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This study investigated the effects of a strain of the fungus Lecanicillium lecanii (Zimm.) Zare and Gams (Hypocreales: Ascomycota) on the aphid Schizaphis graminum (Rondani) (Hemiptera: Aphididae). The fungus was administered to fourth instar nymphs and to alate and apterous adult morphs as a ground rice-kernel formulation. This study showed that L. lecanii formulation affected the survival of the aphids and interacted differently with the studied morphs, the Lethal Time values being lower for alate compared to apterous morphs and nymphs. The treatment also caused a significant reduction in the fecundity of the three treated aphid groups. Histological analysis revealed that the hyphae invaded the host hemocoel of a limited number of alate and apterous morphs: the fungus only entered through the spiracles. Scanning Electron Microscope observations revealed that L. lecanii adhered to the body surface of both adults and nymphs without differentiation. In conclusion, the present study suggests that this strain might be a good candidate for a programme of biological control of S. graminum and other aphid species.

Chromatin organization in the holocentric chromosomes of the aphid Schizaphis gruminum has been investigated at a cytological level after C-banding, NOR, Giemsa, DAPI and CMA, staining. C-banding technique showed the presence of numerous C bands on the two X chromosomes both in telomeric and intercalary regions, whereas autosomes show a small number of heterochromatic bands. Contrary to the results with other aphid species, in S. gruminum the C-banding pattern is peculiar to each chromosome pair, thus allowing the identification of homologues and the reliable reconstruction of a karyotype. These cytogenetic data could be useful for the identification of chromosomal rearrangement eventually occurred between different S. gruminum biotypes. Moreover, silver staining and fluorescent in situ hybridization (FISH) with a 28s rDNA probe localized rDNA genes on one telomere of each X chromosome; these are the only brightly fluorescent C-positive regions revealed after CMA, staining, whereas all other heterochromatic bands are DAPI positive. Giun Curlo Manicurdi, Dipartimento di Biologiu Animule, Vide Berengario 14, 41 100 Modena, Italy. E-mail: mani

Fungal strains belonging to the genera Fusarium, Paecilomyces and Trichoderma were tested in vitro in order to study their effects against Schizaphis graminum, one of the major pests of cereal crops around the world. Biological assays were performed using a solid formulation that was obtained from fungal cultures grown on rice and then finely ground ( 60%) within 10 minutes after application. As F. larvarum ITEM 2139 did not produce metabolites toxic to mammals, it might be a good candidate as a biocontrol agent of S. graminum in the field.