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Classification and host plants
Species: Cetonia aurata L. - Tropinota hirta Poda
Host plants: Rosaceae and other fruit and ornamental plants.
Identification, damage and biological cycle
These two beetles are reported more for their diffusion and their general biological interest than for the actual damage caused. The golden Cetonia (Cetonia aurata L.) is a Scarabeid with adults (about 15-20 mm long) that have a showy bright green-golden livery (in some bluish varieties) and with metallic reflections, the elytra have two longitudinal reliefs and sometimes light stripes; morphologically very similar to the Cetonias are the Potosias, they are also very common and have similar ecological roles. Tropinota hirta or black Cetonia (about 8-12 mm long) has a blackish livery with whitish-stained elytra; the body is covered with yellowish-whitish hairs; Similar to Tropinota is the species Oxythyrea funesta, however, it is smaller, has a body less covered with hair, therefore the black color is brighter, finally the corset and the elytra are stained with white. In all the species considered, the larvae develop in the soil, on the roots, or at the base of the plants, in the dead stumps or in the perishable wood. The damage, which occurs on the flowers (especially on the white-flowered varieties) is however caused by the adults who feed on the reproductive floral organs; the attack causes the petals to fall and a faster necrosis of the standard flower structures. These beetles are annual cycle insects, winter as mature larva, or as adults; they appear in April-May, in correspondence with the flowering.
Golden Cetonia - Cetonia aurata L. (photo http://dic.academic.ru)
Golden Cetonia - Cetonia aurata L. (photo Sebastien Bedani)
Black cetonia - Tropinota hirta Poda (photo www.kerbtier.de)
The fight against these beetles is almost never justified; in some cases it can be carried out against Tropinota hirta, if the infestations are so serious as to compromise a large quantity of flowers.
In any case, the interventions must also be assessed on the basis of the presence of pollinating insects and of the Diphtheria, frequent visitors of the flowers.