| dc.description.abstract |
Field trails were conducted on three cotton hybrids (MECH 1, MECH 12, and RCH 2) grown
alone, and with a sorghum hybrid (CSH 1) as a neighbouring crop at two villages, Ravulapally
and Sankeypally, in Ranga Reddy district. Cotton hybrids grown neighbouring to sorghum had
significantly higher levels of egg parasitism by Trichogramma chilonis than in a monocrop. The
enhanced level of parasitism was due to a temporal shift in T.Chilonis population from sorghum
to cotton during the cropping season. Parasitism on sorghum increased slowly in relation to host
egg density at both the village sites and reached a peak of 70% and 60% by mid-September at
Ravulapally and Sankeypally respectively. The mean clutch size on sorghum was
2.06, with a maximum of parasitoids emerged per egg. Parasitism of Helicoverpa armigera eggs
on cotton by T.Chilonis reached a maximum of 68% in mid-October when grown as a
neighbouring crop to sorghum and 45% as a monocrop. The mean clutch size on cotton was 2.24,
with a maximum of 5 parasitoids emerged per egg. Among the three cotton hybrids tested,
parasitism was significantly higher on MECH 12 either grown alone or neighbouring to sorghum.
The results are discussed in terms of the dynamics of T.chilonis build up on sorghum and its
subsequent migration to cotton as management strategy to suppress the population carryover
H.armigera on cotton. |
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