Woes with weeds

Woes with weeds

Features - Weed/Disease/Insect Control

Here’s a review of what weeds gave LCOs problems this year, and what will be popping up in 2012.

December 13, 2011
Lawn & Landscape Staff
Industry News

Last month, we tackled what pests LCOs had to fight in 2011 and what they can expect to face in 2012. This month, we delve into the world of weeds in different parts of the country. We reached out to a number of experts to find out what weeds were most common across the country in 2011 and what was done to control them. We also look to 2012 to find out what weeds will be common next year. – Lawn & Landscape staff


Weeds: Ground ivy, wild violet, crabgrass, goosegrass, nutsedge, dahlisgass.

Control: Most weeds are easy to control with the right chemistry and timing. Products containing the active ingredient triclopyr are the best solution. Aside from chemical control, weeds can be controlled by keeping mowing heights high and maintaining dense turf through good fertilization. – Dan Loughner, business development leader, Dow AgroSciences

Nutsedge is one of those weeds that is sometimes hard to control. There are several herbicides that are very effective for control. Many people will actually attack them as a post-emergent control once you see them come up, so you put out post-emergent control products like sulfentrazone, mesotrione, halosulfuron-methyl. For crabgrass, preemergent is still the way to go. I think if people put it on too early or too late this past year, they would have seen crabgrass breakthrough.

You have to get it on before the soil temperatures are consistently at 65 degrees. I think the best way to approach it, if you've had difficulty controlling crabgrass, is to do a split application. Put on half your herbicide early, prior to breakthrough and about four to six weeks later put on the second application. Prodiamine and dithiopyr are probably the two preemergent herbicides that are most used by lawn care companies. – Mike Agnew, senior technical manager, Syngenta

What to expect in 2012: Excessive rains late summer and early fall should cause heavier crabgrass and broadleaf weed pressure in 2012.  Turf that has weakened and thinned from the hurricane will see more weeds. Applications of DNA (dinitroaniline) herbicides this fall for next year's crabgrass control can become a problem if over-seeding is necessary. – Loughner


Weeds: Crabgrass and spurge in the summer. Poa annua and numerous winter annual broadleaf weeds in winter (e.g., chickweed, bittercress, henbit, burweed, dandelion, wild garlic) and Rhizocotonia species diseases, such as brown patch, brown ring patch, zoysia patch.

Control: Good cultural practices to maintain a dense stand of turf (i.e., correct mowing height, fertility, irrigation, thatch management, overseeding of cool season grass in fall). Application of preemergent herbicide at spring green-up to control crabgrass and again in the fall to control Poa. In addition, early postemergent herbicides can also be used to control perennial weeds. – Joe Chamberlin, regional field development manager for Valent Professional Products

The best solution for these patch diseases is to treat preventatively. A preventative application of a broad spectrum fungicide, normally one that is based on strobilurin and/or DMI (de-methylation inhibitor) chemistry, provides excellent activity on the Rhizocotonia based diseases. Any of these products are best used preventatively since curative control once the patches begin to develop is much more difficult to achieve without loss of turf. For the warm season grasses this means applications in the late summer and early fall.

Warm season grasses should have an additional application directly before green-up in the spring to provide clean up of any infection. – Kathie Kalmowitz, market development specialist, BASF Professional Turf & Ornamentals

What to expect in 2012: It is a given there will be some environmental conditions develop someplace in the U.S. in 2012, which will necessitate pest management for the lawn care operator. Keeping the turfgrass healthy by growing under proper fertility and mowing heights does a lot to help manage through insect and disease attacks. – Kalmowitz


Weeds: Dandelions

Control: A preventative application of a three-way herbicide in mid-October for dandelions is key, followed by spot application with the three-way herbicide in the spring as needed.  

What to expect in 2012: LCOs can expect more of the same – these are ever-persistent and historical problems; preventative action is the only way to keep them in control. – Sam Wineinger, key account manager/territory sales manager Western U.S., Arysta LifeScience


Weeds: Crabgrass, Yellow nutsedge, brown patch, leaf spot, red thread, dollar spot.

Control: On lawns with a history of crabgrass, application of pre-emergent herbicide remains the best way to control crabgrass. Treating yellow nutsedge as soon as it starts to grow improves control. Yellow nutsedge needs to be treated with a herbicide by mid-summer at the latest before it has a chance to spread by rhizomes or produce tubers, which allow it to return the following year. – Dave Heegard, general manager, LebanonTurf

Leaf spot, red thread, rust and dollar spot typically develop on turf that is low in fertility, especially nitrogen. For cool season turf, the best thing to do is fertilize when the turf is growing best and temperatures are moderate: make your nitrogen and other fertilizer applications in the spring and fall. Fertilizer is plant food; too little and you have problems, too much and you get a set of other problems. – Frank Wong, technical service specialist, Bayer Environmental Science

What to expect in 2012: As long as summers are hot, cool season turfgrass lawns will be under stress, making them less competitive with weeds. – Heegard


Weeds: Nutsedge, spurge, creeping chaffweed, Poa annua, goosegrass, crabgrass and southwestern cupgrass.

Control: Properties with a history of a specific weed would be wise to plan a preventative treatment with products that contain dithiopyr or isoxaben as the main active ingredient for weed control.

What to expect in 2012: Poa annua will continue to be a problem given the limitations of several herbicides relative to the practice of overseeding bermudagrass with perennial ryegrass. Proper identification, mapping and understanding life cycles will help professionals design an effective management program. In light of weather models forecasting lower than normal rainfall, turf managers will need to monitor unfavorable soil conditions due to their reliance on poor quality irrigation water. Stressed turf will present opportunities for disease and weed issues to arise. – Vince Aguiar, sales representative, Dow AgroSciences