Combining Sterile Insect Techniques and augmentative biological control for the control of Thaumatotibia leucotreta in South Africa
Thaumatotibia leucotreta (Lepidoptera: Tortricidae, EPPO A2 List) is native to sub-Saharan Africa, and in South Africa it has a wide host range, including citrus. Sterile Insect Technique (SIT) and augmentative biological control using the egg parasitoid Trichogrammatoidea cryptophlebiae (Hymenoptera: Trichogrammatidae) have been employed simultaneously to manage T. leucotreta in South Africa. To assess this combined approach, a laboratory study was conducted to explore the susceptibility of T. leucotreta eggs from both sterile and fertile moths to parasitism by T. cryptophlebiae. Different ratios of sterile to fertile adult moths (0:1, 10:1, 20:1, 40:1, and 60:1) were used to produce a total of 200 eggs per ratio and the eggs were exposed to the parasitoid. Additionally, sterile male and female moths were crossbred with fertile counterparts and the eggs were exposed to the egg parasitoid. Both studies assessed parasitism rates on 24 h, 48 h and 72 h old eggs. The results showed that generally, eggs from all ratios were used for oviposition and T. cryptophlebiae can hatch from eggs from different sterile to fertile moth ratios. Parasitism rates were reduced with egg age across all ratios. The results suggest that a combination of SIT and augmentative release of egg parasitoids could provide an enhanced effect.
Sources
Githae MM, Coombes CA, Mutamiswa R, Moore SD, Hill MP (2024) Suitability of false codling moth eggs from different sterile to fertile moth ratios in the sterile insect technique programme, to parasitism by Trichogrammatoidea cryptophlebiae. Crop Protection 182. https://doi.org/10.1016/j.cropro.2024.106744