The Preference of Thrips tabaci for Allium cepa , Allium fistulosum , and Allium roylei

Thrips tabaci Lind. (Thysanoptera: Thripidae) is a key pest of onions worldwide. It causes both direct and indirect damage to onion crops, resulting in high yield losses. Today, the Integrated System of Production and Plant Protection requires onion growers to use onion- thrips-resistant cultivars. It has become apparent that the improvement of existing onion cultivars may not be a sufficient, so it is necessary to search for desirable plant traits related to disease and pest resistance among existing and wild cultivars. For this purpose, we conducted bioassays on the possible preference of T. tabaci for three different cultivars of Allium cepa L., namely, Alibaba, Bila, Tęcza, one cultivar Kroll of Welsh onion, Allium fistulosum L., and the wild species Allium roylei Stearn. The settling preference and the oviposition rate of female onion thrips were evaluated using choice and no-choice laboratory tests, respectively. During the bioassay, on leaf sections of the A. roylei species, a significantly higher number of T. tabaci females was recorded compared to the cv. Tęcza of the A. cepa species and the cv. Kroll of the A. fistulosum species in each observation period. Significantly more thrips settled on cv. Kroll compared to Alibaba and Bila. Regarding the results obtained on A. cepa , significantly fewer females were found on cv. Bila compared to cv. Tęcza. Opposite results were observed in a combination of cvs. Tęcza–Alibaba, where significantly more insects settled on the leaves of cv. Alibaba. Statistically significant differences between cultivars/species were found in the number of hatched larvae on the leaves of the tested cultivars/species of onion. The lowest number of larvae hatched from eggs laid on A. roylei , as compared to A. fistulosum and the cultivars of A. cepa, except for Bila.