Which Herbicide to use…

Photo by Nic Colgrove

Spring is coming. And with the onset of warm weather and more spring rains, comes many different lawn weeds. Each year we tend to find new herbicides in the garden center of our favorite stores. However, when dealing with pesticides, it is very important to know what you are purchasing and how to correctly use it so as to not harm the environment, pollinators, and beneficial plants.

One of the things we all need to remember when using pesticides is to use the right product for the job and to know what you are using. To use the trade name Roundup isn’t going to be enough anymore. There are a lot of new Roundup brand products that each have a different combination of chemicals.

Roundup 365 is a new product from Scotts that contains both glyphosate, which is the active ingredient in the general Roundup product, as well as Imazapic. Imazapic is a selective herbicide used to control annual and perennial grasses as well as some broadleaf weeds. It has a trait that allows it to last longer in the soil than a regular glyphosate product which is essentially deactivated when it hits the soil. In accordance with the label, Roundup 365 should only be used in cracks and crevices in sidewalks, driveways, walkways, and tennis courts, amongst patios and paths, along fences, foundations, curbs, retaining walls, and landscape borders, and in gravel areas and parking areas. It is not to be used in areas where planting or seeding will occur for the next year or in the root zone of plants or in any other garden setting where desired plants are. Also, be careful when applying this to fenced areas as it should not be applied where there are desired plants on the other side of the fence that could be damaged with the application of this product.

Roundup for Lawns is another new product made by Scotts that actually contains no glyphosate. Roundup for Lawns contains MCPA, Quinclorac, Dicamba, and Sulfentrazone. MCPA is a herbicide similar to 2,4-D for broadleaf weeds. Quinclorac is a post-emergent crabgrass and annual grass herbicide. Sulfentrazone is the active ingredient found in Sedgehammer that is often used on yellow nutsedge. Dicamba is one of the 3 active ingredients in Trimec that is used for broadleaf weed control in a lawn. This product can be used over an established lawn because it has no ingredients that will kill established turfgrass.

*Reference to commercial products or trade names is made with the understanding that no discrimination is intended of those not mentioned and no endorsement by University of Nebraska–Lincoln Extension is implied for those mentioned.

Dicamba is a pesticide that we should be very careful with, as well as any pesticide that contains dicamba which includes Roundup for Lawns and Trimec. Dicamba can turn into a gas and move to non-target plants as a vapor in temperatures of 85 degrees and above. This volatilization can occur for the day and even a couple of days after application. So Dicamba products shouldn’t be used in the summer months. Also, be very careful with Dicamba products in your lawn around trees and shrubs. This product can cause injury to these plants when it moves through the soil and comes into contact with the roots. Limit use of this product to no more than twice per growing season around tree roots to avoid injury.

Each of these Roundup products are labeled for different uses. So, make sure that you always read and follow the label instructions provided with the product to ensure that you are using the product correctly and so that you don’t harm the environment or any non-target plants. Always keep the label and product instructions with the product so you will always know how and where to properly apply it.

*Reference to commercial products or trade names does not imply endorsement by Nebraska Extension or bias against those not mentioned.

Pesticide Safety

*Reference to commercial products or trade names is made with the understanding that no discrimination is intended of those not mentioned and no endorsement by University of Nebraska–Lincoln Extension is implied for those mentioned.

Pesticide safety is always an important consideration when caring for your landscape plants. If used correctly, pesticides can help improve the health and longevity of our plants. However, if used incorrectly, they can harm and even kill our plants or our neighbor’s plants.

Pesticide is the general term for any type of chemical we apply to our plants. This can include insecticides for controlling insects, herbicides to help us control weeds, and fungicides to help with fungal diseases in our plants.

Always read and follow the pesticide label instructions. Remember, the label is the law. Pesticides can only be used in the location and on the plants that are listed on the label. For instance, Tordon is a common pesticide used along roadsides and in fencerows as a stump treatment for weedy tree species growing where they are not desired. Tordon and many of the other products used on parking lots have varying degrees of solubility and will move with water to non-target areas and can cause damage. These products can move off of the parking lot to nearby greenspace and through the rootzones of trees to nearby plants causing damage and possibly death to your desired plant species. That is why these products are only to be used in the locations listed on the label, and not in your home landscape. Instead of using Tordon, a good alternative would be one of the brush killers that are found in many different formulations that are labeled for use in our landscapes and won’t harm our non-target plants.

