Common diseases and insect pests of Robinia pseudoacacia and their control techniques

Common diseases and insect pests of Robinia pseudoacacia and their control techniques

Robinia pseudoacacia, also known as Sophora japonica and Sophora pseudoacacia, is a leguminous tree of the genus Sophora, which is native to China. It grows fast and has strong adaptability to various types of soil. It can watch flowers in late summer and early autumn, and it is also a high-quality honey source tree.

1 morphological characteristics

Robinia pseudoacacia, deciduous tree, up to 25 m high; bark grayish brown, longitudinally cracked, current year's branchlets green. Apical buds, lateral buds substipitate, leaves odd-pinnate, leaflets 7-17, shortly stipitate, ovate to lanceolate-ovoid, apex acute, base rounded or broadly cuneate, abaxially pale, strigose; stipules subulate, caducous. Panicle terminal, Corolla white or yellowish. Pods beaded, 2.5-8 cm long, fleshy indehiscent. Seeds 1-6, reniform, yellowish green when young, dark brown when mature. The flowering period is from June to August and the fruiting period is from late August to October.

2 growth habits

Robinia pseudoacacia is a little shady when it is young, and likes light when it grows up. It also has strong adaptability in dry and cold climate, and grows most vigorously on sandy loam soil with deep, humid, fertile and well-drained soil, and can adapt to neutral, calcareous and slightly acidic soil. It can grow normally in mild saline-alkali soil (salt content is about 0.15%), but it grows poorly in long-term water shortage, barren or low-lying waterloam land. It has strong resistance to SO2 CL2 HCL and smoke. It began to blossom and bear fruit in 5 ~ 7 years, and the seeds germinated and propagated. Deep-rooted, strong wind resistance, fast generation.

(3) main diseases and control measures

3.1 peptic ulcer

The canker of Robinia pseudoacacia caused by Fusarium oxysporum mostly occurred on the green trunk of 2-4-year-old young trees and 1-2-year-old branchlets of big trees. At the initial stage of the disease, a yellow-brown watery round spot appeared on the branches, and then expanded into a fusiform, the larger spot slightly sunken in the center, with the smell of dregs, showing a typical wet rot, after about 20 days, orange-red conidia pile appeared on the spot. The disease spot can often be circumscribed from the main stem, causing the upper branch to die. If the disease spot has not been circumferential cut the tree trunk, then the disease spot can heal in the same year. The disease was at its peak from the middle of March to the end of April, and the disease gradually stopped when it entered the peak growing season at the beginning of summer.

Prevention and control methods: 1. The incidence of disease can be effectively reduced by reducing the water loss rate of seedlings as far as possible and keeping the degree of bark expansion below 85% in artificial operations such as seedling raising, pseudo-planting, pulling and transportation, planting and so on. two。 Remove diseased branches and withered branches in time, scrape off disease spots and apply medicine to protect them. 3. In the initial stage of the disease, the trunk was sprayed with 70% methyl thiophanate wettable agent 800 times or 70% chlorothalonil 300 times. Spray once in 10 days, 2 times in a row.

3.2 powdery mildew

Powdery mildew is a fungal disease, which occurs mostly on leaves and sometimes on young fruits and twigs. There is a layer of white powder in the affected area, so it is called powdery mildew. In the later stage, scattered, needle-sized black particles, or even even pieces, were slowly appeared on the powder layer, covered with a gray-white mold layer. If it is not removed and treated in time, the pathogenic bacteria (fungi) will overwinter on the plants, and the peak period of the disease is from July to August in the north, especially after autumn.

Prevention and control methods: 1. Remove the diseased branches in time and destroy them. two。 At the initial stage of the disease, 0.2-0.3 degree stone-sulfur mixture was sprayed once every semimonthly, 1500 kg / ha each time, and was sprayed for 2 times. 3. During the peak period, 50% carbendazim wettable powder was sprayed with 1000 times of carbendazim wettable powder and 50% methyl topiramate.

