How to control common pests and diseases of crape myrtle trees?

1. Crape myrtle powdery mildew.

Powdery mildew mainly affects crape myrtle leaves, and young leaves are more susceptible to infection than old leaves. Young shoots and flower buds can also be infected. Small white pink spots appear on the leaves, which enlarge into round lesions and are connected into patches.

Severe cases cause the whole leaf to wither yellow, cause early defoliation, temperature in 19-25, relative humidity of 100% conditions are most prone to disease, mainly in spring, autumn, especially in autumn is the most serious, pathogenic bacteria to mycelium in the bud or to close the capsule shell on the leaf overwinter, spread by the airflow, the growing season can be infected many times. After the occurrence of powdery mildew, the photosynthesis intensity decreases by more than half, and the transpiration intensity of diseased leaves increases, which accelerates leaf senescence and death.

Prevention and control methods: 1. Strengthen fertilization, pay attention to drainage to avoid excessive humidity;

2. Reduce the source of infection, combine pruning in autumn and winter, eliminate diseased branches and burn them intensively, and pay attention to timely removal of diseased buds, diseased leaves and diseased shoots during the growing season.

3. When the plant is sick, it can be sprayed with 3000 times of 25% powdery rust wettable powder, or 1000 times of 70% methyl tobuzin wettable powder, or 500 times of 80% zeb zinc wettable powder, and the effect of several agents is better alternately.

Second, crape myrtle velvet.

Also known as pomegranate felt, it occurs in 2 generations in 1 year, and overwinters with eggs or nymphs. Female adults and nymphs suck sap on the bud axils, leaves and branches, resulting in black branches and leaves, leaf shedding, seriously affecting the growth and development of trees, and its excrement can induce coal stain disease, which is one of the main insect pests that harm crape myrtle.

Prevention and control methods: 1Strengthen quarantine, prevent the influx of pathogens, rationally fertilize, enhance the insect resistance of plants, maintain ventilation and light transmission, avoid excessive plant density, and combine winter and early spring pruning to burn insect branches. A few hours, manual scraping.

2.Chemical control. (1) Spray 10-15 times of pine resin mixture or 40-50 times of engine oil emulsion 1-3 times in winter to eliminate overwintering female insects.

2) Before germination, spray 3-5 degree stone sulfur mixture or 3-5% diesel emulsion to eliminate overwintering nymphs. (3) nymphs are the key to control, first of all, for the first hatched nymphs unearthed, spray 50% carbaryl wettable powder 500 times or 5% phoxanthion emulsifiable concentrate 1000 times on the soil surface around the roots in early spring. Seize the critical period when the shell has not thickened and the agent is easy to penetrate during the peak incubation period, spray once every 7-10 days, 2-3 times in a row, and use 40% dimethoate emulsion, 80% dichlorvos emulsion, 50% phosphine octathion emulsifiable concentrate, 25% imidophos emulsion 1000-1500 liquid evenly sprayed.

3.The use of polymer film mixed spray, sprayed on the plant to form a layer of film, so that the insect body breathing difficulty, suffocation and death, and the use of natural enemies red dot lip label insect predation can receive good results.

1. Powdery mildew.

Symptoms: This disease mainly harms its leaf part, the chance of infection of young leaves is large, there will be small white pink spots on the leaves, and then expand into round spots, and in severe cases, it will cause the leaves to wither and yellow, causing the leaves to fall.

Prevention and control: fertilization needs to be strengthened, and attention needs to be paid to drainage to prevent excessive humidity. Reduce the source of infection, eliminate dead branches and diseased branches during winter pruning, spray powdered rust and zeb zinc when the disease occurs, and several agents can also be used in turn.

Lagerstroemia. 2. Brown spot disease.

Symptoms: This disease also affects the part of the leaves, usually starting from the lower leaves, and then gradually spreads upward, with many lesions, and when the disease is severe, it will also cause the leaves to turn yellow quickly, and will fall off early.

Lagerstroemia. 3. Crape myrtle velvet.

