In the climatic conditions of Lower Silesia, Poland the European corn borer lays eggs on sweet corn during 3-5 week period between the 3rd decade of June and the 2nd decade ofAugust. The eggs are laid on leaves L1 to LS ofmain and lateral stems of the plants. Caterpillars start to hatch at the beginning ofJuly, but in 1998-2000 a massive hatching was observed only in the 2nd and in the 3rd decade ofJuly, whereas in 2001 - in the 3rd decade of this month and in the l st decade of August. Larvae are capable of migrating between plant rows on the soil surface, which was observed in 1998-2000 from the end ofJuly till the end of October. Most caterpillars migrated in the 2nd and in the 3rd decade of August and in the first days of September. The cob damage by caterpillars ranged between 31 and 46%. Delayed harvest caused a substantial increase in damage.

Research was carried out in 2001-2002, in the Plant Breeding Station of Mikulice near Przeworsk. The occurrence of European corn borer (Ostrinia nubilalis Hbn.) on corn, as well as the effects of its chemical control were assessed. It was found out that in 2001, caterpillars damaged 40.5% of plants, while in 2002 - 99.3% of plants. As a result of double lambda cyhalothrin application (Karate 025 EC), high pest reduction was achieved: 91.4% in 2001 and 88.9% in 2002. Corn yields increased by 1.8 t/ha in 2001 and 4.3 r/ha in 2002 in comparison with yields in untreated fields.

The trials conducted with selected chemical and biological insecticides in 1998-2000 showed the highest effectiveness of Karate Zeon 100 CS (lambda-cyhalotrine) in European corn borer (ECB) larvae control in sweet corn. The efficacy of biological insecticides containing Bacillus thuringiensis ssp. kurstaki: Biobit 3.2 WP and Lepinox WDG was very variable between the years. Reasons for insufficient efficacy of these products are discussed. The most appropriate time for the application of a chemical insecticide against ECB larvae are plant developmental stages since the beginning of pollen shedding to full blooming (63–67 BBCH scale). The efficacy of treatment was the highest at that time.