Toxic and Repellent Characteristics of Some Plant Extracts used against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) Improve the Grain Quality of Stored Wheat

Abstract

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) is one of the key insect pests of stored grains. Due to export regulations and zero-tolerance for alive insects in trade commodities, synthetic pesticides are often used to eliminate pest infestation in consignments. Phosphine is currently one and the only acceptable chemical used in stored grains, but due to their overuse, stored grain pests become resistant to this fumigant. There is, therefore, a great need to find alternatives. In this study insecticidal efficacy of different plant extracts viz. Ginger (Zingiber officinale), Neem (Azadirachta indica), Clove (Syzygium aromaticum) and Tobacco (Nicotiana tabacum) was compared against T. castaneum infesting stored wheat. The results have suggested that mortality and repellency in T. castaneum increased as the dose rate of crude plant extracts and exposure interval increased. The maximum mortality (86.67%) was achieved with the highest dose of crude extract of Z. officinale (80mg per 7.5g wheat) at 10 days exposure interval. Similarly, the highest dose of Z. officinale extract (80ml) was responsible to cause 100% repellency at 2 hours exposure interval. Results also suggested that grain damage and grain weight loss due to the feeding of T. castaneum decreased as the dose rate of crude plant extracts increased, while an increasing trend was found in these parameters with the increase in exposure interval. The maximum grain damage and grain weight loss (10.27% and 0.346%, respectively) were recorded at the lowest dose of A. indica crude extract at 10 days exposure interval. The result of Feeding Deterrence Index suggested that it increased as the dose rate of crude plant extracts increased while a decreased trend was found with the increase in exposure interval. The maximum feeding deterrence index (86.48%) was recorded at the highest dose of Z. officinale crude extract at 5 days exposure interval. The results of this study supported the use of Z. officinale to reduce the population of T. castaneum by its toxic and repellent characteristics which ultimately improve the grain quality of stored wheat.

Repellent and Toxicological Impact of Aqueous Extracts of Leaves of Aegle Marmelos and Solanum Torvum Plants against Tribolium Castaneum (Herbst)

“…The main effects and interaction of various crude plant extracts and their doses are highly significant (P < 0.05) on percent mortality of T. castaneum at two different exposure intervals. The highest and lowest percent mortality (55.83±2.17% and 29.17±1.65%) was recorded in Z. officinale and A. indica treated wheat after 10 DEI, respectively, while no mortality was recorded in control treatment at both exposure intervals [15]. [16] observed that neem controlled up to 45.63% red flour beetle population after 168 h interval.…”