Because ginger has been reproduced asexually for a long time in production, it is planted continuously. It causes the accumulation of various pathogenic bacteria, aggravates the disease, seriously affects the yield and quality of ginger, and brings certain losses to the production.
According to preliminary statistics, there are about 11 kinds of ginger infectious diseases, including fungal diseases, bacterial diseases, viral diseases, and nematode diseases. This article summarizes the ginger disease symptoms, pathogenic bacteria, and disease prevalence in ginger cultivation, and provides a reference for targeted prevention and control.
Ginger Fungal Diseases
1. Ginger Soft Rot
It mainly occurs at the base of the ginger stem and underground tubers, and yellow-brown spots appear at the base of the stem at the initial stage of onset. Subsequent to soft rot, the stems and leaves above the ground become yellow and wither and die, and the tubers below the ground become soft and rot when infected and lose their edible value. Spider filaments (white mycelium) sometimes appear on the base of the stem of the diseased plant and the underground stem when it is wet.
The pathogen of the disease is Pythium of the flagellum subphylum, including Pythium monospermum Pringsheim, P. myriotylum Drechsher, P. aphanidermatum Eds. Fitzp. and P. zingiberum Takahashi.
The soft rot caused by Pythium is an important disease on ginger in the ginger-producing regions of the world, among which Pythium aphanidermatum is the main pathogen of ginger soft rot in India. The pathogen can survive in the soil in the form of oospores, using zoospores as a source of initial infection and reinfection, and spread by irrigation water or rainwater.
Once the disease occurs, it spreads quickly and even causes ginger to die. Weather with a large temperature difference between day and night, large soil water content, and heavy soil are conducive to the occurrence of ginger soft rot disease.
2. Ginger Blight
Also known as ginger tuber rot disease, it mainly harms underground tubers.
The aboveground part of the diseased plant was withered, the underground tuber turned brown and rotted, and the clear liquid exuded from the affected part. The surface of the diseased tuber often grew yellow and white mycelium.
The pathogen of the disease is Fusarium of the Deuteromycotina, including Fusarium oxysporum f.sp. Zingiberi Trujillo and F. solani (Martius) Apple et Wollenweber.
Their mycelium and chlamydospores overwinter in the soil along with the diseased remains. Ginger with bacteria and manure with bacteria are important sources of infection in the second year. The conidia produced in the diseased part are spread by rainwater splashing and irrigation water to infect again.
The pathogen prefers wet conditions, especially in low-lying terrain, poor drainage, and heavy soil, which is conducive to blight disease. Continuous cropping or application of unmatured manure is prone to disease.
Both ginger soft rot and ginger blight are important fungal diseases that damage ginger tubers, and the symptoms are similar. The difference between these two diseases: the base of the stem of the first onset of Fusarium wilt will change color without becoming soft and rot, and it will develop a colored mildew layer after moisturizing.
When the soft rot disease first occurs, the base of the plant stem becomes soft and presents wet rot to soft rot. After moisturizing, it develops white mycelium, and some are like wet cotton.
3. Ginger Anthracnose
The disease mainly damages the leaves. Spots appear at the tip or edge of the leaf at first, with small water-stained brown spots at first, and then expand downward and inward, showing irregular brown spots such as elliptical or spindle shape, and multiple spots. . The leaves become brown and dry, and small black spots appear on the mottled surface when wet.
The pathogen of the disease is Colletotrichum capsici (Syd.) Butler et Bisby and (C. gloeosporioides (Penz.) Sacc.) belonging to the genus Deuteromycotina.
They all live in the soil with mycelium and conidia discs along with the diseased remains, which are the main source of initial infection of the disease in the coming year. Pathogens use conidia to invade wounds or pores to cause disease by wind, rain splashing, insect activity, etc.
Continuous cropping, heavy field humidity, partial application of nitrogen fertilizer, and excessive plant growth are all conducive to the occurrence of the disease. The prevention and control of the disease should strengthen field management, timely drainage, keep good ventilation and light, enhance plant disease resistance, and timely remove diseased bodies during the growth period.
4. Ginger Leaf Spot Disease
Ginger leaf spot disease mainly occurs on the leaves. The mature disease spots are long fusiform or oblong, with gray-white in the middle and brown edges. When dry, the diseased part is cracked or perforated. In severe cases, the diseased spots are densely distributed, and the whole leaf looks like white stars.
The pathogen is Phyllosticta zingiberi Hori of the deuteromycotina. The pathogen overwinters in the soil with mycelium and conidia, and uses conidia as a source of reinfestation, and spreads by rain sputtering.
Warm and high humidity, dense planting, canopy between plants, and continuous cropping are all conducive to the occurrence of the disease.
5. Ginger Wilt
Early damage to seedlings, causing ginger to wither. The above-ground disease usually starts to infect from the base of the stem. The diseased area becomes water-stained and necrotic, and then becomes brown and shrinks. The diseased spots of leaf sheaths and leaves are enlarged and become moire-like.
