Herbicide Tolerant Biotech Cotton: The Resistance Issue in the USA

摘要

Weeds may be annual or perennial, but they are always found in cotton fields everywhere unless proper control measures are taken. Early weed competition in the first few weeks after germination can cause significant yield losses. Weed infestation candeprive the cotton plant of proper growth, change its branching scheme, and change the overall shape of the plant. When cotton is in its flowering stage, weeds compete with the cotton plant for nutrients, and they also harbor pests. Furthermore, weeds growing outside the cotton crop serve as hosts for insects, mites and pathogens. When harvest time comes along, particularly if the cotton is machine picked, weeds interfere with defoliation. While defoliants will cause cotton leaves to dry and fall, weedsmay not defoliate or be killed. Machine picking of weed-ridden fields will produce higher trash content in the cotton lint and result in stained cotton. Thus, a cotton field must be free of weeds from sowing until harvesting. Studies carried out in some countries have indicated that the optimum benefits of fertilizer and insecticide applications can only be achieved if there are no weeds in the field.