There are numerous pests and diseases that affect longan trees, but the main issues are five insect and disease problems, including the litchi moth, longan moth, litchi scale, longan cheekwood, and lychee pteridophoria. Most of these pests tend to appear during the shoot growth stage, flowering period, and early fruit development. Therefore, the prevention and control strategy should focus primarily on these five key pests and diseases, implementing effective protective, conservation, and safety measures.
In addition to pruning infested branches, dead wood, and weak shoots, attention should also be given to managing winter shoots and applying lime sulfur sprays. This not only helps eliminate overwintering pests but also promotes better flowering and fruiting in the following season.
It is important to protect beneficial insects while controlling harmful ones. For pests like the horned cheeked plucked scorpion, thrushes, moth larvae, and tipped moths, spraying should be done when new shoots emerge and before they turn green. Apply either deltamethrin at 1000–1500 times dilution or 90% trichlorfon at 800 times. If pupa symptoms are observed on shoots or flower spikes, they should be cut and burned immediately to capture larvae and adults and prevent egg laying.
During the spring shoot or flower bud stage, special attention should be paid to controlling litchi pod borers and similar pests. In the fruit development phase, the primary focus should be on litchi lice and locusts, with other pests also being managed. Use 90% trichlorfon at 800 times dilution, or 10% cypermethrin at 2000 times, or a combination of 90% trichlorfon 800 times with 25% chlorpyrifos 500 times for better results.
During fruit development, controlling insect populations is crucial to reduce fruit drop and worm-infested fruits. Locusts often cause damage by infesting fruit pods or fruits. Based on the forecast of locust activity, spraying should begin when adult emergence reaches 30–40%. A heavy spray every 5–7 days is recommended, ensuring pests are eliminated before they lay eggs. Typically, the critical periods for locust control are late June to early July, early July to mid-July, and late July to early August, depending on the species' maturity.
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