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Post-harvest bruchid
richness and residual activity of pirimiphos-methyl on
Callosobruchus maculatus F. infested pigeon pea (Cajanus
cajan L. Millsp.) in storage
Dasbak, M.A., Echezona, B.C.* and Asiegbu, J. E.
Department
of Crop Science, University of Nigeria, Nsukka, Nigeria.
*Corresponding author. E-mail:
chezbon2001@yahoo.co.uk.
Accepted
23 October, 2008 |
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The residual activity of actellic dust (pirimiphos-methyl) on
Callosobruchus maculatus F. and the field-to-store
bruchid richness of pigeon pea grains were studied at Nsukka,
Nigeria. Results of the bruchid richness study showed that
there was no emergence or infestation of bruchids from both
the treated and untreated grains six months post harvest.
Assessment of the residual activity of pirimiphos-methyl on
C. maculatus six months post treatment revealed that
although C. maculatus could not be controlled
completely, its developmental potential and extent of grain
damage were drastically reduced, which showed the continued
activity of the pesticide six months post treatment.
Incremental doses of actellic dust produced residual effects
which significantly (P<0.05) reduced the number of F1-emergence,
adult bruchid emergence, total mortality count, grain weight
loss and grain damage. Half-dose of pirimiphos methyl was
not as effective as its full dose in controlling C.
maculatus infestations under comparable residual level
and grain post harvest storage period. Pigeon pea varieties
differed significantly (P<0.05) in their grain
susceptibilities to C. maculatus as assessed by the
quantity of damaged grains, grain weight loss, mean
developmental days of insects (MDD) and adult emergence of
the pest; the characteristics which allowed the varieties be
classified as moderately resistant to the bruchid attack.
Residual effect of pirimiphos-methyl when combined with the
varieties did not result in any significant effect on C.
maculatus or grain damage by them.
Key
words:
Field-to-store pest, pirimiphos-methyl, bruchid richness,
residual activity, pigeon pea. |
