Vegetable Insect Control with Minimal Use of Insecticides

Abstract

Large scale commercial vegetable producers rarely adopt minimum input or sustainable agricultural practices for altruistic reasons. While some family-owned concerns have followed this approach with the intent of passing their land onto the next generation in as pristine a state as possible, much of California’s vegetable hectarage is managed by large corporations. Thus, development and implementation strategies using reduced pesticide input are less likely the result of environmental concerns and more likely due to economic incentives, legislation limiting pesticide use, or the development of significant levels of pesticide resistance. In terms of pesticide use, the California vegetable industry is approaching a critical period. California’s expanding urban population has led to an increase in the influence of environmental activists, labor unions, and other consumer groups that are increasingly vocal in their opposition to pesticides. In addition, the current senate and assembly, committees in California that deal with pesticides have few members with rural or agricultural backgrounds. This situation has lead to an increase in legislation restricting pesticides. At least 26 new bills relevant to the subject were introduced in California in 1987 alone. Nearly all of these would require further restrictions on the use of chemicals for insect control. The impact of the new laws dealing with ground water contamination -and plant-back restrictions has dramatically changed pesticide use patterns in California; as a consequence, the application of persistent pesticides has declined appreciably. The impact of laws generated by referendum (placed on the ballot after proponents file the required number of signatures on petitions) is less well-defined. Such consumer-generated legislation provides evidence of the growing perception that consumers take the risk when pesticides are used, while growers reap the profits. There also has been a resurgence in environmental concern by the general population. In the past few years, incidents of environmental concern at Love Canal and Kesterson Reservoir, as well as the tragic events at Bhopal, India, have been given considerable time on television. The publicity associated with the watermelon contamination incident in California and the recent National Academy of Sciences report (National Research Council, 1986) highlighting the potential for pesticidal contamination in vegetables, have brought this concern into nearly every household in the country. Our ability to find residues at the parts-per-trillion level has aggravated this problem. Many consumers do not recognize differences in risk levels between parts per hundred and parts per trillion, they only recognize that no level of risk is acceptable. An additional stimulus for reduced insecticide use is the declining availability of efficacious insecticides. The rate of development of insecticide resistance is increasing exponentially (Georghiou, 1986). Nearly every entomologist study vegetable crop production can cite cases of extensive losses resulting from insecticide resistance. The $20 million loss documented by California’s celery industry in 1984 following the development of resistance by the leafminer [Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)] to diverse chemicals provides an excellent example (California Celery Research Advisory Board, 1986). Thus, the need has been adequately demonstrated to