An ecological analysis of stink bug and lepidopteran borer complexes associated with pecan and citrus orchards in the Vaalharts region

[摘要] English: This study investigates the insect-plant interactions on citrus fruit and pecan nuts in South Africa. The aims of this study were to determine whether lepidopteran borer pests shuttled between adjacent citrus and pecan orchards, and to establish the cultivar preference of the most prevalent stink bug borer species in Vaalharts pecan orchards. Pheromone trap data indicated that there was a significant overlap between the populations of false codling moth (Thaumatotibia leucotreta) and carob moth (Ectomyelois ceratoniae) between adjacent citrus and pecan orchards. Both species of moth were found within the citrus and pecan orchards. Larval eclosions indicated that false codling moths shuttled between adjacent citrus and pecan orchards; however, the direction of the shuttling could not be established. An abundance of citrus fruit drew false codling moths from an adjacent pecan orchard, which increased infestation in the citrus orchard. No significant evidence of carob moth shuttling was found. Adult false codling moths were found to be active throughout the winter, albeit in decreased numbers. Adult carob moths were almost entirely absent during the winter months, although larvae were still present in pecan nuts and citrus fruit. Grey-brown stink bugs (Coenomorpha nervosa) were found to be the most prevalent hemipteran pest on pecan trees in the Vaalharts region. Coenomorpha nervosa demonstrated a significant preference for pecan trees of the Wichita cultivar. Adult and nymph grey-brown stink bugs preferred the Wichita cultivar to Choctaw, Barton, and Navaho cultivars. The investigation could not find C. nervosa exploiting other viable food sources close to pecan orchards; even potential host plants that were not dead or defoliated during winter. Overall, the study indicates that adjacent citrus and pecan orchards will accommodate shuttling of false codling moths between orchards. Furthermore, grey-brown stink bugs were found to be the dominant hemipteran pest on pecan trees the Vaalharts region. Grey-brown stink bugs prefer the Wichita cultivar and do not exploit food sources near pecan trees of the Wichita cultivar.

[发布机构] University of the Free State