The Evolution of Insect Resistance to Bt Crops

A group of scientists at the University of Arizona have this week published a paper in Nature Biotechnology on the evolution of resistance in insect pests populations to insecticidal proteins from Bacillus thuringiensis (Bt) that are produced by transgenic crops. Resistance is defined as the phenotype of an individual that gives the individual the ability to survive on a transgenic insecticidal plant from egg to adult and provide viable offspring. The team analysed field and laboratory data from seventy-seven studies of thirteen pest species in eighteen countries across five continents. Entomologist Bruce Tabashnik and colleagues found well documented cases of field-evolved resistance to Bt crops in five major pests as of 2010. 60% of these cases occurred in the U.S.A, where approximately half of the world’s Bt crop acreage is planted. In some cases, resistance to Bt evolved within as little as two to three years, whilst in other cases Bt crops have remained effective for more than 15 years. The research team aimed to better understand how quickly insect populations are evolving resistance to Bt crops and how this is occurring.

Workshop participants assess a range of fodder and cereal crops that can be used as “refugia”, fostering stem borers susceptible to the Bt toxin. In a longstanding partnership under the Insect Resistant Maize for Africa (IRMA) project , CIMMYT works with the Kenya Agricultural Research Institute (KARI) to offer farmers maize varieties that resist borers, which otherwise cause heavy losses (approximately 12% of Kenya’s annual maize crop). In addition to conventional breeding, one source of resistance in developing these varieties has been the soil bacterium Bacillus thuringiensis. A gene from this bacterium inserted into “Bt maize” causes it to produce a protein that is selectively toxic to certain borer species. However, mutant resistant borers unaffected by the toxin will flourish and eventually predominate, unless farmers use refugia to maintain a susceptible population. At this workshop in December 2005, sponsored by IRMA at KARI’s Kitale center, 50 participants—including researchers, extension workers, and farmers—learned about progress in the development of insect-resistant maize and the importance of refugia, evaluating numerous crops in the field for their potential as refugia. For more information, see CIMMYT's December 2005 e-news story "Bug Havens Keep Maize Pest-Proof," available online at: http://www.cimmyt.org/newsletter/86-2005/344-bug-havens-keep-maize-pest-proof.  Image © CIMMYT (CC-BY-NC-SA 2.0)
Women assess a range of fodder and cereal crops that can be used as “refugia for stem borers susceptible to the Bt toxin. In a longstanding partnership under the Insect Resistant Maize for Africa (IRMA) project , CIMMYT works with the Kenya Agricultural Research Institute (KARI) to offer farmers maize varieties that resist borers, which otherwise cause heavy losses (approximately 12% of Kenya’s annual maize crop). In addition to conventional breeding, one source of resistance in developing these varieties has been the soil bacterium Bacillus thuringiensis. A gene from this bacterium inserted into “Bt maize” causes it to produce a protein that is selectively toxic to certain borer species. However, resistant borers unaffected by the toxin will reproduce and eventually predominate, unless farmers use refugia to maintain a susceptible population. 
Image © CIMMYT (CC-BY-NC-SA 2.0)

Continue reading

Colorado Potato Beetles Left With A Sour Taste As Clover Is Found To Be As Effective As Pesticides

An adult Colorado Potato Beetle (License CC-BY-NC 2.0. via Flickr)

Eggplant or aubergine (Solanum melongena) is a crop often attacked by the Colorado Potato Beetle (Leptinotarsa decemlineata), a major insect pest of  plants from the Solanaceae family including potato, tomato and eggplant throughout North America, Europe and Asia. This insect pest is exceptionally destructive to crops and readily develops resistance to a wide variety of chemical insecticides, making research into alternative control methods vital. Now new research has revealed that the use of clover cover crops in agricultural fields of eggplants may provide an economically and ecologically viable method of Colorado Potato Beetle management that is as effective as chemical insecticides in regulating the beetle populations.

Continue reading

Colorado Beetle Threatening Potato Crops in Finland

Colorado Potato Beetle. Flickr/Andriux-uk

Finland is experiencing a longer and warmer summer than normal which is threatening their potato crops. The warmer temperatures have led to increases in the prevalence of the Colorado potato beetle which has been attempting to establish in Finland for the past decade. The Colorado potato beetle itself is a highly effective reproducer and necessitates a wide range of control methods to prevent its spread.

Continue reading