Host Plant Preference of Plutella Xylostella (Linnaeus) (Lepidoptera: Plutellidae).

• Metspalu L., Grishakova M., Hiiesaar K., Jõgar K., Luik A., Mand M.
• Institute of Agricultural and Environmental Sciences, Estonian Agricultural University, 64 Kreutzwald St., 51014 Tartu, Estonia
• The Third International Conference onIPM Role in Integrated Crop management and Impacts on Environment and Agricultural Products. 26-29 November 2005, Giza, Egypt.

Abstract

The aim of the present study was to elucidate plants preferred by the Diamondback Moth (DBM), Plutella xylostella (Linnaeus) and the dynamics of their number on these plants. The experiments were carried out in the experimental garden of the Estonian Agricultural University in the summer of 2004. The experiment included white cabbage (Brassica oleracea var. capitata f. alba), rutabaga (B. napus var. napobrassica), collard (B. oleracea var. acephala), red cabbage (Brassica oleracea var. capitata f. rubra), and nasturtium (Tropaeolum majus L.). The criterion for choosing plants was that they all contained glucosinolates. Our experiments revealed that P. xylostella preferred rutabaga; 50% of larvae counted during the observation period were gathered from this plant. The next choices were white cabbage (22%), collard (18%), and red cabbage (10%). On nasturtium only few larvae of P. xylostella were found. The dynamics of the number was similar on rutabaga and collard throughout the observation period. Population trends were upwards early in the season, followed by a decrease in the number in mid-July and a new substantial increase in the first decade of August and a decline thereafter. During the observation period, the number of P. xylostella larvae on rutabaga was considerably higher than on collard. If, in the first part of the experiment, there occurred simultaneous increases and decreases in the number of P. xylostella in all the test variants, another increase in the number occurred on white cabbage at the end of August, when the numbers in the rest of the test variants showed a diminishing tendency. One of the reasons for the growth in the number of DBM larvae was the extensive immigration of P. xylostella in the first decade of August, i.e. in the third and fourth weeks of the observation. Another reason for the growth of the numbers was the emergence of a new generation of P. xylostella and the lasting warm and dry weather in this period.