The efficiency of entomopathogenic nematodes, Steinernema carpocapsae and S. riobravae for controlling Aedes aegypti larvae in natural condition, Muang District, Ratchaburi Province

Abstract

This research aims to study the efficiency of the two selected entomopathogenic nematodes which showed a good efficacy in killing Aedes aegypti larvae in the laboratory, that are Steinernema carpocapsae and S. riobravae. The research consisted of the study on effectiveness of nematodes in the natural condition, the cost comparison between using the nematodes and temephos sand granules to control larvae, evaluate the difficulty and the public acceptance of using the nematodes. The study was conducted at Nongsara community, Moo 9, Pongsawai subdistrict, Muang district, Ratchaburi province. The effectiveness study was done in the water containers outside the house which are the importance sources of mosquito breeding. The study was conducted by selecting only water containers that found larvae, then put nematodes amount 10,000 per 200 sq.cm. and followed up the results from the first day to the fifth day. The cost comparison between using nematodes and temephos sand granules, calculates from the number of nematodes per one container multiply by cost of nematode then compare with cost of using temephos sand granules. The difficulty evaluation of using nematodes was considered from the providing, procedure and frequency of repeat procedure. Data was analyzed from this experiment and literature review. The public acceptance of using nematodes was done by interview volunteers using questionnaires which were developed during the study. The results showed that the effectiveness of nematodes on killing effect of larvae of S. carpocapsae, S. riobravae and the control are 68.00, 46.67, and 0.33 respectively. Both species had peak period on killing effect on larvae at 48 hours and remark decreased at the day 5. The cost of using nematodes was higher than using temephos sand granule about 80 times. For difficulty of using nematodes found that this method is difficult implement because of the few suppliers, complicated procedure that general population cannot self-manage and it need to repeat procedure every 5 days. For public acceptance, it was found that the majority of people (>70%) accepted this measure. In summary, the using of nematodes can be an alternative method for larvae control, but should use S. carpocapsae as the first choice because of its high effectiveness. However this method is not suitable for the national program in controlling Ae. Aegypti larvae due to low effectiveness at 70%, high cost, and complicated procedure.