Nature and extent of damage caused by insect pests on stored pepper, cardamom, ginger and turmeric

Abstract

The occurrence and distribution of insect pests in stored ginger, turmeric, pepper and cardamom in five districts of Kerala were assessed in a survey conducted at bimonthly intervals for a period of six months. In stored ginger, the major pests recorded were L. serricorne and A. fasciculatus and in turmeric, L. serricorne. Low infestation Of S. paniceum occurred in pepper. Cardamom was relatively free of insect infestation. Both adult and larval stages of these pests damaged these produces. Besides these, damages by T. castaneum, L. minutes, O. surinamensis and R. dominica in ginger and turmeric were observed in a few samples. Stray samples of turmeric also showed infestation by adults and grubs of S. paniceum. Caterpillars of P. manihotalis, E. zebrine and S. ruttella were seen infesting neglected stocks of ginger and P. manihotalis and E. zebrine in neglected stocks of turmeric and pepper respectively. Quantitative loss studies revealed a loss of 13.01 per cent and 17.97 per cent respectively in ginger and turmeric by L. serricorne in six months, where as A. fasciculatus caused 11.58 per cent loss in ginger. Pepper exposed to S. paniceum caused only 1.2 per cent loss over a period of six months. While the volatile oil content of ginger infested by L. serricorne and A. fasciculatus reduced significantly after five months, the non volatile acetone extract reduced significantly in the sixth month compared to the fixed quality standards. In turmeric L. serricorne infestation resulted in a significant decrease in volatile oil content after three months of storage and non volatile acetone extract after five months. Significant positive correlation existed between the population build up and weight loss in ginger infested by L. serricorne and A. fasciculatus and turmeric by L. serricorne. In pepper exposed to S. paniceum the correlation was not significant. Significant negative correlation existed between the population build up of L. serricorne and A. fascicultus and volatile oil content and non volatile acetone extract of ginger and L. serricorne and volatile oil content of turmeric. The correlation between the population build up of L. serricorne and non volatile acetone extract in turmeric was not significant. Significantly high incubation period of L. serricorne was recorded in ginger compared to turmeric and only insignificant differences were noticed in larval and pupal duration and adult longevity. S. paniceum showed significantly high incubation and pupal period in pepper compared to that in turmeric where as the adult longevity was significantly higher in turmeric. Compared to L. serricorne, A. fasciculatus took longer period to complete its development in ginger.