Symptoms: Female adults and nymphs are mainly parasitic in the bud axils, which will suck the sap in the leaves and branches, causing the branches and leaves to turn black, prompting the leaves to fall off, seriously affecting the growth and development, and their excrement will also induce coal stain disease, thereby causing other pests.

Prevention and control: It is necessary to strengthen inspections to prevent the invasion of disease sources, and apply fertilizers reasonably to ensure that disease resistance is improved.

When crape myrtle trees are growing, they need to strengthen the management of fertilizer and water, and they must be watered with an appropriate amount of coarse residue, so as not to cause water accumulation, and they should be pruned reasonably in ordinary times, and it is best to prune them in winter in a timely manner, and they need to be pruned in time with the corresponding drugs after the occurrence of pests and diseases.

Common diseases in crape myrtle tree planting.

Crape myrtle tree in the growth, often occur powdery mildew, the plant is very harmful, in spring and autumn is the most likely to occur, after the disease of the leaves will appear white lesions, and then will gradually expand, in more serious times will cause the leaves to wither yellow, and will fall.

The main insect pest of cultivated crape myrtle trees.

Crape myrtle velvet: This insect pest is the most harmful to crape myrtle trees, when the insect infestation occurs, it will adsorb on the leaves and branches and suck the sap, resulting in black branches and leaves, and the leaves will gradually fall off.

Crape myrtle aphid: This insect pest generally occurs in May, and is the most serious in June when it is hotter, often gathering together to damage the leaves, suck sap, and affect the growth and development of crape myrtle trees.

Crape myrtle tree pest control.

When crape myrtle trees are growing, they need to strengthen the management of fertilizer and water, and they must be watered in an appropriate amount to not cause water accumulation, and they should be pruned reasonably in ordinary times, preferably in winter, and the diseased branches need to be cut off in time, and the corresponding drugs should be used in time after the occurrence of pests and diseases.

Symptoms Crape myrtle powdery mildew generally occurs on tender and flower buds. In spring and summer, the leaves become distorted and covered with a layer of white powder. Round lesions will appear on the leaves, and in severe cases, they will be connected into a pure brother. The damaged leaves will fall off prematurely due to the diseased spots.

Prevention and control method Potted crape myrtle flowers should be removed from the diseased leaves in time and moved to a ventilated and light-permeable place.

Once the lesions on the leaves are found, spray the agent in time. You can choose 500 times of Zinc Dyszeb wettable powder, 1000 times of methyl tobuzin, Bordeaux liquid, etc., spray once in 10 days, spray 3 4 times can get better.

Symptoms Soot disease mainly affects the leaves and branches of crape myrtle flowers. A layer of black mold appears on the petioles, affecting the photosynthesis of the plant. Coal sludge disease is mainly caused by insect infestation or fungal infection, and the disease is more serious in high temperature and rainy weather.

Prevention and control methods Strengthen side ventilation to reduce humidity in the air. Don't water when you're okay and keep the potting soil relatively dry.

Be prepared for insect control, the temperature gradually rises after May, and spray the flower protector once a month to avoid aphids or scale insects.

Prune diseased leaves and spray with fungicides. For blackened leaves, after rinsing with water, if they are wilted and yellow, they need to be cut off immediately, and then sprayed with fungicides to avoid the spread of diseases.

Aphids: can be sprayed with 1000-2000 times of rotenol or 1000-1500 times of 40% acemethamidophos. It is advisable to alternate the use of drugs so that pests do not develop resistance.

Alternatively, color swatches can be used for booby-trapping. Velvet insects: Promptly cut and destroy branches and leaves with pests and eggs.

The plants are then sprayed with an insecticide to eliminate the remaining pests.

Spotted aphid infestation of crape myrtle flowers

Symptoms 5-8 generations occur in the north every year, overwintering with eggs, the initial stage of the disease is in May, and the peak period of the disease is in June. Aphids suck the sap and damage the young leaves, posing a threat to the growth of crape myrtle flowers.

