Early-maturing maize cultivars identified with index FAO 190-220 were more susceptible to damage caused by caterpillars of the European corn borer (Ostrinia nubilalis Hbn.) than medium-late maturing cultivars with index FAO 270-280. The conducted analysis of coefficients of correlation and regression demonstrated that the cultivars earliness had a significant effect on the number of caterpillars found on a plant, the percentage of damaged plants and grain yield. The increase in the FAO index was correlated with a significant decrease in the number of ECB caterpillars inside the plant (r = –0.87; p < 0.001), reduction in the number of damaged plants (r = –0.64; p < 0.001) and with an increase grain yield (r = 0.62; p < 0.001). The formulated regression equations demonstrated that the increase in the FAO index for maize cultivars by 100 units results in a decrease in the number of caterpillars in the plant, on average by 2.6 caterpillars, decrease in the number of damaged plants on average by 24.38%, and increase in the grain yield by 5.07 t·ha^-1.

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