Mahan: Home and farm weed control


By Jerry Mahan

Fall is weed control time and if you have a problem with perennial weeds in your lawn, pasture or fields the fall is the best time to control them with a herbicide (weed killer). The weeds are in the part of their life cycle when they are storing carbohydrates in their roots so material applied to the leaves of the plant will be translocated downward to the roots. Spraying for broadleaf weeds is best done when air temperatures are in the 40s and 50s.

A fall application also works better in helping minimize spray drift problems in non-target shrubs and trees as these plants are in the process of losing leaves. Common weeds this strategy works well for includes Dandelion, Plantain, Wild Violet, Indian Mock Strawberry, Wild Carrot, Canada Thistle, White Clover, and Ground Ivy.

Since the air temperatures are cooler in the fall weeds will not metabolize or translocate the material as quickly as when air temperatures are warmer. You may not think the spray material is working but if you return in a few days or next spring the weed will be gone. Remember to apply the weed control products on sunny days when no rainfall is expected for 24 hours so the material will be absorbed into the leaves and not washed off. This is true for products containing 2-4-D, MCPP, and other products like triclopyr.

The window of opportunity for fall application usually persists through November and the first week of December depending on the weather. Applying weed control products this time of year also gives you the opportunity to control winter annual broadleaf weeds like Common Chickweed, Henbit and Shepard’s Purse. We normally do not apply weed killers to annual weeds like Spurge, Purslane, Oxalis, Lambsquarters, or Mallow unless the weeds are so thick as to inhibit reseeding an area. These weeds will be killed with the first hard frost.

This is an ideal time to control problem perennial weeds in pastures as well. This could include Dandelion, Curly Dock, Canada Thistle, Bull Thistle, Poison Hemlock (biennial), Ironweed, Poison Ivy, and Poke Weed among others.

Farmers with problems of Marestail (Conyza canadensis (L.) Cronq.) in soybeans need to strongly consider fall applications of 2-4-D with glyphosate or dicamba. This weed according to Mark Loux Weed Specialist with OSU Ext. was the most problematic weed across the Midwest in soybeans surpassing the invasive weed Palmer Amaranth. Marestail is both a summer and winter annual making it hard to control.

Always follow label restrictions when applying pesticides.

Identifying weeds

You may be wondering what weeds you have to control. Here are some books and internet sources which might help you identify the ones you have. One book I use is “Weeds of the Northeast”. It contains good pictures and descriptions. A good website is: Another one is:

You can also check with your garden center, agronomist with Sunrise Cooperative (formerly Trupointe) if you are a client, Greene Soil and Water Conservation office or local Extension Office for help in identification of weeds.


The late fall (November) is also the time to make your last and best application of fertilizer to your lawn. As state above the plants are taking nutrients into the plants and storing them in the roots for next spring. By far this is the most important time to fertilize your lawn and will do more to affect the health of your lawn than any other feeding. You can apply the fertilizer any time the ground is not frozen or a heavy rainfall is expected. Several companies make a “fall fertilizer” for lawns.

Sadly many box stores and other garden centers literally close down their sales of important lawn care products like weed control products and fertilizers just when you need them the most.

Weed and feed verses sprays

I often get questions on whether weed and feed application of dry material is as effective as a spray on material. Generally granular weed control products do not work as well as materials applied as a spray. There is too great a possibility of the granular material not getting to all of the weeds and being held up on the leaves of some plants. According to Dr. John Street, OSU Turfgrass specialist the lone exception is the application of granular products in control of crabgrass.

Jerry Mahan is a retired OSU Extension Educator Agriculture and Natural Resources for Greene County. He can be reached by email at: [email protected].

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