CHEMICAL UPDATE: Non-Selective Chemicals
Selective herbicides seemingly provide the ultimate in pest control: the ability to eliminate weeds without harming desirable turf and ornamentals. However, sometimes you need the opposite — a product that completely eliminates vegetation for renovations, vegetation management or simple spot spraying. For these situations, you need a non-selective chemical.
Non-selective herbicides work in different ways. Some are soil-applied and enter plants through root uptake, providing immediate, as well as soil-residual, control. Others are foliar-applied and eliminate existing vegetation, but with little or no residual. A few have both types of activity. All have their place, depending on your specific needs.
Systemic herbicides are effective at killing woody and perennial plants. By contrast, contacts tend to work very quickly, earning them the nickname of “burndown” herbicides, but may not be the best choice for controlling perennial weeds. Foliar-applied products with little or no soil residual, whether systemic or contact, are by far the most widely used non-selectives in grounds care. These are the chemicals used for spot spraying or general “clean-up” weed control.
Fumigants are valuable tools for treating soil prior to planting and may control nematodes, insects and diseases, in addition to weeds. Traditionally, methyl bromide has been one of the mainstay soil fumigants. However, the Montreal Protocol, an international treaty for reducing ozone-depleting chemicals, will eliminate nearly all uses of methyl bromide before 2005. Fortunately, other chemicals are still available for pre-plant fumigation.
Use this Update for preliminary planning only. Remember that you must follow all label instructions any time you apply a pesticide. Non-selective pesticides are valuable tools, but must be used with care. After all, their defining characteristic is their broad spectrum of activity, so misapplications carry potentially great risks. Their safe use depends on proper application. Properly used, however, non-selectives can be one of the most valuable tools that landscape professionals possess.
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