Pear-lime moths, commonly known as "stratum worms" by fruit farmers, are pests that can cause mild to severe damage to fruit trees. While they may not immediately kill the trees, they can significantly reduce fruit yields and, in extreme cases, lead to the death of pear trees.
**I. Occurrence and Symptoms**
These moths typically have two generations per year. The first-year larvae overwinter inside the tunnels they create in damaged twigs. In late March of the following year, they become active, feeding on the sap of branches by creating small tunnels. Initially, these tunnels are very narrow, but as the larvae grow, the tunnels expand. By the fifth instar stage, the tunnels merge into a single, layered sheet. At this point, the larvae stop expanding the tunnels and instead move to the skin or the inner layer of the pear fruit, where they feed. This feeding causes the affected area to develop multiple layers of dead, paper-like skin, which eventually splits from one side, leading to shrinkage and distortion of the fruit.
**II. Prevention and Control Measures**
1. **Timing of Control**
The best time to implement control measures is between December and early March, before the pear buds begin to open. This period is critical for targeting overwintering larvae.
2. **Control Methods**
(1) **Manual Control**
Farmers can perform winter pruning and remove any branches that show signs of infestation. These cut branches should be collected and burned to eliminate the overwintering insect population.
(2) **Chemical Control**
During the adult moth emergence period, spraying with a 50% parathion solution diluted at 2000 times or dichlorvos at 1000–1500 times concentration can effectively reduce the pest population. It is recommended to spray 2–3 times, ideally once a month. Additionally, when larvae are actively tunneling, applying parathion directly to the affected areas can help kill them.
(3) **Methyl Bromide Fumigation**
For young seedlings, fumigation using methyl bromide is an effective method. Seedlings are placed in a room maintained at 8–9°C, and 45 grams per cubic meter of methyl bromide is applied. The room is then sealed for 6 hours. This method achieves 100% mortality of larvae without harming the seedlings.
By combining these methods, farmers can effectively manage pear-lime moth infestations, protecting their crops and ensuring better fruit quality and yield.
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