Effect of ethylene dibromide on the control of white grubs and its impact on cordyceps in soils of the TPC Sugarcane Estate Moshi, Tanzania
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Date
2001
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Sokoine University of Agriculture
Abstract
The populations of white grub pest of sugarcane, and that of Cordyceps, a naturally
occurring fungal pathogen of white grubs, were determined in the four fields of the
TPC sugarcane estate. The effects of ethylene dibromide (EDB), a commercially
used soil fiiniigant, was assessed in controlling the white grubs and its impact on
Cordyceps. Also the contribution of Cordyceps as the biocontrol agent of white grubs
was evaluated both in fields and in the laboratoiy. White grubs populations (in the
four fields) varied significanlly among four selected fields with grub densities
vaiying from 25 000 to 93 000 grubs per hectare. These variations were possibly due
to difierences in field location and soil types and also the number of crop ratoons.
Similarly the populations of Cordyceps differed significantly between fields ranging
(Yom 600 to 4000 Cordyceps clavac per hectare. The variations were attributed by
initial population of white grubs, and soil properties. Ethylene dibromide
significantly reduced the populations of both white grubs and Cordyceps in the
treated plots, with maximum impacts at the third week after EDB application. In the
laboratory, reduction in the population of white grubs by EDB was consistent to the
sliding scale of concentration. Although EDB reduced significantly the germination
of the Cordyceps clavac from infected cadavers, its effect on fungal growth and the
branching of genriinated clavae were not significant. Although estimated mortality of
white grubs caused by Cordyceps in stress rearing experiment was low (0.27-27%),
from field surveys the contribution of the fungus as a natural control agent of white
grubs was very high (54-94%). Studies on the effect of EDB on non target organisms
Description
Dissertation
Keywords
Sugarcane, Entomogenous fungi, Cochliotis melolonthoides