Evaluation of biological traits, morphometric characteristics, feeding preferences, and infestation potential of pulse beetle (Callosobruchus maculatus fab.) on various pulse crops

Abstract

The pulse beetle, Callosobruchus maculatus (Fab.), is a major invasive pest of stored legume seeds in Pakistan. This study aimed to investigate the biology, morphometrics, feeding potential, and seed damage caused by the beetle on different pulses under laboratory conditions in 2023. The insect laid the highest number of eggs on Vigna unguiculata (8.53±0.95), followed by V. radiata (7.55±0.78), V. mungo (6.66±0.75), Phaseolus vulgaris (6.61±0.63), and Cicer arietinum (5.02±0.37). The mean egg incubation periods were recorded as follows: black gram (5.60±0.54), cowpeas (5.50±0.21), chickpea (4.00±0.72), green gram (4.00±0.37), and kidney bean (0.00±0.00) days, respectively. The egg hatching rates were (39.30%) green gram, (36.10%) cowpeas, (19.50%) chickpea, (5.10%) black gram, and (0.00%) for kidney beans. Notably, while (23.30%) of the eggs were laid on kidney beans, none hatched, and no adults emerged due to the smooth surface of the seed coat. The larvae and pupae development period lasted (24-27) days on black gram, (23-25) days on white gram, (19-21) days on cowpeas, and (18-20) days on green gram. Adult females survived for (14-15) days on cowpeas, (10-15) days on green gram, (12-14) days on black gram, and (10-11) days on chickpea. The mean fecundity was recorded at (6.12±3.17) eggs when two males fertilized one female and (8.73±4.22) eggs when one male fertilized two females. Cowpea seeds were identified as the preferred food source for C. maculatus compared to other pulses. Therefore, effective control of this pest is crucial to protect legume crops.