Description about 17 species of citrus pests and their damage and host plants
- Asian citrus psyllid
Distribution and damage: The Asian citrus psyllid is widely distributed in southern Asia. It is an important pest of citrus as it is a vector of a serious citrus disease called greening disease or Huanglongbing. On chronically infected trees, the leaves are small and exhibit asymmetrical blotchy mottling. Fruit from HLB-infected trees are small, lopsided, poorly colored, and contain aborted seeds.
Description: The adults are 3 to 4 mm long with a mottled brown body. The nymphs are 0.25 mm long during the 1st instar and 1.5 to 1.7 mm in last (5th) instar. Their color is generally yellowish-orange.
Host plants: curry leaf, ornamental orange-jasmine, and all the varieties of citrus, including kumquat, mandarin, grapefruit, orange and all of their hybrids.
- Citrus swallowtail
Distribution and damage: This species is found throughout tropical and subtropical regions of southern Asia, ranging from Saudi Arabia, Iran, and the Middle East to India, Nepal, southern China, Taiwan, and Japan. It is also found in Malaysia, Indonesia, New Guinea, and Australia. Adults feed on the nectar of flowering plants and thus do not cause damage to citrus. The larvae are the damaging stage and feed only on citrus young leaves.
Description: The adults range in wingspan from 80-100 mm. The hindwing has no tail. The upper portion of the forewing is largely black and the outer wing margin has a series of irregular yellow spots. Two yellow spots are present at the upper end of the discal cell with several scattered yellow spots in the apical region. The upper hindwing has a red tornal spot and the discal black band is dusted with yellow scales. The under side is paler yellow with the black areas more heavily dusted with yellow. First instars of larval are black with a black head, with two sub-dorsal rows of short fleshy spines. Second, third, and fourth instars have a dark brown, glossy head capsule. Fifth instars are cylindrically shaped and tapered anteriorly.
Host plants: The food plants of larval in Asia are from family Rutaceae while in Australia and Papua New Guinea the butterfly also feeds on host plants of family Fabaceae.
- Forktailed bush katydid
Distribution and damage: The pest is widespread in the eastern and southeastern United States. Nymphs of this species feed on young fruit at petal fall. Katydids take a single bite from a fruit and then move to another feeding site on the same or nearby fruit. In this way, a few katydids can damage a large quantity of fruit in a short time. They also eat holes in leaves and maturing fruit, creating injury that resembles damage by citrus cutworm.
Description: The adults are 14 - 75 mm in length, dark green, Narrow wings with rounded tips are held along the body at rest. Males have an unusual forked appendage at the end of their abdomen called a furcula. Katydids have much longer antennae than grasshoppers, averaging 39 mm. The white rings evident on the immature katydids are faintly visible.
Host plants: sweet orange, Citrus sinensis
- Southern green stink bug
Distribution and damage: The southern green stink bug is believed to have originated in Ethiopia. Its distribution now includes the tropical and subtropical regions of Europe, Asia, Africa and the Americas. The damage on fruit from their punctures is hard brownish or black spots. These punctures affect the fruits edible qualities and decidedly lower its market value. In addition to the visual damage caused by southern green stink bug feeding, the mechanical transmission of bacterial spot may also result.
Description: The nymphs in the first instars are light yellowish in color with red eyes and transparent legs and antennae. The second instar has black legs, head, thorax, and antennae. The third and fourth instars differ from the second in size and an overall greenish color is becoming apparent. The adult is shield-shaped with an overall dull green color. The eyes are dark red or black. Small black dots can be found along the sides of the abdomen. The wings completely cover the abdomen.
Host plants: It prefers woody hosts including basswood, mulberry, pear, maple; yet it is a common pest of vegetable and field crops such as lima beans, green beans, soybean, tomato, cotton, eggplant, and cucumber.
- Fruit piercing moth
Distribution and damage: This species of pest is found in large parts of the tropics, mainly in Asia, Africa and Australia but introduced into other areas such as Hawaii, New Zealand and the Society Islands. It is one of major fruit pests in the world. Both sexes of adult fruit piercing moths puncture fruit with their long, stout proboscis which is adapted to penetrate the rind of firm, intact fruit allowing moths to feed on fruit juice and pulp. Secondary invasions by micro-organisms spread into damaged tissues causing rot and premature fruit-fall.
Description: The adult moths are large and stout-bodied, with a wingspan of 100 mm. The forewings can be mainly brown, cream or green. Hind wings are yellow orange, with black patches and spots.
