Weed Management
Weeds reduce agronomic crop yields through competition for resources. On this page, find recommendations for managing weeds in agronomic crops such as corn, grain, soybeans, small grains, and forages.
Weed Management Best Practices
Agronomic crop weed management requires year-round vigilance and control. Weeds can be broken down into annuals, biennials, and perennials, each of which has its own life cycle. Understanding these life cycles, for example, helps agronomic crop producers decide whether they can control annual and perennial weeds after silage harvest or in fallow areas.
Not only are there different types of weeds, but there are also many different methods for controlling them. Penn State Extension’s Introduction to Weeds and Herbicides covers the important issues surrounding weeds and their control. Weed management plays an important part in agronomic field diagnostics.
The use of herbicides is just one method, with new herbicide products entering the market every year. The Agronomy Weed and Pest Management Tour is one way you can find out about the new herbicide products.
Conservation tillage systems are another way of managing weeds that uses cultural, mechanical, and chemical control tactics.
The effectiveness of any weed control method depends on a number of different things, such as the time of the year, unstable weather conditions, crop injury, and tank-mixing. Mid-season weed control issues also include herbicide drift.
Weed Management in Agronomic Crops: Corn, Soybean, and Wheat
Corn, soybean, and wheat have specific weed management issues to contend with. When spring is approaching, for example, populations of winter annual weeds become prevalent, thereby competing with wheat and barley. Certain herbicides can be applied in nitrogen carriers, but it’s important to get the timing right. There is a temptation, when applying herbicides, to wait until all the weeds have emerged, but this is counterproductive.
Some winter annual weeds are easier to manage in the fall rather than waiting until the spring. There are many options for fall herbicide applications, such as Harmony Extra, a broad-spectrum herbicide. Glyphosate is another broad-spectrum herbicide and is a herbicide option for burndown in no-till corn.
Herbicide-resistant weeds are a common cause for concern, too, with Marestail, or horseweed, being one of the most challenging.
Producers use cover crops as part of their weed management program, but it’s important to remember that some herbicides can persist and potentially influence the establishment of cover crops.
Soybean producers can attend the Soybean Management Workshop and Herbicide Demonstration workshop to learn more about herbicide usages along with variety selection, management strategies, insect, and disease management.
Chemical Free Weed Management for Agronomic Crops
The application of herbicides is not the only way to manage weeds successfully, especially if producers want to “plant green”. Organic producers use cover crops, for example, as well as a number of other non-chemical control strategies in their weed management plans that are cultural and mechanical.
The focus of organic weed management is prevention, crop rotation, crop competition, and cultivation. Hairy vetch, for example, mixed with a winter grain, can be used before corn, and cereal rye is predominantly used before soybean. Hairy vetch would typically be terminated with a roller crimper before planting corn.
Harvest weed seed control using a Harrington Seed Destructor is a way of managing herbicide-resistant weeds. It is used as part of the harvesting process and is currently being tested in Illinois.
Herbicide Application and Timing for Field Crops
Timing is crucial when it comes to the successful application of herbicides. Spring herbicide applications, for example, include Broadworks and Pindar GT, used in stone fruits, and Zeus Prime, which is currently only used for apples.
Certain residual herbicides can also be applied close to the time for planting. However, timing is critical, as Early Preplant (EPP) Herbicide applications that are too early may require a post-application.
As well as timing, there is the problem of herbicide drift and drift-related damage to consider. The issue is a very serious one because if a substantial amount of drift-related damage occurs there are legal ramifications.
Soil persistence or soil residual life is another factor to consider when applying herbicides to crops. Herbicides vary in their potential to persist in the soil. There is a very fine line between controlling weeds for a growing season and then planting a sensitive rotation crop.
- News
Burndown after Ryelage Harvest
Date Posted 4/23/2024Here are some suggestions to control ryelage stubble after spring harvest. - News
Termination Options for Cover Crops and Winter Cereal Forages
Date Posted 4/9/2024Best management practices for terminating winter cereal forages and cover crops with pre-plant burndown programs. - News
Hay, Grassy Weeds, and Prowl
Date Posted 3/25/2024As first cutting hay is being harvested, grassy weeds tend to emerge. The below article provides details about which pendimethalin products can be used in these settings. - News
Spring Weedy Grass Control in Grass Hay and Pasture
Date Posted 3/25/2024Considerations for weedy grass and broadleaf control options in grass forages during early spring. - News
Spring Burndown: Consider Spraying Early, But With What?
