REGIONAL COMPARISON OF WHITEFLY RESPONSES TO DANITOL + ORTHENE: REDUCED SUSCEPTIBILITY IN MEXICALI VALLEY

Authors: Castle, Steven; GONZALEZ-LOC, M - INIFAP, MEXICALI, MX; LEON-LOPEZ, R - INIFAP, MEXICALI, MX; PRABHAKER, NILIMA - UNIV OF CA, RIVERSIDE, CA; TOSCANO, NICK - UNIV OF CA, RIVERSIDE, CA; Henneberry, Thomas

Submitted to: National Research and Action Plan for Silver Leaf Whitefly
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Differences in responses to various insecticides among regional populations of Bemisia tabaci in the southwestern USA and Mexicali Valley, B.C., Mexico have been detected the past few years using a yellow-sticky card bioassay technique. The widest range of responses by far has been to the insecticide mixture of Danitol+Orthene. This treatment has been used intensively to combat whitefly infestations in mid to late season cotton from 1993 in Arizona and 1994 in California and Mexico to the present. A significant difference in relative susceptibility to Danitol+Orthene between Imperial Valley, CA and Maricopa, AZ whiteflies was first observed in late season 1995. The following year, whiteflies collected at various times during the cotton season from the same two regions as well as from Yuma, AZ and Mexicali Valley displayed significant variation among locations. Over a five month period from July-November, mortalities at a diagnostic dose of 75 ug (a.i. Danitol)/ml were consistently lower for Maricopa whiteflies than for any other location. Responses of whiteflies from the other three regions varied slightly, i.e. between 91-100% mortality at the diagnostic dose compared to less than 40% for Maricopa whiteflies in three out of five tests. Whiteflies from Mexicali and Yuma were generally slightly more susceptible to most insecticide treatments than ones from the Imperial Valley.