The study was carried out on plants infested by the European corn borer (ECB) (Ostrinia nubilalis Hbn.): fodder maize Wilga cultivar, sweet maize Candle cultivar, and sweet sorghum Sucrosorgo 506 cultivar. Observations on the types of plant damage caused by caterpillars were carried out in 2008-2010 in south-eastern Poland, in Terliczka, near Rzeszów (50°06’ N; 22°05’ E). Damages caused by O. nubilalis varied according to plant species and weather conditions. The greatest harmfulness of ECB caterpillars during the analyzed three-year period was recorded in sweet maize, of which from 89.5 to 93.0% of plants, and from 53.5 to 76.0% of cobs were damaged. Lower harmfulness of the European corn borer was recorded in fodder maize, of which from 58.0 to 80.2% of plants and from 29.5 to 42.2% of cobs were damaged by caterpillars. Sorghum was the least infested and damaged species by O. nubilalis, with from 3.0 to 16.2% of its plants being damaged by caterpillars. Broken stems were the most common form of damage found in the analyzed plants. The greatest damage rate was found in sweet maize (34.7 to 66.7%), followed by fodder maize (29.7 to 52.5%), and a very low damage rate was found for sorghum (0.7 to 1.5%). The type of damage to maize and sorghum plants caused by ECB caterpillars largely depended on the number of pests. The highest number of caterpillars was found on sweet maize plants, while sorghum plants were infested only by single individuals.

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