Sunday, March 6, 1994 - Page updated at 12:00 AM

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Practical Gardener

How Safe Is Weed-B-Gon?

WSU / King County Cooperative Extension

Q: I would like some information on Weed-B-Gon. How is it different from pre-emergent herbicides, and what are its effects on perennials? How about its overall environmental effects?

A: Weed-B-Gon is a weed killer specifically labeled to control a wide range of broadleaf weeds in lawns. It will not harm lawn grasses, nor will it control grassy weeds such as annual bluegrass. It is not labeled for dealing with weeds in flower and vegetable gardens, or around shrubs, perennials or other ornamental plants. Any spray drift or possibly even volatilization could damage or kill desirable plants.

Weed-B-Gon is a postemergent herbicide, meaning that it is applied to already-growing weeds to control them. Pre-emergent weed killers are applied to the soil environment, before weeds emerge, to keep them from coming up.

Weed-B-Gon is safe to use in lawn areas if instructions are rigidly followed. Overuse of lawn herbicides, especially on grades, could lead to runoff and surface-water contamination with some negative effects on certain aquatic life.

Under ideal conditions of temperature and moisture, the herbicides in Weed-B-Gon are degraded by soil microorganisms in about a month; however, if such chemicals are over-applied, especially on sandy soils, because of their high solubility they might contribute to groundwater contamination.

Q: When should I spray my apple trees?

A: To deal with scab and mildew on apples, WSU plant

pathologists recommend spraying with benomyl, captan, lime sulfur or wettable sulfur during the bloom cycle. Apply a spray at the pink stage (blossom buds out, but not yet open), another at petal fall, and then a third one 10 to 14 days later.

Dormant sprays in winter are of no benefit to control these two common diseases. Some insects can be eliminated or reduced in numbers by applying a delayed dormant spray of horticultural spray oil plus lime-sulfur. The delayed-dormant stage occurs after growth starts pushing out, but before any pink shows in the buds.

Q: My female dog kills my lawn in patches with her urine. Can anything be done?

A: It's the concentration of salts that kills the grass, but since they are highly soluble, you should be able to reduce the damage by heavily watering the areas your dog seems to favor.

Q: I moved into a house recently with roses in the yard over 8 feet tall. Can I cut them back by two-thirds, and when?

A: Large overgrown roses should be reduced in size, and removing two-thirds of the stems should be fine. Remove all dead and weak stems at their points of origin and cut the rest back to healthy, outward-facing buds. Do this in late February or early March.

Gardening runs Friday in Scene and Sunday in Home/Real Estate. It is prepared by George Pinyuh and Holly Kennell, Washington State University/King County Cooperative Extension agents, Mary Robson, Master Gardener program assistant, and volunteer Master Gardeners.

Copyright (c) 1994 Seattle Times Company, All Rights Reserved.


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