Retinia
A genus of small moths, belonging to the group of Tortricidae, of some importance because of the damage inflicted by them on Scotch Firs and other Coniferae. Several species occur in Great Britain, and the larvae of all, so far as known, feed in the buds or young shoots of the Coniferae. The moths vary from 1/2in. to nearly 1in. in spread of wing; the front wings are nearly three times as long as broad, with the tip rather rounded, and the front and hind borders slightly rounded; the hind wings are rather broad and pointed.
These species are almost all considerably more common in Scotland than in England, though most of them may be met with wherever the food-plants grow. All reach the perfect stage some time between June and August. The females lay their eggs on the young buds and twigs. The larvae hatched from these eggs gnaw their way into the buds and leading shoots, and bore into the pith, there to remain usually all winter, since they are still feeding in the following spring. They are of the usual form of the larvae of Tortricidae, with rather cylindrical, naked bodies and dark, horny heads and shields on segments just behind the heads. They have six true legs and ten prolegs, or claspers. Almost any one of the species would deserve the name of Pine-bud Moth; but the name has been given to the species R. turionana.
The result of an attack on Firs by these larvae is that the leading shoots may be hollowed out, even in the bud state, or they become bent, brown, and brittle; and the trees become distorted, because of the loss of these shoots, and the ill-development of the shoots that have taken their place in the course of growth. In general, there is a considerable outflow of resin from the wounds made by the larvae; and this resin hardens on the surface and forms a protection during winter to the larvae. R. turionana is hurtful especially to the buds. R. Buoliana and the others are more dangerous to the newly-formed shoots. R. resinana is called the Resin-gall Moth, because of the fact that the larva produces a false gall of resin, by exudation of resin over the place where it is boring into the wood. It is not unlike a half walnut in form, and may even reach nearly or quite to this size; but it is dirty-white in colour, and remains soft while it is occupied. The larvae are said to pass two winters before they become pupae, which they do in spring, and the moths emerge in June.
Remedies. Owing to the larvae living entirely under cover, no external applications are of the least use: the only method found at all successful has been the removal and burning of all shoots that show signs of attack by any of the species of Retinia.