Date Posted 3/19/2024Early burndown herbicide applications can be effective and certain herbicides provide flexibility if you need to switch between corn or soybean crops. - News
Early Season Weed Control in Wheat and UAN Carrier Issues
Date Posted 3/5/2024Spring herbicide suggestions for certain problem weeds in wheat. Recommendations for herbicides that can be applied in nitrogen fertilizer carriers. - News
The Dicamba Rollercoaster: Xtend-specific Dicamba Registration Updates
Date Posted 2/19/2024Important notes on EPA’s cancellation order and use of existing stocks provision. What does this mean for Pennsylvania farmers? - News
Warm Winter Weather and Weeds
Date Posted 2/6/2024Some are asking if it is feasible to apply herbicides this early in the year. Consider some factors before being too hasty. - Articles
Questions About Your Pesticide Points?
Is your pesticide license due to expire on March 31? Not sure how many points you need? Do you need to find upcoming meetings? Here's a simple way to check! - News
Tosh Mazzone Joins Crops Team in Franklin County
Date Posted 1/9/2024The Field and Forage Crops Team welcomes new Extension Educator, Tosh Mazzone, of Franklin County. - News
What's New for Agronomic Weed Control in 2024
Date Posted 1/5/2024New herbicide products, label updates, and industry news about weed management are highlighted in the article. - Guides and Publications
Starting at Free
2023 Agronomy Research Report
A research report highlighting the results of new, continuing, and completed agronomic projects conducted by Penn State investigators and their collaborators in 2023. - Guides and Publications
Starting at $8.00
Mid-Atlantic Field Crop Weed Management Guide
Get strategies and peruse herbicide tables for managing weeds in corn, sorghum, soybeans, small grains, and forages. - News
How to Become a Private Certified Pesticide Applicator
Date Posted 11/28/2023New applicator? First time using restricted-use pesticides? Fumigants? Retesting after a lapsed license? These are the simplified steps to obtain a private pesticide license. - News
Can Weeds still be Controlled in November?
Date Posted 11/14/2023As temperatures drop, many wonder if it is too late to control weeds like marestail, chickweed, thistle, roughstalk bluegrass, and others. Read below for some comments about this question. - News
Scout Fields for Palmer Amaranth and Waterhemp to Prevent Spread with the Combine
Date Posted 10/17/2023Make plans now to prevent the spread of Pennsylvania's herbicide-resistant weeds. - News
Fall Burndown of Weeds and Declining Forage Stands
Date Posted 10/3/2023Fall is a great time to control winter annuals and perennials weeds as well as declining sod stands. - News
Herbicide Recommendations for Winter Small Grains
Date Posted 10/3/2023Small grain establishment and growth can be hindered by weeds, below are some herbicide options to consider for problem weeds species. - News
It's Getting Late to Control Certain Weeds
Date Posted 9/19/2023Fall is a good time to manage biennial and perennial weeds; however, some species need to be controlled sooner than others. - News
Are Harvest Aids the Answer for Large Palmer and other Late Season Weeds?
Date Posted 9/12/2023Late season weeds can cause issues with corn and soybean harvest. Consider some of the harvest aid options or other tactics to manage problem weeds including Palmer amaranth. - News
Fall Weed Control in Forages
Date Posted 9/5/2023Fall is an excellent time to manage biennial and perennial weeds and Japanese stiltgrass in pastures and hay and to control problem weeds after silage harvest. - News
Can Burcucumber be Controlled at this Time of Year?
Date Posted 8/21/2023If corn fields are infested with burcucumber, consider chopping it for silage. If not, herbicides used as grain harvest aids are generally not effective on burcucumber. - News
Weed Seeds This Fall Means More Weeds Next Spring
Date Posted 8/21/2023Control annual weeds now in fallow areas to prevent seed set. Also, now is the time to start considering ways to manage perennials in small grain stubble. - News
Corn and Soybean Weed Control in July
Date Posted 7/3/2023Herbicide options are dwindling as corn and soybean crops are approaching maximum growth stages for post herbicide application, so what are some considerations? - News
Double-Crop Soybeans: Weed Management Considerations
Date Posted 6/19/2023As small grain harvest begins, double-crop soybean planting will soon follow in some areas of the state. Below are considerations for weed control.