PERSPECTIVE ON AGRICULTURE : Whitefly Was Invited to Dinner : Farmers all but ensure disaster by single-crop plantings and overuse of pesticides. We must seek biological controls.
The poinsettia whitefly is causing devastating losses to California crops. Experts predict damage to 33% to 40% of winter vegetable production in the Imperial Valley alone.
The whitefly is an unwelcome visitor, but this pernicious pest did not arrive uninvited. Current farming practices in the Imperial Valley and throughout much of California set the stage for such disasters. Infestations like the whitefly are predictable and, without a dramatic change in agricultural practices, are certain to reoccur.
Many insects species, including the whitefly, are able to survive year-round in the desert climate of the Imperial Valley. Farmers plant the same crops year in and year out: broccoli, melons, lettuce and cotton, with few variations. Hot and arid conditions allow for crop production throughout the year. This monocultural practice provides a constant host, a breeding ground where insects like the whitefly can feed.
To combat these pests, farmers resort to toxic insecticides, many of which pose serious risks to human health and the environment. Each year, an estimated 200 million pounds of pesticides are used in California agriculture. High insecticide use, particularly in the Imperial Valley, has created two significant problems:
-- Pesticide resistance. An increasing number of pests are developing a genetic resistance to pesticides. According to the National Academy of Sciences, close to 450 different species of insects have developed a resistance to some pesticides. Growers typically apply chemicals more frequently and in greater quantities to achieve a measure of control.
-- Loss of beneficial insects. Heavy use of pesticides kills the natural enemies of insects and transforms once innocuous bugs into harmful pests. An estimated 24 out of California’s top 25 agricultural pests became so because excessive use of pesticides wiped out natural enemy populations.
While the poinsettia whitefly has no natural enemy as yet in California (entomologists are seeking one in the Middle East, where it is believed the pest originated) general predators and parasites exist that provide a great deal of control as long as insecticides are not used. In non-agricultural areas of the Imperial Valley, natural control of the whitefly is estimated to be as high as 70%.
California agriculture is not an innocent victim of unexpected pest outbreaks; it is a victim of chemical pest control gone awry. Researchers are already aware that chemicals are not the cure for the poinsettia whitefly. Fortunately, efforts are focused on locating a natural enemy. If such biological control is found, dramatic changes in pest-control practices in infested areas will be necessary to ensure the whitefly predator’s survival.
Regaining a biological balance on the farm and preventing destructive pest outbreaks in the future is possible only if growers dramatically reduce dependence on chemicals. A Natural Resources Defense Council study shows that alternative pest-control strategies are already available to reduce pesticide applications in California crops by 25% to 50%, with minimal impact on farm production costs or yields.
The whitefly devastation has prompted Gov. Pete Wilson to declare a state of emergency to assist farmers and researchers in finding a solution. While important in the short term, this triage approach will not protect California agriculture from future pest outbreaks, nor will it address the continuing environmental degradation caused by the overuse of pesticides.
The governor has before him a golden opportunity to establish a policy for California to significantly reduce pesticide use and promote the adoption of sustainable farming practices. Not only would this save the state’s vital agriculture from future pesticide-induced disasters; it also would make California a national, if not an international, leader in agricultural innovation and environmental protection.
