Common Wood-Boring Pests of Landscape Plants and Integrated Control Methods

Landscape plants are easily harmed by wood-boring pests in daily life. These pests live hidden, cause serious damage and are difficult to control, which brings certain difficulties to landscape plant protection. Below, the editor will introduce the common wood-boring pests and control methods.

I. Main Types

They mainly include longhorn beetles, bark beetles, jewel beetles and weevils of the order Coleoptera; carpenter moths, clearwing moths and snout moths of the order Lepidoptera; and horntails and stem sawflies of the order Hymenoptera. Most wood-boring pests are "secondary pests", harming plants with weakened vigour or on the verge of death. Their larvae bore into the trunks and are called the "hidden threat to the heart and abdomen".

II. Damage Characteristics

1. Hidden life: except for the adult stage, when they live exposed, all other life stages live hidden in the phloem and xylem. Pest damage is not easily detected in the early stage, and once obvious signs of damage appear, the favourable opportunity for control has already been lost;

2. Stable population: most branch and trunk pests live inside plant tissues, are little affected by environmental conditions and have few natural enemies, so their population density is relatively stable;

3. Severe damage: branch and trunk pests feed on the phloem and xylem, thereby affecting the transport system's delivery of nutrients and water, leading to weakened vigour or death of the tree. Once attacked, the plant is very difficult to revive;

4. Difficult to control: because they cause damage inside branches and trunks, manual control is inefficient, and chemical control suffers from the problem that pesticides cannot easily reach the pests, so integrated control methods are generally adopted.

III. Control Plans

The occurrence of wood-boring pests is closely related to the tending and management of landscape plants. Matching species to site, strengthening tending and management, pruning reasonably, and watering and fertilising at the right time to promote healthy plant growth are the fundamental ways to prevent outbreaks of secondary pests; when pest damage has already occurred over a large area, special control measures should be adopted promptly to reduce the damage to a minimum.

1. Match species to site and adopt integrated control measures focused on prevention

In green areas where wood-boring pests occur severely, resistant tree species should be selected according to the tree species that longhorn beetles feed on, so as to avoid serious damage; management should be strengthened at ordinary times to improve tree vigour; apart from ancient and famous trees, source trees with severe damage should be felled, pruning should be reasonable, and dead standing trees, wind-broken trees and the like in the garden should be removed promptly.

2. Manual control: this method is especially suitable for the larger longhorn beetles. ① Use the period after adult emergence when adults are active in the canopy (supplementary feeding, mating and egg-laying) to manually capture and kill the adults. ② Search for egg-laying notches and destroy the eggs in them by hammering or peeling them off by hand. ③ Use wire hooks to kill the larvae. This method is especially easy to carry out for small larvae shortly after hatching in the current year.

3. Trap logs: for longhorn beetles on ancient and famous trees in parks and other scenic areas, trap logs can be used, and tree holes should be repaired promptly and the trunk base painted white, so as to reduce population density and ensure their ornamental value.

4. Protect and utilise natural enemies, such as artificially attracting woodpeckers, and using longhorn beetle Sclerodermus wasps and Tetrastichus wasps.

5. Chemical control

Chemical control of wood-boring pests has the advantages of being immediate and fast, highly efficient and low in cost, so it is easy to use this method when they occur over a large area. It can be used flexibly according to different species, different periods and different parts.

(1) Trunk application method: it has a very good effect on controlling aphids, leaf beetles and red spider mites on trees such as trident maple, Chinese elm, Japanese camellia and crape myrtle, and scale insects on pines.

(2) Poison stick insertion method: after inserting the pre-made poison stick into the insect tunnel, the poison contacts the water in the tree sap and insect frass, producing a chemical reaction that forms a highly toxic gas, causing the pests inside the trunk to be poisoned to death. The control effect against wood-boring pests reaches more than 90%.

(3) Trunk injection and sealing method: longhorn beetles, willow gall midges, pine tip borers, bamboo weevils and others bore into and damage the trunks, branches and bark of forest trees. Injection with a syringe gives remarkable control effect, and the pests can die in large numbers within one week after injection.

(4) Hanging bottle method: hanging a bottle for a tree means hanging a bottle filled with pesticide solution on the trunk, and using a cotton rope and cotton core to transport the pesticide solution in the bottle through the ducts in the trunk to the branches and leaves, thereby achieving the purpose of control.

(5) Root pesticide method: the root pesticide burial method includes directly burying pesticide and burying pesticide bottles at the roots. Both methods can effectively control pests.

