THE HARMFULNESS OF WESTERN CORN ROOTWORM (Diabrotica virgifera virgifera LeConte) UNDER THE CONDITIONS OF PERENNIAL REPEATED MAIZE SOWING

The western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) is one of the most important maize pests. The research was conducted in Gorjani during 2020, with the aim of determining how repeated maize sowing affects the occurrence and abundance of WCR, the level of root damage, plant tolerance, and yield. The OS 378 maize hybrid was sown in two treatments (repeated sowing and monoculture for three years). A damage caused by larval feeding was determined by the root damage, and plant tolerance was determined by the root size and secondary root regrowth. The imago flight was monitored by the yellow sticky boards on both investigated plots. The average number of adults per day and trap in repeated sowing amounted to 1.07 and to 0.99 in the three-year monoculture, respectively. The root damage was rated by an average of 0.75 (repeated sowing) and 1.25 (three-year monoculture). The root size was rated by an average of 2.50 (repeated sowing) and 3.70 (three-year monoculture), and the average increase in secondary root was averaged the values of 3.20 (repeated sowing) and 3.05 (three-year monoculture), respectively. The higher root rates in maize cultivation in a three-year monoculture indicate that an additional monoculture year may cause a greater damage. The maize yield in a repeated sowing was higher by 2.53 t/ha when compared to the three-year monoculture. It is recommended to avoid further maize sowing on these plots and to respect the perennial crop rotation.