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Purdue report: Lawn weed poisons killing pollinators

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Purdue University scientists are saying that folks should be cautious in using pesticides, as pollinators feed on many of the weeds which lawn owners use poison to kill.

While flowering weeds may be unsightly to you, they’re food to bees and other pollinators, the researchers report. If you must spray, mow the weeds down first to remove the flowers, according to an article published in the Journal of Integrated Pest Management (JIPM). The guide also outlines other recommendations to protect pollinators, including preferred times to apply pesticide.

It’s important to consider the consequences of treating your flowers, including flowering weeds, said Doug Richmond, an associate professor of turfgrass entomology and applied ecology for Purdue’s College of Agriculture. “We must understand that there are some tradeoffs,” he said. “These pollinators live in our urban environment. There are many ways we can expose them to pesticides unintentionally. If you spray your flowers to protect them from pests, you may be increasing the chance that pollinators will be exposed to that same pesticide.”

American homeowners often think of clovers and dandelions as weeds that need to be destroyed, rather than flowers that attract pollinators, said the guide’s lead author Jonathan Larson, a extension educator for the University of Nebraska-Lincoln. “If you’re going to treat your lawn for pests, consider the effect on pollinators,” she said. “A lot of people often forget that weeds like dandelion and clover are flowers, resources for pollinators. We tend to think of roses, lilacs and violets as flowers.”Ê

Recommendations made by the guide:

* Wait until May or June to apply pesticides. Early-season pollinators and colonies of bees are still recovering from winter stress in March and April.

* Use granular formulations of insecticides, which fall to the ground and avoid direct contamination of flowering portions of blooming plants.

* Select and plant grass breeds that are resistant to pests.

* Maintain a high mowing height for grass to promote deeper root systems and enhance tolerance to stress and injury from pests.

* Introduce biological control agents, such as parasitic nematodes and fungi that attack pest insects but are generally safe for non-target organisms.

* Establish plots of pollinator-friendly plants, which is an increasingly growing practice among golf course managers and homeowners.

With Americans spending about $75 billion a year on lawn care expenses, the impact of certain lawn care practices on pollinators could be more far-reaching than scientists realize. Richmond said there hasn’t been extensive research on the effect of urban lawn care practices on pollinators, an increasing source of concern among scientists because of their vulnerability to environmental stressors.

Richmond and Larson stressed Americans may need to change their definition of a perfect lawn. “We have been convinced, over time, that a perfect lawn is nice, green, lush and completely uniform with no other plants,” Richmond said. “But that’s perfect for what? It’s a human construct.”

Richmond suggested that a “perfect” lawn, which includes turfgrass and other plants, should be considered one that is beneficial “for filtration, cutting down on the heat in urban areas and serving as a habitat for pollinators.”

Larson, who noted that he doesn’t treat his own lawn with pesticides, said many Americans aren’t satisfied until their lawn looks like a golf course. “Understand what your lawn is for. If you want it to look nice, there are more sustainable ways of doing it.”

 

 

Posted 8/7/2017

 
 
 
 

 

 

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