''Cacopsylla pyrisuga'', or the large pear sucker, is a species of

true bug Hemiptera (; ) is an order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to around ...

in the family Psyllidae known as a

pest Pest or The Pest may refer to: Science and medicine * Pest (organism), an animal or plant deemed to be detrimental to humans or human concerns ** Weed, a plant considered undesirable * Infectious disease, an illness resulting from an infection ** ...

of pear trees (''

Pyrus Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the family Rosaceae, bearing the po ...

'') in Central and North Europe.

Description

A relatively large

pear psyllid ''Psylla pyri'', commonly known as the pear psylla or pear psyllid, is an insect in the family Psyllidae. Originating in Europe and Asia, it has spread to North America. It is a pest of pear trees, sucking the sap, damaging the foliage, flowers ...

, adults reach 3.5–4 mm length. Young adults in spring and early summer are green with yellowish head and thorax, whereas they darken to a rusty red hue towards the autumn. In general, psyllid taxonomy is often complicated due to morphological similarities; ''C. pyrisuga'' forms the group "pyrisuga" with the closely related species ''C. burckhardti'' and ''C. accincta'', within which it is nearly impossible to distinguish individual species. The latter two species are only foud in

East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. China, North Korea, South Korea and ...

, however, and European specimens belong exclusively to ''C. pyrisuga''. Eggs are not stalked, while nymphs resemble those of ''

Cacopsylla pyricola ''Cacopsylla pyricola'', commonly known as the pear sucker, is a true bug in the family Psyllidae and is a pest of pear trees (''Pyrus''). It originated in Europe, was introduced to the United States in the early nineteenth century and spread ac ...

''. The nymphs are green with varying amount of black markings.

Ecology and distribution

The species is an important pest of pear trees, its main host. Adults overwinter on

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

s in the wild, and migrate to pear plantations at the beginning of spring. There, they reproduce and then die. The new generation develops on young shoots until emerging as adults in May/June, after which they migrate to overwintering sites where they stay dormant until the next spring. Paradoxically, they are thus absent from their main host most of the year. As other psyllids, they mainly cause damage indirectly by exuding sticky liquid which stains the fruits and promotes growth of mold. Only large outbreaks can cause defoliation, reduce fruit growth and cause early fruit loss. Additionally, they can act as vectors of microbial plant pathogens, such as

phytoplasm Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-lik ...

s. ''C. pyrisuga'' has been confirmed as a vector of "''Candidatus'' Phytoplasma pyri" which causes pear decline, a devastating disease of pear trees. The species has a West

Palearctic The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa. The realm consists of several bioregions: the Euro-Sibe ...

distribution, i. e.

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and

West Asia Western Asia, West Asia, or Southwest Asia, is the westernmost subregion of the larger geographical region of Asia, as defined by some academics, UN bodies and other institutions. It is almost entirely a part of the Middle East, and includes Ana ...

, limited by the distribution of its main host. Its area extends northwards to

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...

, but only one record is known for the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

Sexual behavior

''C. pyrisuga'' male emitting a vibrational signal; 200× slowed. Like other psyllids, ''C. pyrisuga'' adults use a combination of pheromones and vibrational signals to recognize and locate mates on the host plant. Cuticular hydrocarbons, predominantly long-chain

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

s act as pheromones in pear psyllids. Likewise, vibrational duet resembles that of other known pear psyllid species. The female spontaneously emits calling signals composed of several short pulses, which stimulates the male to reply with own signal comprising a series of short pulses and a longer "buzz". Recordings of this species have revealed that psyllids do not produce vibrational signals with stridulation (rubbing of body parts together) as was commonly thought. Instead, wing flapping ("buzzing") approximately 150 times per second is involved. This buzzing is not transmitted as sound but through the legs to the branch the animal is standing on.

References

{{Authority control Psyllidae Hemiptera of Asia Hemiptera of Europe Insects described in 1848 Taxa named by Arnold Förster