1998 Results of Monitoring Diabrotica virgifera virgifera LeConte in Croatia

Abstract

In 1998, 90 monitors were placing traps on 136 sites in Croatia. One pheromone and one Multigard trap was placed at each site. Trapping began 25 June. Both trap types were replaced with new traps at 25 days intervals. Sixty-two (45.6%) sites were located in previously infested regions, 37 (27%) along the line of spread in 1997, and 37 (27%) within uninfested areas. Ten permanent sites were established. At 4 these sites after a WCR beetle was captured, a ring with 12 additional traps was established. The fast catch was recorded the day following initial trap exposure, i.e. 26 June. This fact shows the need of an even earlier start of the monitoring action. The last catch was recorded on 5 October. Altogether 5.933 beetles were captured. Approximately 95% of all beetles captured occurred on pheromone traps whereas, approximately 5% of the beetles captured occurred on Multigard traps. The highest capture rate was recorded between July 10 and 31 August. The increase factor of the population density in 1998 was 2.8. In 1998, WCR spread west (37 km) to the village Gornji Varos 150 km from the Yugoslav border and 150 km from the Slovenia border. This spread occurred along the Sava river, which is the shortest pathway to western Europe. In the middle part of north Croatia, WCR spread only 8 km to the west spaces. In the northern part of Croatia, along the Croatia-Hungary border no further spread was recorded. Altogether an area of almost 10,000 km 2 is infested with WCR in which approximately 140,000 ha of corn is grown.