Abstract
The pine processionary moth (PPM), Thaumetopoea pityocampa (Denis and Schiffermüller, 1775) (Lepidoptera, Notodontidae), is considered one of the main insect defoliators of conifers in Southern Europe and North Africa. The species is oligophagous on pines and cedars in Mediterranean countries. This 6-year investigation (2014–2019), carried out in Aosta Valley (NW Italy), on Pinus sylvestris L. aimed to: (i) Monitor the PPM population with pheromone-baited funnel traps; (ii) assess the infestation index (0–5 classes) according to the degree of defoliation; and (iii) apply control strategies, namely Bacillus thuringiensis var. kurstaki (Btk) and mating disruption (MD). In total, 9618 ha were visually monitored and assigned an infestation index. The percentage of woodland stands that were strongly defoliated by PPM (infestation index ≥ 3) increased progressively between 2015 and 2016, affecting from 8% to 19% of the total area monitored; this area decreased to 16% and 13% in 2017 and 2018, respectively, followed by an abrupt decline to 4% in 2019. Both Btk applications and mating disruption significantly reduced the infestation. Where Btk was applied, the rate of larval mortality ranged from 79.47% to 98.43%; conversely, in the control plots, the larval mortality was, on average, 1.56%. The mean number of PPM males captured in traps was significantly lower in the plots where MD was performed, ranging from 8.36 ± 2.37 to 13.47 ± 4.68. The mean number of males captured in the control plots was, on average, 119.16 ± 12.68. The total number of nests recorded per tree was significantly lower in MD plots, ranging from 0.41 ± 0.05 to 0.94 ± 0.14. In the control plots, there were, on average, 4.37 ± 0.76 nests per tree. As already documented for several defoliating forestry insect pests, both Btk and mating disruption proved effective in controlling PPM infestations, and thus, microbial insecticides should be strongly encouraged and adopted by forest managers.
Highlights
The pine processionary moth, Thaumetopoea pityocampa (Denis and Schiffermüller, 1775)(Lepidoptera, Notodontidae), is one of the most economically important pine defoliators
Aosta Valley is a mountainous autonomous region located in the north-western part of Italy
The Aosta Valley pine forests mainly consist of black pine and Scots pine; defoliation damage ranging from mild to very severe, due to pine processionary moth (PPM) feeding activity, has been observed in about 50% of this area over the years (IR and LD)
Summary
(Lepidoptera, Notodontidae) (hereafter referred to as PPM), is one of the most economically important pine defoliators. It is a very ravenous species and is the major phytophagous insect pest in Mediterranean. Forests 2020, 11, 1253 forests, being distributed in the Mediterranean Basin in southern Europe, the Balkan area, and North. Changes in the distribution of the pest have been recorded, with its range greatly influenced by winter air temperature and annual solar radiation [4]. The PPM caterpillar is herbivorous and is a very severe defoliator, causing significant pine tree health decline [5]. The moth is typically found in the pine forests of the Mediterranean area, but the urban environment is a suitable habitat. Larvae feed on a wide range of Pinus species, especially
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