Geneticists trick cabbage pest on to tobacco
By Farmbiz | Wed 15 Aug, 2012

A scientist from the University of Copenhagen has made a breakthrough in deceiving the voracious diamond back moth - responsible for over 60 per cent of yield losses in cabbages and most common in Eastern and Southern Africa – at a time when Europe has locked out Kenyan vegetables contaminated by the main pesticide used to fight the moth. According to Morten Emil Møldrup, the researcher, the pest is turned off by components in tobacco plants and this could be the best remedy for farmers planting cabbages. "We have discovered a way to cheat the diamond-back moths to lay their eggs on tobacco plants.

As their larvae cannot survive on tobacco leaves they will soon starve to death. In the mean time, you can cultivate your cabbage at peace,"he said while launching the solution.. Møldrup has exhaustively studied the defence compounds of the cabbage family, which are toxic to cabbage pests in general, but which actually attract the diamond-back moth. The odour of the cabbage defense compounds attracts the pregnant diamond-back moths, signaling .an ideal place to lay their eggs to ensure their larvae plenty of food without competition from others. After having established how a cabbage plants produce these defence compounds, Morten and his colleagues successfully transferred the genes responsible for the production of the defence compounds from cabbage into tobacco plants. "Our experiments show that it is indeed possible to fool the diamond-back moth to lay its eggs on tobacco plants.

This is fantastic because the larvae are a major problem all over the world. The goal is to avoid diamond-back moths' larvae in cabbage by cultivating tobacco and cabbage plants together. In this way a lot of money is to be saved, and in addition the growers do not need to use the big amounts of pesticides commonly used today. In this way one may say that our discovery is also of benefit to nature," said Møldrup. Without protection, the damage to cabbages from the moth is often extensive. Newly hatched caterpillars feed inside the leaf tissue, with caterpillars and pupae are found on damaged leaves. Older caterpillars feed around the growing bud of young plants and on stems, deforming the plant. In addition, marketable parts become contaminated with excrement, which makes the produce unsaleable. Kenya currently spends close to Sh5bn a year on pesticides, much of it to battle insects.

Cabbage farmers buffeted by the back moth have turned to the popular dimethoate pesticide. However, this has seen Kenyan produce rejected by European Union, which has banned vegetables from Kenya using this pesticide, cited the high chemical presence in the produce.

Written by Bob Koigi for African Laughter

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