Whitefly Resistance to Imidacloprid, and Cross-Resistance to Other new Nicotinoid Insecticides
Dr. David Smitley, Michigan State University, $29,000, 3 year project
Other Project Team Members -
Mamy Rakotondravelo, PhD. Student, Michigan State University
Executive Summary
It appears that the nicotinoid insecticides will soon dominate the insecticide market for the
greenhouse industry in North America. Imidacloprid (Marathon) is already the most heavily used
insecticide product by greenhouse growers, and in 2005, five new nicotinoid products were labeled
for greenhouse use: thiamethoxam (Flagship), dinotefuran (Safari), clothianidin (Celero),
flonicamid (Aria) and acetamiprid (Tristar). These products are used for a wide range of
greenhouse pests including whitefly, aphids, mealybugs, fungus gnats and thrips. In the 1970’s and
1980’s, greenhouse growers relied heavily on pyrethroid insecticides for pest control. But spider
mites, aphids, thrips, fungus gnats and whiteflies all developed resistance to them, and if they were
became resistant to one pyrethroid insecticide, cross resistance allowed them to quickly develop
resistance to all the other pyrethroid insecticides (Costa and Brown 1991, Cahill et al. 1995). Now
we are facing the same issue with nicotinoid insecticides. Greenhouse growers have relied almost
exclusively on imidacloprid for whitefly control the last 12 years. Unfortunately, in the last 5 years,
some greenhouse growers began to report that imidacloprid did not provide adequate control, and
even more disturbing is a report that a new nicotinoid insecticide did not work for whitefly the first
time it was used. The resistance problem could be severely compounded if imidacloprid-resistant
whiteflies are cross-resistant to other nicotinoid insecticides. This could lead to some production
disasters when growers try to use these products. Once resistance occurs, cross-resistance among
nicotinoid insecticides is also expected for other groups of insects as well, like aphids, mealybugs
and thrips. Because we already have a colony of whitefly that is resistant to imidacloprid, we can
use whiteflies as an indicator species to alert us to potential cross-resistance problems with other
insects as well.
Our research group is in a unique position to test cross-resistance among nicotinoid insecticides
because we have been conducting research for two years with a culture of greenhouse whitefly that
is resistant to imidacloprid. We are now also looking for a source of the ‘Q’ biotype silverleaf
whitefly in Michigan for resistance testing. The proposed research will document the resistance of
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greenhouse whitefly to imidacloprid (for the first time with this species), determine the level of
cross-resistance to other nicotinoid insecticides, and determine if cytochrome P450 is part of the
resistance mechanism in our imidacloprid-resistant culture of greenhouse whitefly. We will also
duplicate the same experiments with the ‘Q’ biotype of silverleaf whitefly as soon as we culture it in
Michigan.
For further information, contact Dr. David Smitley at smitley@msu.edu