Of course, different tree species in different regions, environments and maintenance management will suffer from different pests and diseases, so specific control measures still need to be adjusted according to the specific target. The above are the common wood-boring pests of landscape plants and their control measures; we hope they are helpful to you. To learn more agricultural technical knowledge, please follow Huinong Classroom!

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Control of Wood-Boring Pests in August

I. Damage Symptoms and Main Characteristics of Wood-Boring Pests

Damage symptoms of longhorn beetles: mainly the larvae harm the phloem and xylem of the host. Newly hatched larvae bore vertically from the phloem into the sapwood, feed transversely along the spring wood part of the outermost annual ring of the branch or trunk, and then feed inward. The tunnel is zigzag-shaped. Adults feed on the tender bark of new shoots for supplementary nutrition; the edges of the fed parts are neat; they are not good at flying and fall to the ground very easily when disturbed. They make egg-laying chambers in bark cracks and other places to lay eggs, then cover the eggs with a grass-green secretion. (Main characteristics and damage symptoms of longhorn beetles in pictures).

Damage symptoms of jewel beetles: the larvae bore and feed in all directions between the cambium and xylem, destroying the transport tissues, causing weakened tree vigour, gradual death of the trunk and even death of the whole tree. Generally, trees under extensive management, with weakened vigour and many wounds, suffer severe damage, while trees with strong vigour suffer light damage. (Pictures of jewel beetles)

Damage symptoms of dahlia snout moths: the larvae bore into and feed on the stems of garden flowers and plants such as dahlia, chrysanthemum, Populus cathayana, canna, gladiolus, palm and hemp. When the damage is severe, almost all the stems are bored and damaged and the plant cannot bloom. Affected plants have stems that break easily, cannot bloom, and the upper part of the stem turns yellow and dies. (Pictures of dahlia snout moths).

Damage symptoms of rose stem sawflies: the larvae bore into and feed on the stems of flowers, often causing breakage and wilting at the boring holes, causing great harm to roses. (Pictures of rose stem sawflies)

II. Control Measures for Wood-Boring Pests

(I) Control measures in August:

1. Pay attention to inspection. When branches of flowers and trees damaged by dahlia snout moths or rose stem sawflies are found, they should be cut off promptly with pruning shears, and the branches should be collected and burned to kill the larvae; longhorn beetles and jewel beetles mainly harm the main trunk of trees. When the larvae are still feeding under the bark at the root crown, or have bored into the xylem but not deeply, hook and kill them promptly.

2. Chemical poisoning of larvae: when the larvae have bored relatively deep into the xylem, chemical pesticides can be used for poisoning.

Inject 80% dichlorvos, 40% omethoate or 50% phoxim into the boring hole, then seal the opening with poisonous mud mixed from pesticide, which can poison the larvae to death.

Insert poison sticks into the boring holes to poison the larvae to death (poison sticks can be made by yourself with zinc phosphide, peach gum, oxalic acid and bamboo sticks).

In the early stage of larval damage, you can use 5% beta-cypermethrin or 50% methamidophos emulsifiable concentrate at 5-10 times dilution, or 80% dichlorvos emulsifiable concentrate at 5 times dilution, or a 1:20 dichlorvos-kerosene solution to brush the epidermis of the damaged part (where the damage shows slight depression and blackening) or the trunk. The effect of poisoning the larvae is very good.

(II) Other control measures

1. Strengthen quarantine when transporting seedlings. For pest-carrying logs in transport, use methyl bromide, sulfuryl fluoride or 56% aluminium phosphide tablets for fumigation, with dosages of 20-30 g/m³and 12-15 g/m³, fumigating for 24 h and 72 h; or soak the pest-infested wood in water for more than 1 month; or after peeling the logs, dip thin branches in 20% fenvalerate emulsifiable concentrate at 20 times dilution, or 40% omethoate emulsifiable concentrate, or 2.5% deltamethrin emulsifiable concentrate at 10 times dilution, and insert them into the insect holes to poison the pests.

2. Strengthen management and improve tree vigour; during the dormant period, scrape off the coarse and cracked bark of the main trunk and main branches, and prune pest-infested branches. Eliminate part of the overwintering pest sources; promptly remove and burn dead trees and dead branches to reduce pest sources.

3. Manual control

a. Manually capture adults. Late June is the peak period of adult emergence. Before the emerging adults bite through the emergence holes and fly out, they can be stabbed to death with a screwdriver; when adults have just emerged from the emergence holes, they crawl on the trunk and are gregarious, so they can be captured directly at this time.

b. Manually kill eggs and newly hatched larvae. Late June to early July is the adult egg-laying and hatching period. Newly laid eggs are green and easy to identify; newly hatched larvae are on the outer layer of bark and easy to remove, so manual egg removal and larval capture can be organised at this time.

c. Egg-trapping control: use woven bags such as those for packaging chemical fertiliser, wash them clean and cut them into strips 20-30 cm wide. Before star longhorn beetles lay eggs, wrap the strip 2-3 times around the main trunk where eggs are likely to be laid, leaving no gap at the joins between wraps, then tie it tightly with hemp rope; the control effect is very good. Through this wrapping barrier, the longhorn beetle can only lay its eggs on the woven bag, after which the longhorn beetle eggs lose water and die.

