Pest control of prurigo

Lagerstroemia indica is a kind of landscaping tree species susceptible to diseases and insect pests. As far as Tianshui area is concerned, it is the most suitable place for Lagerstroemia indica to grow because of its beautiful scenery and pleasant climate. However, in the long-term cultivation and management process, we also found many problems. Below, the occurrence regularity and control methods of some main pests and diseases of Lagerstroemia indica are introduced as follows. Powdery mildew is a worldwide disease with a wide range of hosts, and Lagerstroemia indica is its 1 important target. Powdery mildew of Lagerstroemia indica is common in the provinces and cities where Lagerstroemia indica is planted in China. After the onset of Lagerstroemia indica, the leaves often turn yellow and fall off, which directly affects the tree potential and ornamental effect.

1. 1 Symptoms-powdery mildew is a fungal disease, which mainly harms leaves, and young leaves are more susceptible to infection than old leaves. The disease also harms branches, shoots, buds and buds. At the early stage of the disease, small white speckles appeared on the leaves, which became round or irregular faded spots after expansion, covered with a layer of white powdery mildew, and turned gray in the later stage. After the flowers are infected, the surface is covered with white powder, and the flower spikes are deformed, losing ornamental value. The plants affected by powdery mildew will become shorter, the tender leaves will be twisted and withered, the leaves will become smaller without spreading, and the branches will be deformed. If it is serious, the whole plant will die.

1.2- The occurrence of powdery mildew of Lagerstroemia indica overwinters on diseased buds, diseased branches or fallen leaves. When the temperature is suitable in the next spring, the overwintering hyphae begin to grow and develop, producing a large number of conidia, which spread and infect with the airflow. In Tianshui area, the disease usually begins in April and tends to be serious in June. It will slow down or stop in July and August because of the hot weather, but it may reappear in September to 65438+ 10. Powdery mildew occurs seriously in rainy season or under high relative humidity. Partial application of nitrogen fertilizer, too dense planting of plants or poor ventilation and light transmission are all beneficial to the disease.

L3 Prevention and control methods-

1.3, 1 Gardening has a strong ability to control the sprouting of Lagerstroemia indica, so for plants with serious diseases, all the annual branches can be cut off and burned in winter, thus completely eliminating the source of the disease. If Lagerstroemia indica planted at home is found to be infected with powdery mildew, the diseased leaves should be removed in time and the potted flowers should be placed in a ventilated and light-transmitting place. In field cultivation, it is necessary to control planting density, strengthen daily management, pay attention to increasing the application of phosphorus and potassium fertilizer, control the application amount of nitrogen fertilizer, and improve the disease resistance of plants; At the same time, we should also pay attention to the selection of disease-resistant varieties.

When1.3,2 is used to control serious diseases, Pomei 3 ~ 4 lime-sulfur mixture can be sprayed before germination in spring; When the disease occurs in the growing season, it can be prevented by spraying 500 times 80% zineb wettable powder, 1000 times 70% thiophanate-methyl, 1500 times 20% triadimefon emulsifiable concentrate or 800 times 50% carbendazim wettable powder. Brown spot disease is also a common disease of garden plants, which often occurs in the growing season of Lagerstroemia indica. The occurrence of brown spot disease often leads to a large number of dead leaves and fallen leaves of plants. Affect viewing and flowering.

2. 1 Symptoms-The pathogen of Lagerstroemia indica brown spot disease is also fungi, which mainly invades the leaves, usually the lower leaves begin to get sick, and then gradually spread to the upper parts. At the beginning of the disease, the lesions were round or nearly round, with different sizes and a few irregular shapes. The focus is purple-black to black with light edge color. Then the color of the lesion deepened, showing black or dark black, and the boundary with the healthy part was obvious. In the later stage, the color of the lesion center becomes pale and small gray-black mildew spots appear. When the condition is serious, the diseased spots become one piece, the whole leaves turn yellow quickly and fall off early.

