Role of Egg Parasitoids in Controlling the Pine Processionary Moth in the Cedar Forests of Chréa National Park (Algeria)

Abstract

The sustainable protection of cedar stands in Chréa National Park can only be accomplished through the stability of the ecosystem. Outbreaks of Thaumetopoea pityocampa are a major threat and are largely attributed to the high population fecundity, changes in the diversity of natural enemies and global interactions within the ecosystem. Egg parasitoids (Hymenoptera) are essential in the biological control of T. pityocampa. To assess the impact of the parasitoids on the populations of the pine processionary moth, egg masses from cedar plantations were collected, reared in a laboratory and checked regularly for the emergence of the egg parasitoids: Trichogramma embryophagum, Baryscapus servadeii and Ooencyrtus pityocampa. Observations showed an inter-annual variation in the abundance of the three parasitoids as a result of the variation in the population density of the processionary moth, and on the underlying effect of temperature. Parasitoids had variable parasitism rates, with yearly averages ranging from 3.86% to 51.14%, dependent on the spatiotemporal distribution of the host populations. The aggregate effect of multiple parasitoid species could optimize control of T. pityocampa in cedar stands.

Global change and forest disturbances in the Mediterranean basin: factors affecting pine processionary moth populations in two different bioclimatic strata in Northern Algeria

“…PPM occurrence rates are much lower in recent years than in previous seasons. These changes can be attributed mediated by global climate warming and repeated continuous insect control operations (Feracini et al, 2020;Sebti & Chakali, 2022). According to Ziouche et al, (2017), the insect is present in all bioclimatic stages, from the coast to the Saharan Atlas, and finds its optimal growth mainly in semi-arid and sub-humid areas.…”

A review of Trichogramma Westwood parasitoids on eggs of Thaumetopoea pityocampa (Denis & Schiffermüller) in habitats of the Balkan Peninsula and Asia Minor

“…In the Chréa National Park in Algeria T. embryophagum parasitised between 1.95 and 8.81% of the eggs of pine processionary moth during the period 2010-2014 (Sebti et al, 2022). Two more species of egg parasitoids (O. pityocampae and B. servadeii) were found in cedar plantations in Algeria, but T. embryophagum dominated (Ayache et al, 2021).…”

Ecological characteristics of pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Notodontidae) larval nests in pine and cedar forests of Algeria

“…In addition, several studies have shown that the natural enemies (e.g., parasitoids, predators, fungi, etc.) can play a significant role in the natural regulation of T. pityocampa and contribute to maintain their populations at low abundance levels within its distribution range (Tarasco et al 2016;Zamoum et al 2017;Rahim and Chakali 2022;Sebti et al 2022;Hein et al 2023;Lagogiannis et al 2023). Pimentel et al (2017) showed that the population density of T. pityocampa decreases dramatically after a year of severe defoliation as a consequence of both activity of the natural enemies and change in food quality (Pimentel et al 2017;Rahim et al 2021;Sebti et al 2022).…”

“…The PPM has a univoltine lifecycle. In Algeria, the adults emerge, mate and lay eggs in a single clutch on pine needles or the underside of cedar twigs in July at colder sites and in August at warmer sites (Hezil et al 2018;Sebti et al 2022). Each egg batch contains, on average, in the northern regions of Algeria 220 eggs covered with protective scales, which are produced by the female .…”

“…In Algeria, outbreaks occur in the Aleppo pine (Pinus halepensis) forest in the semi-arid area and Atlas cedar forest (Cedrus atlantica) in the sub-humid elevation area (El-Mokhefi et al 2016). The expansion areas of this species in Algeria were favored by the recent large afforestation program of Barrage Vert (plantation of pure stands of Aleppo pines to serve as a barrier to desertification) along the Saharian Atlas (Zamoum 1998), and large areas of forests are periodically affected by severe episodes of defoliation (Ayache et al 2021;Rahim and Chakali 2022;Sebti et al 2022). Thaumetopoea pityocampa attack can reduce tree leaf cover by up to 20 to 80%, along with a decrease in the tree's ability to photosynthesize and store energy (Jacquet et al 2012).…”