Randy said:

"Yes, your condescending attitude toward the members of the List perhaps
provoked off track discussion.

The answer to your question seems obvious--resistance develops (as it
quickly did with the Colorado Potato Beetle, which was already preadapted
for resistance to alkaloids) by allelic or epigenetic tweaking of the
molecular structure of the receptor site."

In the meantime, someone directed me to a publication off-list, and within that one, I found reference to this paper:

"SELECTIVE TOXICITY OF NEONICOTINOIDS ATTRIBUTABLE TO SPECIFICITY OF INSECT AND MAMMALIAN NICOTINIC RECEPTORS", by Tomizawa and Casida, in Annu. Rev. Entomol. 2003. 48:339–64  doi: 10.1146/annurev.ento.48.091801.112731

Here's an excerpt about their predictions vis-a-vis how resistance will develop:

"Resistance in Pests
Three types of resistance to IMI have been observed under field conditions. The
first is for some insects feeding on tobacco, presumably as a cross-resistance
associated with evolutionary selection for nicotine tolerance. A Japanese strain
of a tobacco-feeding form of M. persicae, a species closely related to M. nicotianae,
also displays a low level of sensitivity to IMI (73). A French strain of
M. nicotianae showed 192-fold and >22-fold resistance to IMI and nicotine, respectively,
compared to susceptible M. persicae (70). A positive relationship between
IMI and nicotine resistance has also been demonstrated for Bemisia (9). This
difference between tolerant or resistant and susceptible Myzus is not due to modified
nAChR sensitivity to nicotine and IMI (71, 73), and the nAChR of nicotineinsensitive
Manduca has the same sensitivity to cholinergic ligands and IMI as that
of nAChRs from other susceptible insects (21). The second type of resistance is
from preexisting metabolic and excretion patterns selected by previous exposure to other insecticides, illustrated here by Colorado potato beetle (Leptinotarsa decemlineata )
adults and larvae with 100- and 13-fold resistance to IMI, respectively
(78, 129). Several neonicotinoid-resistant strains of M. persicae  are more strongly
synergized by piperonyl butoxide than the susceptible strain (I. Denholm, personal
communication). DDT resistance in Drosophila  correlates with overexpression of
Cyp6g1  (an isozyme of CYP450), which appears to confer cross-resistance to IMI
(19). The third and greatest concern is for the type of resistance from long-term
selection with IMI and other neonicotinoids. IMI resistance of at least 15-fold was
observed in field-collected B. tabaci  from the Almeria region of Spain (10) and
B. argentifolii  from the Imperial Valley in California (80). Continuous laboratory
selection with IMI elevated the resistance of B. argentifolii  to > 80-fold after 24
generations (80). This indicates that IMI resistance genes exist in some whitefly
populations at high frequency. Increased levels of resistance to neonicotinoids in
some pests with concomitant control failures will inevitably result from continued
selection pressure. Although a modified nAChR due to neonicotinoid selection has
not yet been reported, it remains to be seen if metabolic or target site resistance
will ultimately prove to be of greatest importance."

To put this into layperson English:

1.  Neonic resistance is correlated with resistance to nicotine.  Some insects have evolved with tobacco plants, and they have nicotine resistance.
2.  The Colorado potato beetle developed resistance by utilizing preexisting metabolic and excretion patterns selected by previous exposure to other insecticides (CW says...yikes, both larvae and adults can do this!)
3.  Some insects in California and elsewhere have already developed genetic long-term resistance.

Conclusion:  "... it remains to be seen if metabolic or target site resistance
will ultimately prove to be of greatest importance."

Interesting!  And food for some serious thought.

Christina

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