Larval and adult food preferences of the poinsettia thrips Echinothrips americanus Morgan, 1913 (Thysanoptera: Thripidae)

Numerous occurrence of Echinothrips americanus Morgan, 1913, a relatively newly established pest in European greenhouses, on a wide spectrum of cultivated plants throughout Slovakia has encouraged us to present current data on its food ecology. Analysing 1,650 plant species, the poinsettia thrips was found on 106 species (48 families) including 19 showing sporadic, 75 moderate and 17 high infestation. Larvae were detected on 25 plant taxa from 13 families, most of them being new hosts. Mature clusters of Acalypha hispida, showing moderate to high infestation level and carrying both larvae and adults, were selected for more detailed statistical evaluation. Preference of adults for upper and lower leaf surface tends to be without statistical significance, the larvae on the contrary were strongly related to the lower side (Pearson's chi(2) = 13.3552, P = 0.0013). Concerning the age, increased occurrence was apparent on younger leaves for both larvae and adults. For larvae the nonparametric test gives the statistical difference between three age categories of leaves with the following values: Kruskal-Wallis chi(2) = 6.6384, P = 0.03618. The statistical significance of age seems to be more crucial for younger shoots, as proved by the statistics for both larvae (Kruskal-Wallis chi(2) = 8.4852, P = 0.0144) and adults (Kruskal-Wallis chi(2) = 7.1049, P = 0.0287). Different food preferences of larvae and adults may result in specific approach when applying an effective biological or chemical control. Narrower tolerance of larvae could make them more manageable target in plant protection instead of efforts to control the whole thrips population.