exudes a white, milky juice from broken or cut surfaces. It can be very problematic when left to develop into a thriving stand which has spread into a hay field.
• Poison hemlock: Penn State Extension’s Poison Hemlock Identification video shows you how to identify this toxic weed.

Learn about management and herbicide use for perennial weeds and earn pesticide applicator recertification credits with Penn State Extension’s Problem Weeds in Field Crops: Managing Perennials online courses.

Forage Crops Herbicides Application

You must take a number of factors into account when applying herbicides. Making sure they stay on target, for example, is essential. Particular care is necessary when applying burndown herbicides close to vineyards and other sensitive areas. Herbicide drift and drift-related damage could prove very costly. Luckily, there are ways you can reduce spray drift. You can reduce spray pressures and only spray at low wind velocities, for example.

Timing is another crucial factor. There are herbicides that are more effective when applied in the spring. Anthem Flex, Axial XL, Dimetric EXT, and Huskie are better applied in the fall. You can use certain herbicides over the top of emerging crops such as soybeans. Some winter annual weeds are easier to manage in the fall. Application restrictions apply if a crop is being harvested for silage, forage, grazing, or grain.

The weather can be a determining factor. Soil-applied herbicides cannot be properly activated for weed control if there has been a lack of rainfall. The weather can also affect the spraying of burndown herbicides. Air temperatures, in particular, can influence control with burndown herbicides.

Herbicides are very effective at controlling weeds, but there’s the issue of persistence to consider, as it can affect subsequent crop growth.