Diseases and insect pests of Platycladus orientalis leaves and their control methods

The main diseases of Platycladus orientalis leaves are Platycladus orientalis leaf blight, Platycladus orientalis leaf blight, Platycladus orientalis caterpillar (Platycladus orientalis larvae), Platycladus orientalis aphids and longicorn beetles. The following describes the manifestations and control methods of diseases and insect pests.

Disease

1. Platycladus orientalis leaf blight: Platycladus orientalis leaf blight is a major disease of Platycladus orientalis. When the damage is serious, it can cause a large area of Platycladus orientalis leaves to wither and burn. The tree is seriously weak, which is easy to cause secondary pests such as cypress, sequoia, longicorn beetles and bark beetles, which accelerate the death of trees.

The regularity of the disease: the bacteria spent the winter on the diseased leaves and began to move in April of the following year. In May, it began to infect the lower leaves of the crown, and the diseased leaves appeared macula at the initial stage, which gradually expanded, making the whole cypress leaves yellow and finally yellowish brown. In June, black spots appeared on the diseased leaves, that is, the reproductive organs of the bacteria, and released spores for re-transmission. If the forest is dense, the humidity in the forest is high, and the temperature is suitable, it will spread and infect in large numbers, resulting in a pandemic of the disease, with the most serious disease from June to July. There is often a disease center in the dense forest, which gradually spreads out into a piece, and when it is serious, it looks like a fire, and a large number of diseased leaves fall off, often sprouting clumps of new leaves from the branches of the tree trunk, and people call it "tree beard."

In general, the disease in the gully is more serious than that on the top of the mountain, the shady slope is more serious than the sunny slope, the dense forest is more serious than the sparse forest, and the rainy and humid weather is more serious.

Control methods (1) sweep the diseased leaves under the tree in autumn and winter to burn and dye the source. Eliminate the winter germs and reduce the first invasion. (2) from May to August, Bordeaux solution was sprayed once every two weeks. Special attention should be paid to the strict control of primary infection, and blockade should be carried out to prevent the spread of primary infection. (3) the over-dense cypress forest should be thinned properly to make the forest ventilated and transparent and reduce the disease conditions.

2. Platycladus orientalis leaf blight: the disease infects new leaves, young twigs and scale leaves of the same year. The susceptible plants showed no symptoms in that year, and the leaves withered rapidly in March of the following year. Around the middle of June, black particles were produced on the dead scale leaves and twigs, which were the ascomycetes of the pathogen. The ascus disk is cup-shaped and olive-colored when it is wet and absorbs water. After Platycladus orientalis was injured, the crown withered like a fire, a large number of diseased leaves fell off, and the branches withered. Clusters of twigs and leaves sprout on the trunk or branches, the so-called "tree beard". The damage for several years caused the whole plant to die.

The regularity of the disease: the occurrence of the inside and lower part of the crown was serious, and the autumn shoots basically did not suffer in that year. High temperature and heavy rainfall in June, cold and dry winter, serious illness the following year, and vice versa. The pathogen is a kind of disk bacteria with weak parasitism, and the plant growth is weak and easy to infect. all the factors that affect the growth of Platycladus orientalis are beneficial to the infection and development of the pathogen.

Control methods: (1) moderate pruning to improve the growth environment of Platycladus orientalis and reduce the source of infection. (2) apply more fertilizer to promote growth. (3) during the peak period of ascospore release, 40% aldicarb, or 40% carbendazim, or 40% chlorothalonil 500 times solution was sprayed for control. (4) selecting disease-resistant varieties.

Insect pest

1. Platycladus orientalis caterpillar (Platycladus orientalis larva): the larva of Platycladus orientalis is the main leaf-eating pest in Platycladus orientalis shelterbelt. The insect has two generations a year, and the 5th instar larvae of 3murmure overwintered under the deciduous layer or stone. It harmed the trees in the middle of March the following year, aged and pupated in the middle of April, hatched the first generation larvae in the first ten days of June, pupated in the early and middle of July, hatched the second generation larvae in the middle and last ten days of August, and overwintered in the first and middle of October.

Main points of prevention and control: (1) agricultural prevention and control. Strengthen the forest management, prune and cut in time, peel the bark around and burn it centrally during the overwintering period, and can be caught artificially when the larvae occur. (2) physical control. According to the phototaxis of adults, a black light is set to trap and kill adults. (3) biological control. There are many kinds of natural enemies of this insect, try not to use chemical prevention when the occurrence is small, pay attention to protect the natural enemies, such as releasing parasitic wasps and so on. (4) Chemical control. When the larva density is high, it should be treated early. Using aircraft to spray 25% diflubenzuron No. 3 with low capacity to control larvae, 23-45g per mu and 10.5kg, the control effect can reach 98%. Aircraft control should be carried out in sunny days and under the condition of wind force below grade 3. Artificial spraying of 25% diflubenzuron 3, 1RU 1500 times solution can control larvae, and the effect can reach more than 90%. Generally, the control should be carried out at the age of 2-4 instar, and a small amount of pyrethroid pesticides can be added as needed.

2. Platycladus orientalis aphid: also known as cypress aphid. It belongs to Homoptera, Aphididae. It is widely distributed. Damage to Platycladus orientalis, Sabina vulgaris, Sabina vulgaris and Sabina vulgaris, etc. It is one of the most important pests on cypress, especially to Platycladus orientalis hedge and Platycladus orientalis seedlings. The worms on the twigs are covered with layers, excreting a large amount of honeydew, causing coal pollution disease, light ones affect the growth of trees, heavy young trees dry up and die.

Prevention and cure method

(1) protect and utilize natural enemies such as Coccinella septempunctata, Coccinella axyridis, solar wasps, aphid wasps, ash-eating aphid flies, lacewings and aphid-eating gadflies. When the occurrence of spring is not serious, try not to apply medicine, but spray clear water to wash the insect body to protect the reproduction and development of natural enemies in the future.

(2) when the chemical control is serious, spray 25% Aktai water dispersible granule or 20% Kangfuduo concentrated solvent 5000 times. About 20 generations occur every year, which is large and harmful all the year round. The control can be controlled by spraying 1.2% bitter tobacco EC 1000Mel 1500 times, or spraying 10% imidacloprid wettable powder 2000 times.

3. Monochamus alternatus: also known as wood borer, which belongs to Coleoptera longicorn beetles and is the main pest of fir and cypress. The larvae feed between bark and wood, cut off the transport of water and nutrients, cause needle yellowing, growth decline, heavy cause wind fold, snow break, and in serious cases quickly cause the death of the whole plant or the whole tree. It directly affects the rapid growth and high yield of Chinese fir and cypress and the formation of high quality wood.