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The citrus Longhorn Beetle Anoplophora chinensis

What is this quarantine invasive insect? Anoplophora chinensis (Förster) is a longhorn beetle native to China, Japan, Korea and other Countries in the South East Asia, and is commonly known as the Citrus Longhorn Beetle (CLB) due to the severe damages recorded in the past in citrus orchards in its area of origin. Despite this common name, A. chinensis is able to attack, develop and damage an extreme large number of broadleaved plants, including shrubs and trees of forest, urban, fruit and ornamental species. A. chinensis attacks plants of almost any size and age, from potted plants, “bonsais” and freshly planted young trees, up to centennial and monumental exemplars.

Why the concern? A. chinensis is a serious pest accidentally introduced into Europe more as a decade ago, and in Italy there are currently two outbreak sites (both under eradication): one in the Lombardy Region and one in the city of Rome; infestations have occurred also in other countries of Europe. Interceptions in ports of entry and early detections postentry in plant nurseries, by plant sellers or in public areas are made by Plant Protection Organizations of many countries of the European Union, by company employees or by the public, and in most cases imported plants from the East Asia where the suspected way of introduction of the insect.

A. chinensis is a quarantine invasive pest and strong phytosanitary measures are applied worldwide to prevent introduction and spread, and to eradicate it in the infested areas. Eradication measures are currently carried out by destructive methods including chipping or burning of infested trees, involving not only trunks and branches, but also the root system. A. chinensis is a woodboring insect which generally colonizes healthy trees, but can repeatedly attack the same tree for many years causing severe physiological and structural weakness, both of which can lead to tree death. The beetle needs approximately 1 - 2 years for juvenile development (or longer in colder countries), and the females lay their eggs at the base of the trunk of susceptible trees or on exposed roots. The larvae feed at first in the phloem tissue under the bark and later create large oval-shaped tunnels in the xylem, either in the trunk and in the roots. After pupation, the adult beetles emerge producing a circular exit hole by chewing a thin portion of bark separating the pupal chamber from the external environment.

What does it look like and what are the symptoms? Detection of A. chinensis is possible by observing adults in activity in the environment, mainly moving on host trees, feeding on plant twigs or during ovipositioning on the bases of plants or on exposed roots. Adults of this species are quite easy to identify and separate from the species of the native European longhorn fauna: adults are relative large (females approximately are up to 3,5 cm long and males up to 2,5 cm) and glossy black with variable white markings on the dorsal part of the body; legs are black/light blue colored and antennae are long (twice long the body in males and quite a bit longer than the body in the females) mainly black with white/light blue bands at the basal portion of the segments. At contrary, the larvae present not clear distinctive features (larvae are legless cream colored and up to approximately 5 cm long when mature) and species assignment is more difficult, thus detailed laboratory analyses are to be performed. However, A. chinensis spend most of their life as larvae inside trunks or roots, and hence there can be little or no sign of their presence. The most obvious symptoms of A. chinensis presence are the adult exit holes on infested trees, which are approximately 10-15 mm in diameter (but can be large up to 2 cm in diameter) and are generally found towards the bases of trunks and on exposed roots. Other symptoms are piles of larval frass at the base of attacked trees, produced during the feeding activity of the larvae and expelled from their tunnels.

Arrives from Asia this dangerous insect that can cause considerable damage to all plants