Cultural practices for weed resistance management

Cultural practices, such as delayed crop seeding, tillage, black fallow, cr op rotation, hand weeding, and competitive crops, when used to replace herb icides, provide an opportunity to reduce the selection pressure that causes weeds to become resistant to herbicides. Herbicides on the other hand redu ce the selection pressure that causes weeds to resist cultural practices. R otation of the two systems should then delay resistance to both systems. Gr owers consider many factors in addition to weed resistance in selecting her bicide or cultural weed control, from associated convenience to economic po tential. Rotation of different types of weed control practices would delay resistance, compared to a continuous single practice. The extent of the del ay depends upon genetics of resistance, weed reproduction characteristics, weed seed survival, and fitness of resistant weed plants. An understanding of the basic aspects of weeds and herbicides, as well as their interaction with the environment, would help in predicting the delay in resistance to a n herbicide from use of cultural practices in the rotation. A grower's fina l choice of a weed control practice will involve available equipment, time, markets, and soil erosion in addition to potential weed resistance. Weeds that develop resistance to a control practice still allow for reversion to preresistance practices, an important component of a grower's decision. The rate of resistance development is dependent upon the removal of susceptibl e genes from the population and fitness of the resistant plants. Resistance might be delayed for many years or be manageable when the resistance is ge netically recessive or resistant weeds are poorly fit. Growers may not want to accept alternative cultural practices as long as there is the potential for development of another herbicide or reversion to cultural control afte r resistance occurs.