2.2 Occurrence regularity-Lagerstroemia indica brown spot is caused by the infection of Cercospora crassipes. The pathogen overwinters in the form of mycelium or conidia, and then carries out primary infection and reinfection through conidia in the following year, and spreads through airflow or wind and rain. Brown spot disease in Tianshui area generally begins in early summer and is seriously harmful in autumn. It is easy to break out in hot and rainy seasons, especially in years or seasons with frequent rainstorms; Generally speaking, the lower leaves are more susceptible to infection than the upper leaves.

2.3 Prevention and control methods-

2.3. 1 early detection of horticultural control, timely removal of diseased branches and leaves, centralized incineration or deep burial, and reduction of pathogen sources. Strengthen cultivation management, plastic pruning, so that plants are ventilated and transparent. It is best to change the soil for family potted plants every year.

2.3.2 At the initial stage of chemical control, 500 times of 50% carbendazim wettable powder, 65% zineb wettable powder 1000 times of liquid or 800 times of 75% chlorothalonil wettable powder can be sprayed for control. Sooty blotch, also known as soot disease, is widespread among garden plants in China. The invasion of Lagerstroemia speciosa is mainly due to the harm of Lagerstroemia speciosa and Lagerstroemia speciosa, that is, the mucus secreted by them is used as nutrition to induce a large number of bacteria polluting coal to multiply. After the disease, the leaves of diseased plants are covered with black mold layer, which not only affects the ornamental value of Lagerstroemia indica, but also affects the photosynthesis of leaves, resulting in the weak growth of plants and early defoliation.

3. 1 Symptoms-Pathogens in sooty blotch, Wei Zi belong to fungi, but there are many kinds of pathogens in sooty blotch. The same plant can be infected with a variety of pathogenic bacteria, and its symptoms are slightly different, but the black mold layer or black pulverized coal layer is an important feature of the disease. Sooty blotch mainly attacks leaves and branches. The disease first infects the front of the leaf along the main vein, and then gradually covers the whole leaf surface. In severe cases, the surface of leaves, branches and even petioles will be covered with black coal powder, which will block the stomata of leaves and hinder normal photosynthesis.

3.2 Occurrence regularity-sooty blotch pathogenic bacteria overwinter on diseased leaves and branches in the form of mycelium or ascomycetes. Because the mucus secreted by Lagerstroemia indica and Lepidoptera Lagerstroemia indica will provide nutrition for pathogenic bacteria in sooty blotch, generally, after the occurrence of these two pests, sooty blotch will occur in large numbers. However, from late June to early September, the damage of Lagerstroemia speciosa and Lagerstroemia speciosa reached its peak, and the high temperature and humidity at this time were also conducive to the occurrence of the disease. Therefore, spring (caused by overwintering bacteria) and autumn (caused by Lagerstroemia speciosa and Lagerstroemia speciosa) are the heyday of sooty blotch, and 1 ~ 2 generation occurs in Tianshui area 1 year.

3.3 Prevention and control methods-

3.3. 1 Horticultural prevention ① Make trees ventilated and transparent by thinning and pruning; (2) timely control aphids, scale insects, whiteflies, etc. Because the secretion of these insects is the basis of the existence of pathogens in sooty blotch.

3.3.2 The commonly used chemicals for chemical control are lime-sulfur mixture, Pomei-3 lime-sulfur mixture in winter and 0.3 lime-sulfur mixture in summer and autumn. It can also be controlled by phosphorus trichloride and litsea cubeba leaf juice. Or spray 50% carbendazim wettable powder 500? 800 times solution, 70% thiophanate-methyl 500 times solution, etc. Yellow thorn moth, with medium size and caterpillar larvae, is one of the main omnivorous leaf-eating pests of garden flowers.

4. 1 hazard characteristics-the main hazard caused by the larvae of yellow thorn moth is eating. Newly hatched larvae generally gather on the back of leaves to feed on mesophyll, making the leaves sieve-shaped; Older larvae will crawl and spread harm and eat leaves directly. In severe cases, the leaves are eaten up, leaving only petioles and veins.

4.2 Occurrence Regularity —— The yellow thorn moth overwinters in cocoons on the damaged branches as mature larvae. 1 generation larvae can be observed in late June after adult emergence and mating and spawning in May and June every year. Larvae is 7 years old and often crosses generations. July to September is the peak of victimization.