Host plants: A wide range of cultivated and wild fruits, including banana, citrus, 5-corner fruit, guava, mango, passion fruit, pineapple, and in outbreak years, capsicum, melon and tomato.
- Citrus long-horned beetle
Distribution and damage: Citrus long-horned beetle is native to China, Japan, and Korea. This species has now been accidentally introduced into the United States, as well as Canada, and several countries of Europe. The majority of damage associated with citrus long-horned beetle is caused by the larval stages which feeds and tunnels on the woody portion of the host plant trunk. The wounds created during the course of feeding increase the host susceptibility to various secondary plant pathogens.
Description: The beetle is large, stout, and approximately 21 to 37 mm (~1 - 1.5 inch) long with shiny black elytra marked with 10 to 12 white round spots. Antennae are at least as long as the body and have alternating black and white bands. The ventral surface is pubescent. The color of the pubescence varies from white to blue depending on location.
Host plants: Its primary hosts include citrus, apple, Australian pine, poplars, and willows.
- Garden snail
Distribution and damage: Garden snail is native to the Mediterranean area and Western Europe, but now its distribution includes the tropical temperate and subtropical areas worldwide. Garden snail creates holes in fruit and leaves, the small holes allow the entry of fungi and decay of the fruit, the larger holes result in fruit dropping from the tree.
Description: They have a brownish soft body, covered with slimy mucus and yellow or cream-colored shells with brown spiral stripes.
Host plants: a wide range of crops and ornamental plants are reported as hosts: these include vegetables, cereals, flowers and shrubs. In particular, it causes serious damage in citrus groves and vineyards.
- Brown marmorated stink bug
Distribution and damage: This pest is native to China, Japan, the Korean peninsula, and Taiwan. It is now established in many parts of North America and has recently established itself in Europe and South America. As with other stink bugs, both nymphs and adults use piercing-sucking mouthparts to feed on leaf and fruit tissue. This feeding, specifically the injection of digestive enzymes to facilitate nutrient extraction, results in localized necrotic spots.
Description: Adult brown marmorated stink bugs have typical “shield” shaped bodies approximately 15mm in length that are mottled brown. Its abdominal edges and last two antennal segments have alternating broad light and dark bands. Newly hatched nymphs have dark red eyes and the abdomen is yellowish, mottled with black and red. Older nymphs are darker with black and white bands on the legs and antennae. Similar to other stink bug species, all nymphs lack wings.
Host plants: Crop hosts include apple, pear, peach, grape, blueberry, soybean, tomato, and corn. Several ornamental and landscape plants are also used by the brown marmorated stink bug.
- Citrus fruit fly
Distribution and damage: The species is native to sub-Saharan Africa, but has spread invasively to many parts of the world, including Australia, China, Korea, Europe, and North and South America. Fruit infested with Medfly larvae may show ‘sting’ marks on the surface where females have deposited eggs. Larvae feed inside mature fruit, creating tunnels from the surface to the centre. Fruit rot due to secondary infection often occurs with fruit fly infestations. Infected fruit will drop from the tree or rot on the tree.
Description: The adult fly is 3.5 to 5 mm in length. The color is yellowish with brown tinge, especially on abdomen, legs, and some markings on wings. The lower corners of the face have white setae. Eyes are reddish purple . Ocellar bristles are present. Larva are white with a typical fruit fly larval shape.
Host plants: Thin-skinned, ripe succulent fruits are preferred, such as apple, peach, persimmon, cherry, citrus, pear, guava, and host preferences vary in different regions.
- Citrus mealybug
Distribution and damage: The pest is a native of Asia but is also found throughout the Americas, Europe, and Oceania. Citrus mealybug feeding results in wilted, distorted, and yellowed chlorotic leaves, premature leaf drop, stunted growth, and occasional death of infested plants or plant parts. The sugary honeydew secreted by citrus mealybugs falls on leaves and fruits below, resulting in the growth of sooty mold which may degrade fruit quality by reducing the photosynthetic capacity of leaves.
Description: Adult size ranges in length from 3 mm (females) to 4.5 mm (males). The females are wingless, white to light brown in color, with brown legs and antennae. Males are similar in color to females and have two long backward-projecting, white wax threads. Adult males are winged and thus capable of flying to new host plants for mating purpose. The nymphs are yellow, oval-shaped with red eyes, and covered with white, waxy particles.
