Abstract:
Various experiments were carried out under laboratory conditions in the period from (March-June 2004) to investigate the efficacy of ushar Calotropis procera Ait leaves as a natural products on the African Bollworm Helicoverpa armigera (Hub.)
The study highlighted the effect of ushar leaves extracts (water and organic-extracts) on the feeding rate of the larvae and its growth rate as well as the mortality and deformation of the 5th -instar larvae of the ABW.
Results of the water extracts of the ushar leaves on the larvae of the ABW was effective and caused significant antifeedant effect compared to control. The effect was dose related as it increased with the increase in the dose, it ranges from 19.8%-52.5%, 21.4%-49.5% and 59.5%-80.8% to 2.5%, 5% and 10% in 24-48 hrs respectively. i.e the conc.10% caused the highest antifeedant followed by 5% and 2.5%. Also results of water extracts of ushar leaves showed clear reduction in the larval weight compared to control and ranged between 40%-29.5%, 45%-26% and 45%-36.9% for 24-48hrs to 2.5%, 5% and 10% respectively.
Evaluation of the mortality of the test insect (5th instar larvae) caused by the water extract of ushar leaves and standard pesticide (Avaunt) resulted in 100% mortality of the larvae caused by the standard pesticide compared to less than 40% mortality for usher leave extract after 48 hrs. However after 24hrs no mortality was recorded by the extract.
Results of organic extract of ushar leaves against ABW larvae showed significant effect (antifeedant) compared to the control .The results of the effect were dose related as it ranged between 33.6%-28.3%, 34.5-30.7% and 83.2%-95% for the conc. 2.5%, 5% and 10% in 24-48 hrs respectively. ie 10% concentration found to cause the highest antifeedant to the larvae followed by 5% and 2.5% e respectively. Also results of organic extract of ushar leaves showed clear great reduction in the larvae weight especially after 48 hrs and the weight ranged from 52.4%-57.9%, 38%-55.2% and 57.1%-63.2% for the 3conc.respectively.
Evaluation of the organic extract of the ushar leaves and the standard pesticide (Avaunt) on the ABW larvae showed that the standard pesticide caused 100% mortality compared to organic extracts which caused lower than 60% mortality after 48 hrs. However the organic extract caused less death to the larvae after 24 hrs. Moreover the organic extract prolonged the larvae age from three to four days compared to control. Deformation of the adult was noticed in some cases (lost part of wings).
