THE VIRGINIAN-PILOT
Copyright (c) 1995, Landmark Communications, Inc.
DATE: Sunday, June 25, 1995 TAG: 9506230070
SECTION: HOME PAGE: G3 EDITION: FINAL
SOURCE: BY ROBERT STIFFLER, GARDENING COLUMNIST
LENGTH: Medium: 54 lines
``DO THESE THINGS really work the next day?'' a woman in a garden center asked me last week. In her hand, she had ``Next Day'' weed and grass killer, made by Enforcer, now being widely advertised on TV.
Roundup, the granddaddy of all weedkillers, requires two weeks to show results. This is much longer than most homeowners want to wait. Thus, many new and faster-acting products have entered the market. Do they work?
Jeff Derr, weed scientist at the Virginia Tech Research Center in Virginia Beach, says only a few active ingredients are used in the new one-day formulations, which are generally available both as a concentrate to be mixed with water and as a ready-to-use form.
``Diquat (diquat dibromide) is the active ingredient in Enforcer Next Day, KGRO Grass & Weed Killer and Spectracide Grass & Weed Killer,'' Derr said. ``Diquat is a contact herbicide, meaning it does not translocate to the roots. Therefore, repeat treatments of diquat would be needed to control perennial weeds that regrow from the root system.''
Glyphosate is the primary active ingredient in Roundup and a variety of other weedkillers such as Shoot Out, Kleenup Systemic and Kleenup Grass & Weed Killer. ``The concentration of glyphosate in these products varies widely,'' Derr said. ``The use rate, therefore, varies widely among them. But since glyphosate is systemic, it will kill root systems and is the compound of choice for controlling perennial weeds.''
Finale is a new product that contains glufosinate, Derr said. It is primarily a contact killer with limited systemic action. It is an intermediate between glyphosate, a systemic herbicide and diquat, the contact herbicide.
``As a general rule, the quicker a herbicide acts, the less likely it will be to control perennial weeds,'' Derr said. ``Weeds treated with rapid-acting products like diquat may show symptoms (of dying) within hours after application in hot, sunny weather. Annual weeds can be controlled easily with these contact herbicides, especially if treated when small. However perennial weeds treated with a diquat product will regrow from the root system.
``In the long run, greater control of perennial weeds is achieved through the slower-acting chemicals, such as glyphosate.''
If you're smart enough to know which weeds are perennial and which are annuals, you can spray the fast-acting products on annuals. If you're not sure and don't want to spray again, the long-acting products like Roundup are the most dependable.
Diquat, glyphosate and glufosinate are all inactivated upon contact with soil, so areas treated with any of them can be replanted after a short time, Derr said. by CNB