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The present paper presents details of the population dynamics of Diabrotica v. virgifera LeConte beetles on six maize varieties of three different maturity classes, i.e. early (FAO 190), medium-early (FAO 250) and mediumlate (FAO 280-300), grown in Central and Eastern Europe. The study was conducted in 2009/10 in the southeastern part of Poland. The D. virgifera beetles were captured using two types of trap: pheromone (PTs) and floral-baited (FTs). Significant differences in beetle counts were found between: (i) the first and second year of the study (higher in 2009 than in 2010); (ii) the varieties of maize and their different growth stages; (iii) early and medium-late varieties of maize. Initially, depending on the availability of maize silk and pollen, the most numerous D. virgifera beetles were found on the early varieties followed by the medium-late varieties. The study also revealed a significant difference in the performance of the two types of trap used to monitor the number of adults, particularly during the initial period when arrival rates were high. Pheromone traps were more effective in catching D. virgifera beetles, especially during the flowering stage of maize. Floral-baited traps were most effective at the end of the active growth of maize, when the preferred food of D. virgifera was unavailable.

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is an important pest of maize. The diet of the D. virgifera imago is rich in starch and other polysaccharides present in cereals such as maize. Therefore, knowledge about enzymes involved in digestion of such specific food of this pest seems to be important. The paper shows, for the first time, the activities of main glycolytic enzymes in the midgut of D. virgifera imago: endoglycosidases (α-amylase, cellulase, chitinase, licheninase, laminarinase); exoglycosidases (α- and β-glucosidases, α- and β-galactosidases) and disaccharidases (maltase, isomaltase, sucrase, trehalase, lactase, and cellobiase). Activities of α-amylase, α-glucosidase, and maltase were the highest among assayed endoglycosidases, exoglycosidases, and disaccharidases, respectively. This indicates that in the midgut of D. virgifera imago α-amylase, α-glucosidase and maltase are important enzymes in starch hydrolysis and products of its digestion. These results lead to conclusion that inhibition of most active glycolytic enzymes of D. virgifera imago may be another promising method for chemical control of this pest of maize.

Summary. The study was carried out in 2011-2012 in Sławików, southern Poland, on a maize crop monoculture. Diabrotica virgifera males were controlled with insecticides containing active ingredients: acetamiprid, dimethoate, indoxacarb, lambda-cyhalothrin, methaflumizon, thiacloprid and thiacloprid with deltamethrin. The optimum dates of beetle control were established by using PAL pheromone traps from Csalomon ® company. Plants were sprayed once or twice with the investigated insecticides during the peak of beetle population in the second half of August. All investigated active ingredients effectively reduced the pest population, usually within 7 days of plant spraying. The second chemical treatment effectively reduced the pest population for a further 7 days.

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