What is drupe leaf shrinking disease?

Cao ruobin

A fungal disease in which the leaves of drupe swell and shrink due to the outer membrane, and then turn black and dry. Including peach leaf shrinkage disease and Xing Li leaf swelling disease. /kloc-It was first reported in Europe at the beginning of 0/9th century and first recorded in China at the end of 0/9th century.

Distribution and harm

Peach leaf shrinkage disease is a worldwide disease, which occurs all over China. In severe cases, the diseased leaves dried up and fell off in the early stage, which affected the yield of the current year and the formation of flower buds in the next year. 1983, the disease was prevalent in Kunming, Chuxiong and other places in Yunnan, with the disease plant rate of 100% and the disease leaf rate of over 80%, and most of the peach orchards basically failed to produce. Plum and apricot leaf swelling is more common, but less harmful. Plum bag fruit disease is characterized by fruit cyst and normal leaves, which is also caused by ectospora. It is widely distributed and only harms local areas.

Pathogens mainly infect the young tissues of the host. Peach, plum and apricot are mainly tender leaves, and tender buds, flowers and young fruits can also be fatal. In spring, leaf buds will be invaded when they are stretched. After spreading leaves, diseased leaves turn red, shrink or uneven, and mesophyll is obviously swollen and thickened. Soon, white powder (embryo sac layer) appeared on the surface of the affected area. When the temperature is high in June and July, the diseased leaves turn black, dry and fall off. If it is serious, it will fall off before it turns black, and the branches will die. The tender shoots are damaged, the internodes are shortened, and the tender shoots are rod-shaped from top to bottom. The disease of plum bagging mainly harms the fruit. The diseased fruit is deformed, hollow, bag-shaped, dark green, slightly shriveled, with white powder on the surface and falling off early.

The cause of disease

The pathogen of peach leaf shrinkage disease is Myzus persicae. )Tul。 The pathogen of leaf swelling of plum and apricot is plum blossom. The pathogen of plum fruit diseases is Trichoderma listeria. All belong to Ascomycetes and Exophytes. Ascomycetes are naked on the surface of the affected area, without coating, and are closely arranged in a layer of Ascomycetes. Ascomycetes are cylindrical, with podocytes connected with host epidermal cells at the base and flat and colorless at the top, containing 4 ~ 8 ascospores. Ascomycetes are nearly round and colorless, and can germinate inside and outside Ascomycetes after maturity, producing two kinds of spores: thin-walled and thick-walled. Peach leaf shrinkage pathogen not only harms peach, but also infects nectarine, almond and flat peach. The pathogen of leaf swelling of plum and apricot only infects plum and apricot; Lead-coated pathogens only infect plums. Peach varieties have different susceptibility to diseases. Generally, the diseases of early-maturing varieties are more serious, while those of middle-late-maturing varieties are less serious, and the diseases of "Maotao" are more serious than those of ordinary improved peaches. The occurrence of diseases is closely related to the speed of temperature rise and rainfall in spring. Low temperature and rainy in spring, especially the long duration of cold in late spring, are conducive to the occurrence and prevalence of diseases; Taoyuan, which has extensive management, no pruning and unclear disinfection in the garden, is seriously ill.

Infection process and disease cycle

The three diseases are basically the same. Take peach leaf shrinkage disease as an example: the pathogen mainly overwinters on the scales of peach buds, the epidermis of branches or cracks in summer. When the peach buds germinate in the following spring, spores germinate, directly invade the epidermis or invade the unfolding young leaves from the stomata, and soon after the leaves unfold, a white powdery ascomycete layer grows. The optimum temperature of pathogen infection is 10 ~ 16℃, which exceeds 265438+. Generally, it will not cause reinfection. If the external conditions are particularly suitable, reinfection will occur and the symptoms will be very mild.

disease control

In the early spring, when the petals are red (or white) but not unfolded, spray Bomei 3-degree lime-sulfur mixture, Bordeaux mixture or carbendazim in time; At the early stage of the disease, remove the diseased leaves and fruits in time.

Anthracnose of drupe

Anthracnose of drupe

Cao ruobin

Fungal diseases such as fruit rot, branch blight and leaf spot caused by anthracnose infecting stone fruit trees. Fruits are the most affected. China was recorded at the end of 19.

