The ancient bombyx (Orgyia antiqua) is an insect belonging to the order Lepidopterafamily Lymantriidaewhich is often called more simply orgy. It is a parasite present in all Italian regions, which lives mainly at the expense of fruit trees, causing significant damage when populations are numerous. It has many similarities with another bomb that we have already studied, namely the limantria (odd bombyx).
In this article we discover the characteristics and the life cycle of theOrgyia antiquathe damage it causes to fruit trees and the related biological defense.
Description of the ancient bombyx
L’Orgyia antiqua adult is a medium-sized butterfly, which has a marked sexual dimorphism, that is, notable differences between individuals of different genders.
Females
The adult females are in fact microterras, that is to say with wings reduced to small stumps. The body is hairy, light gray, about 15 mm long.
Males
The males, on the other hand, have ocher-reddish front wings, each of which carries, in the lower corner, a white semilunar-shaped spot. The hind wings, on the other hand, have a reddish color. Its dimensions, considering the wingspan, are 30-40 mm.
Egg
The egg of the ancient bombice is almost spherical in shape with a sunken micro-pile area. As soon as they are laid, they are greyish-white, then light brown. They are easily recognized as they are usually gathered in thick ovules left on the underside of the leaves or on the cocoon abandoned by the female.
Larva
The mature larvae of Orgyia antiqua they have a unique and eye-catching appearance. In fact, on the whole body they have plumed blackish bristles. On the back, on the first four segments, there are also four brushes of erect hair. Also in the dorsal part there are red and velvety pads, each of which bears whitish bristles. At full maturity they measure 30-35 mm in length.
Chrysalis
The chrysalis are yellowish-brown in color and are protected within a light brown silky cocoon.
On which trees does ancient moth live
L’Orgyia antiqua it’s an insect rather polyphagous. It lives mostly on fruit trees, such as: Apple tree, However, peach, plum, Cherry tree, apricot, almond tree. It also infests broad-leaved trees, shrubs and trees, such as: hawthornrose, oaks, Elm tree etc.
From time to time, attacks of ancient bombice have also been reported on conifers, namely larch, fir and pine.
Damage to vegetation and fruits of bombyx
The damage of the ancient bombyx is due to the trophic activity of the larvae. These feed on the leaves, making extensive erosions and sparing only the thickest veins and the petiole. The larvae are also able to damage the fruits, both the young ones and those in the ripening phase, making more or less extensive superficial erosions. For example, on apples their damage is recognized by the appearance of rusty and rounded growths. Another common damage is on plums, where, following the attack, suberified depressed areas are formed.
Biological cycle of the Orgyia antiqua
The ancient bombyx overwinters in the state of eggs, deposited on the cocoon abandoned by the female and adhering, often together with a dry leaf, to the branches.
The larvae come out in the month of May and feed on leaves only and then also on fruits. After about a month they reach maturity and crystallize inside a cocoon adhering to a green leaf or a sprig. The new adults flicker from mid-June to mid-July, with the females being fertilized by the males even while still in the cocoons. Each female lays 150 to 200 eggs, under the leaves or on the remains of her cocoon. After about two weeks of incubation, the second generation larvae are born, the adults of which flicker in August. Then two more generations follow, for a total of four.
How to get rid of ancient bombice
Following the life cycle of the insect, the defense of the trees can begin already in winter, in particular at the time of pruning. With a little attention, it is in fact possible to identify the ovature of the ancient moth on the branches and destroy them.
Monitoring
Placing the pheromone traps it is possible to monitor theOrgyia antiqua and, possibly, decide whether to intervene with more incisive treatments. Traps with aggregation pheromone should be used in June.
Biological defense
In case of strong pressure from the parasite, one can intervene directly on the larvae using the bacillus thuringiensis var. kurstakiwhich you find in specialized stores. The product acts by ingestion.
For a better effectiveness of the treatment, it is advisable to carry out a wide spraying of the foliage, better in the evening hours and taking care to wet the underside of the leaves where the larvae nest.
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