Main pests of Lagerstroemia indica and their control methods
1, crape myrtle
Lagerstroemia speciosa, also known as pomegranate scale, belongs to Homoptera and Coccidae. Scale insects occur in many parts of the country, especially in North China and Central China, and have become important pests of garden plants.
Morphological characteristics:
Female adults are flat, oval, about 2-3 mm long, dark purple, and covered with a layer of white velvet shell when they mature. The male adult is about 0.3 mm long, and its wings spread about 1 mm, which is purple. Oval, purplish red, about 0.25 mm long. Nymphs are oval, purplish red and have spines around their bodies. The male pupa is purple-brown, oval, and wrapped in a bag-like velvet white cocoon.
Occurrence law:
The generation algebra of the insect varies from region to region, with 2-4 generations a year; For example, there are two generations in Beijing, three generations in Shanghai and four generations in Shandong. The overwintering period of scale insects is fertilized females, 2nd instar nymphs or eggs, which varies from place to place. Usually overwinter in the cracks of branches. Early June to mid-July and mid-August to September are the peak periods for nymphae hatching, but in Shanghai and Shandong, there are 3-4 generations a year, and the first generation of nymphae can be found in late March and early April. Scale insects reproduce quickly in warm and high humidity environment, and dry heat is not conducive to their development.
Damage characteristics:
Nymphs and female adults of Lagerstroemia speciosa mainly gather at the base of main vein of branchlet leaves and suck juice on bud axils, twigs or branches, which often causes the tree to be weak and grow poorly. Moreover, a large amount of honey dew secreted by it will induce severe sooty blotch, which will lead to the blackening of leaves and branchlets and lose their ornamental value. If the insect population density is too high, the branches and leaves will turn black, the leaves will fall early, the flowering will be abnormal, and even the whole plant will die.
Prevention and control methods:
○ 1 horticultural control combined with plastic pruning in winter to remove branches with serious pests and overwintering status.
○2 Chemical control In severe areas, in addition to strengthening pruning and maintenance in winter, Pomei 3-5 degree sulfur mixture can be sprayed before germination in early spring to kill overwintering nymphs. In the growing season of seedlings, if we want to use this pesticide in the incubation period, we can choose to spray 1500 times of 40% Zygorskite EC, 1200 times of 48% chlorpyrifos EC (Lesburn), or 1000 times of 40% omethoate EC, or
2. Lagerstroemia indica
Lagerstroemia indica, also known as Lagerstroemia indica, belongs to Homoptera, Aphidoidea and Aphididae. Mainly distributed in China, Beijing, Shanghai, Jiangsu, Zhejiang, Taiwan Province and other places. At present, there is no other report about the host except Lagerstroemia indica.
Morphological characteristics:
Female adults of Lagerstroemia indica have several insect states. The winged solitary aphid ○ 1 has yellow body, black stripes, triangular body width, length of 2. 1mm and width of1.1mm. The abdomen is pale yellow, and there are 1 pairs of raised black tumors in each section, of which the pair in the second section is the largest and connected at the base. There are stripes on the back of the body, and the top of the antenna and the whip joint are black. ○2 The wingless parthenogenetic aphid is yellow-green, with a body length of 1.5mm, round shape, black spots and orange belly eyes. ○3 winged viviparous female aphid is similar to○○○○○○○○○○○○○○○○○○○○○○○○○○967
Occurrence law:
In Jiangsu, Zhejiang, Shanghai and other areas, Lagerstroemia indica can produce more than 10 generations a year, and overwinter with eggs in bud axils, bud seams and branches. Wingless viviparous aphids began to appear when the new buds of Lagerstroemia indica were elongated in the following spring. After June, the insect population continued to rise, and with the increase of temperature, winged aphids were constantly produced, which would migrate and spread.
Damage characteristics:
The damage of this insect to Lagerstroemia indica occurs every year. The back of young leaves is often covered with pests. After the injury, the new buds are twisted and the young leaves are uneven, which affects the formation of flower buds, shortens inflorescences and even leads to no flowering. At the same time, it can induce sooty blotch's disease and spread viral diseases.
Prevention and control methods:
○ 1 horticultural control combined with winter pruning can eliminate some overwintering eggs by removing branches of diseases and pests, twigs and over-dense branches. Family potted plants should also make the branches as smooth as possible, pay attention to removing the pterygoid cortex at the branches, and focus on burning to reduce the oviposition of overwintering aphids.
○2 Chemical control can spray 10% chlorpyrifos WP 1500 times, or 50% chlorpyrifos EC 1000 times, 40% omethoate EC 1000 times and 80% dichlorvos EC 1000 times. At the same time, both diseases can be cured.
