The Sichuan pepper tree, originally named *Zanthoxylum bungeanum*, also known as prickly ash, is a deciduous small tree belonging to the Rutaceae family and the *Zanthoxylum* genus. The thorns on its trunk usually fall off early, while its branches have short thorns. The thorns on the twigs are broad, flat, and straight, forming long triangles. The current year's shoots are covered with short, soft hairs. It is cultivated in most parts of China, from southern Northeast China in the north to the northern slopes of the Five Ridges in the south, southeast to the coastal areas of Jiangsu and Zhejiang, and southwest to southeastern Tibet. It is not grown in Taiwan, Hainan, or Guangdong. The most important aspect of Sichuan pepper cultivation is the prevention and control of pests and diseases. Farmers often ask about common pests and diseases affecting Sichuan pepper and how to control them. Below, we will discuss the common pests and diseases of Sichuan pepper trees and their control methods.

I. Common Diseases

1. Root rot of Sichuan pepper

Most commonly occurring in nurseries and mature pepper orchards, this soil-borne disease is caused by Fusarium solani. Affected plants exhibit root discoloration and rot, with a foul odor. The root bark separates from the woody trunk, and the woody parts of the trunk turn black. Above-ground parts show small, yellow leaves and underdeveloped branches; in more severe cases, the entire plant dies.

Prevention and control methods

(1) Adjust the layout reasonably and improve the pepper garden with poor drainage and damp environment to make it ventilated and dry.

(2) Perform seedling management well, select nurseries carefully, and disinfect the soil with 15% carbendazim solution diluted 500-800 times. Plant trees on raised beds, dig deep trenches in the soil, and apply heavy base fertilizer. Remove diseased seedlings in a timely manner.

(3) When transplanting seedlings, soak the roots for 24 hours with a solution of 50% methyl thiophanate at 500 times dilution + Jiamihongli at 1000 times dilution. Disinfect the soil with quicklime. Then drench the roots with a solution of methyl thiophanate at 500-800 times dilution, or a solution of 15% triadimefon at 500-800 times dilution + Jiamihongli at 1000 times dilution.

(4) In the early stage of the disease, drench the roots with 15% carbendazim at 300-800 times dilution + Jiamihongli at 1000 times dilution (Note: for mature trees) to effectively prevent the disease. Drenching the roots in summer can reduce the severity of the disease, while drenching the roots in winter can reduce the overwintering structure of the pathogen.

(5) If a diseased or dead tree is found, its roots should be dug up and the tree burned to eliminate the source of infection.

2. Pepper rust

Sichuan pepper rust is one of the important diseases affecting the leaves of Sichuan pepper, and it is widely distributed in Sichuan pepper cultivation areas in Chongqing, Shaanxi, Sichuan, Hebei, Gansu and other provinces. In severe cases, Sichuan pepper leaves fall off prematurely, directly affecting the fruit production in the following year. In the early stage of the disease, 2-3 mm water-soaked chlorotic spots appear on the upper surface of the leaves, and yellow-orange pustules, which are uredinia, appear on the lower surface of the leaves opposite the lesions.

This disease is caused by *Zanthoxylum bungeanum* rust. The urediniospore and teliospore stages occur on the *Zanthoxylum bungeanum* tree. The occurrence of *Zanthoxylum bungeanum* rust is mainly related to climate. It is more likely to occur when there is abundant rainfall, especially during the third quarter when there are many rainy days. Similarly, prevention of other diseases can be achieved through early intervention.

Prevention and control methods

(1) Chemical prevention: Before the disease occurs, Bordeaux mixture or 0.1-0.2% Baume lime-sulfur mixture can be sprayed. In particular, from June to late July, 200-400 times diluted chlorothalonil can be sprayed on the pepper trees for protection.

(2) Chemical control: For diseased plants, spray with 65% mancozeb wettable powder at a dilution of 400-500 times or 15% triadimefon wettable powder at a dilution of 800 times to control the production of uredinia. During the peak of the disease, spray with Bordeaux mixture at a dilution of 1:2:200, or lime sulfur mixture at a dilution of 0.1-0.2 Baume, or 10% tebuconazole at a dilution of 2000-3000 times, or 15% wettable triadimefon powder at a dilution of 1000-1500 times + Jiamijindian at a dilution of 1000 times.

(3) Strengthen fertilizer and water management. Fertilizer should be applied according to the tree's growth in spring, late June to early July during the middle growth period, and after the pepper harvest to supplement nutrients. Apply 1 bag of Jiaming Hongli + 2-3 kg of Jiaming Hailibao per mu by drip irrigation or fertigation; or 1 bag of Jiaming Hongli + 4-5 kg ​​of Jiaming Yinglilai. Remove weeds and prune properly. In late autumn, promptly remove dead branches, fallen leaves, and weeds and burn them.

(4) Cultivate disease-resistant varieties. You can interplant pepper varieties with strong disease resistance.

