Cys

774 safflower, and a single insecticide treatment when 70% of the insects are third- to fifth-instar nymphs, largely eliminated the threat to adjacent cotton fields. Monitoring by means of light traps and pheromone traps (using gossyplure, which has been particularly valuable for assaying pink bollworm movements into the San Joaquin Valley) is also routinely employed to determine the relative abundance of adult pest Lepidoptera.

Hagen and Hale (1974) suggested another potential cultural method, namely, the use of food sprays in attempts to prolong the seasonal effectiveness of natural enemies whose populations frequently decline after midseason. In experimental cotton plots adult Chrysopa were attracted to the food sprays and produced more eggs, resulting in significantly less injury to plants by corn earworms. In the mid-1990s, a commercial product, Envirofeast, was made available, and though this is not used in the San Joaquin Valley, it has been incorporated into some cotton IPM systems elsewhere.

Notwithstanding the increased importance placed on biological and cultural control methods, cotton growers in the San Joaquin Valley continue to apply insecticides as part of the IPM system. In part this is due to a change in the pest spectrum. Specifically, honeydew-producing homopterans, especially aphids and whiteflies, have become significant mid-and late-season pests. The feces of these insects can severely reduce the quality of the lint, creating "sticky" cotton. Cotton producers can choose from a battery of insecticides, including "traditional" synthetics and more recently developed insect growth regulators, avermectins, spinosyns, and microbials. For insecticide-resistance management, the insecticides can be arranged in groups according to their mode of action. Cotton growers are encouraged to follow a spray strategy based on the insecticides' mode of action; specifically, insecticides from the same group (having the same mode of action) should not be used in consecutive applications, or more than twice per season. Other guidelines stress the need for regular scouting (preferably twice-weekly), treatment only when pest threshold densities are reached, application of insecticides at the recommended rate, and whenever possible incorporation of biological and cultural controls.

Genetically engineered cotton, containing the Bt toxin, is available, though has found little use in the San Joaquin Valley where Lepidoptera are minor pests. It is, however, in widespread use where bollworms, beet army worm and other Lepidoptera are the primary pests; for example, in Mississipi more than 85% of the cotton grown is Bt-transgenic.

IPM has resulted in substantial savings, both financial and in terms of pollution, through the greatly decreased use of insecticides. For example, in the San Joaquin Valley, the pre-IPM insecticide-based control program for cotton pests cost about twice as much per hectare as the integrated program. From 1976 to 1982, the average quantity of insecticide applied per hectare to cotton decreased by 72% for the United States as a whole. In part this was due to the introduction of synthetic pyrethroids, which initially provided very effective control, though by the mid-1980s pyrethroid resistance had been documented in the tobacco budworm (Luttrell, 1994). Mainly, however, it was the result of introducing the cotton IPM program, which led to a decrease from 60% to 36% in the proportion of hectares treated. As a consequence, cotton's share of the United States field crop insecticide market dropped from 49% to 24%), while the benefit:cost ratio has been estimated at 4.6:1 (Frisbie and Adkisson, 1986).

Despite these remarkable statistics, many crop growers and government officials remain convinced that the unilateral use of insecticides is best. Persuading these individuals that to continue with this approach is not only economically unsound but will lead to long-term, perhaps irreversible deterioration of environmental quality is perhaps the greatest challenge that scientists have faced.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

Get My Free Ebook


Post a comment