Weeping willows are important ornamental trees in gardens since ancient times, and can also be used as street trees, shade trees, dike-fixing trees and plain greening trees. However, there are many kinds of diseases and insect pests of weeping willows, which often cause great harm if they are not prevented in time.
The first is the willow gall midge.
Willow gall midge is a kind of Diptera gall midge. It mainly harms willows, especially dry willows and weeping willows. The branches of trees become thicker rapidly after being damaged, showing spindle-shaped tumor-like processes, commonly known as willow cancer.
Morphological characteristics Adults are like mosquitoes. Eggs are oval, orange and translucent. The larvae are milky white and translucent when they are first hatched; Mature larvae are orange-yellow, with sharp front end, thick abdomen, body length of about 4 mm, and pupae are reddish brown.
Occurrence regularity: the gall midge occurs once a year, and the mature larvae concentrate on the bark of the damaged part for the winter. In Cao Xian County, pupation begins in March every year, and it becomes an adult from late March to mid-April, with the peak of adult emergence in early April. The eclosion time is 9:00- 10 every morning, and the eclosion is more frequent when the temperature is high, especially on sunny days after rain, and the pupa skin after adult eclosion is concentrated on the eclosion hole, which is easy to find. After eclosion, adults quickly mate and lay eggs. Most eggs are laid in the old feather holes on the original gall tumor, and the depth is between the cambium and xylem, and dozens to hundreds of eggs are laid in each egg hole. The newly hatched larvae spread harm nearby and drilled into branches from the base of buds. In late June, most larvae ate phloem and ate phloem and cambium.
Gall formation When the gall midge first attacked, the larvae attacked the cambium, which stimulated the abnormal growth of the cells in the affected area, and the branches quickly increased like tumors in the affected area, and then mild tumors began to appear on the branches. In the coming year, after the feather holes appear in the branches, adults will lay eggs in the original feather holes and their vicinity, and the hatched larvae will continue to harm the healing tissues around the gall, resulting in the proliferation of new tissues and the growth of gall. If the diameter of the damaged branches is less than 5 cm, the insect population density is relatively high, the branches grow weak quickly, and will dry up and die after two or three years.
Prevention and cure method
It is best to control adults before emergence and diffusion. (1) The damaged trees are small or early. In winter or before the end of March, the bark of the damaged parts shall be shoveled, or the gall shall be sawed off, and centralized incineration shall be conducted. ② At the end of March, the larvae, eggs and adults can be completely killed by brushing the galls and newly invaded parts with 40% omethoate stock solution, adding 2 times of water and wrapping the coated parts with plastic film. ③ In spring, the mature larvae, pupae and eclosion adults can be killed by carefully scrubbing the galls and newly invaded parts with oil emulsion or waste oil before eclosion. (4) In May, 40% omethoate secondary solution was used to make a hole in the base of the trunk (the aperture was 0.5-0.8cm, and the xylem was 3cm deep), and 65,438+0.5-2 ml was injected with a syringe, and then sealed with mud to prevent the liquid from volatilizing, or scraping the skin and applying drugs to poison the larvae in the gall. ⑤ From May to June, drill 2 ~ 3 holes (0.5 ~ 0.8cm in diameter and 3cm deep into xylem) on the gall, then inject 1 ~ 2ml with 3 ~ 5 times of 40% dimethoate into the holes, and then seal them with mud to prevent the liquid from volatilizing. The effective rate of this method to control gall midge can reach 100%.
Second, willow rust.
Symptoms:
Weeping willows began to get sick from late May to early June. Summer spores accumulate on both sides of leaves, mostly on the back of leaves, and a few on shoots. The primary conidia are small, solitary and round, with a diameter of 0.1~ 0.5mm. In the later stage, most conidia are clustered into large piles with a diameter of1.5 ~ 2.5mm, which are orange. In July and August, the leaves are covered with summer spore piles on both sides, and the leaves curl or fall off in advance due to water loss. In late August, reddish brown and slightly raised spots appeared on both sides of the leaves, which were the winter spore piles of the pathogen. The winter spore pile is small and round, with a size of 0. 1 ~ 0.5 mm. In severe cases, the winter spore piles are contiguous with each other, and the back of leaves is still the most.
The main host of weeping willow rust is corydalis. There is no summer from late April to early May. Diseases occurred on leaves, stems and fruits, at the same time, pale yellow herpes appeared on the affected area, and light brown punctate spores were born on the herpes. Bubble-like bulges are successively produced near it, and yellow and powdery rust spore piles are exposed after breaking the skin. After the rust spores fly away, leaves, stems and fruits die.