3, yellow thorn moth
Yellow thorn moth, also known as spicy fruit, caterpillar and star anise, belongs to Lycopodiaceae, is an omnivorous leaf-eating pest, which can harm many kinds of garden trees and fruit trees, and is an important pest in forest belts, street trees, garden trees and fruit trees. The yellow thorn moth is distributed in most parts of the country.
Morphological characteristics:
The adult body length is about 1.5cm, the head, chest and back are golden yellow, the abdomen and back are yellow brown, the inner half of the front wing is yellow, the outer half is brown, and the rear wing is light yellow brown. Larvae is 1.6-2.5 cm long, fat, rectangular and yellow-green, with a purple-brown dumbbell-shaped spot on the back and a blue edge. Small head, yellow-brown; Chest shield. There are four rows of fleshy protrusions on the abdomen after the second quarter, and there are poisonous hairs with thorns on them.
Occurrence law:
There are 1-2 generations a year in North China and 2 generations a year in the lower reaches of the Yangtze River. The yellow thorn moth overwinters in cocoons on damaged branches as mature larvae. Adults emerge in May and June every year, and the first generation of larvae can be observed in late June after mating and spawning. Larvae is seven years old and often crosses generations. July to September is the peak of victimization.
Characteristics of damage: the damage is mainly eaten by larvae, and the newly hatched larvae generally cluster on the back of leaves to feed on mesophyll, making the leaves reticulate; Older larvae will crawl and spread harm and eat leaves directly. In severe cases, the leaves are eaten up, leaving only petioles and veins.
Prevention and control methods:
○ 1 horticultural control combined with winter pruning can remove overwintering cocoons from branches, thus eliminating or reducing insect sources.
○2 The overwintering cocoon can be directly removed manually after physical control of fallen leaves of Lagerstroemia indica planted in home, which can completely eliminate the insect source; In field production, black light can be set to trap and kill adults in the emergence stage.
○3 It is best to use chemicals before the larvae spread, spraying 80% dichlorvos EC 1000 times, 50% phoxim EC 1000 times, or 2.5% deltamethrin EC 4000 times.
(Remarks: In some areas, Lagerstroemia indica may be damaged by green moth or brown moth, but all of them belong to Lagerstroemia indica. Except for a slight difference in morphology, they have great similarities in life habits and occurrence laws, and they can be treated at the same time when controlling yellow thorn moths, so I won't go into details here. )
4. Green-tailed silkworm moth
Green-tailed silkworm moth, alias Shuiqing moth, Papilio formosana and Long-tailed Moon moth, belongs to Lepidoptera, Bombycidae; It is distributed in most provinces and cities such as North China, Central China, East China and Southwest China. Can harm a variety of fruit trees and garden seedlings.
Morphological characteristics:
The adult is 35 to 40 mm long, and its wings spread about122 mm; There are dark white hairs on the body surface, and the wings are pink-green. The front edge of the front wing runs through the chest and is purple-brown. There are eye-shaped markings in the center of the wing, and the tail-shaped protrusion of the rear wing is 40 mm long. Oval slightly flat, 2 mm long, taupe. Larvae can be as long as 80 mm, 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, which is non-toxic. The pupa is 45 to 50 mm long, reddish brown, and has 1 spot on its forehead. Cocoons are ovoid, grayish yellow or grayish brown.
Occurrence law:
There are some differences in different places. North China can have two generations a year. It overwinters on the branches by cocoon pupation. Overwintering pupae emerge from mid-April to early May to lay eggs. The egg period is 10 to 15 days. 1 generation 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 15 ~ 20 days. The first generation of adults emerged from late June to early July to lay eggs, larvae hatched in early July, and mature larvae cocooned and pupated at the end of September. The overwintering pupa period is 6 months.
Damage characteristics:
It is harmful for larvae to eat leaves. Larvae eat leaves into notches or holes, and when they are a little bigger, they eat up the whole leaf, leaving only petioles or thick veins.
Prevention and control methods:
○ 1 horticultural control of green-tailed silkworm moth, the overwintering pupa is very large, which is convenient for artificial killing; Older larvae can be as long as 80 mm, with strong resistance, amazing food intake and great difficulty in chemical control, so they can be captured manually.
○2 In chemical prevention, attention should be paid to early detection and prevention, and drugs should be used before the age of 3 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.
