Effect of azadirachtin applied as seed dressing on the larval density of and root injury caused by the western corn rootworm/Diabrotica virgifera virgifera

The western corn rootworm ( Diabrotica virgifera virgifera LeConte) is one of the most important pests of maize in Hungary. As both larvae and imagoes are capable of causing major economic losses, their control in continuous maize cropping systems is essential. The control of larvae is costly and the related use of large doses of soil disinfectants places an increased burden on the environment. In recent years, several chemical products used as soil insecticides and seed dressings have been phased out, thus increasing the value of environmentally friendly biological products that provide effective protection against the pest. The active ingredient azadirachtin, the extract of the seeds of Azadirachta indica is one of such biological agents. In our experiments, we studied the efficacy of two azadirachtin products, Neemazal T/S (1% azadirachtin; 10 g/l) and Neemazal F (5% azadirachtin; 50 g/l) used as seed dressing against western corn rootworm larvae. The products were used in different concentrations (10–150%) in different regions and on various soil-types in Hungary. The active ingredient could effectively control the pest in its larval stage. Treatments with concentrations exceeding 50% were effective in all the replications.