4. Chemical pesticide control
b. During the peak activity period of older larvae (late March to mid-April), inject a 30-times dilution of fenpropathrin, dichlorvos, fenvalerate or monocrotophos into the frass holes or breathing holes with a syringe, then seal the holes tightly with yellow mud.
c. From mid-June to mid-July each year, during the peak adult activity period, spray the host canopy with 2000-times dilution of fenvalerate, once every 15 days, spraying twice in succession, which can achieve a relatively good effect.
d. Before overwintering (November and December), make a whitewash with 10 kg lime + 1 kg sulfur + 10 g salt + 20 kg to 40 kg water, and paint the trunk to prevent egg-laying. (Source: China Lawn Network, compiled by Yang Yanwei and Xie Xiaomin)

What are the piercing-sucking pests of landscape plants? How to control piercing-sucking pests?

Piercing-sucking pests are very common in landscape plants. These pests are small in size but extremely numerous, and the early symptoms of plant damage are not obvious, so people easily overlook them. Below, we will introduce what the common piercing-sucking pests are and how to control them.

Piercing-sucking pests often gather in groups on tender branches, leaves, buds, flower buds and fruits, sucking plant sap and robbing their nutrients, causing branches, leaves and flowers to curl and even the whole plant to wither or die. At the same time, they induce sooty mould, and sometimes the pests themselves are vectors of viral diseases, causing huge harm to landscapes.

1. Occurrence characteristics of piercing-sucking pests

Both adults and nymphs have piercing-sucking mouthparts and can harm plants;

(1) They cause a reduction in plant nutrients and water, affecting growth and development, and in severe cases can cause plant death;

(2) They can secrete large amounts of honeydew, causing sooty mould;

(3) Many species may transmit viral diseases of flowers and trees;

(4) Some species have well-developed ovipositors, which create wounds on plant branches and leaves when laying eggs, and their body shape varies greatly;

(5) They have strong reproductive capacity; besides sexual reproduction, there is also parthenogenesis, and all undergo incomplete metamorphosis.

2. Damage characteristics:

(1) Leaves lose green colour and develop yellow spots or red spots, etc.;

(2) Leaves curl, shrink and deform;

(3) Various galls are formed;

(4) Tender shoot tips discolour and wilt, bend and droop, become deformed and cluster, and even die;

(5) Branches and leaves have honeydew that induces sooty mould.

Below we mainly introduce the identification and control plans for these piercing-sucking pests: psyllids, lace bugs and leafhoppers.

I. Psyllids

(1) Main species of psyllids: Photinia psyllid, Chinese parasol psyllid, rose apple psyllid, citrus psyllid, camphor psyllid, etc.

1. Photinia psyllid

The Photinia psyllid has 3 generations per year and overwinters as eggs on branches and trunks. Damage is severe from April to August each year. Generally 5-20 individuals gather together, covering their bodies with each other's waxy secretions.

2. Chinese parasol psyllid

The Chinese parasol psyllid has 2 generations a year and overwinters as eggs on branches and trunks. Both nymphs and adults are gregarious, often gathering in groups of more than ten to several dozen on the underside of leaves and other places. Nymphs live hidden in white waxy material and move quickly; adults are poor at flying but have strong jumping ability.

3. Albizia psyllid

The albizia psyllid has 3-4 generations a year. It enters the peak damage period in late May and overwinters as adults in bark cracks, tree holes and under fallen leaves.

4. Camphor psyllid

(2) Integrated control of psyllids

① Strengthen inspection when transporting seedlings, and prohibit the transport out of pest-carrying materials.

② In conjunction with pruning, cut off egg-carrying branches.

③ Protect and utilise natural enemies, such as Chinese stink bugs, green lacewings, parasitic wasps, etc.

④ In the early stage of occurrence, spray pesticides such as imidacloprid, chlorpyrifos and methomyl for control. It is recommended to use the garden-specific insecticide Baoyazhen for control. During the peak period of occurrence, the garden-specific insecticide Yashilandai can be diluted 800-1000 times (mixed with 160 kg-200 kg water) for spray control.

