Sterile insect technology to control the emerging global invasion of a Drosophilid fruit fly
The first import of an SWD colony from Italy arrived at the FAO / IAEA Insect Pest Control Laboratory (IPCL) in Seibersdorf, Austria in 2015. Since then, the laboratory has been investigating the radiation biology of the SWD, i.e. the influence of ionizing radiation on the induction of sterility. “For a new species, we need to evaluate various 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 on nuclear technology in food and drink Agriculture.
To encourage the mass production of fruit flies for research, scientists have developed egg systems and cages for adults. In the case of SWD, the egg-laying or egg-laying system developed 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 board, ”explains Caceres. “Females lay eggs – or lay eggs through the panel, then the eggs are collected on the outside of the cage.” Scientists have found that SWDs are attracted to black panels, which maximizes the number of eggs collected.
As soon as larvae hatch from the eggs, they are fed with carrot powder, sugar, yeast and water. Within a few days, the larvae transform into pupae. Once the pupae are fully grown, they are collected and irradiated, rendering them sterile. After irradiation, the pupae are placed in cages in which sterile adult flies appear. “The holding cages consist of an aluminum frame that is covered with a fine plastic net. The cage has a supply of sugar and yeast as a source of nutrients and a sponge soaked with water 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, which prevents offspring. This will consequently lead to a decline in the wild population with each generation.