THE RESULTS OF INVESTIGATIONS OF WCR (Diabrotica virgifera virgifera Le Conte) ATTACK ON THE AREA OF GUNJA IN 1999

Western Corn Rootworm (WCR) (Diabrotica virgifera virgifera Le Conte) is very important corn pest. The pest was spread in Croatia from 1995 to 1999 on 12,750 km2. In the area of Stara Gunja, hybrid OSSK 444 was sown in order to investigate the possibilities of controls WCR with below ground insecticides - Counter G-5, Dursban G-7,5 and Dotan G-5. With checking root for larvae and cocoons 0.02 larvae was estimated on treated plots and 0.05 larvae on untreated plots. The number of cocoons was 0.12 in treated, and 0.25 on untreated plots. The number of imagoes on silk was 0.05–0.10 per plant. The imagoes of the WCR were caught with Pheromone and Multigard traps from the third decade of June until the first decade of October. On the traps settled on the treated plot (336 m2), 1,376 imagoes were caught, compared to untreated plot (112 m2) where 431 imagoes were caught. The yield of corn was 8.03 t/ha in treatment with Dotan, 8.44 t/ha in treatment with Dursban, and 8.72 t/ha in treatment with Counter, while the lowest 7.98 t/ha was in control plot was. Low number of caught imagoes per plant, shows that, for now, the implementation of chemical preparations wasn’t justified. This kind of investigations should be continuing in the future, and the checking of corn roots must be done earlier in order to determine correct number of larvae on roots and the root damages.