National Silverleaf Whitefly Progress Review  National Research, Action, and Technology Transfer Plan, 1997-2002: Fifth Annual Review of the Second 5-Year Plan February 10-12, 2002

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

By studying whitefly growth on various crops throughout the year, scientists have developed crop rotation strategies which result in breaking the seasonal life cycle of this polyphagous pest. Understanding how whiteflies migrate and establish new populations in fields has resulted in sampling protocols forgotten and melons, giving growers the tools they need to decide when and where control strategies should be implemented.

Computer simulation models utilize data on whitefly immigration and parasite efficacy to estimate appropriate times for release of natural enemies.

Fundamental Research

Research on the biology of SLWF has lead to several novel control tactics. Studies on whitefly flight behavior and attraction to yellow have led to a new whitefly trap which does not disrupt biological control. Courtship and mating behavior, coupled with biochemical and molecular techniques, have been employed to sort out the identity of SLWF and its relationship to other species within the Bemisia complex.

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

Research on the synthesis, development, application methodology, field evaluation, and registration of several novel insecticides (both synthetic and naturally based) has led to new materials, including imidacloprid (marketed as Admire, Gaucho, Marathon, Merit and Pravado); buprofezin (marketed as Applaud); and pyriproxyfen (marketed as Knack). Studies also have shown that certain combinations of registered materials, such as fenpropathrin (Danitol) - acephate (Orthene) on cotton, provide substantial improvement over single material application.

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.

Biological Control

Studies on the nutritional requirements of predators, such as ladybird beetles and lacewings, have resulted in artificial diets which facilitate rearing . These and other predators have been evaluated in field release trials, and mass-rearing and release are now taking place in certain field and greenhouse situations.

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

Research has proven that growing high-value vegetables over reflective mulches slows development of whitefly populations. Intercropping with whitefly suitable hosts using trap crops can effectively protect some commodities. Mixing plant communities around fields can preserve and enhance effectiveness of predators and parasites.

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

Advances in computer technology linked to satellite imaging allow large area-wide mapping of crop types. Coupled with whitefly sampling techniques, these models can be used to design crop sequence patterns to the detriment of the SLWF. Scientists have organized community-wide task forces which have facilitated the delivery of information to the growers. Workshops have shown growers how to sample whiteflies and when to initiate control methods. Scientific publications and various meetings facilitate communication among scientists, while numerous pamphlets and electronic media have been written and distributed to the grower community.

National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
703-487-4650

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
311 College Building North
University of California
Riverside, CA 92521

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