Host plants: Citrus, pineapple, eggplant, apple, strawberries, sweet potato, mango, banana, guava, pear, etc
- Cicada
This kind of insect is often discovered in citrus plantations, but the damage caused by it is minor. Its appearance is similar to that of other pests, we add this species to the image data to avoid the misclassification of this insect.
- Citrus scale
Description and damage: There are two major types of scale on citrus plants: armored scales and soft scales:
Armored scale – Female armored scales, from the family Diaspididae, insert their mouthparts and never move again – eating and reproducing in the same spot. Male armored scales are also immobile until maturity. This type of scale bugs on citrus exudes a protective coating made up of wax and cast skins of prior instars, which creates its armor. These citrus scale pests not only wreak the havoc mentioned above, but the armor will also remain on the plant or fruit long after the insect is dead, creating disfigured fruit.
Soft scale – Soft scale bugs on citrus also form a protective coating via wax secretion, but it is not the hardened shell that the armored scale produces. Soft scales cannot be lifted from their shell and females roam the tree bark freely until eggs begin to form. The honeydew secreted by the soft scale attracts the sooty mold fungus, which in turn covers the citrus leaves preventing photosynthesis.
In this dataset, four types of soft scale are collected, including Florida wax scale, white wax scale, pink wax scale, and Hard wax scale. In the future, I will try to add some categories of armored scale to the dataset.
- False codling moth
Distribution and damage: The moth is believed to have originated in Sub-Saharan Africa and occasionally found in Europe and United States. Eggs are laid on the surface of the fruit. After emerging from the egg the larvae burrow into the rind. Once the fruit has been penetrated it is no longer a marketable item, and once compromised, the incidence of disease and mold increases.
Description: Adult moths are 15-16 mm (males) and 19-20 mm (female) in length. Forewings have grey, brown, black and orange-brown markings. A triangular marking on the outer part of the wing with a crescent shaped marking above it distinguishes the False codling moth from other species. Young larvae are yellowish-white with dark spots but bright red or pink when fully grown (15 mm), with a yellow-brown head.
Host plants: In Africa, it is a major pest of citrus and cotton. Other commonly grown agricultural hosts in California include grapes, peach, plum, cherry, beans, tomato, pepper, persimmon, apricot, olive, pomegranate, English walnut, and corn.
- Citrus aphids
Description: In this dataset, three kinds of citrus aphids are collected. The reference about their description are as follows:
Black citrus aphid: https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=54271
Cotton or melon aphid: http://ipm.ucanr.edu/PMG/r102300411.html
Spirea aphid: http://idtools.org/id/citrus/pests/factsheet.php?name=Spirea+aphid
- Citrus root weevil
Description:
diaprepes root weevil： https://entnemdept.ifas.ufl.edu/creatures/citrus/diaprepes_root_weevil.htm
blue-green citrus weevil： http://idtools.org/id/citrus/pests/factsheet.php?name=Southern+citrus+root+weevil
http://idtools.org/id/citrus/pests/factsheet.php?name=Northern+citrus+root+weevil
Sympiezomia citri Chao： http://www.piweevils.com/?xcsjk3_en/id/49.html
- Citrus flatid planthopper
Distribution and damage: The species is native to North America, but today is found throughout southern Europe, in the Neotropical ecozone and in South Korea. Dense populations of nymphs cause stunting of the shoots, while those of adults produce large quantities of honeydew on which sooty mold develops.
Description: Flatids have broadly triangular front wings that are held close to the body in a vertical position and give the insects a wedge-shaped, laterally compressed appearance from above. The color of the adult varies considerably from brown to gray, due chiefly to the presence or absence of a bluish-white waxy powder. A characteristic pair of dark spots is located in the basal half of each forewing.
Host plants: It has been reported on a long list of plants, including many forest trees, orchard and citrus trees, grape and other vines, numerous shrubs, and some herbs.
- Glassy winged sharpshooter
Distribution and damage: Glassy winged sharpshooter is indigenous to the southeastern United States and northeastern Mexico, and extended its range into California USA in 1989. The insect feeds on the nutrient-poor xylem of the plant, the adults and nymphs excrete large amounts of liquid while feeding, which gives the fruit and foliage a whitewashed appearance.
Description: These sharpshooters are about 12 millimeters in length. Their color is dark brown to black with black-and-yellow undersides, with yellow eyes, and the upper parts of the head and back are speckled with ivory or yellowish spots. The wings are transparent with reddish veins.
Host plants: Its known host range is vast, including more than 100 plant species, the preferred species include crape myrtle, citrus, and holly.
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