The vineyard is growing very well, the leaves are dark and green, and there is nothing wrong with it, but the leaves will involute, what is going on?
Grape leaf curls are usually divided into two types: upper (inner roll) and lower (outer roll), and the direction of curl varies depending on the cause. Let's take a look at the causes and prevention methods.
Grape leaf roll (involution)
1. Drought watering
Persistent drought leads to severe soil water loss, followed by sudden overwatering or sudden rainfall after successive dry weather, and the field is not drained in a timely manner, resulting in excessive soil moisture. In this case, transpiration of the grape leaves is inhibited, and the leaves show symptoms of reverse curling (downward curling) and wilting.
Prevention and control methods:
Growers need to hydrate and cool their grapes in a timely manner. If the temperature is high during the day and it is not suitable for watering, you can change the watering time to evening or night, and drip irrigation or micro-spraying is recommended.
2. Improper ventilation
If there is a large temperature difference between the inside and outside of the shed, the exchange of cold and warm air is strong, which will also cause the leaves of the grapes to roll upwards in front of the air outlet. In this case, the leaves are generally rolled from the tip of the leaf, which is in the shape of a chicken claw, and in severe cases, the dry tip has a white edge.
Prevention and control methods:
In early spring, the temperature is higher inside the grape shed and cooler outside. It is advisable to open the vents slowly in the middle of the day when the temperature gradually rises, but be careful not to make the vents directly facing the plants.
3. The effect of drug damage
When the ingredients of the applied pesticides (including pesticides, hormones, etc.) are unsafe, the concentration is too high, or the temperature is high during application, and the plants are more sensitive, it is easy to cause pesticide damage to grapes, resulting in leaf discoloration or spots, leaf rolling, etc.
Prevention and control methods:
When administering the agent, the instructions should be strictly followed, and the recommended dosage should be applied according to the instructions. Field application should avoid high temperature, strong wind, strong ultraviolet weather, etc., and it is recommended to apply before 9 o'clock in the morning or after 4 o'clock in the afternoon when there is no wind.
If there is pesticide damage due to improper application, it is necessary to water immediately, wash the leaves with a large amount of water, dilute the concentration of the agent, and also spray low-concentration foliar fertilizer or regulator (brassinolide, etc.) to restore the plant until the plant returns to normal.
4. Excessive fertilization
Excessive fertilization or high fertilization concentration will hinder the absorption of water by the roots, resulting in a lack of water in the leaves, and the symptoms of leaflet flipping and rolling. For example, the application of excessive ammonium nitrogen fertilizer in the soil will cause the leaflets on mature leaves to show an inverted bottom shape, leaf upturning, and rolling, and the phenomenon of leaf roll-up is also more likely to occur in saline-alkali areas.
Prevention and control methods:
Grape growth period of the whole growth period needs a large amount of fertilizer, in the orchard management throughout the year, should be done scientific and reasonable fertilization, to achieve a small number of times, targeted fertilization, must not be for a temporary convenience, perfunctory, can not increase the concentration and dosage at will.
5. Improper field management
Premature topping or pruning too early or too heavy can also cause leaf roll-up. Premature topping will promote the growth of axillary buds, hinder the transport of phosphoric acid, and lead to the aging and curling of lower leaves, while premature and heavy pruning will hinder the development of root system and make the aboveground growth poor, resulting in leaf curling.
Prevention and control methods:
When the fruit growers carry out grape branch tip management (bud cutting, topping, pruning, etc.), they need to combine the plant growth and actual growth to carry out reasonable operations.
6. Lack of nutrients
Vitamin deficiency in grapes may cause physiological leaf rolling, such as calcium deficiency will cause leaf rolling, and potassium deficiency will cause leaf roll-up or roll-down.
Prevention and control methods:
The supply of nutrients should be combined with the characteristics of grape fertilizer demand, such as large amount of fertilizer, stage of fertilizer demand and specific fertilizer demand to carry out timely and appropriate fertilization.
The need for calcium and potassium during the whole growth period of grapes is much higher than that of other nutrients. Calcium supplementation in the early stage can increase the hard thickness of the grape skin, and calcium supplementation in the later stage can effectively improve the toughness of the grape skin, so as to greatly prevent and reduce the problem of fruit cracking on grapes.
7. Caused by disease
Grape disease will cause the whole or part of the leaves of the grape from top to bottom to bend upward, accompanied by the symptoms of greening, smaller, shrinking, clumping, etc.; in the later stage of grape leaf mildew, the leaves will also appear from the bottom to the top, and the whole leaf is yellow-brown and dry, and the whole plant can be curled when the disease is severe.
Prevention and control methods:
For leaf mold, it is recommended to control it by foliar spray or Kaiser and other agents.
Tebuconazole is a triazole high-efficiency and low-toxicity fungicide, and the mechanism of action is mainly to inhibit the synthesis of ergosterol, and oxystrobin is a methoxyacrylate fungicide, which is a mitochondrial respiratory inhibitor, and has protective and therapeutic effects after the combination of the two, and can prevent and control almost all fungal diseases.
The above is a summary of the causes of grape leaf curling, and fruit farmers can prescribe the right medicine according to the specific situation of the orchard!