Control method In early spring, scrape off the old bark of crape myrtle trees, prune the damaged branches at the same time, and burn them intensively to eliminate the overwintering insect eggs as much as possible. Cultivation management should be strengthened in ordinary maintenance to reduce the source of disease.

When the aphid is serious, you can choose 1000-2000 times of spray fish vine or 40% dimethoate, 40% acemethamidophos 1000-1500 times solution to eliminate, but at the same time, pay attention to avoid pesticide damage. Where conditions permit, artificial propagation and scattering of natural enemies can also be adopted, and free-range ladybugs or grass ridge larvae are good choices. In addition, color plates can also be used to trap and trap winged aphids or white tin foil to reflect light and prevent migratory aphids.

Velvet insect pest of crape myrtle flowers

Symptomatic manifestations occur in 2 generations per year, overwintering with eggs or nymphs. Female adults and nymphs often suck sap on the axils, leaves and branches of crape myrtle flower buds, resulting in black branches and leaves and leaf shedding, which is not conducive to the growth of crape myrtle flowers. In addition, the excrement of this pest can also induce coal stain disease, which is a potential risk.

Prevention and control methods In winter and early spring, prune the branches, burn the insect branches intensively, try to eliminate the eggs, and manually scrape the found pests. Strengthen management and quarantine, reasonable fertilization, in order to enhance the insect resistance of plants, while avoiding excessive plant density, maintain plant ventilation, and do a good job of light transmission. The polymer film can be mixed with spray, and then evenly sprayed, which will form a layer of film on the surface of the plant socks potato culture, which will cause the insects to breathe hard, and then suffocate to death; Or use its natural predator, the red-spotted lip marker, to hunt and exterminate.

Chemical control can also be used if necessary.

Crape myrtle is a disease caused by the fungus Botrytis cinerea, which is characterized by gray mold spots on leaves, flowers and fruits, which can lead to plant death in severe cases. Methods for the prevention and prevention of gray mold include the following:1

Prevention first, pay attention to the growth environment and management of plants, maintain air circulation and the health of plants, and avoid tree injuries and leaf waterlogging. 2.Clean up the wilted leaves, flowers and fruits in time to avoid the growth and spread of germs.

3.The use of fungicides for prevention and control, the active ingredient is morphoconazole, carbendazim and other fungicides, and spray treatment according to the method and concentration on the instructions. 4.

In the early stages of the disease, physical methods such as sulfur fumigation can be used**.

1. Crape myrtle brown spot disease: Autumn ploughing is carried out on crape myrtle orchards or street crape myrtles, and the surface leaf litter is turned into the deep soil to reduce the source of infection at the beginning of next year. Trim at the right time to ventilate and let in light.

At the beginning of the disease, spray 1000 times of 50% benzomyl wettable powder, or 800 times of 75% chlorothalonil wettable powder.

2. Crape myrtle long-spotted aphid: 10% aphid lice net wettable powder can be sprayed 1500 times, or 50% pine moth emulsifiable concentrate 1000 times, 40% dimethoate emulsifiable concentrate 1000 times and 80% dichlorvos emulsifiable concentrate 1000 times, etc., and can also play a role in the treatment of crape myrtle velvet scale and other pests.

3. Crape myrtle scale: spray 10-15 times of pine resin mixture or 40-50 times of engine oil emulsion 1-3 times in winter to eliminate overwintering female insects; Before germination, spray 3-5 degree stone sulfur mixture or 3-5% diesel emulsion to eliminate overwintering nymphs.

Specific measures for pest control:

1. Soot disease often occurs on the leaves and branches of plants, mainly transmitted by aphids and scale insects, so the prevention and control should be mainly insect control, which can be sprayed with 40% dimethoate EC 1500 times or 80% dichlorvos 1500 times.

2. Powdery mildew harms young shoots and leaves, and when the shoots die, the plants can not bloom normally, and can be sprayed 3 5 times with 800 times of 70% methyl tobuzin wettable powder.

3. The large decay moth harms the branches and leaves with larvae in July and September, and can be sprayed with 1000 times of 90% trichlorfon.