FINDING ANSWERS

PESTICIDE POLICING

Q

Do you know where I can find information on pesticides that could damage ornamentals if misapplied? — California

A

As you know, you should always refer to label directions and apply pesticides at label rates only to tolerant plants indicated on the label. However, misapplications can occur for reasons other than not following these basic label directions. Sloppy application and drift can injure susceptible non-target plants. Applications to water or heat-stressed plants can injure plants that are normally tolerant. A malfunctioning sprayer, drizzling spray nozzles or poor tank agitation can also cause problems. We have covered these topics in Grounds Maintenance (“Phytotoxicity: The unexpected danger” By Dr. Beverly Sparks, March 1997, and “Avoiding phytotoxicity” By Dr. Thomas L. Watschke, May 1993.)

Related Topics



Unfortunately, I do not know of a list of plants that are susceptible to injury from particular pesticides. Because of the almost endless list of ornamentals and varieties, manufacturers only list on labels those species that are tolerant and have been thoroughly tested. You may be able to get additional information on a specific plant if you contact the manufacturer of the particular pesticide in question. If you are needing information on turfgrass tolerance of herbicides, we publish this information in our annual (January) series “Chemical Update: Turfgrass Herbicides.”

RE-JUSTIFIED

Q

Recycling clippings sounds like a good idea, but doesn't it contribute to thatch? — via the Internet

Leaf clippings contribute very little to thatch accumulation, justifying the recommendation that clippings should be recycled back into the lawn rather than bagged. Dead and decaying roots, rhizomes, stolons, and shoots are major contributors to thatch since these structures have a high lignin content and resist decomposition. The exception may occur if you have a thick thatch layer (greater than ½ inch) already. In this case, clippings sit on top of the thatch and are prevented from contact with the soil borne decay microorganisms that break down clippings.

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