INVESTIGATION ON PENETRATION OF THREE CONVENTIONAL FOODSTUFFS PACKAGING POLYMERS WITH TWO DIFFERENT THICKNESSES BY LARVAE AND ADULTS OF MAJOR SPECIES OF STORED-PRODUCT PEST INSECTS

摘要

Despite modern methods of packaging, stored agricultural products are still under attack by stored-insect pests. Therefore, determination of the best polymer and appropriate thickness inhibiting the penetration of the insects must be considered. In this study, we investigated the ability of penetration and the rates of contamination by nine important stored product pest insects for three conventional flexible polymers (polyethylene, cellophane and polypropylene) at two thicknesses (16.5 and 29 pm), which are used as pouches for packing of agricultural products. We used adults of T. castaneum (Coleoptera), S. granahus (Coleoptera), R. dominica (Coleoptera), C. maculates (Coleoptera), 0. surinamensis (Coleoptera), and larvae of P. interpunctella (Lepidoptera), E. kuehniella (Lepidoptera), S. cerealella (Lepidoptera) and T. granarium (Coleoptera). Results showed that for most of the species penetration occurred between 4 days and 2 weeks, but there were significant differences (p<0.05) in the penetration of three polymers (cellophane, polyethylene and polypropylene) by the insects. Among the polymers, polyethylene with a thickness of 16.5 pm showed the highest degree of penetration and was the most unsuitable polymer for packaging of foodstuffs. Application of this polymer led to a complete infestation of the product and a lot of punctures were created by the insects. In contrast, no penetration was observed in polypropylene polymer with a thickness of 29 pm. Furthermore, adults and larvae of all species showed a much lower penetration when there was no food present in the pouches and this was the case for all polymers tested.