Detailed Explanation of Key Technical Points for Pest and Disease Control in Jujube Trees

To achieve high yields in jujube cultivation, pest and disease control measures must be well implemented. Currently, jujube pests and diseases are widely distributed and cause severe damage. They are the main cause of low yield and poor quality in jujube trees, so timely control of jujube pests and diseases to ensure healthy tree growth is the key to achieving a bountiful jujube harvest.

I. Major Diseases and Control Measures

1.1 Jujube Anthracnose

Jujube anthracnose, commonly known as “roasted eggplant” disease, mainly affects jujube fruit but also infects bearing shoots, leaves, jujube heads (fruiting branch tips), and jujube spurs. Initially, small brown water-soaked spots appear, which expand into nearly circular sunken lesions. The lesions enlarge and become densely covered with gray to black small granules, causing fruit drop. Diseased fruit tastes bitter and is unfit for consumption. When leaves are affected, they turn yellow and drop, and disease severity increases during rainy periods. The pathogen overwinters as mycelium in remnant bearing shoots and jujube heads, which together with diseased berry-like fruit serve as the primary infection source for the following year. The conidial masses contain water-soluble gelatinous substances and, under natural conditions, require dew and stormy weather for dispersal.

Control measures:

(1) Thorough orchard sanitation combined with pruning: Prune off remnant bearing shoots, diseased and pest-infested branches, and dead branches remaining on the tree. Strengthen fertilizer and water management, improve the soil. In late autumn and early winter, apply 50-60 kg of decomposed barnyard manure or human excrement per tree. In June after rain, apply 2-3 kg of potassium sulfate compound fertilizer per tree as a top dressing to enhance tree disease resistance.

(2) Chemical control: Before jujube bud break, spray once with 5 degrees Baume lime sulfur mixture. In late June, before the disease onset period, eliminate pathogen sources on the tree. Commonly used agents include 40% flusilazole emulsifiable concentrate at 5000 times dilution and 50% iprodione wettable powder at 1500 times dilution. Near the disease onset period, control can be combined with jujube rust management by spraying once in mid-to-late July with 200 times Bordeaux mixture at double strength, or 10% polyoxin at 800 times dilution, used alternately.

1.2 Jujube Rust

An epidemic disease of jujube leaves caused by fungi, it triggers massive leaf drop during the fruit enlargement period. The disease mainly affects leaves, sometimes also infecting fruit. On the underside of affected leaves, scattered pale green dots appear, gradually turning pale grayish-brown, and finally the lesions turn yellowish-brown, producing raised urediniospore pustules. On the upper surface of the leaf opposite the urediniospore pustules, irregular brownish-green small spots appear, gradually losing luster and becoming yellowish-brown angular lesions. The pathogen mostly overwinters on diseased leaves. After rainfall in late June, overwintered spores begin to germinate and invade leaves. Disease onset begins in mid-July, and from August to September the pathogen continuously reinfects, causing severe leaf drop on heavily affected leaves. Rainy conditions and high humidity are the main conditions for jujube rust epidemics.

Control measures:

(1) Strengthen cultivation management: New jujube orchards should not be planted too densely. Overcrowded branches should be pruned in a timely manner to facilitate ventilation and light penetration and enhance tree vigor. During the rainy season, drainage should be timely to reduce orchard humidity. Do not plant tall crops between rows, especially crops that require frequent irrigation.

(2) Foliar fertilization: Foliar feeding of jujube trees improves photosynthesis and fruit set rate, and can also help control jujube rust. During the susceptible period, spray 0.5% urea or 0.3% potassium dihydrogen phosphate solution 2-3 times. In winter and spring, carefully sweep up fallen leaves and burn them in a centralized manner to reduce overwintering pathogens.

(3) Chemical control: In late June, before the pathogen begins to invade, spray for protection, once every 15-20 days, for 3-5 consecutive applications. Commonly used agents include 50% carbendazim at 600-800 times dilution, 200 times Bordeaux mixture at double strength, and 25% triadimefon wettable powder at 800-1000 times dilution. Alternating use gives better results.

1.3 Jujube Witches' Broom

Local fruit growers also call it “broom disease” or “mad jujube tree.” It is a disease caused by phytoplasma. It mainly affects jujube trees and wild sour jujube trees and is a devastating disease of jujube. After infection, both aboveground and underground parts show abnormal growth states. Aboveground symptoms include floral organs transforming into leaves, abnormal bud development and growth causing clustered branches and leaves, and yellowing and cupping of young leaves. Underground symptoms mainly manifest as clustered root suckers. Young trees die after 1-2 infections, while large trees gradually wither and die over 2-3 years. Jujube witches' broom is transmitted through grafting or by leafhopper pests feeding in the field. In the early stage, it usually starts from one or several large branches and root suckers, though whole-tree simultaneous onset can also occur.

