THE SILVERLEAF WHITEFLY
From 1992-1997, scientists participated in a nationally coordinated research effort, with the objective of developing management strategies for the silverleaf whitefly (SLWF). This insect is responsible for over $2 billion in crop loss damage and control since its introduction into the US in 1986. Technologies which have resulted from research are summarized below within the six subject areas defined in the U.S. plan.
Ecology, Population Dynamics, and Dispersal
Computer simulation models utilize data on whitefly immigration and parasite efficacy to estimate appropriate times for release of natural enemies.
By studying the molecular components of whitefly-transmitted viruses, scientists are learning more about how pathogens are acquired and transmitted. Field research to determine how virus epidemics occur has resulted in the implementation of host-free periods, effectively breaking the disease cycle.
Biochemical research has lead to a novel method of treating cotton tainted by whitefly honeydew, using an enzyme that breaks down the specific sugars excreted by the SLWF.
Scientists have developed an artificial rearing system for whiteflies--a tremendous tool that allows further detailed study into how this insect interacts with the chemical components of its hosts. Artificial rearing techniques also are being used to produce natural enemies without the necessity of growing plants. Additional work has lead to the discovery of chemical signals involved in plant resistance to whitefly feeding.
Chemical Control, Biorationals and Pesticide Application Technology
Natural-based products such as neem seed oil (marketed as Trilogy, Triact and Rose Defense) and extracts of Nicotiana gossei, a wild cousin of tobacco are also being developed. A significant related technology is the design and implementation of integrated programs which prevent the rapid onset of insecticide resistance. Finally, researchers have adapted conventional equipment and designed new techniques for more precise application of materials.
Researchers have conducted regional surveys documenting existing parasite fauna, to aid in determining which exotics may have the most impact on whiteflies in these regions. A worldwide search for parasites has resulted in evaluation, mass rearing, and release of numerous populations (often new species) throughout the US, contributing significantly to the natural mortality of SLWF.
Research on pathogens which attack SLWF has enabled companies to culture and formulate large amounts of these important natural enemies which can be sprayed in field situations. Several fungal-based products now are available to the grower. Researchers have developed integrated programs which enable releases of natural control agents in concert with chemical insecticide applications.
Crop Management Systems and Host Plant Resistance
Manipulation of fertilizer rates and irrigation frequency and timing can alter plant growth to be less suitable for whitefly population development. Scientists are making progress toward developing resistant varieties of various commodities, such as alfalfa and cotton, with release just a short time in the future.
Integrated Techniques, Approaches, and Philosophies
National Technical Information Service
Individuals whose efforts are presented in this document represent: USDA (APHIS, ARS, CSREES), Israel, Mexico, U.S. State Depts. of Agriculture, County Ag. Commissioners, Univ. of Arizona, Arizona State Univ., Univ. of California, Univ. of Florida, Univ. of Hawaii, Texas A&M Univ., Grower groups, and Private industry.
Written and produced by the University of California, Riverside. For copies of this brochure write to:
CNAS Dean's Office