Species of Piercing-Sucking Pests on Landscape Plants and Their Control Methods
Piercing-sucking pests are very common on landscape plants. These pests are small in size but extremely numerous, and the early symptoms of damage on plants are not obvious, which makes them easy for people to overlook. Below is an introduction to the common piercing-sucking pests and how to control them.
Piercing-sucking pests often gather in colonies on tender twigs, leaves, buds, flower buds and fruits, sucking plant sap and robbing the plant of its nutrients, causing twigs, leaves and flowers to curl and even the whole plant to wither or die. At the same time, they trigger sooty mold, and sometimes the pests themselves are vectors of viral diseases, causing enormous harm to landscapes.
1. Occurrence characteristics of piercing-sucking pests
Both adults and nymphs have piercing-sucking mouthparts and can both damage plants;
(1) They cause a reduction in plant nutrients and water, affecting growth and development, and in severe cases can cause the plant to die;
(2) They can secrete large amounts of honeydew, leading to the occurrence of sooty mold;
(3) Many species may transmit viral diseases of flowers and trees;
(4) Some species have a well-developed ovipositor, which creates wounds on the twigs and leaves when laying eggs, and their body shape varies greatly;
(5) They have strong reproductive capacity; besides sexual reproduction, they also reproduce by parthenogenesis, and all undergo incomplete metamorphosis.
2. Damage characteristics:
(1) Leaves lose their green color and develop yellow spots or red spots, etc.;
(2) Leaves curl, wrinkle and become deformed;
(3) Various galls are formed;
(4) Tender shoots become discolored and wilted, bend and droop, grow in deformed clusters, and even die;
(5) Honeydew on twigs and leaves induces sooty mold.
Below we mainly introduce the identification and control solutions for these piercing-sucking pests: psyllids, lace bugs and leafhoppers.
I. Psyllids
(1) Main species of psyllids: Photinia psyllid, Chinese parasol tree psyllid, rose apple psyllid, citrus psyllid, camphor psyllid, etc.
1. Photinia psyllid
The Photinia psyllid has 3 generations per year, overwintering as eggs on branches and trunks, and causes severe damage from April to August each year. Generally 5-20 of them gather together, covering each other's bodies with a waxy substance.
2. Chinese parasol tree psyllid
The Chinese parasol tree psyllid has 2 generations per year, overwintering 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 undersides of leaves and other places. The nymphs live hidden within a white waxy substance and move quickly; the adults are poor fliers but have a strong jumping ability.
3. Silk tree psyllid
The silk tree psyllid has 3-4 generations per year. It enters its peak damage period in late May, and overwinters as adults in bark crevices, tree holes and under fallen leaves.
4. Camphor psyllid
(2) Integrated control of psyllids
① Strengthen inspection when transporting nursery stock, and prohibit the shipment of pest-infested materials.
② In combination with pruning, cut off and remove egg-bearing branches.
③ Protect and utilize natural enemies, such as predatory stink bugs, green lacewings, parasitic wasps, etc.
④ In the early stage of occurrence, insecticides such as imidacloprid, chlorpyrifos and methomyl can be sprayed for control. It is recommended to use the landscaping-specific insecticide Baoyazhen for control. At the peak of occurrence, the landscaping-specific insecticide Yashilandai can be diluted 800-1000 times (mixed with 160 kg-200 kg of water) for spray control.
⑤ Use Yiguanshu Wuchong (Xinmie) to drench the roots, killing insects in the tree through root application.
II. Lace bugs
(1) Lace bugs include the azalea lace bug and the sycamore lace bug.
1. Azalea lace bug:
It is distributed in Guangdong, Guangxi, Zhejiang, Jiangxi, Fujian, Liaoning, Taiwan, China and other places, and is a major pest of azaleas.
Adults and nymphs damage leaves, sucking sap and excreting feces, causing the undersides of leaves to turn rusty yellow and the upper surfaces to develop white spots, seriously affecting photosynthesis, causing plants to grow slowly and shed leaves early. It occurs severely under high temperature and drought, and mainly damages the undersides of leaves. It is also known as the pear lace bug, pear flower lace bug and pear armyworm bug. It damages 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 undersides of leaves. The damaged areas have many mottled brown spots and fly-speck-like black spots left from egg-laying; the undersides of damaged leaves are rusty yellow while the upper surfaces are pale white.
In North China there are 3-4 generations per year, and in Central and South China 5-6 generations per year, overwintering as adults in bark crevices, dead branches and leaves, among weeds, or in cracks in the soil. In early to mid-April of the following year, overwintering adults begin their activity, with the most severe damage in July-August throughout the year, and after mid-to-late October the adults begin to overwinter.
