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Fruit Nut Tree Insects

Fruit Nut Tree InsectsThe fat whitish maggot found in Filberts and Hazel nuts is the larva of the Nut Weevil. These beetles, or weevils, may be seen about the Nut bushes early in the summer, the females usually creeping along the twigs, the males often on the wing. Whilst the Nuts are still young the female pierces a hole through the soft shell by means of the jaws with which she is furnished at the end of her long snout. In this hole she lays one egg, which hatches in about ten days.

The maggot feeds inside the Nut, consuming a large part of the kernel. When full-grown it is of the shape and size figured above, of an ochreous white, with horny chestnut-coloured head, furnished with strong black jaws; without legs, but supplied with muscles inside the large transverse folds or wrinkles, which enable it to draw itself through the earth.

When full-fed the maggot eats a hole through the Nut shell, sometimes whilst the Nut is on the bush, sometimes after it has fallen to the ground in the premature ripening which appears to follow on the maggot-attack. It then buries itself, forms a cell in the earth, and "frequently rests there during the winter, and only changes in the following spring or later" to a pupa or chrysalis of whitish colour, like the future weevil in shape, but lying quiescent with its limbs folded against it.

The weevils are described by John Curtis as of a tawny brown colour, densely clothed with short depressed hairs, the proboscis polished and bright chestnut-colour, the wing-cases clouded or variegated with ochreous and reddish brown transĀ­verse marks, and with ten lines of punctures on each, wings ample. Other writers describe this weevil as being clothed with greyish or yellowish down, and with a whitish or yellowish scutellum, but it is very variable in colour. The very great length of the proboscis is one distinction.

The weevils may be found as early as May, at which time development from the chrysalis has been recorded, but it is stated that some of these beetles do not develop till July or August, and it is still open to observation whether some of these do not hybernate and appear with those newly out of the chrysalis in the following May.

In this case the best means of prevention lie in the regular measures of good cultivation. It is stated the Filbert likes a Hazel loam of some depth, "which should be dressed every year, as the Filbert requires a considerable quantity of manure." It is also mentioned by Mr. C. Whitehead that "The Nut grounds are well-manured every other year with rags, shoddy, fish, or fur waste, and are always cultivated by hand, and kept scrupulously clean."

This course of treatment, that is, treatment which involves stirring the surface-soil as well as additions, is suited to expose some of the chrysalids and bury others deeper, and is generally useful for insect prevention, but especially as regards the Nut Weevil, which (in instances observed) has been found to be so tender at the time of its transformations as to require eight or nine days to gain its colour and hardness, and also strength enough to force its way up through the ground. Looking at these points, it seems likely that if the chrysalids were buried a little beyond the natural depth many of the weevils from them would not be able to come up at all.

Where weevils are very abundant on the trees, it has been advised to beat them down, but this should not be done on a sunny day, or they will speedily take flight and escape.

It is desirable to remove all Nuts that fall before their proper time, that the maggot inside may thus be carried away before it has bored its way out ; and also, looking at the powers of flight of the weevils, it would be well not to have many Hazel Nut bushes in copses adjacent to Filbert ground.