Suppression of <i>Sitophilus zeamais</i> Motschulsky by the ectoparasitoid, <i>Anisopteromalus calandrae</i> (Howard)

Abstract

The use of natural enemies to control insect pests has been developed to reduce using insecticides for safety of human, animals and the environment. Most of the biological control practices are aimed for control of insect pests in the field and there is very little work done for post-harvest sector. Anisopteromalus calandrae (Howard) is an ectoparasitic wasp that is found throughout Thailand. The goal of this study is to describe the biology of Anisopteromalus calandrae and determine if it can control stored rice insect pests. An experiment on biology of this parasitoid wasp was tested for the wasp progenies in the Sitophilus zeamais when fed with milled rice at 32.5°C and 70% r.h. The egg laying stage observed is 1 d, 4.1±0.7 d for larvae, 6.3±0.9 d for pupae and 9.6±1.0 d. for adults. The life span from eggs to adults was 11.4 d. Female parasitoid wasps laid on average 37±14 females and 42±14 males for a total of 79±13 insects. The duration for egg laying is 11 d with the peak 12±5 insects on the 5th day. The parasitoid wasp sex ratio for female to male was 0.88: 1. Maize weevil larva at 21 d old reared on brown rice at 21d gave the highest yield of wasps (65±17). The number of the wasps produced was reduced to 57±17, 56±21 and 40±22 when raised with the weevil larva ages, 19, 23, and 25 d, respectively. The weevil larva age at 21 days was the most economic stage for the parasitoid wasp mass rearing. To obtain 1,124±236 wasps will use 220 g brown rice after 33 d rearing. The efficacies of the reared parasitoid wasps on controlling the S. zeamais was conducted by releasing 1,000 and 800 wasps into 25 kg rice at Rachaburi Rice Experiment Station yielded good control of the S. zeamais and with good rice quality. The rice without the parasitoid was heavily damaged and it had poor quality.

Keywords: Sitophilus zeamais, Ectoparasitoid, Anisopteromalus calandrae, Life cycle, Control efficacy