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Recently, a cold joke circulated on the Internet, "Do you believe there are dragons in this world?" Believe me, because I've been served one-stop. "But when you think of citrus, you can't laugh out loud — yellow dragon disease!" Citrus huanglongbing disease is the most important disease of citrus in Guangdong, Guangxi, Fujian and other provinces and regions. Why is it called Yellow Dragon Disease? Because the branches of the citrus that have this disease are yellow, and the Chaoshan region of Guangdong calls the branches dragons, this is how the name comes from.
Source: Color Atlas of Diagnosis and Control of Fruit Tree Diseases and Pests
<h1>Citrus's "ninety-nine eighty-one difficulties" - yellow dragon disease</h1>
It can be said that this is a disease that fruit growers are most afraid of, "preventable and incurable", "citrus cancer", "citrus AIDS" These are its labels. It is a bacterial disease that causes gram-negative bacteria. At present, the research history of huanglongbing disease has exceeded 100 years, but no direct and effective eradication methods have been found. For example, in Guangxi, citrus huanglongbing disease is becoming more and more serious, with an average annual incidence of more than 5%, and the direct economic losses caused by it exceed 805 million to 962 million yuan per year.
Why does huanglongbing disease spread so quickly? It is because it has a powerful accomplice "citrus wood lice". At present, it is mainly through the cultivation of disease-free seedlings, the prevention and control of citrus lice, and the digging of diseased trees for prevention and control, so it is very important to understand citrus psyllids for the prevention and control of citrus yellow dragon disease.
According to the study, it was found that the northernmost boundary of citrus lice in China in 2014 was Xiangshan County (29 °29') in Ningbo City, Zhejiang Province, while in the 1980s it was Jinyun County, Zhejiang (28 °45 '). Compared with before and after, the whole spread northward (Jiang Hongyan, Wu Fengnian, Wang Yanjing, Tao Lei, Wang Jifeng, Liu Zhe, Cen Yijing. Research progress on the origin, distribution and diffusion capacity of Asian citrus lice[J]. Acta Environmental Entomology,2018,40(05):1014-1020.] ）。
Citrus wood lice
<h1>Citrus wood lice is "what kind of demon"</h1>
Citrus psyllids, also known as oriental citrus psyllids, belong to the family Psyllidaceae. The nymphs are goose-yellow and raised on the back. It has five ages, the second age begins to appear wing buds, and the third age becomes yellow and brown. The adult body surface is bluish gray with brown markings and white powder. In different regions, different generations of wood lice occur, for example, 6 to 7 generations can occur in 1 year in southern Zhejiang, and 8 to 14 generations can occur in 1 year in Guangdong and Fujian. You can see different insects all year round, it is a pest with great vitality! However, citrus is smoked 4 to 6 times a year, so it generally occurs in the field for 5 to 6 generations.
Citrus wood lice are mainly harmful to new shoots and young shoots, and different insect forms are very harmful to citrus. Nymphs, for example, secrete a secretion containing sugar, which causes coal disease, which affects the photosynthesis of the leaves. Adults suck sap on leaves and shoots, becoming vectors for spreading huanglongbing disease.
According to the research of Zhao Yuanyuan and others, it was found that in the initial invasion of citrus orchards with roads and rivers, Asian citrus lice first occurred at the edge of the orchard, and then spread inward along the boundary, rather than from the center of the orchard, that is, there was a "marginal effect" on the occurrence of Asian citrus lice.
<h1>How to subdue the "Great Devil" - citrus psyllids</h1>
No matter what kind of pests and diseases, our control ideas are the same, mainly from three perspectives, namely agricultural control, biological control and chemical control.
The first is agricultural control. According to the previous content, we can know that citrus wood lice are with the shoots, so in order to facilitate management, it is recommended not to mix multiple varieties, because it is difficult to make the shoots consistent. If the citrus is growing strongly, it is necessary to smear the shoots before flowering. All spring shoots outside the canopy should be erased, 1/2 to 2/3 of the middle and lower spring shoots should be erased, and the rest of the spring shoots should be left with 3 to 4 leaves. As a result, the summer and late autumn shoots of the tree should be completely erased. According to the overwintering characteristics of psyllids, the winter garden is cleared and other rue plants in and around the garden are completely removed. In addition, plants such as Asteraceae herb pseudo-stink grass, leguminous forage, spinosa green bean, guava and other plants can be planted in orchards, which are conducive to the reproduction of natural enemies. Building shelterbelts around orchards can reduce the occurrence of citrus psyllids.
The second is biological control. The so-called biological control is mainly to treat insects with insects. The natural enemies of citrus psyllids are mainly predatory and parasitic predators. Among them, predatory predators such as tortoiseshell ladybirds, grasshoppers and twill cat spiders have obvious predation effects on citrus psyllids. Parasitic natural enemies such as The Ji Wasp, the Ali Lice Jumping Wasp, and the Citrus Pyllid Werep release the bees during the peak of the occurrence of The Asian citrus psyllid nymphs in the spring and autumn, which can achieve a good control effect. In addition, in recent years, the prevention and control of microbial-derived pesticides has also achieved remarkable results. For example, the fatality rate of adult citrus lice and eggs carried by predator mites was 98.8% and 98.4% after 3 days, respectively, and the infection rate of young nymphs reached 100%. Or the coccidioides albicans and methylaminoavermectin were formulated into special oil suspension agents for aircraft control in a ratio of 1:5, and the control effect on Asian citrus pyllids reached 90.26% on the fifth day after aircraft spraying.
Ji Little Bee
Finally, there is chemical control. The agent can be selected from 52.25% high chlorine chlorine chlorpyrifos EC1000 times, 10% imidacloprid EC1500 times, 70% imidacloprid 7000 times, 25% thiamethoxazine WG3500 times, 22% flufenoxonitrile SC 4000 times, 24.5% avicide mineral oil 1500 times, etc. In general, when the taping is relatively neat, spray 1 to 2 times per shoot stage; in the case of irregular extraction, long pumping period and continuous occurrence of citrus lice, spraying is required 2 to 3 times per shoot stage.
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<h1>summary</h1>
Citrus dragon disease is "preventable and incurable", "citrus cancer" and "citrus AIDS". It is a bacterial disease that causes gram-negative bacteria. At present, the research history of huanglongbing disease has exceeded 100 years, but no direct and effective eradication methods have been found. At present, it is mainly through the cultivation of disease-free seedlings, the prevention and control of citrus lice, and the digging of diseased trees for prevention and control, so it is very important to understand citrus psyllids for the prevention and control of citrus yellow dragon disease. Citrus is smoked 4 to 6 times a year, so it generally occurs in the field for 5 to 6 generations. Citrus wood lice are mainly harmful to new shoots and young shoots, and different insect forms are very harmful to citrus. The first is agricultural control, so that the citrus shoot stage is consistent, the implementation of winter garden clearance, the planting of Asteraceae herbaceous false stink grass, leguminous forage, twisting mountain mung bean, guava and other plants, conducive to the reproduction of natural enemies. Building shelterbelts around orchards can reduce the occurrence of citrus psyllids. Turtle pattern ladybirds, lisgrass grasshoppers, twill cat spiders, ji small bees, Ali lice jumping bees, citrus wood lice rattling wasps, etc. have a good effect on the control of citrus wood lice. The agent can be selected from 52.25% high chlorine chlorine chlorpyrifos EC 1000 times, 10% imidacloprid EC 1500 times, 70% imidacloprid 7000 times, etc.
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