2. Sycamore lace bug
The sycamore lace bug has 3 generations per year in northern regions, and 5-6 generations per year in Central and South China. It begins activity in early to mid-April of the following year, lays eggs on the undersides of leaves in late April, causes its first damage in June, with the most severe damage in July-August, and overwinters after mid-to-late October.
It exhibits overlapping generations, with adults and nymphs causing damage alternately, and control is most effective during the nymph stage.
(2) Integrated control measures for lace bugs
① In winter, clear away weeds and dead branches and leaves and destroy them in a centralized manner.
② Protect natural enemies.
③ When individual newly emerged white adults are found among the nymph colonies on leaves, it indicates that the first-generation nymphs have basically all hatched, and this is a favorable time for control. Chlorpyrifos, methomyl, Yechongjing (abamectin and beta-cypermethrin), fenobucarb, buprofezin, pymetrozine, Baoyazhen, etc. can be sprayed. Yashilandai emulsifiable concentrate at 1000 times, and 10% imidacloprid wettable powder at 1000 times.
④ Use Yiguanshu Wuchong (Xinmie), with a residual effect lasting two months.
III. Leafhoppers
(1) Leafhoppers: the genus Cicadella belongs to the order Homoptera, family Cicadellidae. The body is slender, gradually tapering toward the rear, often able to jump, and has a habit of walking sideways; commonly known as leafhoppers, with many species. The main ones are: the green leafhopper, the smaller green leafhopper, the cotton leafhopper, etc. Adults and nymphs pierce and suck plant sap; damaged leaves show small white spots, and twigs die, affecting growth and development, and they can also transmit viruses.
1. Green leafhopper
It has 2-6 generations per year and overwinters as eggs in the cortex of twigs. In late March of the following spring, the 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 leaf surface to the underside.
2. Spotted lanternfly
It damages tree of heaven, silk tree, Boston ivy, Sorbaria kirilowii, glossy privet, crabapple, ornamental peach, boxwood, Chinese parasol tree, etc. Adults and nymphs pierce and suck plant sap, causing nutrient deficiency or stunting of the plant, and their excrement leads to the occurrence of sooty mold. It has 1 generation per year and overwinters as egg masses on tree trunks or nearby buildings. In mid-to-late April of the following year, the nymphs hatch and cause damage; adults appear in mid-June, and 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 garden green spaces and weed frequently; in combination with pruning, cut off and remove damaged branches and leaves to reduce pest sources.
(2) Set up black light traps to kill adults.
(3) During the damage period of adults and nymphs, use 25% buprofezin wettable powder diluted 1500-2000 times for spray. 10% imidacloprid at 2000-3000 times, 2.5% decamethrin at 2000 times, and 20% fenvalerate at 2000-3000 times for control.
In landscape management work, piercing-sucking pests must not be neglected. At ordinary times, management should be strengthened and integrated control work done well to ensure that plants can grow healthily.
Control of Piercing-Sucking Pests on Garden Flowers
Piercing-sucking pests: among flower pests, piercing-sucking pests are an important group, mainly including: mosquitoes, aphids, spider mites, thrips, whiteflies, leafhoppers, etc.
Control methods:
① 73% propargite emulsifiable concentrate: can kill adult mites, young mites and eggs. It is harmless to beneficial mites and other natural enemies; generally used at 1000-3000 times dilution, with an effective period of 14-35 days.
② 5% hexythiazox emulsifiable concentrate: a low-toxicity acaricide, safe to natural enemies, with very low toxicity to bees and birds, for example. It has strong young-mite-killing properties against various plant pest mites; its control effect on adult mites, rust mites and gall mites is relatively poor. For common spider mites, use 1500-2000 times dilution.
③ Petroleum emulsion: a mineral-source pesticide, effective against the “five small” pests, and has unique advantages when applied at scenic spots and orchards.
④ Dicofol: effective against spider mites and root mites; if mixed with tetradifon, it has a long-term control effect on mites. For root mites, diluting 1000-1500 times also gives good results.
⑤ Pyridazinone (15% emulsifiable concentrate): a high-efficiency, low-toxicity, broad-spectrum acaricide and insecticide, with good control effects on piercing-sucking pests such as whiteflies, leafhoppers, thrips and aphids, and very high activity against both adult and young mites; use at 2000-3000 times dilution.
⑥ Imidacloprid: also known as Bilin, it is a 12.5% imidacloprid water-soluble concentrate, a high-efficiency, strongly systemic, broad-spectrum insecticide, with special effectiveness against piercing-sucking pests such as aphids, planthoppers, psyllids, thrips and scale insects, and is excellent for controlling the bamboo stem flat aphid.