Along with following the label instructions, make sure you are applying the pesticide at the correct rate for best control. The company that developed the product went through a great deal of research to ensure that they gave you the correct amount to apply to your weeds or insects. Do not apply more than what is recommended, and remember to be patient, the death of a weed takes around a week for many general use herbicides.

We have been seeing a great deal of weeds in our lawns this year, and with all of the rains, it has been hard to spray chemicals or have effective treatments for those weeds. However, we should now begin putting our 2,4-D products away for the summer months. 2,4-D can volatilize, or turn into a gas, and move to non-target plants in temperatures of 80 degrees or higher for up to 72 hours following application. 2,4-D should not be used in the summer months due to this issue. Also, most of the broadleaf plants we typically use 2,4-D on will be controlled better in the fall. So enjoy the flowers in the lawn until fall comes and mark your calendar for 2-3 applications of a 2,4-D product in September and October when the temperatures are cooler and the plants will take the chemical back into the roots with their winter storage nutrients.

Another issue with using pesticides, insecticides in particular is the harm to pollinating insects. June 15-21, 2015 was National Pollinator Week. We need to make sure that we are applying chemicals at the right rate, right time, and right location to not harm beneficial insects. If it is a plant that bees or butterflies are common on, use insecticides only as necessary and at dusk when the pollinator insects are not around and avoid spraying the chemical on the flowers. If the pest is a caterpillar, like bagworms, choose Bt instead of general insecticides. Bt is only harmful to caterpillars and won’t harm bees or beetles, but it will harm monarchs so be careful around milkweed plants with Bt. If you are spraying any kind of chemical on your lawn, it is beneficial to bees if you mow the lawn first to cut off any blooms that bees may forage on, reducing the risk of the chemical getting on the bees.

Fall Lawncare

As we draw closer to fall, we can start to prepare our lawns for winter. I wanted to take time, this week, to cover all of those items on your fall lawncare “to do” list.

It is now time to reseed your lawns for the fall. This is best done in the late summer or early fall, anytime between August 15 and September 15 of the year. The rule of thumb is that that for each week grasses are seeded before Labor Day, maturation is speeded by two weeks. If you reseed after September 15 you will probably have some success, but not as much. The seed that you put out on the ground may sprout and some might even overwinter, but much of it may die from winterkill because the root systems will not be fully developed. If you are a homeowner who wants to sod an area of your lawn, you can do that until they can no longer cut it from the fields. Do remember to keep newly seeded or sodded areas watered throughout the fall and in the spring.

Bare lawn in need of overseeding.

Good turfgrass choices for Southeast Nebraska include Turf-type tall fescue or Kentucky Bluegrass.   Using seed that is 100 percent of either of these or a mix of the two types would be great choices for Nebraska. You can buy mixes of turfgrass seed, but avoid mixes that contain annual ryegrass, ‘Linn’ perennial ryegrass, or ‘Kenblue’ Kentucky Bluegrass. Make sure that the grass you buy contains less than 0.3 percent weed seed and no noxious weed seeds. We can also use Buffalograss in our lawns for a warm season grass, but warm season grasses should be plugged in June and July.

As for fertilizer applications, the fall fertilization is the most important fertilizer application for a lawn. Two applications in the fall are recommended for Kentucky bluegrass and only one is recommended for tall fescue, but one application for either species is better than none. The timing for fall fertilizer applications is Labor Day and Halloween if you do two applications and Halloween if you do only one application.

The fall is the best time to control broadleaf perennial weeds such as dandelion and clover. You can add a broadleaf herbicide to your lawn fertilizer to get a two-for-one application. It is often sold in stores as a combined product. The best herbicide choices for homeowners would be anything that contains 2,4-D or a triclopyr product for clover and ground ivy or creeping Charlie.

Photo by Nic Colgrove

If you need to aerate your lawns, now is a good time to do that. You can still aerate your lawns into November if you don’t get around to it until then. Aeration is best done in the spring or the fall of the year, but it is not necessary to do it every year, if you don’t want to. Aeration is done to break up a heavy thatch layer in the grass and to reduce the compaction of the soil. The thatch layer is the layer of dead organic matter in between the grass blades and the soil line. Leaving the clippings on the lawn does not increase the thatch layer, in fact it can actually give you enough nitrogen to replace one fertilizer treatment for the year. If your thatch layer is more than one half of an inch, you may want to aerate your lawn, if it is less than that, you may decide that it is not necessary to aerate this year.