ABSTRACT
The enormous task of controlling insect pests has exercised the minds of entomologists, farmers and advisors for more than 100 years. Even with all the sophisticated equipment, techniques and armoury of chemicals available, pests continue to reduce significantly the production of onions and related crops. There are several reasons for this: insecticide-resistant strains of pests, inefficient application of pesticides, inaccurate timing of treatments, as well as enhanced degradation of insecticides in the environment. Many insecticides are available for the control of aphids including organophosphorus compounds, carbamates, synthetic pyrethroids, and naturally occurring plant extracts such as derris, nicotine, and pyrethrum. Apart from the damage inflicted by feeding, the insects transmit Tomato Spotted Wilt virus. Adult hoverflies are attractive insects and familiar to most people as they are seen commonly wherever hedgerow or garden flowers are in bloom. These insects are controlled most easily when they are feeding on the flowers or foliage of crops.
