Franja BACA1, Jovo STOJCIC2,
Vojsilav TRKULJA2, Slavko RADANOVIC3, Dragisa LOPANDIC1,
Dragica ZIVANOVIC3, Dusko PARAVAC4
1 Maize Research Institute,
Zemun Polje, Belgrade-Zemun, Yugoslavia
2 Institute of Agriculture,
Banja Luka, Republic of Srpska
3 Agricultural Station, Bijeljina,
Republic of Srpska
4 Agricultural Station, Doboj,
Republic of Srpska
Pheromone traps "Csalomon" have monitored the territorial distribution of Western Corn Rootworm (WCR) over the regions of Republic of Srpska (RS) and abundance of beetles since 1998. The survey encompassed 50 locations in 24 communities.
A pheromone trap was set per each observed location. Imago flights were monitored during two months, i.e. 56 to 61 days depending on location. Traps were set up, as a role in large areas under maize on July 18 and 20. The first trap survey was done on July 30 and August 3 and 4 (traps set on July 18 and 20). The second trap survey and their replacement were done on August 15, 17 and 18. The succeeding two surveys were performed on August 30 and 31 and September 14 and 15.
Considering the beginning of the flight of WCR registered in Belgrade - Zemun Polje in 2000, it started one month earlier (third decade of June), monitoring in RS cover about 80% period of WCR eclosion. Comparing the flight dynamics, the data registered in 2000 in RS cover about 62% of the total WCR population. Out of 1972 beetles registered, 1247 in 11 location, or 133,4 per location were found within the first 50-km from Yugoslavian border. At the distance of 51 - 100 km to the west it was registered 234 beetles in 4 location or 58,5 per location. At 101 - 150 km it was registered 480 beetles in 7 location or 68.6 per location. The beetles were trapped in 31 of 50 locations (62.0%). The insect abundance in 1999 was 1.8 times as great as in 2000. The decrease from 3532 to 1972 was as a consequence of extremely dry and hot summer. Weather conditions differ particularly in reduced amount, almost total absence of precipitation during second half of July and the whole August.
Precipitation during the two months period (July 10 to September 10) amounted to 28.7 mm and 90.6 mm in the Eastern, i.e. Western part of RS, respectively. The greatest abundance and mass migration of WCR were recorded during the period with some rain. In the second and third decade of July 1214 or 61.6% WCR beetles were trapped. In August 357 in the first and 342 beetles i.e. 18.1% and 17.3% in the second half of months, respectively. During 15 days of September 59 WCR, or only 3.0% of the total number of 1972 was registered. Precipitation amount in August was 5.0 mm in Bijeljina, Eastern part, and 13.2 mm in Banja Luka, Western part of RS. According to the obtained data in 2000 the total insect abundance decreased almost two times due to the environmental conditions. Spreading to the Western part of (RS) continued. Percentage of WCR trapped according to the average number of beetles per location/distance was 22.4%, 26.3%, 0.2%, and 14.9%, 15.0% and 0.1% in 2000 and 1999, respectively.