Distribution and harm

It is distributed in stone fruit cultivation areas in China, especially peach, and anthracnose is common and harmful. In Jiangsu, Zhejiang, Anhui and Shanghai, anthracnose often causes a large number of early fruit drop and late rotten fruit. Colletotrichum gloeosporioides occurred seriously in Guangdong, causing young trees to die and unable to blossom and bear fruit. The anthracnose of plum and apricot is serious in some areas, causing fruit rot.

Pathogens can infect fruits, leaves, stem tips and flower heads, as well as young fruits before the onset of hard core. At first, light brown water-stained spots appeared, and then they expanded into round or nearly round reddish-brown concave spots. Under wet conditions, many orange conidia piles grow on the diseased spots, many diseased fruits fall off, and a few diseased fruits shrink and remain at the shoot tips, becoming stiff fruits. In the middle and late stage of fruit growth, especially when it is close to maturity, the symptoms are different from those in the young fruit stage, showing concentric annular shrinkage in concave spots, irregular large spots after mutual healing, and finally the diseased fruit is soft and rotten. When the new shoots are invaded, long oval and slightly concave brown lesions appear, and the diseased shoots bend to one side. The leaves on the diseased branches wither and droop, and roll vertically into a tube, and the seriously ill branches and flower heads often die. The diseased leaves of peach trees are round or semi-circular, reddish brown to brown, with clear edges, and the diseased leaves fall off early.

The cause of disease

The pathogen is Staphylococcus aureus a (stonem. )Spauld。 Belongs to Ascomycetes, Coccidae. The asexual state of Colletotrichum gloeosporioides belongs to Alternaria. Under natural conditions, sessile species have no bristles, conidia aggregate into myxospores (see anthracnose of drupe), and there are more than 100 hosts in China. The optimum growth temperature is 24 ~ 26℃, but it can still grow at 5℃ or 33℃. Generally, the diseases of early-maturing and middle-maturing varieties are more serious, while those of late-maturing varieties are less serious. Among them, Zaosheng Peach, Kobayashi Peach, Taicang Peach, Simian Peach, Liulin Sweet Peach and Huang Guan Peach No.5, 14 are all susceptible. Baifeng and orange were born early; The early growth of Gangshan, Yulu and Baihua has strong disease resistance. Low temperature and rainy weather in spring is beneficial to the occurrence of diseases, causing diseases of young fruits and branches, while warm and rainy weather often leads to fruit rot in the later stage of fruit growth; Extensive management, too many branches, dark crown, poor drainage in orchard and sticky soil are all conducive to the harm of bacteria.

Infection process and disease cycle

Pathogens overwinter with mycelium on diseased branches and diseased fruits on trees, and conidia are produced in the following spring, which infect new branches and young fruits through wind, rain and insect transmission. In Zhejiang, young fruits began to develop in late April, and reached the peak in May, resulting in a large number of fruit drops, and the disease stopped developing in June. When the fruit is close to maturity, if it is warm and rainy, it will form a peak and cause the fruit to rot. In the north, the disease usually begins in May-June, and another peak appears when the fruit is close to maturity.

disease control

In winter, combine pruning to remove dead branches and dead fruits, burn them centrally, and plough the soil; In spring, check repeatedly from germination to flowering, cut off diseased plants and dead shoots in time, and combine with spraying protection. Bordeaux mixture can be sprayed during germination, and fungicides such as prochloraz, thiophanate, carbendazim, thiram anthrax or chlorpheniramine can be sprayed after flowering.

Walnut disease

Walnut and hickory diseases

There are about 150 species in the world, and there are nearly 50 species in China, most of which are wood rot fungi. Among them, bacterial black spot, branch blight, anthracnose and leaf spot are the most serious.

Bacterial black spot

Also known as black rot, it is the most serious disease on walnuts. It has occurred in Hebei, Shandong, Liaoning, Henan, Shanxi, Shaanxi, Gansu, Jiangsu, Zhejiang, Sichuan, Yunnan and other provinces. The United States, Italy, Germany, Switzerland and other countries also have distribution. It mainly harms young fruits and leaves, as well as shoots and inflorescences. Young fruit produces black spots with inconspicuous edges, which can make the pulp and nucleolus all black and rotten and the fruit fall off. Medium-sized fruit, only the skin is black and rotten. There are nearly round or polygonal brown or black spots on the leaves, and there are waterlogging halos around them. In severe cases, the whole leaf turns black, brittle and falls off. The pathogen is Xanthomonas campestris PV. Walnut dye. Harm many kinds of walnut plants. Walnut is most prone to diseases during flowering and leaf spreading, which is beneficial to diseases when it encounters low temperature and rainy weather, stem borer damage, sunburn and hail damage. Pathogens overwinter in diseased spots or buds of branches. It is reported that there are germs on asymptomatic buds, branches, leaves, catkins and nuts. The next spring, bacteria were secreted, first infected by wind and rain and insects, and then infected again. Pollen can also spread germs. Disease control: control the top moth to reduce insect damage and disease vectors; Spraying Bordeaux solution, chlordecone, agricultural streptomycin, thiophanate-methyl, rice blast and antibiotic 402 solution at the leaf opening stage, flowering stage and young fruit stage. Can be mixed with pesticides to control pests at the same time; Cultivate disease-resistant varieties.

