Characteristics of a population of western corn rootworm (Diabrotica virgifera virgifera LeConte) in continuous maize

The characteristics of a population of western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, were studied in a continuous maize cropping system in Szeged, Hungary. In autumn, the estimated egg population density of WCR ranged from about 137,500 to 387,500 eggs per ha. The distribution of the egg population within die maizefield was very heterogeneous, making reliable estimation difficult. On the basis of inverse binomial samples of presence or absence, the estimated larval population density was 6,600 to 54,000 larvae per ha (seeding rate: 60,000 seed/ha). After a 3-year period the larval injury (Hills and Peters 1-6 root rating scale) reached ratings of 3-4 where several roots were eaten off or one node of the roots was completely destroyed. From the literature, it is known that root ratings of 3 to 4 can contribute to economic losses in hybrids. WCR adults emerged from the last week of June to the first week of September. The mean density of WCR adults ranged from 0.5 to 5.17 adults per 0.5 m(2) Soil surface per week. Maximum averages of adult catches were 3 and 67 adults per Pherocon AM trap per week in 2000 and 200 1, respectively. In 200 1, the WCR population reached economically damaging levels in the continuous maizefield (40 adults/Pherocon AM trap/week) as established for maize in the USA. Field data collected in 2002 through larval sampling, and maize root damage rating and yield measurements should give the information necessary for proper conclusions to be drawn. Egg laying by WCR females occurred in the period of July through August. In a laboratory trial, the pre-oviposition period ranged from 5 to 31 days. Additionally, a mean fecundity of 226 (+/-133.4) eggs per female was recorded in 2001.