Between the end of August and the beginning of September it is possible to observe hundreds of birds in the woods, but also in the urban parks of Northern Italy. hairy caterpillars that fall from the trees and move on the grass; this is the larval stage of American Fantasia (Hyphantria cunea), a butterfly of the Erebidae family, accidentally introduced from the United States and whose larvae are voracious leaf eatersThese defoliating caterpillars are harmless to humans and should not be confused with the more fearsome caterpillars of the Processionary Moth (Thaumetopoea pityocampa), equipped with stinging hairs that are sometimes dangerous for humans and domestic animals. Let’s see where the Ifantria comes from and how this species behaves.
Where does the American Hyphantria live and what is its life cycle?
Hyphantria cunea It is a North American species; it is therefore alien to Europe where it has been first accidentally introduced into Hungary in the 1940s and has spread to Northern Italy since the 1980s. Today it is present in Canada, the United States and Mexico, and has also arrived in China, Japan, Korea, part of Europe and Russia.
The adult is a moththerefore a nocturnal butterfly, 11-15 mm long and white in colour; sometimes local variants with white wings dotted with black are seen.
The mature larval stage is about 35-40 mm long, has a broad dark stripe on the back and two series of yellow-orange tubercles along the entire body with characteristic tufts of very long hair (10-12 mm) and white, devoid of stinging properties.
The chrysalis stage is reddish-brown in colour and is the vital phase in which the species spends the winter, hidden in cracks in the bark or in old beams of attics and lofts.
Ifantria presents two generations per year: the adult butterflies of the first generation lay their eggs on the underside of the leaves of host plants between the end of April and May. When the eggs hatch, they emerge very voracious larvae that feed by defoliating many branches and sometimes an entire host plantThe well-fed larvae begin to emit a silky thread and create large cocoons that wrap around an entire branch like a thick spider web.
These cocoons are clearly visible around the month of June and from these the second generation of adult butterflies will emerge which repeats the cycle giving rise to the second generation of larvae, generally more harmful than the first. The new larvae are clearly visible between August and September and can be seen in their hundreds moving on the ground and on the trees until the end of September, when they begin to look for cracks and crevices to nest in the form of chrysalises and to spend the winter.
Infantria hairy caterpillars feed on a large number of plants, but they prefer some. The main host plants are the Apple (Malus domestica) and the Plum (Prunus domestica), but they also attack Maples, Hazels, Mulberries, Poplars, Willows, Limes and Plane trees, often causing damage to parks and tree-lined avenues. Some plant species are used in both the first and second generations, others such as Ash, Hazel and Hawthorn are used only by the second generation.
Natural remedies to control the species
According to the recommendations of the Phytosanitary Service of the Lombardy Region and the Emilia Romagna Region, if you do not want to use insecticides it is possible:
- destroy the cocoons as they form on the plant;
- cover the tree trunk with straw or corrugated cardboard so that the pupae gather on these surfaces and then remove them;
- carry out treatments with Bacillus thuringiensis for biological control of second generation larvae.
Natural predators of the Ifantria are several species of birds, in particular in northern Italy the cuckoo, the golden oriole, the great tit and the starling are considered particularly effective. The larvae of Ifantria are also preyed upon by some species of spiders, by wasps of the genus Polistes and by a Carabid beetle.
