Evaluation of the biological efficacy of milkweed plant, (alotropis gigantean) R.Br. against important storage pests
The investigation was carried out in the Department of Entomology,Faculty of Agriculture, Annamalai University, Tamil Nadu during the year 2002-2004. The following were the important findings from the studies.
Among the five plant part powders of C.gigantea viz., leaf, flower, stem, root and whole plant powder, tested on the insects viz., C.maculates, S.oryzae and T. castaneum. C.gigantea whole plant powder was found to be very effective in causing 47.08, 45.83 and 41.67 per mortality after 7,9 and 9 days of treatment. Among dosage, 10g of C.gigantea whole plant powder was found to be best and recorded 85.0, 85.0 and 80.0 per cent mortality after 7, 9 and 9 days of treatment.
Regarding seed damage, C.gigantea whole plant powder gave good protection to cowpea, maize and groundnut seeds upto 90 days after treatment. With respect to dosage, 10g of C.gigantea whole plant powder provides minimum damage to the above said seeds.
Weight loss was found to be minimum in C.gigantea whole plant powder treatment after 90 days. Among the various doses, 10 g of C.gigantea whole plant powder imparts minimum weight loss. C.gigantea plant part powder pastes gave good protection to maize, cowpea and groundnut seeds when applied over storage structures like gunnybag up to 30 days after application. After 30 days, per cent damage of seeds by test insects increased progressively with the increase in time which indicates the loss in repellant properties of C.gigantea plant parts paste with the passage of time. C.gigantea whole plant powder paste provides maximum protection for the test insects when compared to other plant parts and control.
The germination tests conducted at the end of the experiment reveals that there was no impairment of germination of cowpea, maize and groundnut seeds due to treatment effect in their respective doses. Soxhlet extracts of C.gigantea plant parts was found to possess repellent properties. All the test insects avoided feeding of cowpea, maize and groundnut seeds sprayed with 5 per cent concentration of whole plant extract. On the basis of LC50 values C.gigantea whole plant extract (soxhlet) was found to be most toxic to test insects such as C.maculates, T. castaneum and S. oryzae followed by leaf, flower, stem and root extracts. Biochemical constituents namely protein, sugar and lipids got declined significantly in the C.gigantea plant parts powder treated test insects. Whole plant powder treated test insects shows sharp reduction in bio-chemical constituents compared to other doses and control.
Agriculture Sprayers and Dusters by ASPEE Group Of Companies, India. www.aspee.com
This article is written by Shri. R.Arulprakash of Annamalai University, Tamil Nadu on behalf of ASPEE Agriculture Research and Development Foundation. ASPEE Group of Companies is the leading manufacturer and exporter of Agriculture Sprayers and Dusters
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