Screening and Validation of Botanical Materials For the Control of Some Store Pest in Sudan

Abstract

Laboratory studies were made to explore and screen different plant species to find out the most promising and effective ones as protectant agents against two of the common store pest in Sudan, the khapra beetle Trogoderma granarium and the cowpea beetle Callosobruchus maculatus. 25 plant species were collected from Central, North and West of Sudan. The selection of the species was based on indigenous experiences, folk medicine, traditions and people observations. A series of experiments were made against the two pests in a Randomized Complete Design with three replicates. In the first set of experiments, the screening tests were carried out for all plants species. The extraction was made by ethanol alcohol and some by water. 10 and 90% concentrations of crude extract of each plant were prepared and tested against the two store pests. Observations were lasted for 70 days for glass jars that contained C. maculatus and 120 for Petri dishes that contained T. granarium. The results of these tests revealed that all plants extracts except the ethanol extract of Cassia senna fruits at 10% showed varying degrees of efficacy against the two store pests as feeding repellent, development inhibitor and oviposition deterrent. Also It was found that among the tested botanical species that Catharanthus roseus, Cassia senna, Aristolochia bracteata and Eucalyptus camaladulensis leaves ethanolic extracts completely prevented the female of callosobruchus maculatus from egg laying on cowpea seeds that had been dipped in 10 and 90% of the diluted extracts of the botanical materials mentioned above. When Trogoderma granarium larvae were introduced into Petri dishes that contained sorghum which had been dipped in the different concentrations of the botanical extracts showed that at 10% Cassia senna inhibited 70% of the larvae to develop into pupal stage and 55.53 % of the pupae failed to develop into the adult stage. Eucalyptus camaldulensis inhibited 43.33% of the larvae to develop into iii pupal stage and 94.12% of the pupae succeed to develop into the adult stage. Catharanthus roseus inhibited 73.33% of the larvae to develop into pupal stage and 37.51% of the pupae failed to develop into the adult stage. Aristolochia bracteata inhibited 86.66% of the larvae to develop into pupal stage and 50.03% of the pupae failed to develop into the adult stage. In the second set of experiments jute sacks were impregnated with ethanol extracts of Cassia senna, Eucalyptus camaldulensis, Catharanthus roseus and Aristolochia bracteata (leaves) at 10, 20 and 30% and filled with 500 grams of sorghum grains and stored in store room infested with T. granarium larvae. At regular intervals of 20, 40, 60, 80, 100 and 120 days a samples of 100 grains were chosen randomly to determine the percentage of weight loss each jute sacks. The results of these experiments showed that all the concentrations of the four botanical extracts reduced significantly the percentage of weight loss of the stored sorghum seeds when the khapra beetle T. granarium was the dominating pest in the store. From the recent study it is concluded that most plant species posses defense mechanisms to protect them from being attacked by insects. The chemical compounds comprise the most important constituent of these mechanisms. iv