5. Anoplophora longicorn larvae
There are many kinds of longicorn beetles, including more than 25,000 known in the world and about 2,200 in China. Anoplophora longicorn is widely distributed and harmful. Almost every tree will be harmed by different kinds of longicorn beetles to varying degrees. Anoplophora glabripennis, Anoplophora glabripennis etc. Taking the most common Anoplophora glabripennis on Lagerstroemia as an example, this paper mainly introduces that Anoplophora glabripennis is Coleoptera, Cerambycidae, alias Anoplophora glabripennis; It is distributed in many parts of the country, especially in Chengdu, Nanchang, Fuzhou, Wuhan, Changsha, Suzhou and other places. The damaged Lagerstroemia indica is usually weak, the stem is easy to break, and the whole plant dies in severe cases.
Morphological characteristics:
The adult Anoplophora glabripennis has a body length of 19 ~ 39 mm, and its body is painted black with a slight luster. There is a longitudinal groove in the center of the head, and the antenna is filiform, usually 1 1 joint, and the base half of each joint of the whip is gray. The foreskin is hard with irregular white stripes and membranous hind wings; Mature larvae are 45 ~ 65 mm long, milky white, and their heads are large and flat. The chest backboard is wide and yellow-brown, with "convex" dark brown markings in the back half; Abdominal segment is obvious; Feet slightly degenerated.
Occurrence law:
Anoplophora glabripennis occurs once a year 1 generation in the south and twice a year 1 generation in the north, all of which overwinter as larvae in the wormhole of the trunk xylem. Larvae begin to move in March every year, pupate in the first half of May, and reach the peak of emergence in June and July. It takes several days for early eclosion adults to drill eclosion holes and supplement nutrition with the tender shoots or bark of the host. Then it often migrates to new plants or other hosts to do harm. Adults will mate and lay eggs soon after emergence. On most hosts, before adults lay eggs, they usually bite the cortex into T-shaped spawning grooves on the trunk, and then lay eggs in the grooves, with one egg in each groove; But laying eggs on Lagerstroemia indica is different: because the trunk of Lagerstroemia indica is smooth and the bark will peel off, longicorn usually lays eggs in the bark at the base of the trunk or in the gap between the tillers at the base and the trunk. Generally, June and July are the peak seasons for spawning. At the egg stage of 9- 15 days, larvae hatch and feed under the skin, more than at the base of trunk and root neck. Fecal debris accumulates in the tunnel. After a few months, it eats into the xylem and drills a vent hole outward to discharge the fecal debris from the base of the trunk. The tunnel is also full of fecal debris, and the larvae continue to harm 1 1-65438.
Damage characteristics:
Anoplophora glabripennis can be harmed by adults and larvae, but when it harms Lagerstroemia indica, its harm mode is a little special, because it is generally not harmed by adults eating bark or leaves (Lagerstroemia indica has a smooth trunk, and the bark falls off in pieces after the annual meeting, but traces of adult eating are occasionally found on the branches in that year), but its larvae feed on the stem base or root neck of the trunk (unlike other hosts, it is in the middle and lower part of the trunk) and gradually penetrate into the xylem from the cortex. At the peak of damage, newly discharged sawdust and insect dung are often found outside the wormhole.
Prevention and control methods:
○ 1 Horticultural control Stay away from or cut down the aging poplars, willows and elms around in time; Carry out reasonable pruning and pruning, and pay special attention to thoroughly remove the small tillers at the base of plant stems to prevent adults from laying eggs here.
○2 Physical prevention and control In August and September, according to the insect dung of the larvae in the cave, whether there are pests in the cave is determined, and then a thin iron wire is inserted into the end of the tunnel from the fresh dung discharge hole, which can sting the larvae. The adults on Lagerstroemia indica do little harm. For other fragile plants, adults can be killed artificially in June-August when they move on branches (harm, mate and lay eggs) after emergence, just after going out to eat in the morning or at noon on sunny days. You can also wrap a circle of super glue around the upper part of the trunk, stick it when the adult cattle climb over it that day, and then kill it.
○3 Pesticide control In the egg stage or the early stage of larval hatching, 2000 times of 40% monocrotophos emulsifiable concentrate or 2000 times of 50% phosphoramide emulsion can be sprayed with drugs with internal absorption. In the middle and late August, when the larvae start to eat dry and go deep into xylem, fine iron wire hooks can be used to take out dung scraps from the ventilation and defecation holes, and then cotton balls are dipped in 80% dichlorvos EC or 40% omethoate EC 10-30 times solution to kill the larvae. You can also directly inject 200 times of 50% chlorpyrifos EC or 50% dichlorvos EC from the hole, but the hole should be sealed with yellow mud.