Branch blight

Jiangsu, Zhejiang, Shandong, Liaoning, Hebei, Shanxi, Shaanxi, Gansu and other provinces in China, as well as the United States, Japan, Italy, Romania and other countries. It mainly damages branches, producing reddish-brown to dark gray spots, and then producing small black spots (pathogen sessile). When the humidity is high, black spores overflow from the spore tray. The pathogen is walnut black shell (melon is walnut (ell). Wait a minute. ) groves). Ascomycetes, Ascomycetes, not in China. The asexual state is Cercospora juglandis, belonging to Hemiptera and Cercospora. It also harms pecans and Pterocarya stenoptera. In addition, Cercospora elliptica mainly harms pecans and walnuts. The weak branches suffer from freezing injury or severe spring drought, and their condition is more serious. Pathogenic bacteria overwinter in diseased branches with mycelium and sterile hair, spread by wind, rain and insects, invade from wounds and reinfect. Disease control is to cut off diseased dead branches to reduce the source of bacteria; Increase fertilizer, improve soil and enhance tree potential; Insect-proof and antifreeze; Antibiotic 402 can be applied after the diseased spots on the big branches are scraped off.

anthrax

China Shandong, Hebei, Henan, Shanxi, Shaanxi, Xinjiang, Liaoning, Jiangsu and other provinces. Germany and Korea are also distributed. Damage to fruits and leaves. There are round, brown to black pits on the fruit, and small black spots on the rear wheel (pathogen acervulus). When the humidity is high, pink myxospores overflow from black spots, and when it is serious, the whole fruit turns black and shrinks. Irregular brown spots and small black particles are produced on the leaves. The pathogen is Staphylococcus aureus a (Stonem. )Spauld。 It belongs to ascomycetes of Coccidia, and has not been found in China walnut. The asexual state of Colletotrichum gloeosporioides belongs to Alternaria. The host range is wide, which harms many kinds of fruit trees and other crops (see anthracnose of kernel fruit). Pathogens mainly overwinter in diseased fruits and leaves with hyphae. Disease control is to remove diseased fruits and leaves and control pests; Spraying thiophanate methyl, thiophanate methyl or bordeaux mixture on young fruit and fruit stage.

leaf spot

Hurt pecans. China, Zhejiang, the United States, Britain, Brazil, Mozambique and other countries are also distributed. It mainly harms leaves, and the lesions are brown spots at the beginning, and then expand into nearly round, long or irregular shapes. Most of them are distributed near the leaf margin or main lateral veins, and the edge is not obvious. In severe cases, it will turn into brown patches, and black spots (bacterial hyphae) will grow on the surface in the later stage, and finally the diseased leaves will dry up and fall off. The pathogen is gray spot of walnut. A half-known fungus belonging to the order filamentous fungi. No sexual behavior has been found so far. Extensive management, weak trees and serious diseases in rainy years. Pathogens mainly overwinter on fallen leaves, and a large number of conidia are produced in the following year, which are spread by wind and rain. Generally, the onset begins in early June, and the peak period is July-August. Disease control, timely removal of fallen leaves in late autumn, centralized incineration; Spray Bordeaux mixture, thiophanate-methyl, benomyl or carbendazim at the initial stage of the disease.

Other common diseases of walnut are shown in the left table below. (Zhang Zhiming)

Fusarium fruit rot brown rot fruit rot. Fusarium mycorrhizal root rot white silk disease stem base and root micro-witches' broom, leaf micro-witches' broom, leaf micro-witches' broom, leaf micro-witches' broom, leaf micro-witches' broom, flower micro-witches' broom, fruit micro-witches' broom

Other Common Diseases of Walnut