What are the control techniques for non-disease early defoliation of apple trees?
Control techniques for non-disease early defoliation of apple trees
(Agricultural Wealth Network) In the process of apple cultivation, non-disease factors can also cause early defoliation. The control techniques are described below for fruit growers' reference.
I. Early defoliation caused by insect pests
The main insect pests that damage leaves include the Asiatic apple leafminer (Lithocolletis ringoniella), leafminer moths, Phalera flavescens caterpillars, scarab beetles (white grubs), pear lace bugs (Stephanitis nashi), and red and white spider mites. Spider mites mainly use their piercing-sucking mouthparts to suck leaf sap along both sides of the leaf veins. When the damage is severe, the upper surface of the leaf loses its green color and turns white or red, while conspicuous white flocculent webs are visible on the underside; eventually the leaves drop. When controlling mites, four key periods should be seized: the emergence-from-overwintering period, the egg-laying period, the egg-hatching period, and the period of outbreak under high temperature and high humidity. In the early stage of infestation, 20% Qianniuxing at 3000 times dilution, 10% Mandexjing at 6000 times dilution, etc. can be used to kill the newly emerged female adult mites, mite eggs and hatched young mites; when outbreaks occur in the middle and late stages, 1.8% Miezhengling at 10000 times dilution, 1.8% Chongmanuang at 8000 times dilution, and 200% triazotin at 3000 times dilution can be selected to eliminate adult and nymph mites at all developmental stages. Pests such as the Asiatic apple leafminer and caterpillars are mostly larvae that gather on the underside of leaves to feed on the mesophyll or sap, damaging the leaves and causing premature dropping. Pesticides such as liquid Kung Fu, Mieyouniao No. 3, Wanling, and pyrethroid insecticides can be selected for control.
II. Early defoliation caused by human factors or improper techniques
Defoliation caused by human factors or improper techniques mostly refers to leaf drop caused by mistakes made by some fruit growers in techniques and operations. For example, when spraying pesticides, arbitrarily increasing the concentration causes phytotoxicity and then defoliation; during topdressing, excessive concentrated application of quick-acting chemical fertilizers (especially nitrogen fertilizer) causes fertilizer burn and triggers defoliation; another example is that when thinning flowers and setting fruit, bending branches and pulling branches in the orchard, inadequate technique can also cause defoliation. The preventive methods are: when spraying pesticides, always apply them at the effective concentration and minimum effective dose stated in the pesticide instructions; when topdressing, adjust the amount of fertilizer according to tree age, tree vigor, fruit load, cultivation conditions, fertilizer type, etc., and do not over-fertilize; when working in the orchard, be meticulous and careful, operate in a standardized manner, and never damage branches or leaves.
III. Early defoliation caused by adverse environmental conditions
1. Drought and waterlogging. In the high-temperature dog days of summer, when the temperature reaches above 34°C, the soil moisture in the orchard is quite low and far from meeting the needs of the tree. Under such extreme drought conditions, the tree's suberization accelerates, physiological regulation becomes unbalanced, self-thinning is severe, and ultimately early leaf drop is caused. In addition, sudden heavy rain or continuous cloudy and rainy days over many days will cause waterlogging in the orchard and soil compaction. In such an environment, the physiological function of the root system is most likely to decline, and the conducting tissues are blocked, forcing the tree to be unable to carry out normal physiological operations, causing the leaves to discolor and shrivel, appearing green-dried or withered, and resulting in premature dropping. Therefore, water management in the orchard should achieve: irrigate promptly in drought, drain quickly in waterlogging, and skillfully control water by observing the weather and the trees.
2. Poor light. In some orchards with relatively poor canopy light conditions, the branches and leaves in the middle and lower parts cannot receive direct sunlight for a long time and grow parasitically, mostly in a state of ineffective consumption. In the early stage, the leaves appear pale green, thin and small; in the later stage, they produce and release ethylene, turn egg-yellow, and mature and drop early. This symptom requires major reshaping, adopting measures such as raising the trunk, lowering the head, and bending branches, so that the light penetration rate of the orchard reaches 35%-40%, and then the phenomenon of leaves turning yellow and dropping early will not occur.
3. Hail damage. After the beginning of summer each year, hail disasters frequently occur. After fruit trees are hit by hail, branches break and bark splits, leaves become incomplete, and various organ tissues necrose, so normal physiological functions cannot be carried out. The photosynthesis of injured leaves drops sharply, and before long, early defoliation disease occurs. Rescue measures: First, immediately after the hail disaster, carefully spray a fungicide over the whole orchard to strictly control the disease, then carry out topdressing and foliar spraying to restore the tree as quickly as possible; second, clean up the residual branches and fallen leaves in the affected area to reduce the source of pathogens; third, where conditions permit, install hail nets in the orchard to reduce the disaster.
4. Nutrient deficiency. In recent years, when applying base fertilizer in autumn, fruit growers only paid attention to the use of farmyard manure and macroelement fertilizers, neglecting the combination of trace elements, and failed to achieve the goal of balanced fertilization, so orchards often suffer defoliation due to the deficiency of a certain trace element. It has been found in production that iron-deficient fruit trees show chlorosis and yellowing of the mesophyll of young leaves, and in severe cases the leaves wither and drop. In magnesium-deficient fruit trees, light green patches gradually appear on the leaves at the base of new shoots, slowly turning yellow-brown, curling for several days and then dropping. Therefore, before fertilizing, soil sampling and testing should be carried out, and according to the test results, the fertilization plan should be determined, balanced fertilization should be popularized, and attention should be paid to the nutritional balance of nitrogen, phosphorus, potassium and various trace elements.
