Regional Government moves forward with biological control measures against chestnut gall wasp - Communication

Secretaria Regional da Agricultura e Alimentação

On June 9, the Regional Government, through the Regional Secretariat for Agriculture and Food, launched the first phase of its biological control strategy against the chestnut gall wasp (Dryocosmus kuriphilus) with the controlled release of the parasitoid Torymus sinensis in six locations on Terceira Island.

For the Regional Secretary for Agriculture and Food, António Ventura, this intervention represents “an important step in protecting regional agricultural heritage and safeguarding a crop of significant economic, social and cultural significance for several Azorean communities.”

The fieldwork is being carried out under a contract between the Regional Directorate for Agriculture, Veterinary Affairs and Food and the Gaspar Frutuoso Foundation, representing an investment from the Regional Government of about €71,920.

The primary goal is to conduct a rigorous risk assessment concerning the introduction of this agent and test its adaptation and effectiveness under the edaphoclimatic conditions of the Azores.

“We are currently carrying out, in partnership with the University of the Azores, a trial that includes an assessment of the risks associated with the introduction of this biological control parasitoid. This strategy aims to protect producers, preserve chestnut trees and ensure the continuity of this crop for future generations,” emphasised the government official.

In this first experimental phase, 1,140 parasitoids were released, divided into six groups of 190 specimens (120 females and 70 males).

The releases took place in strategic areas of Terceira Island, namely in Arrochela, Biscoitos, Quatro Ribeiras, Vinha Brava, Terra Chã and Penha de França.

Native to China, and first detected in the country (Mainland Portugal and Madeira) in 2014, this invasive species attacks tree buds and leaves, causing the formation of galls that severely affect chestnut production and quality, and may lead to the progressive decline of chestnut trees.

So far, the relevant authorities have focused on monitoring and the manual removal of these galls.

Although the area under chestnut cultivation in the Azores is relatively small (around 1,589 hectares), the crop represents a very significant niche market and a fine example of agricultural heritage.

On Terceira Island, for example, chestnuts have a strong and long-standing tradition in parishes such as Terra Chã, São Pedro, Posto Santo, São Mateus and São Bartolomeu.

Biological control using Torymus sinensis is now internationally recognised as the most effective and sustainable method for controlling this pest. It has been successfully used across the country since 2015.

With this technical and scientific initiative, the Regional Government reinforces its commitment to protecting regional crops, ensuring safe solutions to safeguard ecosystem biodiversity and the profitability of the Azorean agricultural sector.