3. Sichuan pepper plaster for treating illness

Sichuan pepper leaf spot disease is the most common disease in Sichuan pepper cultivation, especially in trees older than 3 years. The pathogen is *Septiflora*, a fungus belonging to the Basidiomycota. The basidia, resembling plasters, tightly adhere to the branches and trunks of the Sichuan pepper tree. Mild cases result in poor branch and trunk growth and reduced fruit production; severe cases lead to branch and trunk death. The death of branches and trunks, as well as reduced fruit production and small fruit size, are all caused by leaf spot disease. The occurrence of leaf spot disease is closely related to tree age, humidity, and variety. Sichuan pepper leaf spot disease mainly occurs in shady, humid mature pepper orchards. Leaf spot disease feeds on honeydew secreted by scale insects; therefore, pepper orchards severely infested with scale insects experience severe leaf spot disease, indicating a close correlation between the disease's occurrence and scale insect damage.

Prevention and control methods

(1) Strengthen management, prune and remove dead branches and fallen leaves appropriately to reduce the humidity of pepper garden.

(2) Control the planting density, especially in mature pepper gardens during the peak fruiting period. If the garden is too shady, it should be thinned appropriately.

(3) Spray with 150-200 times dilution of 45% crystalline lime sulfur, 1000 times dilution of 22% chlorpyrifos emulsifiable concentrate, or 4000 times dilution of 22.4% spirotetramat. Applying yellow mud to the trunk also has a good control effect. After scraping off the fungal film, apply 200 times dilution of 50% mancozeb wettable powder or 80-100 times dilution of 45% crystalline lime sulfur.

4. Anthracnose of Zanthoxylum bungeanum

This disease primarily affects the fruit. In the early stages, several small brown spots appear on the fruit surface, distributed irregularly. Later, the lesions turn brown or black, becoming round or nearly round with a sunken center. The disease typically begins to appear from late June to late July, peaking in August. Symptoms include leaf and fruit drop, and a decrease in the commercial value of the fruit.

Prevention and control methods

(1) Strengthen pepper garden management, carry out deep plowing and turning, prevent excessive application of nitrogen fertilizer, and apply 1 bag of Jiaming Hongli + 1 bag of Jiaming Naobaijin per mu by drip irrigation or fertigation. Drain water in time after rainfall to promote the growth and development of pepper trees and enhance disease resistance.

(2) Remove diseased and damaged plants in a timely manner and burn them in a concentrated manner to reduce the source of pathogens; improve ventilation and light conditions in the pepper garden by pruning pepper trees to reduce the occurrence of diseases.

(3) In winter, in conjunction with cleaning the pepper garden, spray once with lime sulfur mixture of 3-5 Baume degrees or 45% crystalline lime sulfur mixture diluted 100-150 times, while also treating other diseases and pests.

(4) In the early stage of the disease, use 40% prochloraz and propineb at 800 times dilution, or 36% tebuconazole and propineb at 800 times dilution, or 32% bromodiphenyl ether at 800 times dilution, etc. + Jiamijindian at 1000 times dilution. In the peak period of the disease, spray 25% pyraclostrobin at 1000 times dilution, or 43% prochloraz at 1500 times dilution plus 80% mancozeb at 800 times dilution, or 3% polyoxin at 400 times dilution + Jiamijindian at 1000 times dilution.

5. Sichuan pepper dry rot disease

Sichuan pepper dry rot, commonly known as gummosis, primarily affects branches and trunks. In the early stages, reddish-brown lesions appear on the branches and trunk. As the lesions enlarge, they become sunken and dark brown, accompanied by gum exudation. In later stages, small orange spots appear on the lesions, which then crack and dry out. In severe cases, it can cause extensive bark rot, and even lead to tree and branch death.

Prevention and control methods

(1) Strengthen plant quarantine. When transporting Sichuan pepper seedlings, it is essential to conduct quarantine work for this disease. Seedlings with the disease are strictly prohibited from being transported to other areas to prevent the spread of the disease; avoid transporting seedlings from diseased areas to prevent the introduction of the disease.

(2) Strengthen cultivation management. Change the traditional extensive management method of pepper garden, strengthen fertilizer and water management, prune in time, check and kill longhorn beetles, jewel beetles, scale insects, etc., remove diseased and insect-infested branches, and destroy them in a centralized manner.

(3) Chemical control: For mild lesions on large branches and trunks, scrape off the lesions and apply methyl thiophanate + thiophanate-methyl; or difenoconazole + chlorothalonil, mixing one part medicine with three parts soil and an appropriate amount of water to make a paste for application. In March-April each year and after harvesting Sichuan pepper fruits, spray the trunk 2-3 times with a 1000-fold dilution of pyraclostrobin or difenoconazole + chlorothalonil + Jiamijindian.

II. Common Pests

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1. Sichuan pepper tiger longhorn beetle

This insect is also known as the Sichuan pepper longhorn beetle or wood-boring beetle. The larvae bore into the trunk, while the adults feed on leaves and tender shoots. Damage characteristics: The larvae bore upwards at an angle from the lower part of the trunk, entering the xylem and feeding along the heartwood towards the upper part of the trunk, causing the trunk to become hollow, the tree to wither, and in severe cases, the Sichuan pepper tree to die. The adults feed on leaves and tender shoots.

