Since World War II, organophosphate chemicals have provided an inexpensive, easy-to-use and effective method for controlling insect pests on the farm, in the home and garden, and even on household pets.
But these insecticides are also toxic to many nontarget species, including humans and wildlife, and their uses are being severely curtailed as the result of a major overhaul of federal pesticide regulations triggered by the Food Quality Protection Act of 1996. As of 2002, 42 of 49 organophosphate products that were registered in 1996 had been either cancelled or their uses significantly curtailed.
Fortunately, the demise of organophosphate insecticides -- including well-known products like diazinon, chlorpyrifos and malathion -- has resulted in a trend toward less-toxic and more environmentally friendly insect control on California farms. This includes innovative and technologically advanced methods such as the use of pheromones to disrupt insect mating, "biological control" of nonnative pest insects using their natural enemies, and applications of less-toxic and more insect-specific alternative pesticides.
In a special 48-page issue of the University of California's (UC) peer-reviewed California Agriculture journal (January-March 2005), scientists explore the range of alternatives to organophosphates currently available and look to the future. The current issue of California Agriculture, including PDF versions of all peer-reviewed research articles, can be viewed in full online at: http://californiaagriculture.ucop.edu/0501JFM/toc.html
One classic example of biological control -- using natural enemies to keep insect pests in check -- is the introduction of the vedalia beetle in 1889 (sic) to control cottony cushion scale, which was a major citrus pest at that time. The vedalia beetle has been so successful in controlling cottony cushion scale that it is now virtually taken for granted by growers.
The same is true of many other successful biological control agents. "Growers are naturally concerned with pests that are causing crop damage, and are often unaware of those pests that are present in the crop system but held in check by the continued success of introduced biological control agents," write Nicholas Mills and Kent Daane, co-directors of the Center for Biological Control at UC Berkeley.
The special issue of California Agriculture discusses numerous successful alternatives to organophosphates, including:
* The use of pheromones -- chemicals secreted by insects for communication -- to disrupt insect mating and thereby reduce populations. Important successes to date include the control of codling moth in pome fruit, oriental fruit moth in peaches and nectarines, tomato pinworm in vegetables, pink bollworm in cotton and omnivorous leafroller in vineyards.
* Cultural controls that make the crop less palatable to pest insects, such as improved field sanitation, targeted planting dates, crop rotations, and improved irrigation and fertilization schedules. Successful examples include reducing dust in orchards to prevent the buildup of spider mites, and the cleanup of unharvested grapes to limit overwintering pests.
* Less toxic, more pest-specific alternative insecticides, such as pyrethroids, neonicotinoids, insect growth regulators and other novel chemistries. While these products also have drawbacks -- such as toxicity to nontarget organisms, or the development of pest resistance or secondary pest outbreaks -- they are significantly less toxic than organophosphates.
The special issue of California Agriculture also explores novel strategies such as microorganisms (including widely used Bacillus thuringiensis), beneficial nematodes, petroleum oils and particle films, genetically modified plants, and "natural" products well known to organic growers (including sulfur, pyrethrum, and neem oil). These occupy a small but important niche in insect control for California agriculture.
"The elimination of the uses of many broad-spectrum pesticides has resulted in the development and registration of numerous reduced-risk products, as well as alternative pest- control strategies," said Robert Van Steenwyk, UC Berkeley entomologist with and co-chair of the special California Agriculture issue. "University researchers have been at the vanguard of this change, and in providing cost-effective new methods and technologies that growers can use."
Materials provided by University Of California, Division Of Agriculture And Natural Resources. Note: Content may be edited for style and length.
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