Mb. Thomas et al., REDUCTION OF FEEDING BY THE VARIEGATED GRASSHOPPER, ZONOCERUS-VARIEGATUS, FOLLOWING INFECTION BY THE FUNGAL PATHOGEN, METARHIZIUM FLAVOVIRIDE, Biocontrol science and technology, 7(3), 1997, pp. 327-334
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.