Adults are 1-24 mm long, black in color, and covered with yellowish downy hairs. The head is densely covered with fine punctures. The antennae have 11 segments, approximately one-third the length of the body. The legs are the same color as the body. There are two black spots in the middle of the elytra and a nearly circular black spot on the outer third of the wing surface. Eggs are oblong, 1 mm long and 0.5 cm wide, initially white, turning yellowish-brown before hatching. Newly hatched larvae have pale yellow heads and milky-white bodies; 2nd-3rd instar larvae have yellowish-brown heads; older larvae are yellowish-white with bluish-white intersegments. Pupae are initially milky-white, gradually turning yellow.

Prevention and control methods

(1) Eliminate the source of pests: Collect withered and dead plants in a timely manner and burn them.

(2) Manual killing: Adult insects are manually captured on sunny mornings and afternoons in July.

(3) Biological control: The Sichuan scleroderma wasp is a natural enemy of the Sichuan pepper tiger longhorn beetle. On sunny days in July, release 5-10 Sichuan scleroderma wasps on each affected plant. Practice has shown that the application of Sichuan scleroderma wasps to control the Sichuan pepper tiger longhorn beetle is effective.

2. Sichuan pepper aphids

The damage caused by aphids to Sichuan pepper trees has become not only a systemic problem but also a catastrophic one. Sampling surveys showed that 86.3% of buds, leaves, and tender shoots were affected, with 73.6% of leaves curling into clumps and 62.4% experiencing bud drop. Because aphids, both adults and nymphs, congregate on the undersides of leaves and tender shoots to suck sap, they not only cause leaves to curl into clumps but also severely impact the growth, development, photosynthesis, flowering, and fruit setting of the Sichuan pepper tree, ultimately reducing yield by 20%-30%, and in severe cases, by up to 50%.

Prevention and control methods

(1) Adhere to early treatment. In areas where the damage occurs, focus on spraying pesticides in the early stage of the disease. Avoid the drawback of spraying pesticides indiscriminately when there are aphids or not, which will kill natural enemies.

(2) At the same time, natural enemies can be fed in places where conditions permit for biological control.

(3) Select neonicotinoid agents, such as imidacloprid, acetamiprid, nitenpyram, thiamethoxam, thiamethoxam, dinotefuran, thiamethoxam, etc., plus long-acting agents such as cyhalothrin, bifenthrin, etc., and add penetrant (organosilicon) and Jiamijindian for alternating spraying for prevention and control.

(4) Scrape off the black skin of the main stem with a knife, and apply thiamethoxam around the scraped area. The aphids will disappear in four or five days.

3. Sichuan pepper white butterfly (also known as citrus white butterfly)

This insect has 2-3 generations per year, overwintering as pupae. Adults emerge in March to lay eggs. After hatching, they feed on tender leaves and have a large appetite, sometimes consuming all the leaves of an entire plant, leaving only the main vein on older leaves. They pupate in May when they are fully grown. The spring type occurs in June and July, while the summer type occurs after July.

The adult is 18-30 mm long and has a wingspan of 66-120 mm. The body is yellowish-green with black stripes on the back. This butterfly has two varieties, one for spring and one for summer. The summer variety is larger with a deep yellow tinge, while the spring variety is smaller. The larvae are initially blackish-brown with a yellow head, and turn completely green when fully mature.

Prevention and control methods

After discovery, use cyhalothrin, abamectin, emamectin benzoate, bifenthrin, etc. plus Jiamijindian spray for control.

4. Scale insects of Sichuan pepper

Scale insects that damage Sichuan pepper include the barn scale, the poplar scale, the mulberry scale, and the pear scale. Sichuan pepper scale insects typically have one or several generations per year. Large numbers of nymphs and adults can be seen in May and September. They are relatively small, with their bodies covered in waxy secretions or a shell. When infesting, they use their piercing-sucking mouthparts to feed on the plant's branches and leaves. Affected leaves turn yellow, branches wither, the tree weakens, and in severe cases, the entire plant dies.

Prevention and control methods

(1) Clean up the garden, remove weeds, fallen leaves, diseased and insect-infested branches and dead branches from the ground of the pepper garden and burn them to reduce the source of insects.

(2) Spray the tree with a mixture of 300 times dilution of imidacloprid, 300 times dilution of chlorpyrifos, and 300 times dilution of cymoxanil from late February to early March.

(3) During the egg stage, a mixture of 1000 times diluted spirotetramat, thiamethoxam, and acetamiprid can be sprayed on the entire tree body, canopy, and underside of leaves. If individual trees are severely damaged, the egg sacs should be manually removed to reduce the number of insects.

(4) The scale insects of Sichuan pepper are small and the damage is hidden. Therefore, it is necessary to insist on early prevention and control, and to be meticulous and uniform, leaving no dead ends.

(5) For plants that have become weak due to severe damage, pruning, shortening and cutting back of the damaged branches can be strengthened to restore the tree vigor as soon as possible.