It’s Not Too Late for Fall Weed Control

There’s still time to fight your weeds (Powell Tribune)

By Mary McKinney
Guest columnist

No doubt about it, the crisp change in the weather has us thinking about hunting, harvests, football and those darn corn mazes, of which I must confess I am no good at! We have one of those mazes right here in our own backyard, but I would just as soon drop my drawers and sit in barb wire for sure. Throw in a few scary guys with chainsaws and I’m probably gonna just curl up in a fetal position on the spot and ask for a bottle and a binky!
But hey, those stressful maize quests aside, fall is truly one of the best seasons to get outdoors. Mosquitoes are gone (replaced by snowflakes dancing down the back of your shirt), crowds have thinned out in that big park on top of the hill and there’s sure to be a bargain on summer essentials like flip flops and bug spray. Oh yeah!
Fall is also a GREAT time to tackle some of the noxious weeds that might be growing on your property — especially those weeds that spread via that creeping root (a.k.a. complex perennials), such as Canada thistle and Russian knapweed. Quackgrass is particularly problematic, but don’t despair! We’ll take a look at some effective herbicide options. So don’t let that bit of snow deter you. Dig out that scarf and gloves, grab your sprayer and let’s get outside!

Fall weed treatment
Before we talk about the particulars of dealing with those complex perennial species, I think it’s important to explain why we may tend to talk about herbicides more than other forms of control methods. To begin with, most people know how to run a shovel or a hoe. You know that, if you use them when the ground is
wet and plants are small, you use less energy! Wait until the ground is bone dry and the plants are Boone and Crockett sized and you know you are going to be working a lot harder! Same with hand-pulling the plants out. You hit your foot with one of these implements or maybe a pulaski (which is great for digging out biennial weeds, by the way) and you know exactly what could happen. Same with cultural controls such as burning (oops, that fire got away from us) or we should’ve brought the cows in earlier or grazed them fewer days, etc.
Herbicides, on the other hand, come with many inherent risks — lateral movement, residual effects, etc. — that may not be apparent to those unfamiliar with them. Not to mention that to be effective, they need to be the correct type, applied at the proper time and using the appropriate amount. You must also consider location and the future plans for the application area (will animals be grazing?). Used appropriately and according to label requirements, herbicides are one of the most useful tools available in certain situations — short of preventing these noxious species from establishing in the first place.
Of course, using an integrated approach to managing your property will always result in greater success, so be sure to maintain those desirable species you want by utilizing all the tools in your toolbox. For more information, visit https://bit.ly/2zwGBjf.

Canada thistle and Russian knapweed
Both Canada thistle and Russian knapweed are aggressive, creeping perennial weeds that infest pastures, rangeland, roadsides, crops and non-crop areas. While these species do produce seeds, most of the plant’s energy is utilized in producing new roots and shoots along the root system (rhizomes). Mechanical injury of plant parts via hoeing and mowing will stimulate new growth.
Herbicide choice depends on location. Is it in turf, pasture, under trees, etc.? Recommended products we carry include: 2-D, Chaparral, Milestone, Clopyralid and glyphosate (Roundup generics). Applications can be made even after a few light frosts; Russian knapweed may be treated with Milestone even after a freeze! Both species may require re-applications.

Then there’s quackgrass, a perennial weedy grass growing (usually) in a perennial desirable grass — TURF!  Many landowners mistake quackgrass for crabgrass, an annual nuisance weed. Quackgrass spreads by seeds (few) and creeping rhizomes (many).
As this is found in many lawns that are constantly groomed (mowed), we usually don’t allow this species to get tall enough for seed heads to emerge. However, one plant can produce 300 feet of rhizomes each year. Mechanical removal may spread the roots of quackgrass further; tillage in areas infested with quackgrass can spread thousands of new plants via those rhizomes. Weed barriers suppress growth, but the shoots will creep along until they find a way out!
Chemical control with products containing the active ingredient glyphosate (Roundup) may be used, but applications may require the use of a paintbrush or wipers. Several applications may be required. Garden areas may be treated after harvest. Treat in the fall and in the spring once remaining plants have broken through the soil surface. Allow for the most available surface area for best results. Ortho-Grass-B-Gone (fluazifop) can also be used successfully for residential use with the same application method. Unless you are very careful with these products, expect some of your desired turf grass to experience the same fate!
Larger areas of infestation may require more drastic treatment. This is a tough plant that will require several re-applications of herbicide for success.

(Mary McKinney is an assistant supervisor for Park County Weed and Pest.)

Also check out this issue of our newsletter “The Thistle” for more information.

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