Control measures:

(1) Select disease-free jujube seedlings. Strict quarantine must be carried out for seedlings introduced from other regions. When grafting, use disease-free rootstock and scions, and be sure to disinfect grafting tools to prevent cross-infection of the disease.

(2) Eradicate diseased plants and diseased root suckers to prevent transmission. Strengthen cultivation management, increase application of alkaline fertilizers and decomposed farmyard manure to promote healthy tree growth.

(3) Control vector pests: Spray 20% fenvalerate-malathion at 2500 times dilution to control leafhopper pests.

1.4 Jujube Seedling Stem Rot

Also known as jujube seedling root rot, it occurs in both seedling-grown and nursery-returned jujube seedlings. When seedlings grow to the 3-9 leaf stage (generally May-June in the Tianjin area), stems and leaves turn pale yellow, then pale white, and wither and die, but the dead leaves do not fall. Digging the soil to observe the root-stem area reveals blackish-brown rot in the cortex of the main stem, with necrosis of both xylem and pith, interruption of conductive tissues, and death of the seedling. This disease occurs in all jujube-growing areas in northern China.

Control measures:

(1) Increase application of high-quality organic fertilizer to promote healthy seedling growth. Select strong seedlings for planting to improve disease resistance of jujube seedlings.

(2) Apply chemicals at the roots. Drench roots with a mixture of 40% quintozene wettable powder (at a ratio of 3:1) at 600 times dilution, which both prevents disease and promotes root growth, improving disease resistance.

(3) Soil disinfection. During the jujube bud break period, spray the seedbed broadly with 50% iprodione · thiram wettable powder at 800-1000 times dilution to sterilize and disinfect the soil.

1.5 Jujube Fruit Shrink Disease

Also known as jujube wilt fruit disease, this pathogen only affects mature jujube fruit. Affected fruit first show irregular yellowish-brown discoloration spots on the fruit shoulder or body, then the peel turns earthy yellow, and later the peel becomes dark red, shrinks, and loses luster. Temperatures of 26°C-28°C mark the peak onset period, and when this coincides with continuous overcast and rainy weather or rainy nights followed by clear days, outbreaks are most likely to occur.

Control measures:

(1) Strengthen soil management in jujube orchards. Maintain soil moisture during the period when fruit change color and turn red to prevent fruit shrink disease while strictly preventing fruit insect pests. Strengthen control of leafhoppers, tortoise wax scale, and peach fruit borer to reduce insect population density on the fruit surface.

(2) Autumn orchard sanitation: Thoroughly remove diseased, pest-infested, and rotten fruit, and burn or bury them deeply in a centralized manner to reduce pathogen sources.

(3) Chemical control: Before and after disease onset, spray 12.5% diniconazole wettable powder at 2000 times dilution or 70% mancozeb wettable powder at 8000 times dilution once every 7-10 days, for 3 consecutive applications. These chemicals are best used immediately after preparation.

II. Major Insect Pests and Control Measures

2.1 Jujube Gall Midge

Also known as jujube maggot or jujube bud maggot, it is one of the main pests of jujube leaves. When the first generation emerges each year, it coincides with the jujube bud break and leaf expansion period. The larvae damage the unexpanded tender leaves and feed on the surface sap of tender leaves, causing large numbers of tender leaves to fail to expand. Affected leaves appear pale red to purple-red, become hard and brittle, and finally dry up and drop, which is extremely detrimental to jujube flowering. Early May is the peak damage period. Mature larvae enter the soil after late August and spin cocoons to overwinter.

Control measures: Local fruit growers have insufficient understanding of the living habits and damage characteristics of the jujube gall midge and fail to seize the key control period for targeted treatment, resulting in poor control results. Therefore, effective control plans are:

(1) Manual control: In late autumn and early winter or early spring, deep-plow the jujube orchard to turn old cocoon larvae and pupae into deep soil layers, preventing their normal emergence in spring, and eliminating overwintering adults or pupae.

(2) Ground poisoning: When jujube buds begin to swell, before adults emerge from the soil and before they drop from leaves, evenly broadcast 2.5% trichlorfon powder and then harrow once to poison and kill emerging adults.

