Drosophila suzukii, mild winter and increased population. Onwards with parasitoid launches

04 Aug 2023
1325



In Trentino in the cherry and small fruit fields, the technicians of the Mach Foundation are finding significant damage caused by Drosophila suzukii. Unfortunately, this winter's mild temperatures have reduced the Asiatic midge's winter mortality, creating favourable conditions for the establishment of a high population from early spring.

Meanwhile, launches of parasitoids to combat drosophila continue uninterrupted for the second year at twenty sites, even though ministerial authorisation arrived after mid-June.

"In the January-April period, the monitoring network managed by the Edmund Mach Foundation (FEM) detected catches of Drosophila suzukii up to ten times higher than the average of the last decade," points out Claudio Ioriatti, responsible for FEM's research projects related to the sustainability of agroecosystems. 

"This explains the intensity of the attack recorded on the cherry crop since the last ten days of May.

Monitoring results: high damage mainly in fields not protected with insect covers

FEM supported producers by offering an attack level verification service on cherry samples from off-grid and under-net crops. A total of 345 samples were analysed up to mid-July, of which 59 from unprotected netted orchards and 286 collected in netted cherry orchards. In the case of the unprotected cherry orchards, the analysed samples showed a percentage of infested fruit in the order of 85% already at the end of May. 

Subsequently, thanks to the control measures applied by the growers, the percentage of infested fruit dropped somewhat, but never below 70%. 

The situation in the orchards protected by the insect net was different. Here, infected fruit was detected later and still in almost zero percentages until more than mid-June, then gradually increased towards the end of the season and reached just under 40% in the last samplings in mid-July.

Biological control: authorised launches delayed, but pest control activities continue

With regard to biological control, launches of the exotic parasitoid Ganaspis brasiliensis continued this year at the twenty sites authorised by the Ministry. Unfortunately, the late issue of the authorisation forced the FEM to carry out the first round of launches only at the turn of mid-June, so it is not yet possible to have data on its establishment and parasitisation rates.

On the other hand, the constant spread of the other exotic parasitoid, Leptopilina japonica, which has arrived spontaneously in our areas and was discovered for the first time in Europe by FEM staff in 2019, was also ascertained this year.

The samplings carried out on infested fruit from wild cherry trees revealed not only a further expansion of its presence, but also a significant increase in the parasitisation rate from an average of 6% in 2021 to an average of 20% this year. 

In sampling sites with a lower incidence of cultivated areas, the percentage of parasitised Drosophila suzukii is even higher, exceeding even 40%.

"The biological control techniques we are implementing," Dr Ioriatti points out, "do not aim to establish direct control of the Drosophila suzukii population in the cultivated field, where auxiliaries would be unlikely to survive due to phytosanitary treatments, but rather to control the midge populations in natural areas where they find favourable conditions for their development. 

"By reducing the populations of the Asian midge in these areas, the intensity of migration towards the crops is reduced, giving other means of control (nets, plant protection products, etc.) the opportunity to act on less numerous populations and therefore in more favourable conditions to meet producers' expectations".

Source: E. Mach Foundation


Cherry Times - All rights reserved

What to read next

Stemilt bets on organic cherries: volume boom in 2024 season

Production

26 Jun 2024

"Organic sweet and dark cherries are up from last year," commented Brianna Shales. "Harvest is underway in Washington State, and we will see increased volume of organic cherries through the end of June for promotions.

Henriette*, "the mountain cherry" representing an improvement on Kordia

Varieties

04 Aug 2023

The Fragsburg farm is located at 700m a.s.l. in the hills above the city of Merano (Bozen). There, in the experimental cherry orchard (about 1.5 ha), different training systems, rootstocks, varieties, and pruning techniques are tested with the purpose of supporting farmers.

In evidenza

Drosophila suzukii in France: winter fruits reveal new control strategies

Crop protection

12 Sep 2025

A study in France explores the effects of ornamental winter fruits on Drosophila suzukii, an invasive pest damaging soft fruit crops. Researchers tested thermal regimes to evaluate survival, reproduction, and potential strategies for biological control and prevention.

How cherries in Patagonia survived frosts down to minus 9 degrees

Tech management

12 Sep 2025

Frosts as low as -9°C did not affect cherry production in Patagonia thanks to sprinkler irrigation systems that protect flowers and buds. The Cherry Growers’ Chamber reassures: no damage to crops, but targeted investments are needed to face extreme weather events.

Tag Popolari