The occurrence dynamics and sex ratio of Diabrotica virgifera virgifera adults on different corn hybrids in western Romania

Abstract

Species which are the subject of study for this paper is an invasive insect for corn in Europe and thus in Romania. It is a coleopteran insect from genus Diabrotica, respectively Diabrotica virgifera virgifera Le Conte, known as "western corn rootworm". Adults’ species cause significant loss of production, especially during the appearance of silk and are active in the period from June to September. The objective of this study was to specify the occurrence dynamic of adults on different type of corn hybrids in order to establish the influence of these on development of insects. In addition, their sexual structure (sex-ratio) were specified. Studies were conducted in Timis county, locality Narau, in period of 2015- 2016. Corn hybrids which were made observations have belonged to different maturity groups (FAO), such as follows: DKC 3811 (extra-early type), SY Respect and SY Zephyr (semi-early type) P8523, SY Arioso, SY Irridium (early type) and DKC 5276 (semi-late type). Each plot consisted of 16 rows of corn /hybrid having 4 repetitions. The adults were captured with pheromone traps (Csalomon® type). The observations revealed significant differences between those seven groups of corn hybrids. The most numerous individuals were quantified in lots of semi-early hybrid and semi-late type with average values of 120.22 respectively 283.00/trap. During the flight of adults, the greatest number was registered early August. Females predominated in all versions of hybrids, regardless of group maturity. Their percentage in the total number of captures stood from 63.7 to 86.5. Large presence of adults in the experimental plots was somehow associated with the appearance and maintenance of silk and pollen.