Comparative efficacy of neem Azadirachta indica A. Juss, extracts against powder-post beetle, Lyctus africanus Lesne attacking seasoned wood in Egypt

Abstract: The present study deals with one of the most economic important wood borer; the powder-post beetle Lyctus africanus Lesne (Coleoptera: Lyctidae) which devastates wooden production in industry, forestry and agriculture including timber, bamboo and stored products on both local and global distribution scales. In Egypt, such as in many countries worldwide, control programs of this dangerous pest are restricted to the usage of chemical pesticides. Thus, alternative methods with lower risk of toxicity as neem Azadirachta indica A. Juss (Sapindales: Meliaceae) extracts are encouraged. Through this work, three crude extracts of neem seeds were used against this lyctid borer on seasoned wood cuttings. These extracts were generated from the crude by three solvents apart; petroleum ether, ethanol, and distilled water. A second experiment series for comparison using a commercial neem product “Nemazal” in addition to a reference of standard recommended insecticide “Cidial” were conducted. Experiments were designed to apply protective and remedial techniques against L. africanus attacks by recording the mortality and repellency rates as indicators under natural laboratory conditions. Each extract was tested in three concentrations; 6, 3, 1.5 gm/100 ml for each separate solvent whereas the commercial products were used with their recommended dosages (3 ml/l). Experiments revealed that petroleum ether neem extract in a concentration of 6 gm/100 ml resulted in the highest significant average mortality and repellency rates with L. africanus reached 81.7 and 76.3% at P > 0.05, respectively whereas distilled water neem extracts showed the lowest infestation levels with this lyctid borer at P > 0.05 recording a least average mortality rate of 17.4% and 21.8% repellency rate. These gained results were confirmed by lethal times and toxicity lines which were estimated by the log-time probit model. On the other hand, the commercial products of Nemazal and Cidial resulted in significant higher mortality and repellency levels at P > 0.05 compared with those of the crude neem extracts. Nemazal and Cidial titres scored 90.3 and 97.1% average mortality rates meanwhile the average figures of repellency levels were 87.3 and 93.6%, respectively.