Investigating some biological characteristics of the brown tail moth (Euproctis chrysorrhoea L.) and its infestation level in the Arasbaran forests, Iran

The brown tail moth (Euproctis chrysorrhoea L.) is a significant leaf-eating pest that affects oak trees in the Arasbaran forests of Iran. This study aimed to investigate the biological characteristics, distribution, and demographic changes of this pest. The research was conducted in eight sites located in Ahar and Horand counties, East Azarbaijan province of Iran, during 2020-2021. For the study, 20 oak trees (Quercus petraea (Matt.) Liebl.) were chosen from each site, and 10 wintering nests were collected from each tree and taken to the laboratory for analysis. In the lab, the overwintering larvae were counted and weighed using a digital scale. The researchers also measured the width of the head capsule of the larvae and studied the life cycle of the pest in field conditions. The analysis of variance test was conducted to assess the difference between the eight sites concerning the average number and weight of the larvae in the wintering nests. The comparison of the averages was performed using Duncan's test. The results showed that E. chrysorrhoea has five larval instars, with the majority of the larvae in the wintering nests belonging to the third instar (around 90%). All the sample oak trees from the studied sites were infected with this pest, with several larval nests seen on them. The study found that the average number and weight of larvae inside the nests in the three sites of Horand county were significantly higher than the five sites in Ahar county. The control methods applied in Ahar county, including cutting and collecting larval nests, may have had an impact on reducing the number of brown tail moth larvae compared to Horand county.