⑤ Use Yiguanshuwuchong (Xinmie), applying pesticide to the roots to kill insects in the tree.

II. Lace Bugs

(1) Lace bugs include the azalea lace bug and the sycamore lace bug.

1. Azalea lace bug:

Distributed in Guangdong, Guangxi, Zhejiang, Jiangxi, Fujian, Liaoning, Taiwan, China and other places, it is a major pest of azaleas.

Adults and nymphs harm leaves, sucking sap and excreting frass, causing the undersides of leaves to become rusty yellow and white spots to appear on the upper surface, seriously affecting plant photosynthesis, causing slow plant growth and early leaf fall. It occurs severely under high temperature and drought, and mainly causes damage on the underside of leaves. It is also called the pear lace bug, pear flower lace bug and pear military matching bug. It harms rose, peach, pear, crabapple, azalea, plum blossom, cherry blossom, banana shrub, camellia, jasmine, wintersweet, mulberry, paulownia, poplar, plum, peach and apple.

Adults and nymphs suck sap on the underside of leaves. The damaged areas have many speckled brown frass and flyspeck-like black spots left by egg-laying; the underside of damaged leaves is rusty yellow and the upper surface is pale white.

In North China there are 3-4 generations a year, and in Central and South China 5-6 generations a year. It overwinters as adults in bark cracks, dead branches and leaves, grass clumps or soil crevices. In mid-to-late April of the following year, overwintering adults begin activity. Damage is most severe in July-August throughout the year, and after mid-to-late October adults begin to overwinter.

2. Sycamore lace bug

The sycamore lace bug has 3 generations a year in northern regions and 5-6 generations a year in Central and South China. It begins activity in mid-to-late April of the following year, lays eggs on the underside of leaves in late April, causes its first damage in June, causes the most severe damage in July-August, and overwinters after mid-to-late October.

It has overlapping generations, with adults and nymphs causing damage alternately; the nymph stage is the best time for control.

(2) Integrated control measures for lace bugs

① In winter, remove weeds and fallen leaves and twigs and destroy them in a concentrated manner.

② Protect natural enemies.

③ When individual newly emerged white adults are found among nymph groups on leaves, it indicates that the first-generation nymphs have basically hatched, which is a favourable time for control. You can spray chlorpyrifos, methomyl, Yechongjing (abamectin and beta-cypermethrin), fenobucarb, buprofezin, pymetrozine, Baoyazhen, etc. Yashilandai emulsifiable concentrate at 1000 times dilution, 10% imidacloprid wettable powder at 1000 times dilution.

④ Use Yiguanshuwuchong (Xinmie); the lasting period is two months.

III. Leafhoppers

(1) Leafhoppers: leafhoppers belong to the order Homoptera, family Cicadellidae. The body is slender. The body gradually narrows toward the rear, and they can often jump and have the habit of walking sideways. Commonly known as floating dust insects, there are many species. The main ones are the following: green leafhopper, small green leafhopper, cotton leafhopper, etc. Adults and nymphs pierce and suck plant sap; damaged leaves show small white spots, branches die, growth and development are affected, and they can transmit viruses.

1. Green leafhopper

It has 2-6 generations a year and overwinters as eggs in the cortex of branches. In late March of the following spring, overwintering eggs begin to develop and cause damage. Newly hatched nymphs like to gather and feed, and when disturbed they quickly walk sideways, fleeing from the upper surface of leaves to the underside.

2. Spotted lanternfly

It harms tree of heaven, albizia, Boston ivy, false spirea, privet, crabapple, ornamental peach, boxwood, Chinese parasol and others. Adults and nymphs pierce and suck plant sap, causing nutritional deficiency or stunting of the plant, and their excrement leads to sooty mould. It has 1 generation a year and overwinters as egg masses on tree trunks or nearby buildings. In mid-to-late April of the following year, nymphs hatch and cause damage; adults appear in mid-June; egg-laying begins in mid-August, with eggs laid on branches and trunks sheltered from wind and facing the sun.

II. Integrated control of leafhoppers:

(1) Strengthen the management of courtyard green spaces and weed frequently; in conjunction with pruning, cut off damaged branches and leaves to reduce pest sources.

(2) Set up black light lamps to trap and kill adults.

(3) During the damage period of adults and nymphs, use 25% buprofezin wettable powder diluted 1500-2000 times for spraying. Use 10% imidacloprid at 2000-3000 times dilution, 2.5% decamethrin at 2000 times dilution, and 20% fenvalerate at 2000-3000 times dilution for control.

In landscape management work, piercing-sucking pests cannot be ignored. Management should be strengthened at ordinary times, and integrated control work should be done well to ensure that plants can grow healthily.