I. Early defoliation caused by insect pests
The main insect pests that damage leaves include the Asiatic apple leafminer (Lithocolletis ringoniella), leafminer moths, Phalera flavescens caterpillars, scarab beetles (white grubs), pear lace bugs (Stephanitis nashi), and red and white spider mites. Spider mites mainly use their piercing-sucking mouthparts to suck leaf sap along both sides of the leaf veins. When the damage is severe, the upper surface of the leaf loses its green color and turns white or red, while conspicuous white flocculent webs are visible on the underside; eventually the leaves drop. When controlling mites, four key periods should be seized: the emergence-from-overwintering period, the egg-laying period, the egg-hatching period, and the period of outbreak under high temperature and high humidity. In the early stage of infestation, 20% Qianniuxing at 3000 times dilution, 10% Mandexjing at 6000 times dilution, etc. can be used to kill the newly emerged female adult mites, mite eggs and hatched young mites; when outbreaks occur in the middle and late stages, 1.8% Miezhengling at 10000 times dilution, 1.8% Chongmanuang at 8000 times dilution, and 200% triazotin at 3000 times dilution can be selected to eliminate adult and nymph mites at all developmental stages. Pests such as the Asiatic apple leafminer and caterpillars are mostly larvae that gather on the underside of leaves to feed on the mesophyll or sap, damaging the leaves and causing premature dropping. Pesticides such as liquid Kung Fu, Mieyouniao No. 3, Wanling, and pyrethroid insecticides can be selected for control.
II. Early defoliation caused by human factors or improper techniques
Defoliation caused by human factors or improper techniques mostly refers to leaf drop caused by mistakes made by some fruit growers in techniques and operations. For example, when spraying pesticides, arbitrarily increasing the concentration causes phytotoxicity and then defoliation; during topdressing, excessive concentrated application of quick-acting chemical fertilizers (especially nitrogen fertilizer) causes fertilizer burn and triggers defoliation; another example is that when thinning flowers and setting fruit, bending branches and pulling branches in the orchard, inadequate technique can also cause defoliation. The preventive methods are: when spraying pesticides, always apply them at the effective concentration and minimum effective dose stated in the pesticide instructions; when topdressing, adjust the amount of fertilizer according to tree age, tree vigor, fruit load, cultivation conditions, fertilizer type, etc., and do not over-fertilize; when working in the orchard, be meticulous and careful, operate in a standardized manner, and never damage branches or leaves.
III. Early defoliation caused by adverse environmental conditions
1. Drought and waterlogging. In the high-temperature dog days of summer, when the temperature reaches above 34°C, the soil moisture in the orchard is quite low and far from meeting the needs of the tree. Under such extreme drought conditions, the tree's suberization accelerates, physiological regulation becomes unbalanced, self-thinning is severe, and ultimately early leaf drop is caused. In addition, sudden heavy rain or continuous cloudy and rainy days over many days will cause waterlogging in the orchard and soil compaction. In such an environment, the physiological function of the root system is most likely to decline, and the conducting tissues are blocked, forcing the tree to be unable to carry out normal physiological operations, causing the leaves to discolor and shrivel, appearing green-dried or withered, and resulting in premature dropping. Therefore, water management in the orchard should achieve: irrigate promptly in drought, drain quickly in waterlogging, and skillfully control water by observing the weather and the trees.
2. Poor light. In some orchards with relatively poor canopy light conditions, the branches and leaves in the middle and lower parts cannot receive direct sunlight for a long time and grow parasitically, mostly in a state of ineffective consumption. In the early stage, the leaves appear pale green, thin and small; in the later stage, they produce and release ethylene, turn egg-yellow, and mature and drop early. This symptom requires major reshaping, adopting measures such as raising the trunk, lowering the head, and bending branches, so that the light penetration rate of the orchard reaches 35%-40%, and then the phenomenon of leaves turning yellow and dropping early will not occur.
3. Hail damage. After the beginning of summer each year, hail disasters frequently occur. After fruit trees are hit by hail, branches break and bark splits, leaves become incomplete, and various organ tissues necrose, so normal physiological functions cannot be carried out. The photosynthesis of injured leaves drops sharply, and before long, early defoliation disease occurs. Rescue measures: First, immediately after the hail disaster, carefully spray a fungicide over the whole orchard to strictly control the disease, then carry out topdressing and foliar spraying to restore the tree as quickly as possible; second, clean up the residual branches and fallen leaves in the affected area to reduce the source of pathogens; third, where conditions permit, install hail nets in the orchard to reduce the disaster.
4. Nutrient deficiency. In recent years, when applying base fertilizer in autumn, fruit growers only paid attention to the use of farmyard manure and macroelement fertilizers, neglecting the combination of trace elements, and failed to achieve the goal of balanced fertilization, so orchards often suffer defoliation due to the deficiency of a certain trace element. It has been found in production that iron-deficient fruit trees show chlorosis and yellowing of the mesophyll of young leaves, and in severe cases the leaves wither and drop. In magnesium-deficient fruit trees, light green patches gradually appear on the leaves at the base of new shoots, slowly turning yellow-brown, curling for several days and then dropping. Therefore, before fertilizing, soil sampling and testing should be carried out, and according to the test results, the fertilization plan should be determined, balanced fertilization should be popularized, and attention should be paid to the nutritional balance of nitrogen, phosphorus, potassium and various trace elements.