It is time to control the Xing'an larch sheath moth

Forestry plant protection expert Wang Zhiming

In the central and eastern regions of our province, larch is in a thriving growth stage after it began to germinate long leaves in early May, but sometimes in some places there will be conifer whitish, yellowing and even the whole plant conifer albinism, which is the result of the harm of the Xing'an larch sheath moth.

The larvae of the Xing'an larch sheath moth sheath are sheathed in leaf chip-like capsules, about 0.5 mm in size, and overwinter on larch twigs and trunks. In the following year, when the larch needles are halfway through growth, they begin to crawl with their sheaths, looking for conifers for food. When feeding on the conifers, the larvae reach into the conifers to feed on the flesh, and the rest of the body remains hidden in the sheath, making it less easily detectable. When the number of insect mouths is high, it will eat the leaf flesh of the entire coniferous leaf, leaving only the leaf epidermis, so the whole plant appears white. After a while, the whole plant will turn brown.

In recent years, as farmers apply herbicides to control weeds in early spring, the mist droplets of herbicides will drift to the canopy, making the needles appear white. However, the whitishing of these two larch leaves can be distinguished by careful observation.

Xing'an larch sheath moth due to the negative sheath of the body, when eating larch needles and leaves, the head is extended into the leaf flesh to feed, the whole body is isolated from the outside world, so it is not easy to use pesticides to directly spray to kill. Therefore, it is necessary to seize several key periods in its prevention and control.

At the beginning of May, the larvae have a period of time to make a new sheath, at this time the larvae have a long contact with the outside world, and the spraying of pesticides for control will achieve a certain control effect.

At the beginning of June, the sheath moth will gradually feather into a moth, flying in the forest, mating and laying eggs, which is also a good time for control. The application of cigarettes or sprays kills large numbers of adults and reduces the density of the next generation of insect populations.

In early September, when the larvae are sheathed from the inside and outside of the needles, it is also a good time for control. At this time, spray pesticide control can be carried out to kill the larvae before wintering and avoid pest damage in the spring of the following year.

Although the above measures will control the harm of sheath moths to a certain extent, it is still difficult to control them. The most effective approach is to create mixed forests, where larch is mixed with broad-leaved or other coniferous trees for afforestation, which is a fundamental measure to control sheath moths.