Some biological and morphological differences between gall and vagrant forms of Phytoptus avellanae Nal. (Acari: Phytoptidae)

Abstract

The big bud mite (Phytoptus avellanae Nal.), one of the most important pests of hazelnut (Corylus spp., Corylaceae), has two forms - a gall form and a vagrant form. The gall form lives inside big buds. It has a simple life cycle and a single nymphal type. The vagrant form lives on vegetative and generative organs and inside the big buds. It has a different and rather complex life cycle and two nymphal types. In this study the gall and vagrant forms of P. avellanae were examined biologically and morphologically. Biological studies were performed at 20 ± 1°C and 70% R.H. in the laboratory and mites were reared on leaf discs and the duration of the different stages was determined. The gall form did not survive on the leaf disc after the first instar nymphal stage, whereas the vagrant form survived on the leaf disc. The latter had two nymphal types, one with the normal two nymphal stages, but the other with three nymphal stages. This condition is unknown in any other eriophyoid. Morphological comparisons showed that the gall and vagrant forms were significantly different from each other in size, shape and color.