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How to fight Cossus cossus in a biological way

How to fight Cossus cossus in a biological way

The red wolf (Cossus cossus L., 1758) is a moth of the Cossidae family, widespread throughout Europe. It is a moth, considered an insect of wood, as it lives and develops against the wood of trees that causes considerable damage to some agricultural crops.
The red rod in the adult stage, looks like a big butterfly, with a wingspan around 70-100 mm, with a color that resembles the bark of the trees, which allows these moths to camouflage perfectly on the trunks . The wings are gray-brown with fine black stripes. The head, from which emerge two long black antennae, is more brownish in color, with streaks and regular spots (white, black, gray, brown).
The larvae take on different colors depending on the age.
When they are young they are pinkish, while when grown up they become dark red. The head is always dark, while the belly is lighter, yellow-ocher. When they reach maturity, the red caterpillar larvae have considerable dimensions, which can range from 80 to 100 mm.
The laying of the eggs takes place in the recesses of the bark of the trees, usually at the base; these are quite large, about 1.5 mm, and have a reddish color.
The damages caused by the red rodilegno can be very serious and caused by the larvae that, with their trophic activity, that is the nutrition, dig deep tunnels both on the trunk and in the secondary branches of the tree. Being then a particularly polyphagous species it does damage on numerous tree crops.
Among the most affected species we mention: the pomaceous (apple, pear, medlar, rowan, azar), stone fruit (cherry, almond, walnut, peach, plum, apricot); also some forest plants and of ornamental interest are damaged.
The affected trees undergo general decay. In the affected plants the wood has holes in the passage and an evident crumbling. By cutting the trunk, you can see the tunnels.
To this d primary damage, caused by the red rodilegno, secondary damages can also be added; in fact, the wounds that the larvae cause are an excellent way of passage for fungi, diseases and other pathogens.
The Cossus cossus has a quite particular biological cycle compared to other species of moths of agrarian interest. The red woodworm performs (unlike other lepidopterans of agrarian interest) a single generation every 2 or 3 years. The flickering takes place at the end of spring and lasts throughout the summer. During this period the adults mate and the females lay their eggs. Plants are mainly hit at the base. The young larvae have a gregarious behavior, beginning to immediately excavate the tunnels. The presence of the larvae can also be made by noticing the leakage of sap from the affected plants.

In the first year of life the larvae spend all winter in the tunnels, overwintering them. In the following spring they resume their trophic activity by enlarging the galleries themselves and going deeper into the tree, spending all year round at the larval stage. This corresponds to the period of greater damage.
The flicker then occurs at the end of spring of the third year, after a chrysalis stage that occurs in the outer layers of the tunnel or in the ground, at the base of the affected plant. Once the flicker ends, another cycle of life resumes.
Depending on the long biological cycle of the insect, it is advisable to make the necessary precautions to perform an efficient biological fight.
If it is a few plants, a system is that characteristic of the wire. It is sufficient, in fact, to pass a common metallic wire inside the galleries, until reaching the larvae, which, when hit, die. If the infestation is at an early stage, this can be a solution. Vice versa, if it is advanced, or in case of large extensions, the method is too laborious and often ineffective.
The most effective methods, especially for large extensions, are those of the massive capture of adult red caterpillar butterflies. This system must be applied during the period of flickering, when there is coupling and oviposition. In this sense it is necessary to use specific traps with specific pheromones of sexual attraction that attract and trap the male specimens which, in this way, can no longer fertilize the females, which still lay the eggs, but these not fertilized; in this way it progressively moves towards the sterilization of the population. These traps must be placed with a density that varies from 10 to 20 (depending on the density of planting) for each hectare of orchard.
In addition to this method it is possible to resort to entomopathogenic nematodes which, in the case of red rod, are inoculated directly into the tunnels dug into the tree by the larvae. The nematode reaches it and inoculates symbiotic bacteria that cause death within 72 hours.
Among these nematodes we remember: Steinenerma feltia and Steinernema carpocapsae, among other things, easy to find even in specialized stores.
Another microbiological defense system (allowed in organic farming) can be adopted with the use of Beauveria bassiana which is an entomopathogenic fungus that acts by contact; in fact, the fungus inoculates the micete on the larvae causing its death.
Recall that the proliferation of this insect is also linked, in a considerable way, to the increase in the specialization of crops and the use of pesticides that negatively affect even the natural enemies of Cossu cossus, including the Diptera Larvevoridi (Gen. Phorocera) and some parasitoid hymenopterans. For this reason, it is necessary to restore agroecological principles in agricultural and forest cultivation without which even biological control and containment techniques can become random.

Guido Bissanti

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