Combining techniques offers solution for growers with fruit fly problems

Originally published on Farming Future Food

Researchers in Mexico have underlined the value of combining diverse control techniques against key pests, using both the release of sterilised flies and additional natural enemies to crush populations of the Mexican fruit fly (Anastrepha ludens) in commercial mango production areas.

The pest fly is responsible for widespread damage in a number of Mexican fruit crops. While both sterile insect technique (SIT), where sterilised males of specific pests are released to mate with wild females and cause populations to crash, and releases of parasitoid wasps which lay their eggs in the larvae of the flies, have both been used as control methods, theoretical models have suggested that the two used together may be particularly effective.

Over the course of a year, the government-backed research team, led by Jorge Cancino, set out to test the theory in the field.

Efficacy in action

In four zones in an overall 5000-hectare area in the Soconusco Region of the country, they tested the release of the wasp Diachasmimorpha longicaudata, SIT, a combination of the two approaches and left one zone as a control, with no treatment. They sampled fruit to assess parasitism rates and used traps to catch adult flies, to determine the effectiveness of SIT, and the results were compared to two previous years’ data on fruit fly numbers.

They found that using parasitoid wasp releases alone increased parasitism of A. ludens from 0.59% to 19.38%, while the use of SIT reduced daily fly catches by 30%. They saw even more impressive results when combining the two techniques, with fly populations suppressed by around 98%.

“The joint use of these techniques has two important advantages: the specificity of both techniques and their complementary effect, since parasitoids attack the larval stage of the flies, causing lower emergence rates of wild adults, and thus favouring the proportion of sterile males to wild males,” the researchers wrote in the journal Insects.

Fruit flies a worldwide issue

The work backs up the findings seen in research from Hawaii and Guatemala, which used the combination of SIT and releases of a different natural enemy wasp, Diachasmimorpha tryoni, to control the fruit fly Ceratitis capitata in coffee-growing areas.

With different species of fruit flies posing problems elsewhere in the world, the growing body of evidence provides food for thought for those working on integrated pest management programmes to try and protect valuable fruit crops.