JoAnne Skelly: More on weed management preparedness

I walked around my field this morning to see what plants were coming up. The redstem filaree (aka cranesbill) is lush and widespread.

There are compact grasses doing well; I’m hoping they are not cheatgrass. I even spotted many of my favorite field flowers emerging, common groundsel.

A few weeks ago, I wrote about preemergent herbicides. I’m seeing preemergent products on display at box stores now. One product I saw with the active ingredient trifluralin, claimed to control weeds for six months, guaranteed.

However, a little asterisk next to that claim said, “Click to see a complete list of weeds controlled.” They also have a long list of which groundcovers, shrubs, and trees you can use this material around without damaging them.

However, the manufacturer reminds us that it can’t be used on lawns, vegetable gardens, around fruit-or nut-bearing trees, herbs, or water gardens. Another caution is “When planting or transplanting into an area treated within the past 12 months, use fresh soil to fill in planting holes around plant roots, or injury may occur.”

Trifluralin does reduce germination of a number of weeds that are common in our area such as annual bursage, dandelion (remember, this is not for lawn use), redstem filaree, prostrate knotweed, mallow, black medic, annual sowthistle, spurge, sunflower, Russian thistle, annual bluegrass, cheatgrass, and foxtail, to name a few.

Notice it says redstem filaree. Since my weeds are growing already, this product will not stop them now. I would have had to use it in the fall. Unfortunately, it also controls common groundsel, which to me are lovely wildflowers that cover my field with a welcome mass of yellow each year.

Before purchasing any herbicides in hopes of preventing or controlling weeds, ask yourself if you know what weed it is you are trying to control. After all, these products are not inexpensive.

Unless you know which weed is your problem, you may be wasting your money. And, if you are tempted by products that claim multi-year control, be aware that you are purchasing a soil sterilant that may harm or possibly kill existing trees, shrubs, and other plants. Soil sterilants can also move into wells, drainage ditches, creeks and groundwater causing long-term contamination.

The most helpful and informative tool you have when using herbicides is the label. Read labels before you buy products. I like to take a photo of the product name and look it up online prior to purchase. For detailed information on preemergents, read https://naes.agnt.unr.edu/PMS/Pubs/2011-3172.pdf.

JoAnne Skelly is Associate Professor & Extension Educator Emerita University of Nevada Cooperative Extension.