Report of Porthesia melania Stgr. from Sarsakhti Forest Reserve of Markazi province, Iran

  The abiotic stress factors such as decrease in the rainfall can be led to outbreak of pests and diseases and decrease in the trees growth. It is necessary to establish investigations to identify the causal agents in the decline forests. Therefore, adaptive monitoring improves management decisions by providing information on pest population levels and can be used in identifying high-risk areas pest and disease outbreaks to focus on future management efforts. Accurate identification of species is the first step in an effective pest management program. Therefore, the purpose of this study is to identify and introduce the leaf-eating species of oak in the Sarsakhti Forest Reserve of Markazi province with precision. One of the most important pests of oak trees in Iran is Porthesia melania Stgr. (Lepidoptera: Lymantriidae). In this research, we, for the first time, report P. melania of its occurrence in Sarsakhti Forest Reserve from Markazi province.

Sarsakhti Oak Forest Reserve is about 200 ha in area that is located in Markazi province with a distance of 10 kilometers from Shazand city. In this research, for the first time, Sarsakhti Forest Reserve was investigated and regularly monitored during 2019-2022. The Zobeiri method was used in sampling, so that 10 lines were drawn on the map of the reserve. The location of the first sampling was randomly selected and other sampling lines were determined systematically. Among 10 lines, 4 lines and at least 10 trees were sampled in each line. By observing the amount of damage on each tree and calculating the average, we determined the amount of damage. The damage index ranges from zero (indicating no damage) to 5 (representing maximum damage).

Porthesia melania was observed in the year 2020-2022 in the oak reserve of the Markazi province of Iran. In April, when the weather warms up in this region, the wintering larvae, third instar larvae (seldom forth instar larvae) become active and feed on the young buds and leaves. At this time (early spring), the pest damage is more common, because the trees have few leaves and the larvae of the pest are hungry due to wintering, also in older instars (instars 4 and 5) they need to feed more. The adult insects appear in June. After the mating, the female moth lays her eggs preferably on the underside of the leaf, and covers the eggs with the hairs of the lower part of the abdomen. After the eggs hatch, the young larvae feed on the parenchyma of the leaves. Third-instar larvae hibernate from September to April of the following year and are inactive during this time. In summer, the first to third instar larvae are active and usually, they only feed on the upper surface leaf parenchyma, so the damage is less at this time.

Porthesia melania Stgr. can be extensive feeding damage on heavily infested oak trees. As a result of the leaf-eating activity of P. melania, the trees become devoid of the leaves and with the loss of energy sources, the tree gradually weakens and becomes susceptible to the attack of wood-eating and bark-eating pests. This pest has an outbreak every few years and it is capable for causing a severe damage. The optimal approach for pest management involves collecting larval nests from infested trees during late fall and early spring, before the larvae emerge from their winter shelter.