Weed Control: Safe and Unsafe Spraying Practices

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Credit: Thinkstock

Credit: Thinkstock

Weeds are often a problem in horse pastures, especially areas that are overgrazed, or high-traffic areas around water sources, shade or gates.Whenever the desirable forage plants are compromised, weeds come in.

Dr. J. D. Green, and Extension Weed Scientist, University of Kentucky, said herbicides are one option to help control some of the more difficult weeds.“I put a lot of emphasis, however, on the importance of good management practices to establish and maintain a healthy, viable forage species, to minimize weed invasion,” he explained."Good management allows growth of the desirable forages which compete against many of the weeds we might encounter."

When utilizing herbicides, it is important to choose the right product to deal with the specific weed or weeds you want to control.“There are some herbicides that can be used for lawns and turf but not pastures," said Green. "Make sure you choose a product that is labeled for pastured areas. Herbicides that are not labeled for this use might not cause a problem for the grazing animals, but technically can’t be used because the EPA has not registered the product for that particular use.Read labels to make sure the product will control the weeds you have, and that it is registered for use on pastures or grazed areas.

“You could also check your state’s weed control guides for pastures, or ask your local county extension agent for advice,” Green added.

After choosing the correct product, make sure you apply it at the right time of year.“You need to know the life cycle of the plant you want to control, to know when it grows and when it reproduces," noted Green. "If you plan to use herbicide on annual weeds, they should be sprayed when they are young and actively growing, not when they are mature.”He said it’s too late by then. Unfortunately, sometimes people don’t recognize a problem until weeds are nearly mature.

“Perennial weeds, by contrast, can often be controlled by clipping in summer when they are young, and then sprayed when they regrow in early fall and are moving nutrients down into their roots for winter," said Green. "Then you can get more herbicide into the root system.That’s when the plants are building back their root system to overwinter, and the herbicide is more likely to kill them.”

Decide whether you will do the spraying yourself or hire a custom applicator.If you are doing it yourself, learn how to do it safely.You want a product that will kill the weedy vegetation, but not the desirable plants.If you choose one that kills broad-leaf plants/forbs but not the grass, it will kill any legumes (such as clover or alfalfa) in the pasture.You will sacrifice legumes if you use those herbicides.

Be careful not to spray areas that you don’t intend to target.“Be aware of wind speed and direction to avoid off-site movement of spray particles to nearby vegetation,” said Green.You don’t want to inadvertently send spray onto your neighbor’s property or your garden, for instance.

“Be aware of your surroundings and familiar with the herbicide you are using and what its potential might be for volatilizing," said Green. "All herbicide particles move a fair distance on a windy day, but some of those products can readily volatilize on a hot, humid day and be more subject to movement, even if there isn’t much wind. Under a temperature inversion this can happen and you might not expect the herbicide to travel that much. If there is any wind, you need to know the wind speed and direction.Don’t spray if wind is above 10 miles per hour.Wind speed of about 3 to 10 miles per hour is best, and knowing the direction it is going.”

Green also noted that you need to use the right type of nozzles for proper spray pressure."Some nozzles with high spray pressure create finer droplets that are more subject to movement; they go a lot farther than larger droplets," said Green. "Pay attention to the boom height (if you are spraying with a tractor and equipment).The lower you can get the boom to the target, the better.The higher the boom, the more opportunity for excessive drift.”

If that field might eventually end up being converted to crops or a garden, select your herbicide carefully.Some have more residual effects and you might have to wait a long time before trying to grow something there besides grass.“Even if you simply want to inter-seed some legumes into that pasture, there might be a waiting time before you could do that,” he said.

Wear proper protective clothing for skin and eyes when applying herbicides. Sometimes you also will need protection to keep you from breathing the chemical.