Control Methods for Major Pests and Diseases in Jujube Cultivation
I. Major Diseases
1. Jujube rust. This disease mainly damages leaves, and sometimes also infects fruit. On the back of affected leaves, scattered light green spots appear, gradually turning pale grayish brown, and finally the lesions turn yellowish brown and produce raised summer spore piles. On the front of the leaf, opposite the summer spore piles, irregular brownish green small spots appear, gradually losing their luster and turning into yellowish brown angular spots. The pathogen mostly overwinters on diseased leaves. After rainfall in late June, the overwintered spores begin to germinate and invade the leaves, and the disease begins in mid-July. In August-September, the pathogen continuously reinfects, and severely affected leaves begin to drop in large numbers. Abundant rain and high humidity are the main conditions for the occurrence and spread of jujube rust.
Control measures: (1) Strengthen cultivation management and increase the application of organic fertilizer so that the tree grows vigorously and its disease resistance is improved. (2) During the winter dormant period, through reasonable shaping and pruning, maintain good ventilation and light penetration in the orchard, thoroughly sweep up diseased fallen leaves, and burn them in a centralized manner to reduce overwintering pathogens. (3) Spray control: in late June, before the pathogen begins to invade, spray for protection, once every 15-20 days, for 3-5 consecutive sprays. Commonly used agents include 50% carbendazim 800-1000 times, 200 times Bordeaux mixture with double the lime, 50% thiram 600 times, and 25% triadimefon wettable powder 1000-1500 times, used alternately, with good results.
2. Jujube anthracnose. This disease mainly harms jujube fruit, and can also harm leaves. When fruit is affected, brown water-soaked small spots first appear, and after expansion they become nearly round sunken lesions. As the lesions expand, dense gray to black small granules appear, causing fruit drop. Diseased fruit tastes bitter and is unfit to eat. When leaves are affected, they turn yellow and fall off. Disease severity increases during rainy periods.
Control measures: (1) Strengthen fertilizer and water management, improve the soil, ensure irrigation during drought and drainage during waterlogging, increase the application of organic fertilizer, promote vigorous tree growth, and improve disease resistance. (2) Clean the orchard: after leaf fall, collect all fallen leaves and fallen fruit in the orchard and burn them or bury them deeply. (3) Chemical control: before jujube trees bud, spray once with 5 degrees Baume lime sulfur mixture. In early and mid-June, spray once with 200 times Bordeaux mixture with double the lime. In mid-to-late July and early August, spray a fungicide once each, with commonly used agents including 65% zineb 500 times, 50% carbendazim 800-1000 times, 75% chlorothalonil wettable powder 600 times, and 200 times Bordeaux mixture with double the lime.
3. Jujube witches' broom. This disease mainly harms jujube trees and wild sour jujube trees, and is a destructive disease of jujube trees. After jujube trees are infected, both the aboveground and underground parts show abnormal growth states. The aboveground part shows flowers turning into leaves, dense clusters of branches and leaves caused by abnormal development and growth of buds, and yellowing and curling of young leaves into spoon shapes. The underground part mainly shows dense clusters of root suckers. Young trees die after being affected 1-2 times, and large trees gradually wither and die over 3-6 years after infection. Jujube witches' broom is transmitted through grafting or by piercing-sucking transmission by leafhopper pests in the field.
Control measures: (1) Remove diseased plants and diseased root suckers to prevent transmission. (2) Use disease-free scions and graft to propagate seedlings. (3) Select varieties with strong disease resistance and strengthen cultivation management to promote vigorous tree growth. (4) Control vector pests and spray 20% fenvalerate 3000 times or 10% imidacloprid 3000 times.
II. Major Insect Pests
1. Peach fruit borer. In the northern regions of our country, 1-2 generations occur each year. Mature larvae overwinter as winter cocoons in the soil, begin to emerge from the soil in mid-May of the following year, and emerge continuously in early to mid-June, with the peak emergence period in mid-to-late June. In July, adults emerge and lay eggs. In mid-July, larvae begin to hatch and bore into fruit. The larvae live inside the fruit for about 25 days, leave the fruit, form cocoons, and pupate, continuing to produce the second generation. Larvae that bore into fruit after mid-July mostly enter the soil after leaving the fruit, form cocoons, and overwinter, with only 1 generation occurring.
Control measures: (1) Build up soil around the tree base or cover with film. Before the larvae emerge from the soil, build up soil within 1 m around the trunk and press it firmly to prevent the larvae from emerging. Before covering with film, scatter 5% phoxim granules on the ground, then shallow hoe. (2) Apply chemicals at the right time. When the egg-fruit rate reaches 1-2%, begin spraying for control. Spray 2-3 times continuously, once every 15 days. Commonly used agents include 20% fenvalerate 2000-3000 times and 30% Taoxiaoling emulsifiable concentrate 1500 times. Spray carefully and thoroughly.
2. Jujube inchworm. The larvae harm the young buds, leaves, and flower buds of jujube. One generation occurs each year, and pupae overwinter in soil 10-15 cm deep around the tree canopy. In late March of the following year, they emerge as adults, mate, and lay eggs. Female adults are wingless and must crawl onto the trunk to lay eggs. After an egg period of about 25 days, larvae hatch from mid-to-late April to mid-May and climb the tree to cause damage. Larvae in the 1st-3rd instars eat little and mainly feed on young leaves. Larvae in the 4th-5th instars greatly increase their food intake and often eat all the leaves. After developing through 5 instars, the larvae begin to enter the soil in late May to mid-June to pupate, pass the summer, and overwinter.
Control measures: (1) In winter, combine with deep plowing of the soil, pick out and kill overwintering pupae. (2) In early March, tie a film about 10 cm wide around the trunk base at 20-25 cm above the ground to prevent female adults from climbing the tree to lay eggs. Manually kill adults under the tree every morning and evening, or spray pyrethroid pesticides around the trunk to kill newly hatched larvae. (3) Spray chemicals on the tree for control. If control under the tree is not thorough and some still climb the tree to cause damage, spray agents such as 25% diflubenzuron 2000 times.
3. Jujube leaf roller. Also known as the leaf-wrapping insect, its larvae harm leaves, flowers, and fruit, and spin silk to stick small jujube branches together, rolling the leaves into a dumpling shape and causing damage inside, or bore into the fruit from the fruit stalk and feed on the flesh, causing affected fruit to drop early. This insect occurs 3 generations a year and overwinters as pupae in cocoons under old cracked bark and in crevices. In late March of the following year, adult emergence begins, with the peak emergence period in early to mid-April. They mate 2-4 days after emergence and lay eggs 1-2 days after mating. The egg period is 10-15 days. The peak period of the 1st-generation larvae is in early May, the peak period of the 2nd-generation larvae is in late June to early July, and the 3rd generation is in early to mid-August.
Control measures: (1) Beginning in early September, tie bundles of grass on the trunk to attract larvae to pupate and overwinter there. In winter, collect the grass bundles and burn them or bury them deeply. (2) In winter, scrape off old cracked bark to reduce overwintering sources of the insect. (3) Spray control, focusing firmly on control of the 1st-generation larvae, and spray promptly during the larval occurrence period. Alternating 90% trichlorfon 1000 times and 20% fenvalerate 3000 times gives good results.