NEW TECHNIQUE USES SEX AS A WEAPON TO ERADICATE INSECT PESTS

B3’s Eradication and Response Theme aims to develop new insect pest eradication tools that will be effective as well as economically viable and socially acceptable. One such research project led by theme leader Dr Max Suckling of Plant and Food Research is using insects’ natural mating instincts to control pests without the need for controversial pesticide spraying.

Suckling’s team, in collaboration with the Western Australia Department of Food and Agriculture and the USDA in Hilo, Hawaii, has been investigating control methods for the Light Brown Apple Moth (Epiphyas postvittana). Originating from southeastern Australia, the moth causes significant damage to agriculture and horticulture in the United States, Europe, Western Australia and New Zealand.

The Light Brown Apple Moth is also an interesting case study because its control has highlighted the need for socially acceptable control methods as an alternative to pesticides and aerial applications of chemicals. For example, when the moth was first found in California in 2007, aerial pheromone applications had to be halted due to large public opposition. In fact, there was no scientific evidence of environmental or community risk from the pheromones, despite media and interest group releases. However, as a result, the Light Brown Apple Moth has been used as a model organism to test many new alternative control methods.

One such tool called the sterile insect technique, which was first considered in the 1930s, involves the release of a flood of sterile individuals into a pest population. The sterile insects mate with other fertile insects but are unable to produce offspring, thereby leading to a gradual decline in the pest population.

Suckling and his colleagues have adapted the sterile insect technique to suppress the Light Brown Apple Moth by using “mobile mating disruption”. Suckling first called this method of cross-species behavioural disruption a “ménage-a-trois for insects” when testing it during an OECD Fellowship in Hawaii. This new take works by using sterile Mediterranean fruit flies, which are sprayed with sex pheromones normally found in virgin female moths and then released into the area occupied by the moth population.

The first trials in Perth have shown that male Light Brown Apple Moths were highly attracted to the fruit flies and tried hopelessly to mate with the flies, thereby wasting time and energy. This made it more difficult for males to locate real female moths and thus left females unmated, which eventually reduced the moth populations. 

Key advantages of the mobile mating disruption technique are that the fruit flies can reach areas of the moth population that would otherwise be inaccessible, and that it presents a very low risk to other non-target insect species. In addition, this method is unlikely to face public opposition given that no aerial spraying or use of pesticides is necessary. Eventually the technique itself may also help to control or eradicate other insect pests.

Mobile mating disruption is just one example of the group’s large collaborative projects on eradication tools that extend to Australia, the United States and Europe. Other research on the sterile insect technique currently underway includes the investigation of partially sterile insects to lower the costs of control operations; modelling work to determine the optimum levels of sterilising irradiation and release numbers to achieve eradication. Work is also examining the use of artificial trail pheromones to disorient fire ants; which use the pheromones to organise the retrieval of food back to the colony.

At a broader scale, the group is also doing work on new surveillance systems and other tactics to replace insecticides, including the use of mass trapping and new formulations for mating disruption.