Major Piercing-Sucking Pests in Landscapes ---- Scale Insects
There are no fewer than several hundred species of pests harming landscapes, among which scale insects have the most species, the widest damage range and the greatest harmfulness. In Hangzhou, scenic spots named after pine trees, such as Jiulisong and Wansonglin, were damaged beyond recognition by the pine trunk scale; in Guangzhou and other places, large areas of pine forest were destroyed by the pine armored scale. On street trees in the south, damage by the tortoise wax scale is often found, causing poor growth and the death of some branches and leaves; on garden flowering shrubs there is even damage by various armored scales, mealybugs, wax scales and felt scales, causing poor growth and damage to ornamental value.Scale insects, also abbreviated as scales, belong to the order Homoptera, superfamily Coccoidea. According to classification by relevant experts, they can be divided into the families Margarodidae, Ortheziidae, Pseudococcidae, Coccidae, Kerriidae, Asterolecaniidae, Eriococcidae, Kermesidae, Lecanodiaspididae, Diaspididae, etc. From the main scale insects commonly causing damage in landscapes, we can roughly divide them into the following categories:
1. Wax scale group: the
bodies of this group of scale insects are all covered with a thick waxy layer to protect the body. Different species have different colors and densities of the covering wax; for example, the wax covering the red wax scale is red; the wax covering the tortoise wax scale, horned wax scale and white wax scale is all white, among which the wax layer of the horned wax scale is soft, while the wax layers of the tortoise wax scale and white wax scale are firm. Also, the tortoise wax scale covers each individual body with wax, whereas the white wax scale covers entire branches with the wax of multiple bodies together.
2. Armored scale group: this is the group of scale insects that damages landscape plants the most. Their bodies can all form thin shield shells of different shapes on the outside; this shell can be separated from the body, like a shield, hence the name armored scale. For example, those shaped like a circle are called circular armored scales; those shaped like an arrowhead are called arrowhead scales; those shaped like an oyster shell are called oyster-shell scales, etc. Also, classified by color, those with a white shield shell are called white armored scales; the circular armored scale with a red shield shell is called the red circular armored scale, etc.
3、
Mealybug group: this group of scale insects often secretes a layer of white waxy powder on the outside of the body, so when population density is high, scattered waxy powder can often be seen on the branches and leaves of damaged plants. What makes this group different from other scale insects is that other scale insects, apart from being able to crawl during the newly hatched stage, no longer crawl once they fix themselves to suck sap and cause damage; mealybugs, however, can crawl and move throughout their entire life.
4. Cottony scale group: after the female adults of this group of scale insects mature, they can secrete a white waxy layer or waxy sac at the rear end of the abdomen, in which large numbers of eggs are laid. Different species have different egg sac shapes; for example, the egg sac of the cottony cushion scale is in flat parallel strips; the egg sac of the horned cottony scale is in a flat straight tube shape; the egg sac of the cottony scale is in a long ring shape, so some people call it the ring scale.
5. Globular scale group: the body surface of this group of scale insects hardens into a shell to protect the body, commonly seen examples being the oak red scale, the Korean globular scale, the cocoa globular scale, etc.
After scale insects cause damage, various damage symptoms can appear, briefly listed as follows:
1
Due to the sap-sucking damage of scale insects, the nutritional physiology of the host plant is disrupted, so branches and leaves become smaller and yellow, local branches and leaves wither and yellow, leaves fall early, and growth and development are abnormal.
2
Due to the long-term fixed sap-sucking damage of scale insects, the distribution of chlorophyll, xanthophyll and carotene within the leaves becomes uneven, so yellow or red patches often appear on the leaves; this is an obvious symptom of scale insect damage.
3. Like certain other homopteran pests, scale insects, while sucking sap and causing damage, can excrete a colorless transparent excrement that contains large amounts of sugar, which induces the growth of sooty mold fungi. Therefore, when scale insects break out, a sooty layer is often seen on the branches and leaves of damaged plants; this sooty layer directly affects the plant's photosynthesis and nutritional physiology, and at the same time greatly damages the ornamental value of landscape plants.
4. The damage of certain scale insects not only directly disrupts the plant's nutritional physiology, but also, because they can transmit certain pathogens or toxins while sucking sap, seriously affects the plant's normal growth and development, until it dies. For example, damage by the pine trunk scale to the trunk of masson pine can destroy the pine's conducting tissue and affect its conducting function, so the damaged plant first shows a marked decrease in resin, after which the lower branches gradually wither and yellow and the upper branches droop, followed by secondary pests such as longhorn beetles, weevils and termites infesting it, and finally the whole plant dies.
(Reposted from the Sina blog of Caomu Chunqiu 66)