colorado potato beetle on a damaged plant
damaged stem
pest button
resistance button
history button
management button
links button

Background

Colorado potato beetle has a legendary ability to develop resistance to a wide range of pesticides used for its control. Plants in the family Solanaceae, which are natural food sources for this insect, have high concentrations of rather toxic glycoalkaloids in their foliage. These toxins protect them from a wide range of herbivores. However, the Colorado potato beetles evolved an ability to overcome toxic defenses of its hosts. Apparently, this ability also allows them to adapt to a wide range of human-made poisons. Also, high beetle fecundity (on average, about 600 eggs per female) increases the probability that one of the numerous offspring mutates, just as buying 600 lottery tickets increases probability of getting a winning one compared to buying 6 lottery tickets.

Resistance mechanisms in the Colorado potato beetle are highly diverse even within a relatively narrow geographical area. Furthermore, the beetles show cross-resistance to organophosphates and carbamates, and multiple resistance to organophosphates, carbamates, and pyrethroids. Laboratory selection experiments showed that in addition to the resistance to synthetic insecticides, the beetle has a capability to develop resistance to the Bacillus thuringiensis subsp. tenebrionis delta-endotoxin.


Timeline

The first instance of CPB resistance to synthetic organic pesticides was noted for DDT in 1952. Resistance to dieldrin was reported in 1958, followed by resistance to other chlorinated hydrocarbons. In subsequent years the beetle has developed resistance to numerous organophosphates and carbamates. Presently it is resistant to a wide range of insecticides, including the arsenicals, organochlorines, carbamates, organophosphates, and pyrethroids (Fig. 3.1). The major problem area is the Northeastern United States; however, resistance has also been detected in other areas of the U.S., as well as in Canada, Europe, and Asia. In some cases, a new insecticide failed after one year (e.g., endrin) or even during the first year of use (e.g., oxamyl).

Graph of cumulative number of chemicals to which the Colorado potato beetle developed resistance
Fig. 3.1. Cumulative number of insecticides to which resistance in the Colorado potato beetles has been reported (Arthropod Pesticide Resistance Database, 2007).



Neonicotinoids to the rescue

Resistance problem became completely unmanageable in some areas in the early 1990s, when many potato growers completely ran out of chemical control options.  Fortunately, the situation improved after neonicotinoid insecticides entered the market in 1995.  A novel mode of action made this class of insecticides an effective tool in controlling the beetles resistant to other chemicals.  Long residual activity and low mammalian toxicity provided additional incentive for their wide adoption by commercial growers.


Imidacloprid resistance

Most potato growers apply imidacloprid or thiomethoxam as seed treatment or in furrow at planting. This maximizes plant coverage and significantly increases insecticide persistence in potato foliage. Unfortunately, this also creates strong selection pressure on insect populations towards developing resistance to neonicotinoid compounds. The first cases of field Colorado potato beetle resistance to imidacloprid have already been reported on Long Island, in Delaware, Maine, and Michigan. In some of the resistant hotspots, imidacloprid no longer suppresses Colorado potato beetle populations (Fig. 3.2). There is no reason to believe that neonicotinoid resistance will not spread throughout presently susceptible beetle populations.

Damage by resistant beetles to imidacloprid-treated field

Fig. 3.2. Damage done by imidacloprid-resistant Colorado potato beetles to an experimental plot treated at planting with in-furrow imidacloprid formulation (Admire). Picture is taken on August 4, 2005.



Link to the main page



This website is sponsored in part by:

Copyright 2007 Andrei Alyokhin

For an in-depth scientific review of insecticide resistance in the Colorado potato beetle, please refer to

Alyokhin, A., M. Baker, D. Mota-Sanchez, G. Dively, and E. Grafius. 2008. Colorado potato beetle resistance to insecticides. American Journal of Potato Research 85: 395413.

Click here to read full text of the article free of charge.




Colorado potato beetle bibliography:



Insect, Spider, and Tick News from ScienceDaily.com