The Damage Caused by Cowpea Weevil Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae) to Some Stored Pulses at Different Temperature and Humidity Levels

Abstract

P ulses constitute a main source of food and nutrition for people throughout the world. These are used on daily basis to fulfill the nutritional requirements as these are the major source of proteins, vitamins and minerals (Harrison et al., 2017). In Pakistan, pulses are cultivated only on 5% of the total agricultural land Abstract | Cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae), is one of the major stored grain insect pests of pulses throughout tropical and subtropical world. As pulses are important food source for many people, it is imperative to protect them from the infestation of cowpea weevil which causes considerable economic damage. Using no choice tests, this laboratory study investigated the effect of different temperature (20, 30 and 40°C) and humidity (50, 55 and 60%) regimes on the damage extent and weight loss caused by C. maculatus to some stored pulses i.e. green gram (Vigna radiata (L.) Wilczik), mash gram (Vigna mungo (L.) Hepper), cowpea (Vigna unguiculata (L.) Walp.) and brown colored chickpea (Cicer arietinum (L.). The results revealed that the infestation percentage was significantly (P≤0.05) variable among different host pulses. Moderate temperature (30°C) and high relative humidity (60%) were the most favorable for growth and multiplication of beetles because the maximum damage (97.8, 93.2, 59.0 and 27.7%) and weight loss (58.0, 57.8, 37.8 and 34.46%) was found on cowpea, green gram, chickpea and mash gram, respectively. While the lowest temperature (20°C) and humidity (55%) were found unfavorable for C. maculates as no significant damage and weight loss of pulses induced by C. maculates was observed at these conditions. High temperature (40ºC) and low humidity (50%) also reduced the infestation rate of C. maculatus. Furthermore, cowpea and green gram were the most susceptible pulses, while chickpea and mash gram were moderately resistant to C. maculates infestation. It is concluded based on overall study results that temperature and relative humidity have great influence on insect feeding behavior and reproduction, and could be usefully manipulated for stored grain management.