Introduction:

The chestnut tree has enormous economic, social, cultural and environmental benefits in the Trás-os-Montes region of Portugal, as well as contributing to its characteristic landscape.

The chestnut moth, Cydia splendana (Hübner), is considered a serious crop pest, affecting the quality and quantity of the chestnut fruit.

Objective:

To ascertain more about the biology of the chestnut moth and its economic impact.

Methods:

In 2018 and 2019, in six chestnut orchards in the Trás-os-Montes region, located in the districts of Bragança (Samil, Espinhosela and Parâmio), Macedo de Cavaleiros (Amendoeira), Vinhais (Espinhoso) and Valpaços (Sobrado), each under different climatic conditions, the pest was monitored at different stages of development (immature and adult states) and the damage caused was estimated. Adults were monitored using delta traps, with sexual pheromones (three per orchard), 50 m apart; immature states were monitored by sampling 200 leaves and chestnut husks/fruits for each location. In the laboratory assays, the number of eggs and larvae was recorded. The intensity of attack was assessed by dissecting 1,800 fruits collected during the harvest.

Results:

Chestnut moth was recorded between mid-August and early October 2018, with the peak of flights taking place in late August in most of the orchards. In 2019 the flight period was shorter, ending in late September, with a peak flight period in the second week of September.

In 2018, the first eggs were observed in mid-August and the first larvae in the last week of August. In 2019, the eggs started about a week later. The intensity of attack of the fruits ranged between 10.0% in the Sobrado orchard to 23.3% in Espinhoso.

Conclusion:

The insect’s biology seems to be slightly influenced by local climatic conditions. The catch levels were higher in Macedo de Cavaleiros (Amendoeira), located at an altitude of 766 m, in an orchard with vegetation which is periodically removed. The damage caused by C. splendana was greater in orchards in close proximity to abandoned chestnut orchards and/or scrub containing wild chestnut trees, as in the case of Espinhoso with 23.3%, and Samil with 16.0%, of trees attacked.

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