Weeds & Invasive Plants

All Weeds & Invasive Plants Content

Several plastic bottles of pesticides gathered together in a white tub.

Managing Waste Pesticides: Restricted Use Pesticides

While pesticides are intended only to impact pests, they can have negative consequences on unintended targets, such as humans and wildlife, if not handled properly. Learn what steps you need to take to safely dispose of unused pesticides and comply with regulations.

Small, green and yellow florets being held by a hand.

Isolated Female Waterhemp Plant Produced Seed: Implications that pollen is in the air

Recent observations by the SDSU Extension Weed Science team highlight that pollen can move far distances to pollinate isolated female plants. This reinforces the need to effectively manage weeds in fields and adjacent areas.

Tractor applying residual herbicide to a bare field.

Fall-Applied Residual Herbicides

Many parts of South Dakota can experience dry conditions when residual herbicides are applied, resulting in inadequate weed control. In these areas, residual herbicides can be applied in the fall and take advantage of a longer period to receive activating precipitation.

A white and purple seedhead of a Canada thistle with a blurry, bright green background.

Perennial Weed Management in the Fall

Most herbicide applications to manage perennial weeds have already occurred. However, now is the time to consider fall applications for weeds that were not treated or escaped the spring application.

A green Canada thistle with large, round galls throughout.

Galls on Canada Thistle: Biological Management at Work

A common sight this summer on Canada thistle is odd growths (also known as galls) on stems. These galls are a product of thistle stem gall fly attacking Canada thistle plants.

Tall, green grass surrounding a small, green yellow toadflax plant that hasn’t quite flowered yet.

Yellow Toadflax Has Not Flowered in Some Parts of South Dakota

Yellow toadflax is a difficult-to-manage weed that infests pastures and rangeland. In contrast with other weeds, yellow toadflax should be sprayed when flowers are present for more-effective management.

United States Environmental Protection Agency Sign plate outside the agency’s main office.

EPA Issues Emergency Order: Stop Using Dacthal

Following a review of data associated with the use of dimethyl tetrachloroterephthalate (sold under the most-common trade name, Dacthal), the EPA has issued an emergency order to stop using this active ingredient effective immediately.

Small, green grass plant amongst brown soil.

Woolly Cupgrass Management

Compared to other grassy weeds, woolly cupgrass is difficult to manage due to the large seed and tolerance to select herbicides. Proper identification will ensure proper selection of management tactics.

Weeds growing abundantly between rows of soybean in a research plot.

Weeds Are Starting to Flower: Management tactics to minimize seed production in soybean

Flowering weeds are an indication that seed production is about to occur, and viable seeds can soon be produced. Learn a variety of strategies to manage these weeds before they become a problem in your soybean fields.

Two pictures of green sunflower plants amongst brown dirt and tan crop residue. Taller, green corn plants can be seen in the distance.

Would you rather know or assume? A reminder to check varieties before spraying.

No matter how busy you are this growing season or in the future, you should never be too busy to stop and take a few minutes to double check herbicide types and crop varieties before spraying.