Bad times for cherries. Drosophila suzukii, a small devastating fly from Asia, has been causing panic in the industry since 2010. In 2023, helped by particularly favorable weather, the insect caused production of the AOP Cerises du Vaucluse to drop by 35% compared to the average of the previous five years, assures the general director of the organization Alexandra Lacoste.
And professionals are looking for “all-round” solutions. In the five-hectare orchard covered with an immense net by Laurent Reynard, the cherries are brilliant red, still firm, large in size. They are especially spared from the insect which attacks in particular the red fruits still on their branches, laying its eggs there.
Less effective products
The sector began in 2012 to find a solution and the quest intensified with the ban on chemical pesticides, dimethoate in 2016 and phosmet in 2023, explain officials from the Association of Environmental Protection Organizations. producers. The products still authorized are much less effective, they assure.
The installation of ultra-tight mesh nets, in a single block over an entire orchard or by row of cherry trees, provides a satisfactory response. They also protect against hail and wind and require the height of trees to be limited, making the work of seasonal workers easier. But they are expensive. Prices rise depending on the height difference or exposure to the wind and on average, it costs 80,000 euros per hectare, according to Jean-Christophe Neyron, president of AOP Cerises.
Also less than 10% of cherry producers have equipped themselves with nets, according to Alexandra Lacoste. The creation of a microclimate under the mesh can also encourage other pests, and does not eliminate another harmful insect, the Rhagoletis cerasi or cherry fly, which spends the winter in the soil.
Throwing clay
The sector is also looking for biocontrol solutions. Aliénor Royer, engineer at the Interprofessional Technical Center for Fruits and Vegetables, tests each year several products offered by companies which are currently considered not effective enough or too expensive. Splashing white clay on the tree prevents the insect from recognizing the fruit. But “there is still no solution for cleaning the cherry afterwards”.
In the medium term, the industry is banking heavily on a parasite, ganaspis. Having failed to find local species in France capable of harming Drosophila suzukii, INRAE researchers went looking for them in 2015 in Japan, the fly’s area of origin. After seven years of laboratory work, they obtained authorization to release ganaspis in five experimental areas. This parasite “was selected because it only attacks Drosophila suzukii”, which limits unwanted effects, he explains.
Fewer and fewer farms
In the meantime, managing a cherry orchard requires increased expertise and uncertainty remains over the arrival of a lasting solution, notes Alexandra Lacoste. “Small producers are giving up or focusing on other productions,” she says. According to the latest agricultural census, the number of cherry farms fell by 36% between 2010 and 2020 and the area of red fruit orchards by 21%.