Could Spider Venom Be Used As A Novel Insecticide For Major Crop Pests?

Could spider venom be used as a new novel insecticide? Image ©giovzaid85 via Flickr
Could spider venom be used as a new novel insecticide? Image ©giovzaid85 via Flickr

A new protein discovered in the venom of Australian tarantulas can also kill insect pests that consume the venom orally. The protein known as orally active insecticidal peptide-1 (OAIP-1) was found to be highly toxic to insects that consumed it, with a similar efficacy to the neonicotinoid insecticide imidacloprid. In particular, the protein was found to be highly toxic to the cotton bollworm, Helicoverpa zea.

Many spider species have evolved insecticidal toxins in their venom, which they inject into the prey through their fangs. Consequently it has often been presumed that the venom would not be toxic when ingested orally by insects pests, and therefore would not be suitable for use as an insecticide. Conversely, the scientists in this study discovered it is possible to isolate spider venom peptides with high levels of oral insecticidal activity. The team used the venom from Selenotypus plumipes which is a large tarantula native to Australia which despite its large size is not harmful to humans.

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New Mapping Tool Tracks Insecticide Resistance In Malaria Carrying Mosquitoes

A mosquito in the genus Anopheles, which can transmit human malaria. Image by Yasser via Flickr (CC-BY-2.0)
A mosquito in the genus Anopheles, which can transmit human malaria. Image by Yasser via Flickr (CC-BY-2.0)

Progress in malaria control in the past decade can be attributed largely to a massive increase in the number of insecticide based management programmes targeting malaria carrying mosquitoes, using methods that include indoor residual spraying and insecticide impregnated bed nets. The effectiveness of these management techniques is now being compromised by insecticide resistant mosquito populations. In 2012, the UN World Health Organisation (WHO) launched a strategic plan to help fight insecticide resistance in malaria vectors. A crucial part in the management of insecticide resistant mosquito populations is access to current information on insecticide resistant populations.  IR Mapper is a new interactive online mapping tool used to track insecticide resistance in mosquitoes. The tool collaborates reports of insecticide resistance in malaria vector mosquitoes into maps which aim to assist vector control strategies. Data consolidation for the programme was conducted by Swiss company Vestergaard Frandsen, the Kenyan Medical Research Institute (KEMRI) and the US Centers for Disease Control and Prevention (CDC).   To make this information available to users, an interactive map of all publicly available insecticide resistance data has been developed, with an interface developed by ESRI Eastern Africa

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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)

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Glucose Leaves A Bitter Taste As Cockroaches Learn to Avoid Insecticide Baits

Populations of the German cockroach (Blattella germanica) have rapidly evolved to be repelled by the glucose in insecticide baits that are used to kill them. Scientists found that the cockroaches had a ‘re-organised’ sense of taste which makes them perceive the glucose in the insecticide bait as bitter and repellent rather than sweet. Researchers first noticed that some pest controllers were failing to control cockroaches using insecticide baits mixed with glucose because the insects were avoiding the baits. It was discovered that within a matter of years certain cockroach populations had developed a new behavioural trait known as glucose aversion. A paper published in the journal Science describes the mechanism behind this avoidance.

Blattella germanica, the German cockroach. Populations of this cockroach have evolved an aversion to glucose, which mean they are repelled by insecticide baits containing glucose and avoid them © Luis Miguel Bugallo Sánchez via Wikimedia Commons (CC-BY-SA 3.0, 2.5, 2.0, 1.0)

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