4.3 Prevention and control methods-

4.3. 1 Horticultural control combined with winter pruning can remove overwintering cocoons from branches, thus eliminating or reducing insect sources.

4.3.2 Physical control of home potted Lagerstroemia indica can artificially remove the overwintering cocoon after defoliation, and completely eliminate the insect source. In field production, black light can be set to trap and kill adults in the emergence stage.

4.3.3 Chemical control It is best to use chemicals before the larvae spread. 80% dichlorvos EC 1000 times, 50% phoxim EC 1000 times or 2.5% deltamethrin EC 4000 times can be sprayed for control.

Lagerstroemia indica can also do harm to the green thorn moth or the brown thorn moth, but they all belong to the thorn moth, except for a slight difference in morphology, they have great similarities in life habits and occurrence laws, and can be treated at the same time when controlling the yellow thorn moth. The green-tailed silkworm moth, alias Shuiqing moth, Swallowtail moth and Long-tailed moth, belongs to the five-fingered moth family; It is distributed in most provinces and cities such as North China, Central China, East China and Southwest China. Harm a variety of fruit trees and garden seedlings.

5. 1 morphological characteristics-

The adult is 35 ~ 40 mm long and its wings spread about122 mm; There are dark white hairs on the body surface, the wings are pink-green, the front wings are purple-brown through the chest, there are eye-shaped markings in the center of the wings, and the tail-shaped protrusions on the rear wings are 40mm long. Oval slightly flat, 2mm long, taupe. Larvae can be about 80mm long, yellow-green, with tumor-like protrusions on the body segments, four in the middle and back chest, 1 on the back of eight abdominal segments, and long brown hair on the tumor segments. The pupa is 45 ~ 50 mm long, reddish-brown, with light spots on the forehead. Cocoons are ovoid, grayish yellow or grayish brown.

5.2 Occurrence regularity-Tianshui area 1 year can have 2 generations; Cocoons usually form on branches, and larvae hatch in the first half of May. Larvae * * * 5th instar, lasting 36 ~ 44 days. The mature larvae began to pupate in early June and reached its peak in mid-June. The pupa duration is 65438 05 ~ 20 days. From late June to early July, 1 generation adults emerged and laid eggs; Larvae hatch in early July, and mature larvae cocoon and pupate at the end of September. The overwintering pupa period is 6 months.

5.3 Hazard characteristics-Larvae feed on leaves, and larvae eat leaves into notches or holes, and when they are slightly larger, they eat up the whole leaves, leaving only petioles or thick veins.

5.4 Prevention and control methods-

5.4. 1 Horticultural control-The overwintering pupa of the green-tailed silkworm moth is very large, which is convenient for artificial killing. Old larvae can be as long as 80mm, with strong resistance and amazing appetite. Chemical control is difficult, and artificial capture can be used.

5.4.2 Chemical prevention and control —— Early detection and prevention should be paid attention to during chemical prevention and control, and drugs should be used before the third age as far as possible; 800 times of 50% acetaminophen EC, 1000 times of 80% dichlorvos EC, 1000 times of 90% crystal trichlorfon EC or 3,000 times of 2.5% deltamethrin EC can be sprayed for control. Introduction occurs 5-8 generations a year in northern China, and eggs overwinter near buds and branches. May is the initial stage of the disease, and June is the peak. Nymphs and adults cluster to harm young leaves and suck juice, which affects growth and development. Prevention and control method: 1. In early spring, the old bark is scraped off, the damaged branches are cut off, and centralized burning is carried out to eliminate the overwintering eggs.

2. Strengthen cultivation management measures to reduce the source of disease.

3. When the amount of aphids is large, cough 40% omethoate, 40% acephate 1000- 1500 times or spray spermidine 1000-2000 times, but pay attention to avoid phytotoxicity.

4. Artificial propagation and diffusion of natural enemies, such as harmonia axyridis and grassridge larvae, where conditions permit.

5. Use colored boards to trap and kill winged aphids, or use white tin foil to reflect light and refuse to fly.