Preventive and control measures:
The prevention and control of the disease is mainly through afforestation and tending measures. When raising seedlings in nursery, we should choose the mother tree with strong disease resistance as the propagation material. Appropriate density and watering times should be determined according to the conditions of afforestation sites. In tending management, it is necessary to combine weeding and loosening the soil, eradicate the hosts inside and outside the forest, and cut down the plants with time difference, so as to keep the population structure in a reasonable ecological configuration. Once the disease occurs, 800 times solution of 25% triadimefon wettable powder is sprayed once every 20 days, and the control effect can reach over 90% for three times. 2,4-DJ ester 1000 times can also be sprayed to eliminate the transfer of abundant food, and the effect can reach 92.5%.
Third, the black velvet beetle
Black velvet chafer, also known as oriental chafer and velvet chafer, is commonly known as blind bumper, big velvet jacket and black bean worm. It belongs to COLEOPTERA, Scarabaeidae. Adults are 7-8 mm long and 4-5 mm wide, slightly shorter and bean-shaped. The back is raised, all dark brown, covered with gray or deep purple fluff and shiny. The antenna is black, gill-shaped, leaf-shaped, with 10 nodes, and the peduncle is enlarged with 3-5 bristles on it. There are cilia on the dorsal plate of chest and the lateral side of pterygoid vein. There are nine ridges on both wings. There are two teeth in the tibial joint segment of the forefoot; The tibiofibular joint of the hind foot is slender, and there is a groove-like depression on the inside of its end.
The egg length of black velvet scarab is 1mm, oval, milky white and brown before hatching. When the larvae mature, their body length is16-20mm. A yellow-brown head. The body is bent, dirty and white, and all have yellow-brown bristles. There are 3 pairs of chest and feet, and the hind foot is the longest. There is a nib-shaped notch in the center of the last abdominal hair area, which is bimodal, and there are 12-26 long and slightly flat bristles at the rear edge of the abdominal hair area, which are discharged in an arc shape. The pupa is 6-9 mm long, yellowish brown to dark brown, with 1 buttock spines at the end of abdomen.
Prevention and control methods:
1. Trapping and killing adults: In the nursery or newly planted orchard, when there is no wind at about 3 pm, the branches of poplar, elm and willow with a length of about 60 cm are immersed in the 80% trichlorfon solution which is 0/00 times that of/kloc-(it is best to soak the branches in the solution for 2-3 hours and then take them out for later use), and then scatter them underground to trap and kill adults.
2. Artificial killing: during the adult occurrence period, it is killed at night by using its habit of suspended animation. Therefore, there are many kinds of trees harmed by insects. Besides killing fruit trees, we should also kill other trees around the fruit trees to get better results.
3. Chemical control: According to the habit of adults entering the soil, 5% phoxim granules, 25% parathion capsules, 50% phoxim emulsion, 50% methyl isocarbophos emulsion and granules were sprayed under the tree to treat the soil before occurrence. About 5 grams of crude drug per square meter is diluted 20 ~ 30 times to make toxic soil, and then the topsoil is raked to eliminate the adults in the soil. Spraying 2.5% trichlorfon powder, 2 kg per square meter. Or use 2.5% triamcinolone acetonide, 5% Laifuling, 2.5% Kung Fu, Le Song or 1000 times beta-cypermethrin. , milliliters per square meter, about kilograms of water, and spray.
Four. Poplar moth
Poplar moth: adult, body length 14 ~ 23 mm, wings spread 35 ~ 52 mm, wings are white and slightly shiny; The antenna stem has a black-brown and white ring pattern; There are black and white ring lines on the tibiofibular joint and accessory joint of the foot. Eggs, like steamed bread, are grayish brown at first and dark brown before hatching; The egg mass is covered with gray colloidal foam secretion. Larvae, the last age is 30 ~ 50 mm long and dark brown; The midline of the back is black, and the sides are yellow-brown, with a 1 grayish black longitudinal band under it; Each part of the body has eight black or brown trichomes, and the tumor is densely covered with several short black hairs. The chest and feet are brown, and the abdomen is bluish brown.
Preventive and control measures
1. Before the overwintering larvae get off the tree for overwintering (early September), stick a straw foot with a width of 20 cm at the base of the trunk, check the larvae in March of the following year and burn them. If the larval density exceeds 120/plant, chemical control should be considered, and moths should be removed in time during the colony period.
2. Spraying 2,000-8,000 times of 2.5% dichlorvos, 20% chlormequat or 5% beta-cypermethrin solution on the trunk at the beginning of April to control the upper tree larvae, the control effect can reach more than 85%. A large area of forest can be controlled by using Dimas smoke agent in the middle and late April.
3. Spraying with 2× 108 spores/ml Cordyceps liquid in larval stage.