Recently, many growers have responded that the leaves of their garlic fields are yellowing, and some even have severe yellowing in large areas. What is going on? Is the yellowing of garlic leaves caused by continuous rain? Indeed, continuous rainy days can cause garlic roots and promote the occurrence and development of some diseases. However, how to deal with this phenomenon, the focus still depends on what the reason is, and then “the right medicine”.
The diseases that cause yellow leaves of garlic include garlic blight, leaf blight, gray mold, bacterial soft rot, and white rot. The specifics are as follows:
In the early stage of disease, water-like dark green spots will appear on the leaves. The lesion will soon spread to the entire leaf, and then the leaf will turn yellow and droop, and soft rot. In severe cases, the disease spots will spread to 1/3 to 4/5 of the whole leaf, or the whole leaf will die and die. When the humidity is high, the disease minister develops a gray-white mold. High temperature and humidity, heavy rainfall on cloudy days, water droplets on the tip of the leaf are prone to disease. The germs can infect garlic regardless of the presence of wounds on the leaves.
Pesticides for prevention and treatment include: propadicarb, metalaxyl manganese zinc, carbamox manganese zinc, ethylphosphine aluminum manganese zinc, dimethomorph and the like.
2. Leaf blight:
The leaf damage usually starts from the tip of the leaf. The lesions are small dots at the beginning and then expand rapidly. The lesions are oval or irregular, and the lesions are grayish white or grayish brown. When the humidity is high, there is a black mold on it, and in severe cases, the leaves die.
In severely diseased fields where leaf blight often occurs, early control is needed. Generally, when the incidence of seedlings reaches 1%, comprehensive spraying control should be carried out. The medicines that can be selected are copper carbamoxam, carbendazim, methyltobrazine, etoxystrobin and so on.
3, garlic white rot:
leaves, leaf sheaths and bulbs can be affected. Water-stained lesions appear at the beginning of the disease. Later, the diseased area becomes soft and the ulcer rots. When the humidity is high, white cotton-like hyphae will grow on the surface. Sclerotia will form over time, and the rotten parts will emit strong garlic. Smelly.
Control agents can be selected-carbendazim, thiophanate, prochloraz, etc. Especially for plants with diseased parts in bulbs, spray the roots with medication. Specific precautions are the same as bacterial soft rot.
4. Bacterial soft rot:
Symptoms of bacterial soft rot on the leaves, starting from the leaf margin or midrib, and forming yellow-white stripes along the leaf margin or midrib, which can run through the entire leaf. When the humidity is high, the diseased part is yellow-brown soft rot, and there will be yellow germ fluid overflow and foul odor. In general, the lower leaves of the plants first develop disease, then gradually expand upwards, and eventually make the whole plant yellow or die.
Prevention and treatment method: Plants develop disease during the growth process, and the agents that can be selected include thiabacillum copper, copper hydroxide, bacteramide, bacteriocin, and cumulazole.
(1) In the prevention and treatment of bacterial soft rot, the application method can be spray or root irrigation.
(2) Among them, the effect of root irrigation is better than that of spraying, but if soil moisture is high, it is not appropriate to use root irrigation for control.
(3) If spraying, pay attention to spray to the base and root of the stem, and spray the diseased plant and surrounding plants with emphasis.
5. Universal prevention measures
For all of the above diseases, several control measures are applicable:
The prevention of diseases should be based on the cultivation of disease-resistant varieties, strengthen cultivation management, and supplemented with medicaments when appropriate.
In agricultural control, it is best to carry out crop rotation, especially for crops that have been seriously affected in the past years, it is necessary to implement crop rotation with non-scallion crops for more than three years. If rotation is not possible, in addition to disinfecting and sterilizing the garlic seeds before sowing, attention should be paid to early control.
The prevention and treatment of hoe disease is basically to improve the disease resistance of garlic. In the seedling stage, it is mainly to control the seedlings.
In addition, high hoe cultivation should be adopted, and reasonable drainage and irrigation should be carried out to avoid water accumulation in the field. This cultivation method can best show its advantages when encountering continuous rainy weather.
1. Water big scallion root
In recent rain, the yellowing of garlic leaves is very likely to show stalk root.
For the sticky soil, too dry and wet, yellow leaves and dry tips are easy to appear. If it has been raining for a long time and there is water in the garlic field, the roots are prone to appear for a long time. Be sure to pay attention to trench drainage.
Autumn sowing garlic is now in the stage of bud differentiation to bolting. This period of time is the transition period of garlic’s vegetative growth to reproductive growth, and it is also a period of both. During this time, the stems and leaves and garlic sprouts grew rapidly, and the garlic began to swell slowly, requiring more nutrients, the nutrition could not keep up, and the tip of the leaves would turn yellow.Supplemental nutrition should be taken, and attention should be paid to fertilization measures.
(1) Drug damage
As the temperature rises in spring, weeds in the field also begin to grow. At this time, many people will choose to use chemical methods to weed, and garlic is very sensitive to herbicides, which is very easy to cause harm.
Mitigation measures: watering a lot, using growth regulators such as brassinolide, spraying functional foliar fertilizer, etc. The specific measures depend on the situation.
In addition, if a contact-killing herbicide is used, the phytotoxicity is light, and it can be ignored for the time being.
Improper fertilization can also cause fattening.
Mitigation measures: On continuous sunny days, water is irrigated twice, and foliar fertilizers such as seaweed fertilizer, humic acid, biological bacteria and functional fertilizers that promote rooting are applied. Watering absorbs the heat released by the fertilizer. Foliar spraying fertilizer supplements trace elements and alleviates deficiencies caused by root injury. The application of rooting fertilizer promotes the rapid germination of new roots and enhances the growth of seedlings.