The dry-based injection method is specifically designed for solid mother trees, offering the advantages of saving labor and resources while minimizing waste of liquid medicine. The dosage can be adjusted according to the level of fertility, resulting in a more pronounced effect (Table 7-3).
**Table 7-3 Effect of Dry-Based Injection on Controlling Larch Cone Flies**
| Liquid Name | Female Tree Breast Diameter (cm) | Infusion Liquid Volume (ml) | Number of Investigations | 7-9 Days Larvae Mortality | Instructions |
|---------------------|----------------------------------|-----------------------------|--------------------------|---------------------------|--------------|
| | | | | | |
| Omethoate EC 40% | 8 | 7 | 3 | 83 | Daily survey of 1 dose on each site |
| | 10 | 8 | 3 | 74 | |
| | 12 | 9 | 3 | 81 | |
| | 14 | 11 | 3 | 87 | |
| | 16 | 13 | 3 | 91 | |
| | 18 | 15 | 3 | 94 | |
| Methamidophos 50% | 8 | 7 | 3 | 93 | |
| | 10 | 8 | 3 | 94 | |
| | 12 | 9 | 3 | 86 | |
| | 14 | 11 | 3 | 82 | |
| | 16 | 13 | 3 | 91 | |
| | 18 | 15 | 3 | 90 | |
| **Average** | 12.66 | 10.5 | 3 | 87.1 | |
(3) Forest Management and Prevention: In areas of *Larix principis-rupprechtii* orchards and mother trees, when larvae land and cause defoliation, the method of removing weeds and litter from the forest floor is used to destroy the overwintering environment of the alfalfa. At the same time, soil is combined with green pressure, cultivation, and weeding. Deep plowing and complete destruction of the earthworm's overwintering environment can significantly reduce the population density of the pests. Additionally, large isolation belts around the orchard help effectively reduce fly damage.
III. Investigation and Forecast of Major Pests of *Larix principis-rupprechtii*
Investigating the resistance status of North China larch is essential for forecasting and managing pest outbreaks. Accurate prediction and timely forecasting serve as the foundation for effective pest control and prevention, aligning with the principle of "prevention first, comprehensive treatment." The main goal is to conduct systematic observations of major pests, analyze relevant data, and accurately forecast the occurrence period, quantity, extent, and severity of damage caused by pests. Based on this, appropriate preventive measures are recommended.
(I) Autumn Survey
1. Autumn Pest Survey
(1) Time Requirements: The survey should be completed between August and October.
(2) Survey of Pest Conditions:
- Larch caterpillar: Overwintering larvae
- Larch demoiselle: Underground pupae
- Larch borer: Underground overwintering larvae
- Larch sheath moth: Overwintering larvae on the tree
- Gypsy moth: Overwintering stage
- Larch cone flies: Underground overwintering
(3) Survey of Plant Strain Numbers: The number of samples to be investigated can be determined based on the area of insect-infested small classes using Table 7-4.
**Table 7-4 Determining the Number of Insect Pests to Be Investigated**
*Unit: Mu, strain*
| Insect Pests in Small Classes | Occurrence Area | Should Investigate the Number of Samples |
|-------------------------------|-----------------|-----------------------------------------|
| | 100 or less | 8 to 10 |
| | 100–200 | 11–15 |
| | 201–400 | 16–20 |
| | More than 400 | 20 or more |
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