Different pairs of male and female of Campoletis chlorideae (Hymenoptera: Ichneumonidae) parasitised the chick pea pod borer, Helicoverpa armigera (Lepidoptera: Noctuidae), in Myanmar

In Myanmar, chickpea is of great importance not only for the export but also for local consumption. In 1999-2000, the total area of chickpea was 323,000 acres, with an annual production of 83,000 tons of which 352 metric tons were exported. Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) is a solitary larval parasitoid that parasitises the larvae of Helicoverpa armigera Huebner (Lepidoptera: Noctuidae) in Myanmar. H. armigera is the major insect pest causing damage to the chickpea crop and significantly reducing yields. The attack of pods seeds varies from 3 to 50%. Conservation of the parasitoid C. chlorideae is important to minimise damage by H. armigera during the reproductive stage of chickpea. Laboratory (potted plants) and field experiments were conducted at the Biological Control Laboratory, Paleik, Singaing Township during the 2002-2003 winter season. Results - Laboratory experiments: The number of C. chlorideae (2 pairs, 3 pairs, 4 pairs and 5 pairs / 30 larvae of H. armigera of 1st stage, 2nd stage, and 3rd stage) significantly and differently affected the survival of different stages of H. armigera larvae (p=0.0001 each R2 = 0.963, C. V 10.98) Replication effects of the experiment were not significant (p=0.1718). Different pairs of C. chlorideae significantly affected the mean survival of larvae H. armigera when the results of four different pairs of parasitoid C. chlorideae were compared (Tukey's studentized range test). The largest difference between the means was observed between 5 pairs and 2 pairs of parasitoids released and the smallest was between 4 and 3 pairs of parasitoids. The results from Tukey's studentised range test showed that 2 pairs of parasitoid C. chlorideae significantly affected the 30 larvae of H. armigera. Different pairs of the parasitoid C. chlorideae also significantly affected the mean parasitism when the results of three different stages of larvae of H. armigera were compared (Tukey's studentised test was used). The highest difference was between 2nd stage and 3rd stage of larvae of H. armigera and the smallest was between 1st stage and 2nd stage of larvae of H. armigera. The results from Tukey's studentised range test showed that the 2nd stage of larvae of H. armigera was most affected. Parasitism differed significantly between the 1st and 3rd stage of larvae of H. armigera. The highes rate of parasitism (%) of C. chlorideae on the larvae of H. armigera was found with 5 pairs of male and female (55%) and C. chlorideae affected the 2nd of larvae of H. armigera in the pot experiment of chickpea in 2002-2003 Winter Season at Paleik. A positive linear relationship was observed between mean parasitism rate (%) and different pairs of parasitoids. The regression equation was as follows: Y=2.428x + 25.585; R2=0.6608, r=0.8129. An increase of 2.43% of mean parasitism rate by 2, 3, 4 and 5 pairs of released C. chlorideae affecting the 2nd stage of host larvae of H. armigera was found in the pot experiment. Field experiments: Different pairs of C. chlorideae significantly affected the mean survival of larvae H. armigera when the results of four different pairs of parasitoid C. chlorideae were compared (p=0.0001 each, R =0.96, C. V. =12.18). Replicate effects on the experiment were not significant (p=0.8525). Different pairs of parasitoid C. chlorideae significantly affected the mean survival of population of larvae H. armigera when the results of four different pairs of parasitoid C. chlorideae were compared. The highest difference was between 5 and 2 pairs of parasitoids released and the lowest was between 5 and 4 pairs. The results from Tukey's studentised range test showed that there was not difference between 5 and 4 pairs and between 3 and 2 pairs of parasitoid affecting larvae of H. armigera