3.3 chlorosis

There are many causes, if the soil consolidation stagnant water, we should pay attention to drainage and loosening soil. Sulfur deficiency, nitrogen deficiency and iron deficiency can lead to yellowing of leaves, and foliar spraying of potassium dihydrogen sulfate and ferrous sulfate can relieve symptoms.

Prevention and treatment: use 0.5% ferrous sulfate + 0.05% citric acid aqueous solution for foliar spray or 0.75% ferrous sulfate solution slowly into the tree trunk.

4 main insect pests and control measures

4.1 Locust aphids

The occurrence algebra of Robinia pseudoacacia aphids varies from year to year. In the northern region, more than 10 generations can occur, overwintering with eggs under the branches or buds of trees, and the overwintering eggs begin to hatch slowly with the increase of temperature in March of the following year. With the sprouting of flowers and trees, first gather on the buds to absorb juice harm, and so on the initial development of leaves, and then turn to suck the tender leaves. Generally, it propagates rapidly from late April to early May, and produces winged aphids, and the population density increases obviously. From June to July, the damage on Robinia pseudoacacia is the most serious, the damaged leaves curl to the back, and coal fouling disease is induced at the same time. In the middle and last ten days of October, the temperature decreased gradually, the temperature difference increased in the morning and evening, and the insect population density decreased. In November, it moved to a warm place or overwintered in the rhizosphere of weeds around the roots, and a small amount of eggs overwintered.

Prevention and control methods: 1. Spray stone and sulfur mixture in autumn and winter to eliminate overwintering eggs. two。 When the amount is large, 40% omethoate + 2.5% dimethoate EC 3000 times, or 4.5% cis-cypermethrin EC 2000 times, or 10% imidacloprid wettable powder 50g, water 150kg.

4.2 Locust inchworm

The inchworm of Robinia pseudoacacia, also known as locust moth, the larva is commonly known as "hanging ghost", is an important pest of Robinia pseudoacacia, when other food is insufficient, it often eats up the tender leaves of locust, affecting the normal growth of trees. For 3-4 generations a year, the pupae overwintered in the pine soil about the depth of 4cm near the trees, and the adults entered the peak stage of Eclosion in the middle of April the following year, the first generation larvae hatched in the first and middle of May, the second generation larvae hatched in late June, the third generation larvae hatched in early August and pupae in September. The food marks in the larval stage are reticulate. When the larvae are frightened by the outside world, they immediately spin and droop, and then climb up and continue to eat; they can also spin and droop and spread with the wind, so they are called "hanging ghosts".

Prevention and treatment methods: pay close attention to the first generation, pick and treat the second and third generation. 1. Spray 4.5% cypermethrin EC + 80% dichlorvos EC during larval stage. two。 Spray 2000 times of 1% avermectin EC or 200 times of Green Wiley in the peak period of Eclosion.

4.3 American white moth

American white moth is native to North America and is an important quarantine object in the world. The insect has extremely miscellaneous feeding habits and has more than 300 host plants. For 2-3 generations a year, the pupa cocoon overwintered under the old bark, under the ground litter and topsoil, and began to Eclosion in the first ten days of May of the following year, the first generation larvae from the middle of May to July, and the second generation from the first ten days of August to late September. Soon after hatching, the larvae spin silk and form a net, and gather in the net to eat the leaves into a sieve net. When insects occur for a long time, all the damaged leaves are eaten up, leaving a net to hang on the tree, which in serious cases causes the tree to die. Adults have phototaxis.

Prevention and control methods: 1. Spraying BT+ to control American white moth virus in pre-3rd instar larvae. two。 When the larvae are harmful, spray 3% hypertonic phenoxyvir EC 1000-1500 times, or 1.8% avermectin EC 2000-3000 times. 3. The method of punching holes and injecting chemicals at the base of the trunk was used to control tall trees.