Controlling insecticide resistance

Populations of insects soon become resistant to any insecticide. This applies to artificial and natural insecticides, as well as to those insecticides produced by GM plants.

Two solutions to this problem are being investigated.

Double the genetic punch

One solution is the 'double and triple whammy'. This involves genetically modifying the plant by adding two or three insecticide genes, so that two or three toxins are produced. If an insect becomes resistant to one toxin, the other will still kill them. The number of bollworms that will be resistant to genetically modified plants with two or three different insecticide genes will be very small, and arise only rarely.

Bollgard®II is an example of the 'double whammy' principle at work. It uses two different Bt insecticide genes to deliver insecticides to the insect.

Reduce the chance of finding a resistant mate

The second solution involves refuges, which are areas of land near the crop planted with non-GM cotton. Farmers are not allowed to spray the plants in the refuges.

The bollworm moths will be able to grow and breed safely in the refuges and the population of moths that are not resistant to any pesticide will remain high. These non-resistant moths will be able to breed with the moths that have become resistant to the GM cotton.

The eggs and caterpillars that are produced will probably not all be resistant to the insecticide. These caterpillars will be killed when they eat the GM cotton. However, there will still be moths thriving and laying eggs in the refuges. This will ensure that the numbers of non-resistant moths remain high, and that the environmental benefit of using Bt instead of more toxic synthetic insecticides is not threatened.

The current Australian regulations prescribe that up to 90 per cent of a cotton crop can be planted with Bollgard®II on any one farm. This may be lifted to 100 per cent if other crops such as pigeon peas are planted as refuge crops to slow down the emergence of Bt resistance in cotton bollworms.

A problem with insects - work sheet [PDF 29kb | 2 pages]

Butterflies and Bt - work sheet [PDF 30kb | 2 pages]

People do not agree about genetic modification of crops - work sheet [PDF 29kb | 2 pages]

Looking at media views - GM foods - work sheet [PDF 41kb | 4 pages]

Read about another method being used to disrupt insects from breeding, using pheromones (sex hormones): http://www.abc.net.au/science/news/stories/s199218.htm

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What is biotechnology? Human uses Environment Food and agriculture Feed Me A problem with weeds - the canola story A problem with insects - the cotton story What is cotton? Why do we grow cotton? What's the problem with insects? Using insecticides to kill insect pests Using viruses and venoms to kill insect pests A biotechnology solution to insect pests in the case of cotton Concerns about insecticide resistance Controlling insecticide resistance Other reasons to modify crops - soybeans The international scene Genetically modified food labelling Regulation of research in Australia Ethics for Food and Agriculture research Careers	Controlling insecticide resistance Populations of insects soon become resistant to any insecticide. This applies to artificial and natural insecticides, as well as to those insecticides produced by GM plants. Two solutions to this problem are being investigated. Double the genetic punch One solution is the 'double and triple whammy'. This involves genetically modifying the plant by adding two or three insecticide genes, so that two or three toxins are produced. If an insect becomes resistant to one toxin, the other will still kill them. The number of bollworms that will be resistant to genetically modified plants with two or three different insecticide genes will be very small, and arise only rarely. Bollgard®II is an example of the 'double whammy' principle at work. It uses two different Bt insecticide genes to deliver insecticides to the insect. Reduce the chance of finding a resistant mate The second solution involves refuges, which are areas of land near the crop planted with non-GM cotton. Farmers are not allowed to spray the plants in the refuges. The bollworm moths will be able to grow and breed safely in the refuges and the population of moths that are not resistant to any pesticide will remain high. These non-resistant moths will be able to breed with the moths that have become resistant to the GM cotton. The eggs and caterpillars that are produced will probably not all be resistant to the insecticide. These caterpillars will be killed when they eat the GM cotton. However, there will still be moths thriving and laying eggs in the refuges. This will ensure that the numbers of non-resistant moths remain high, and that the environmental benefit of using Bt instead of more toxic synthetic insecticides is not threatened. The current Australian regulations prescribe that up to 90 per cent of a cotton crop can be planted with Bollgard®II on any one farm. This may be lifted to 100 per cent if other crops such as pigeon peas are planted as refuge crops to slow down the emergence of Bt resistance in cotton bollworms. A problem with insects - work sheet [PDF 29kb \| 2 pages] Butterflies and Bt - work sheet [PDF 30kb \| 2 pages] People do not agree about genetic modification of crops - work sheet [PDF 29kb \| 2 pages] Looking at media views - GM foods - work sheet [PDF 41kb \| 4 pages] Read about another method being used to disrupt insects from breeding, using pheromones (sex hormones): http://www.abc.net.au/science/news/stories/s199218.htm
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