The first import of an SWD colony came from Italy in 2015 at the FAO / IAEA Laboratory for Insect Pest Control (IPCL) in Seibersdorf, Austria. Since then, the laboratory has investigated the radiation biology of the SWD, ie the effect of ionizing radiation on the induction of sterility. “For a new species, we need to evaluate different radiation doses from low to high to determine which radiation dose induces near 100 percent sterility,” said Carlos Caceres, a research entomologist on the joint FAO / IAEA program in nuclear food and agriculture.
To encourage the mass production of fruit flies for research purposes, scientists have developed egging systems and cages for adults. In the case of SWD, the developed egging or egg-laying system consists of plastic containers with holes that allow females to lay eggs. “The egg-laying system is a plate that consists of a fine mesh covering with wax. The females are attracted to a certain color of the egg-laying panel, ”explained Caceres. “Women lay eggs – or lay eggs – through the plate, then the eggs are collected on the outside of the cage.” Scientists have found that SWDs are attracted to black fields, which maximizes the number of eggs collected.
Once the eggs hatch into larvae, they are fed a diet of carrot powder, sugar, yeast, and water. Within a few days, the larvae transform into pupae. Once the pupae are ripe, they are collected and irradiated, rendering them sterile. After irradiation, the pupae are placed in holding cages in which sterile adult flies emerge. “The holding cages consist of an aluminum frame that is covered with a fine synthetic mesh. The cage has a supply of sugar and yeast as a source of nutrients and a water-soaked sponge to keep the flies hydrated, ”said Caceres. A cage measures 50 cm x 50 cm x 50 cm.
After three days in the holding cages, the adult flies become sexually mature and can be released in the target area to mate with fertile females, resulting in no offspring. This will consequently lead to a decline in the wild population with each generation.