Summary:

During the past decade, the silverleaf whitefly in Arizona has been relegated to a managed pest. This was achieved through the development of management programs in cotton, melons and vegetables which utilized cultural practices, selective insecticides, sampling and monitoring plans, and optimally-timed insecticide use. Growers in all commodities have been quick to adopt and modify these management strategies as new insecticide compounds are made available.

Admire® (Section 18) in melons and vegetables, and Danitol® in cotton, were first available to Arizona growers in 1993. However, due to excessive use, pyrethroid efficacy was significantly reduced in some growing areas by 1995. In response, the Arizona Cotton Growers Association (ACGA) requested limited use of and received an emergency exemption for two insect growth regulators, Knack® and Applaud®. Availability of the IGRs made possible the UA Integrated Resistance Management program that promoted non-chemical management of whiteflies, in conjunction with a three-stage chemical use strategy designed to maximize the longevity of insecticide modes of action. Implementation of this program has since reduced insecticide use for whitefly management overall and provided for recovery of pyrethroid efficacy.

Admire continues to provide consistent whitefly control on melons and leafy vegetables. However, the lack of registered foliar insecticides available in melons prompted the Western Growers Association (WGA) in 1998 to request an emergency exemption for Applaud on melons. A Section 18 label (expires 7/14/01; Section 3 pending) is now available on melons to control whitefly and help sustain Admire efficacy. Because whitefly exposure to Applaud may overlap between melons, cotton and fall vegetable crops, cooperation will be needed among growers to harmonize insecticide use across commodities, to cover management needs of the respective groups, and to protect long-term Applaud efficacy. In addition, preserving Admire efficacy is critical for managing whiteflies and sustaining alternative chemistries in vegetables and melons.

In the spring of 1998, the leadership within the WGA and ACGA met to discuss the possibilities of developing a cross-commodity approach for managing whiteflies and sustaining long term insecticide efficacy. A Cross-Commodity Working Group was formed, and discussions focused on formulating practical pest management guidelines for cotton, melon and vegetable growers in Arizona. Participants also included representatives from the Arizona Vegetable Growers Association, Yuma Vegetable Shippers Association, Arizona Cotton Research and Protection Council, Cotton Incorporated, and Arizona Department of Agriculture. A technical committee was formed and comprised of University of Arizona scientists and extension specialists, Arizona Department of Agriculture officials and pest control advisors from each commodity and regional growing area. This group was initially charged with developing insecticide use guidelines for the 1999-2000 growing seasons.

The efforts of the technical committee have resulted in general guidelines for managing whiteflies and specific recommendations for Applaud and Admire use. We achieved this by compiling data for crop production, insecticide use, and simulated whitefly population dynamics for key host crops within three distinct growing regions in Arizona. Graphs were constructed that when overlaid identified important, multidimensional interactions within cropping systems. Recommendations are focused on restricting Applaud use to only once per crop season in use windows, with additional guidelines for reducing the possibility of exposing successive whitefly generations to the same mode of action. The diversification and limitation of Admire and other active ingredients, and the employment of cultural practices should also be considered.

Recommendations:

Ideally, these strategies were formulated to optimize whitefly management and maximize the efficacy and longevity of insecticide chemistries used for whitefly control across commodities. We recognize, that under certain conditions these practices may be difficult to implement, but emphasize they may be necessary for sustainability of chemical efficacy in Arizona cropping systems.

Full Disclaimers

Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona.

The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.

Any products, services, or organizations that are mentioned, shown, or indirectly implied in this web document do not imply endorsement by The University of Arizona.