When the humidity is high, spider filamentous mycelium appears in the affected area, and some gather into dark brown sclerotia. In the later stage, the underground stems are harmed, and the diseased parts become brown and necrotic, followed by decay or shrinkage. The rhizomes are wrapped with spider filamentous hyphae, part of the rhizomes sink, and the internal ginger flesh becomes brown and dry rot.
The pathogen of the disease is Rhizoctonia solani Kuhn. The pathogen is mainly left as sclerotia on the soil, or overwintering with mycelium and sclerotia on-field weeds or other hosts. Sclerotium is spread by running water, germinating out hyphae to infect and cause disease.
In hot and humid weather, too much nitrogen fertilizer can easily induce the disease.
6. Ginger Leaf Blight
After the leaves are damaged, small yellowish-brown spots are first produced in the diseased part, and then gradually expand into elliptical or irregular spots of different sizes, with yellow-brown lesions and brown edges. In severe cases, the whole leaves become brown and withered.
In the later stage, the diseased part often produces many small black particles. The pathogen of the disease is the ginger coccidia of Ascomycotina.
The pathogen overwinters on sick leaves with mycelium and ascostroma, and produces ascospores in the second year, which are spread by wind and rain, insects, and agricultural operations. The pathogen likes high temperature and high humidity, and continuous rainy or heavy fog in the hot season is conducive to the development of the disease.
In addition, continuous cropping, excessive nitrogen fertilizer, excessively long or dense plants, and poor ventilation will aggravate the disease.
Ginger Bacterial Diseases
1. Ginger Blast
Also known as rot disease, once the plant is invaded by pathogens, the stems, leaves, or rhizomes will show symptoms.
The pathogen usually infects the base of the above-ground stems and rhizomes first. At the initial stage of the disease, the leaves become wilted and dull and turn to withered yellow from bottom to top.
After the rhizomes were injured, the base was dark purple at first, then turned into water-stained yellowish-brown, the vascular bundles turned brown, squeezed by hand, it can be seen that the dirty white bacterial liquid overflowed from the vascular bundles, emitting a foul smell.
Ginger blast is a devastating disease that commonly occurs in various ginger areas. The pathogen causing ginger blast is Pseudomonas solanacearum.
The diseased soil of the ginger field is the main source of initial infection.
It is spread by irrigation water, rainwater, and underground pests. The pathogen invaded from the wound of the rhizome and entered the vascular bundle, causing the whole plant to wither. Hot and rainy weather, continuous cropping, low-lying terrain, heavy soil, partial application of nitrogen fertilizer, and other factors are conducive to the serious occurrence of the disease.
The prevention and control of the disease should emphasize prevention, comprehensive control, choose non-bacterial ginger seeds, sterilize seeds before planting, implement crop rotation, strengthen field management, high-border planting, reduce field humidity, ventilate and transmit light, and promptly after diseased plants are found in the field Remove diseased plants and surrounding soil.
2. Ginger Bacterial Streak Leaf Blight
The disease mainly damages leaves and rhizomes. The disease occurs on the leaves, and the lesions usually develop from the tip of the leaf along the vein to the petiole, especially along the edge of the leaf. The diseased part is light brown, transparent, and water-stained at first, and then becomes a dark brown transparent stripe, with clear edges, well-defined diseased parts, and the leaves are necrotic, curled, and withered finally.
The base of the stem and rhizome is onset, the diseased part is water-stained yellowish-brown, gradually losing luster, softening and decaying from the outside to the inside, and the inside is full of gray to gray-yellow viscous ulcerated tissue and juice, with a clear stinking odor, and only the epidermal tissue is left at last.
The pathogen of the disease is a disease-causing species of Xanthomonas brassicae ginger.
It mainly lives in diseased ginger blocks or with diseased remains in the soil overwintering. Ginger with bacteria is the initial source of infection in the field in the second year, and the bacteria are spread by irrigation water and underground pests. It spreads on the ground through contact with wind, rain, human factors, etc. The germs invade from the wounds of the leaves and spread upward and downward along with the vascular bundle.
Ginger Virus Disease
Cucumber mosaic virus (CMV) and tobacco mosaic virus (TMV) has been proven to cause ginger virus disease. Viral diseases are mainly spread by growing ginger, such as sap bruises, and insects such as aphids. At present, there is no good solution for the prevention and treatment of viral diseases, and disease-resistant varieties and virus-free ginger species are mainly used in production.
Ginger Nematode Disease
Ginger nematode disease is mainly ginger skin disease. Diseased plants are characterized by short plants, premature aging and yellowing, few root systems, and rotted root tips.
There are often nodules of varying sizes in the rhizome. The root knots are sometimes connected in clusters, which are yellow-white protrusions at first, and then gradually turn brown, making the surface of the rhizome appear warty or protrusions.
The pathogen of ginger skin disease is Meloidogyne incognita, and there is no compound infection. Continuous cropping, the soil is loose, dry, neutral sandy loam, and excessive potassium fertilizer is prone to disease.