REDUCTION OF FEEDING BY THE VARIEGATED GRASSHOPPER, ZONOCERUS-VARIEGATUS, FOLLOWING INFECTION BY THE FUNGAL PATHOGEN, METARHIZIUM FLAVOVIRIDE

The effect of infection by the fungal entomopathogen, Metarhizium flav oviride, on feeding by the tropical grasshopper pest, Zonocerus varieg atus, was investigated infield-cage studies. A significant reduction i n feeding, as indicated by faecal production, was recorded 2-3 days af ter inoculation for a range of spore doses (10(4), 10(5) and 5 x 10(5) spores per insect). This was before any mortality was recorded due to infection. All infected individuals died by day 7. At this time, faec al production of the treated grasshoppers was equivalent to less than 2 days faecal production by grasshoppers untreated with spores. This r eduction in feeding (69, 71 and 74% total reduction by day 7 in the 10 (4), 10(5) and 5x10(5) noses respectively in comparison to controls) i s a substantial contribution to the overall effects of the slow acting pathogen. Furthermore, the rapid reduction in feeding indicated that this effect was not simply due to invasion of the host tissues by the pathogen or production of secondary metabolites. The possibility that reduction in feeding is associated with a behavioural response in whic h there is a trade-off between host defence and feeding during early s tages of infection is discussed.