Rotations, resistance, management

One of the most commonly used resistance management strategies involves rotating or mixing products from different classes based on modes of action and, where there are multiple applications per year, alternate products of different classes. This assumes a reduction in the frequency of the resistant genotype... 

Where the resistance mechanism is unknown, the intelhgent use of alternations, sequences or rotations of compounds from different MoA classes remains an entirely viable resistance management technique since such a practice will always noinimize selection pressures. 

A more recent factor affecting weed management has been the introduction of crops genetically altered for tolerance or resistance to herbicides. The first herbicide-tolerant field com (IMI hybrid corn) was developed as a way to reduce the effects of carryover from imidazolinone and sulfonylurea herbicides applied to soybean in a corn-soybean rotation. These hybrids also soon found use in areas where triazine use was restricted. 

Duke (1995) contended that resistant weeds have driven growers to develop and use integrated pest management (IPM) or integrated weed management (IWM) methods, such as biocontrol, cover crops, more crop and herbicide rotations, more selective use of herbicides, weed thresholds, etc. 

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