Facing rough weather

A STUDY conducted by British researchers concluded that with rising mercury levels, temperate farmlands face a potential threat in the form of insecticide-resistant aphids (insects of the Homopteran order, which live on plant juices). The aphid population had till date been kept under check due to winter frost, but when the average winter temperatures rise, their population receives a boost (New Scientist, Vol 148, No 2009/2010).

The peach potato aphid (Myzus persicae) which reproduces asexually, except when on a peach tree, is an agricultural pest feeding mainly on potatoes, oil-seed rape and sugar beet plants. These pests feed on the sap of the plant and spread viruses which can wipe out entire fields. These pests had been controlled till date, but researchers now claim that insecticide -resistant clones have developed. These 'super-aphids', are resistant to organophosphates, carbamates and pyrethoid groups of agricultural insecticides.

The defence mechanism of the super-aphids is balanced by their inability to survive in the cold. Stephen Foster and his colleagues at the Rothamstead Experimental Station in Hertfordshire, UK, have conducted experiments on insecticide - resistant aphids to show that they are more likely to die during a cold spell. Clones with varying degrees of resistance were introduced into experimental plots of oil-seed rape. It was found that the most resistant aphids perished in severe wintry conditions when temperatures dipped below 2