Survey of Malacosma castrensis (Linnaeus) (Lepidoptera: Lasiocampidae) in central Alborz

Background and objectives: Knowing the habitat and life cycle of pests forms the basis of the knowledge of pest population control, and its application in pest control operations brings favorable environmental and economic achievements for society. In the years when the climatic conditions are favorable, an optimal opportunity is provided for the vegetation and the population of herbivorous insects to try to increase their population and spread their species more widely. A survey conducted in the central Alborz mountains in Tehran province, specifically in the Imamzadeh Hashem and Shamshak areas, from 1380 to 1400 revealed that the pasture species Ferula ovina grows in these regions. The most significant pest of this plant is the moth Malacosoma castrensis, whose larval stages feed on it. Female moths typically lay their eggs in groups, forming rings on the surface around the stems and branches of the host plant.
Methodology: The outbreak of M. castrensis species in the plant habitats of the southern Alborz slopes, in particular, in two F. ovina habitats located in the mountain slopes in the Emamzade Hashem and Shemshek regions, was observed and investigated. To carry out this research, the population of larvae was estimated using a systematic-random sampling method. The working method was as follows: in three imaginary parallel strips, 50 meters apart and 300 meters long, in a regular random style with a distance of 10 meters, the larvae of M. castrensis were counted on the selected host plant. After taking photos and combining the density of this plant per surface unit, which was the dominant species of the two investigated habitats, the larval population of this species was estimated.
Results: The conclusion is that the most important pest of the F. ovina plant is moth larvae with the scientific name M. castrensis. It lives at an altitude of 2000 to 3200 meters, and the percentage of slope and the direction of the slope do not create a limit for the presence of this type of moth. The average population of these larvae was 1,171,600 per hectare in the Emamzadeh Hashem region and 691,200 in the Shemshak region. Since the observations of the feeding behavior of the larvae were the same in the two regions, and the Ferula ovina plant was their exclusive food, the percentage of coverage and density of the host plant was evaluated as the same in the two regions.
Conclusion: The abundance of food cannot be the reason for the difference in the population of Malacosma larvae in the two regions. Due to the similarity of the ambrothermic diagrams in the two regions, the macro weather indicators were also evaluated the same in both areas. Field observations in the two regions showed that snow melting occurs seven to ten days earlier in the Emamzade Hashem region compared to Shemshek. According to this event, the population difference in the two regions can be attributed to the micro-temperature differences during day and night, as well as the duration of the freezing period in spring. It is concluded that controlling the population of the moth M. castrensis through parasitoids is feasible. By providing the necessary knowledge and methods that do not involve poisons, the damage caused by this species can be managed. Therefore, further research on ecosystem-related and climatic factors is needed to develop integrated management methods for this moth.