A Preliminary Study Of Host Foraging And Dispersal Behaviors Of Meteorus Pulchricornis (Hymenoptera: Braconidae)

Meteorus pulchricornis Wesmael is a promising parasitoid natural enemy in the biological control of some folivorous insect pests of economic importance, such as Prodenia litura, Spodoptera exigua, Helicoverpa armigera, and Lymanstria dispar, etc, and. Though some of its bionomics has been known from previous studies, the host-foraging in the field is still unknown. The current study was designed to investigate dispersal performances and its relevant factors in the field and foraging behavior for host patches of variable quality in the controlled environment.1. To gain insight into foraging behavior of Meteorus pulchricornis in the field, two trials of release-recapture were conducted in soybean fields, in which Spodoptera litura larva hosts were released and collected to measure parasitism as affected by direction, time and distance from the releasing points. The field release trials indicated that direction did not significantly influence parasitism at the wind speed of≤4.2m·s-1, but parasitism varied significantly with the time and distance. Parasitism decreased by> 30% with increasing in time elapsed and by 50% with distance away from the releasing point. The parasitoid could disperse 36 meters away in one day. The results suggested that the distance away from the releasing points and time after the release be key variables affecting parasitism in the fields.2. To evaluate parasitism as affected by host density in the filed, a release-recapture trial was conducted in a soybean field; and to investigate performances of M. pulchricornis on host patches on variable scales, the wind tunnel was used to study foraging behaviors on host patches of plant(s) scale. The field trial result showed that parasitism rate decreased with host density (larvae/plant), as exemplified by 1.5 times difference between host densities of 10-15 and 30-35 larvae per plant. The wind tunnel test indicated that the parasitoid preferred hosts on grouped plant (66.7%) to the others (single plant, triple-leaves, single leaf) (11.1%); but no significant differences were exhibited in residence time and foraging efficiency between host patches. The results suggested that hosts in aggregation would run lower risk of being parasitized than solitary hosts, and the parasitoid would prefer hosts on plants in groups.3. To investigate selection for host patches of variable quality, three treatments of host patch quality were created by combining parasitized and healthy hosts in different ratios. The MANOVA results showed that parasitism incidences were not different between the three host-quality patches; the number of stings was significantly different between treatments of the three host-quality combinations and between host patches within the treatments. The Cox model analysis indicated that the time elapsed from the last sting and number of stings played an active role in extending residence time on host patches. The results suggested that quality of host patches previously visited influenced ensuing foraging behavior for hots patches.