(3) Chemical control: Focus on controlling the overwintering generation and first generation. Spray fenpropathrin emulsifiable concentrate at 2000 times dilution, once every 10 days, for 2-3 consecutive applications, giving good control results.

2.2 Green Plant Bug

Also known as the small stink bug, it is a worldwide omnivorous pest. Adults and nymphs use their piercing-sucking mouthparts to damage tender buds and flower buds of host plants. After young plant tissues are damaged, small dead spots first appear, then turn yellow and wither. Affected bearing shoots cannot extend normally, and after flower buds are damaged, they stop developing and wither and drop. After jujube bud break, nymphs begin to climb the trees and cause damage. Early May, during the jujube leaf expansion period, is the peak damage period. After late May, as temperatures rise, insect population density decreases. Generations 2-4 appear from June to early August respectively.

Control measures:

(1) Eliminate eggs: In spring and autumn, dig around tree bases and remove weeds to eliminate overwintering eggs.

(2) Chemical control: After overwintering eggs hatch in early spring, spray 20% fenpropathrin emulsifiable concentrate at 2000 times dilution on overwintering host crops. In early-to-mid May and during the first generation damage period, carry out further chemical control.

2.3 Peach Fruit Borer

Also known as “jujube maggot,” it commonly occurs in jujube-producing areas of Tianjin. After larvae bore into fruit, they first feed just beneath the peel, then bore to the jujube pit. Larvae mature inside the fruit after 17 days, exit the fruit, enter the soil, and spin cocoons. If uncontrolled, the rate of infested fruit can reach 40%-60%, and their frass remains inside the fruit, seriously affecting fruit quality. In the Jizhou area, 2 generations occur each year. Mature larvae overwinter as winter cocoons in the soil, begin emerging in mid-May of the following year, emerge continuously in early-to-mid June, with peak emergence in mid-to-late June. Adults emerge and lay eggs in July. Larvae begin hatching and boring into fruit in mid-July. Larvae live inside fruit for about 25 days, exit the fruit, spin cocoons, and pupate, continuing to produce the second generation. Larvae that bore into fruit after mid-July mostly enter the soil and spin cocoons to overwinter after exiting the fruit, producing only 1 generation.

Control measures:

(1) Plastic film mulching to suppress larval emergence. In early June, cover the ground within 100 cm around the tree trunk with plastic film, which can suppress larval emergence, pupation, and adult eclosion.

(2) Pick up fallen fruit or larvae that have exited fruit. In early July or early August, pick up fallen jujubes; if done promptly, over 80% of larvae inside fruit can be eliminated. From August to September, pick up larvae that have exited fruit beneath jujube trees (most numerous at the trunk base) and destroy them. Especially after rain, more larvae exit fruit, so they must be picked up and destroyed promptly.

(3) Spray chemicals on trees to control fruit-boring. Tree spraying should be timed during adult eclosion and egg laying and during egg hatching. Spray 20% fenvalerate emulsifiable concentrate at 1500-2000 times dilution or 25% chlorbenzuron No. 3 suspension concentrate at 1500 times dilution to kill adults, eggs, and fruit-boring larvae.

2.4 Jujube Inchworm

Also known as jujube looper, it is one of the most important insect pests of jujube trees. Its larvae are highly voracious, damaging tender buds, leaves, bearing shoots, flower buds, and all green tissues of jujube. One generation occurs each year. Pupae overwinter in soil at a depth of 10-15 cm around the tree canopy. Adults emerge in late March of the following year, mate, and lay eggs. Female adults are wingless and must crawl up the trunk to lay eggs. After an egg period of about 25 days, larvae hatch and climb the trees to cause damage from mid-to-late April to mid-May. From late May to mid-June, they begin to enter the soil to pupate, oversummer, and overwinter.

Control measures:

(1) Dig out overwintering pupae: Before mid-March, within a range of 100 cm diameter and 10 cm depth around the trunk, turn and dig the soil layer to dig out and destroy overwintering pupae. This can also be combined with digging around tree bases in early winter or early spring, picking out pupae whenever found. You can also take advantage of the larvae's habit of feigning death and falling to the ground when startled; during the larval damage period, shake the tree to dislodge larvae and kill them on the spot.

(2) Chemical control: Based on the characteristics and damage patterns of the jujube inchworm, chemical control can be divided into 2 applications. When young larvae are 4-10 mm in body length, carry out 1-3 consecutive chemical treatments. Suitable options include 20% fenvalerate emulsifiable concentrate at 4000 times dilution or 25% carbaryl wettable powder at 300 times dilution.