Detailed Explanation of Key Points for Autumn Pest and Disease Control in Citrus

Autumn is the period when citrus sends out autumn shoots, and also the period of fruit enlargement. Autumn shoots are the fruiting mother branches for bearing trees in the coming year. The quality and quantity of autumn shoots directly affect the yield and quality of the coming year. Therefore, while doing a good job in citrus fertilizer and water management, doing a good job in pest and disease control is particularly important.

I. Guiding principles for control

Citrus fruit is a fresh-eating fruit. When controlling pests and diseases, people should be put first to ensure the physical and mental health of fruit growers and consumers. Therefore, green and pollution-free control technologies should be vigorously promoted, such as the use of frequency-vibration insect-killing lamps, electronic moth-killing lamps, sex pheromone attractants, and sugar-vinegar-alcohol liquid to trap and kill citrus pests; the promotion and use of high-efficiency, low-toxicity, pollution-free pesticides, such as biological pesticides; and the advocacy of bagging citrus fruit to reduce the amount of pesticide used. Pesticides must not be sprayed within 30 days before citrus fruit is harvested.

II. Occurrence and damage characteristics, control thresholds and appropriate timing

1. Red spider mite: mainly damages leaves, branches and fruit. Pale white spots appear on the upper surface of damaged leaves and on the surface of fruit. When there are 5-10 mites or eggs per leaf (fruit), it is the key appropriate period for control.

2. Rust mite: mainly damages leaves and fruit, causing the fruit to become pitted citrus. When there are 2-3 mites per leaf or fruit, or when gray dew-like substances are seen, it is the key appropriate period for control.

3. Scale insects: mainly damage leaves, branches and fruit. Damaged leaves turn yellow, causing branches, shoots and fruit to become rough and uneven. When there is 1 adult scale per leaf (fruit), the peak period of nymphs, especially the peak of the first instar, is the key appropriate period for control.

4. Leafminer: mainly damages leaves. Many silver-white mines appear on damaged leaves. The summer and autumn shoot emergence periods are the key control periods. That is, 7-10 days after shoot release, when 20% of leaves on tender shoots have pests or eggs, it is the appropriate period for control.

5. Citrus canker: mainly damages leaves, branches and shoots, and fruit. The prominent feature of the lesions is sponge-like cracks, with a slightly sunken center. The shoot emergence, flowering and young fruit periods are the appropriate periods for chemical control.

6. Anthracnose: mainly damages leaves, branches and fruit. Black small spots appear on the lesions. The summer and autumn shoot emergence periods and the young fruit period are the key appropriate periods for control.

7. Scab: mainly damages leaves and fruit. The lesions protrude into tumor-like shapes. The spring shoot emergence period and young fruit period are the key appropriate periods for control.

At the same time, control should be strengthened in a timely manner against flat-headed borers (including the two types, the blister beetle borer and the bark-slipping borer) and longhorn beetles (combining manual capture and killing with chemical poisoning), fruit-sucking noctuid moths (combining yellow-light driving with manual capture and killing), and citrus whitefly, etc.

III. Chemical control techniques

1. For primary control of red spider mite and rust mite. The following pesticides may be selected: 10% chongmanling emulsifiable concentrate 4000-fold solution, saomanjing 1500-2000-fold, 70% kemanite emulsifiable concentrate 2000-fold solution, 15% dapentone emulsifiable concentrate 3000-fold solution, 20% manke emulsifiable concentrate 1500-fold solution, 20% weiling 2500-fold solution (special effect for controlling rust mite).

2. For primary control of citrus whitefly. 25% pujiling wettable powder 1500-fold solution and 10% dagongchen wettable powder 1000-fold solution may be selected.

3. For primary control of scale insects. 40% supusha emulsifiable concentrate 1000-fold, 25% jiesijing emulsifiable concentrate 900-fold solution, and 35% kuaike 800-fold solution may be selected.

4. For primary control of leafminer. 20% haoniandong emulsifiable concentrate 2500-fold solution, 18% shachongshuang aqueous solution 400-fold solution, 1.8% abamectin (chongmanke) emulsifiable concentrate 3000-fold solution, etc. may be selected.

5. For primary control of scab, canker, etc. 77% keshadde wettable powder 600-fold solution, 80% chaobangsheng 800-fold solution, 10% shigao water-dispersible granules 6000-7000-fold solution, 50% jiaruinong wettable powder 800-fold solution, etc. may be selected.

6. For control of resin disease. Use a knife to scrape the lesions down to the xylem (collect the scraped bark and burn it), then apply the pesticide. 70% tuobujin wettable powder 80-fold solution, 80% mancozeb 20-fold solution, and 77% keshadde wettable powder 600-fold solution may be selected to apply to treat the lesions.