Herbicide Resistance in Weeds and Crops

Abstract

Weeds resistant to herbicides are rapidly becoming important factors in crop production and agricultural technology. Resistance to triazine herbicides has been confirmed in 55 species with one or more resistant biotypes in 31 states in the U.S., four provinces of Canada and 18 other countries. In addition, there has been a serious spread of weeds having multiple or cross resistances to various classes of herbicides and a recent development of weed biotypes resistant to the herbicides that inhibit acetohydroxyacetate synthase. The need for research on the prevention and management of herbicide resistance is obviously urgent. Herbicide resistant weeds may become a more serious economic problem within five to 10 years than pest resistances to insecticides and fungicides due to the greater use of herbicides in agriculture. This is almost certain to be the case if we depend too much on only a few of the newer herbicides and discard the older ones. We will need all the tools we currently have, as well as those that modern technology can provide, to manage our weed pests while further reducing or eliminating soil tillage, and to conserve essential soil and water for future crop production and public use. Research on herbicide resistant weeds should complement biotechnology research aimed at developing herbicide resistant crops, but the strategy and objectives of the biotechnology research must be altered to some extent. In particular, efforts should be aimed at developing major crops resistant to many herbicides, rather than one or two. This would provide greater flexibility in rotating or alternating herbicides to prevent resistant weeds from evolving, and controlling those resistant populations that appear.