The poplar borer or willow borer or osier weevil or willow weevil (Cryptorhynchus lapathi, Linnaeus, 1758) is an insect belonging to the Curculionidae family.
From a systematic point of view it belongs to:
C. lapathi species.
The terms are synonymous:
– Cryptorhynchidius lapathi (Linnaeus);
– Cryptorrhynchidius lapathi (Linnaeus, 1758);
– Curculio albicans J.A.E.Goeze, 1777;
– Curculio albicans J.F. Gmelin, 1790;
– Curculio albicaudis C. DeGeer, 1775;
– Curculio lapadi J.A.E.Goeze, 1777;
– Curculio lapathi C. Linnaeus, 1758 (Basionimo);
– Rhynchaenus albicaudis L. Gyllenhal, 1813;
– Rhynchaenus lapathi (C. Linnaeus, 1758);
– Tychius lapathi (C. Linnaeus, 1758).
Geographic Distribution and Habitat –
Cryptorhynchus lapathi is a xylophagous Curculionidae native to Europe where it carries out its cycle involving some species of poplar and other plants such as willow.
In Italy it is a fairly widespread insect, especially throughout the poplar cultivation area.
The poplar borer is a xylophagous beetle that measures about 6-9 mm in length at the adult stage. It has a rusty brown color, with a yellow-ocher band in the distal part of the elytra; the livery is completed by the more or less extensive yellowish patches in the anterior part of the body.
The larvae are arched, apod, with a whitish body and a reddish head.
Attitude and Life Cycle –
Cryptorhynchus lapathi overwinters either in the egg or young larva stage. In the northernmost regions, it overwinters at the egg stage in wells dug by the females in the rind, or in the ravines of the same; in the more temperate regions, on the other hand, it overwinters at the stage of young larva, and the flickering of the adults is earlier and oviposition is anticipated.
The adults flicker in a period that goes from the beginning of June to the end of July; the females lay eggs in milder climates until autumn.
The cycle begins with mating followed by oviposition in the bark of the wood; here the eggs can overwinter, originating the larvae in the following spring, or originate the larvae already at the end of the summer of the 1st solar year.
The larvae reach maturity in the summer of the second solar year; in some northern areas it continues for the 3rd solar year.
In this way the Cryptorhynchus lapathi completes a generation every 1-2 years.
However, the young larvae with their trophic activity cause damage to the woody organs which, generally, react to the larval attack, with slight swelling of the affected area.
Ecological Role –
Cryptorhynchus lapathi is a xylophagous insect which therefore feeds on the wood of some plants, especially poplar, willow and other ornamental plants.
The greatest damage occurs on young plants in nurseries but can also affect adult plants and is caused both in the larval and adult state.
The adults make annular incisions along the trunk or on the young branches, feeding on the young rind; in these cases the attack can cause either the death of the overlying part, if the decortication is extensive and complete, or a serious weakening of the organ. In these cases, a bottleneck is formed which can cause the branch to break.
The incisions caused, especially on young plants, can be very serious, even causing death. On older plants, the attack causes localized reactions.
The larvae can cause equally serious damage as they dig cortical tunnels, both longitudinally and transversally, causing a considerable weakening of the attached woody organs which can also dry out if the tunnels take on an annular course with complete degeneration and disconnection of the conductive tissues and of the exchange.
When the tunnels are dug close to a lateral shoot, there is withering and drying of the same. In young organs, the galleries deepen to the central medulla.
To date, the defense against this insect has been of a chemical type but agronomic techniques are spreading which essentially consist in the destruction of plants or organs severely affected, to avoid increasing the potential for infestation.
The chemical fight is carried out only in the presence of strong infestations; it is directed against the larvae, before they deepen in the wood, at the vegetative restart. The execution technique involves direct interventions on the woody organs that are sprayed with insecticidal solutions.
The containment of the parasite, which has limited capacity for active movement, must begin with the planting of healthy nursery material, obtained in properly controlled and disinfested nurseries at the time of eradication.
The chemical fight in infested plantations is fundamental up to the third year of age (if there are adequate guarantees of health of the nursery material, it is possible to omit the intervention in the year of transplantation), while it is normally no longer justified from the fourth year onwards when the the insect, moving on the branches of the canopy, is no longer in a position to cause economic damage to the crop.
Generally, a single insecticide treatment is enough, if correctly performed, which is able to eliminate the young larvae nested in the bark, thus preventing damage: the optimal time for its execution, in poplar groves, is that of the vegetative restart when the buds begin to grow. open, an event that normally occurs between the second half of March and the beginning of April.
Furthermore, it is necessary that the stems are sprayed until dripping, in order to allow the penetration of the insecticide mixture into the larval galleries.
Excellent results have been achieved with pyrethroid-based active ingredients such as deltamethrin
(2.5 g / hl), alfamethrin and cyfluthrin (5 g / hl), cypermethrin (10g / hl), or phosphorganics such as fenitrothion, phenthoate (200 g / hl), chlorpyrifos and chlorpyrifosmethyl (150 g / hl). Using pyrethroids it is possible to obtain satisfactory results even with treatments performed before sprouting, thus improving the selectivity towards useful entomofauna.
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Pollini A., 2002. Manual of applied entomology. Edagricole, Bologna.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.
Photo source: https://www.biolib.cz/IMG/GAL/BIG/396503.jpg