The Saw Fly (Selandria cerasi).

Otago Witness, Issue 2045, 4 May 1893, Page 5

The Saw Fly (Selandria cerasi).

The same gentleman who wrote asking for test samples of the codlin moth, mentioned that at Invercargill they have few fruifc pests except the saw fly (or tree slug as it is sometimes called), and he says that this injures nothing but the late plums, which do not ripen so well with it. This, however, is a great mistake, and the sooner it is rectified the better. This destructive and unsightly pesfe robs the trees of their foliage, thereby not only destroying their appearance, but seriously injuring their constitution. It is the leaf that elaborates the sap drawn from the ground by the roots, and converts it into nourishment for the fruit, without which it cannot attain anything like perfection, even if it remains on the tree at all. The leaves are the life of the tree. When they are destroyed the tree, not being able to do without them, makes abnormal efforts to renew its foliage out of the proper season, and exhausts its constitution, and very often after lingering on for many years in an increasingly unhealthy condition it. dies. The writer has seen many orchards in which the saw fly has caused the plum, cherry, and other trees subject to its attack to become worthless, and a great many of them to die. Denuded of the foliage too, the bark of the trees is exposed to the scorching sun of mid-summer ; and indeed, there are few pests more to be dreaded than the saw fly, or that, if neglected, spread more rapidly. Its life history is very well understood by entomologists. It leaves the pupa early in the summer, and the wings being as yet weak, it first attains the lower branches, in the leaves of which it lays its eggs, which hatch in a few days larvse that devour the leaves, the destruction beginning low down on the tree and gradually ascending. It is needless to go more fully into the history of the pest at present beyond saying that now (on its leaving the egg) is the best time to .attack it. This can be done by poisoning the leaves it feeds upon, by a wash of Paris green, as used against other : caterpillars, or leaf-eating beetles, or a wash of I white Helebore powder and water, two or three applications being generally sufficient to destroy all the' larvse. Or it can be acted upon by external applications. Kerosene emulsions of light strengths will kill all they touch, and if dry lime is shaken over the tree a few times it I will also destroy the pest. This can be done by throwing the lime from the wind side of the trees or using a long pole with a scrim bag at the end of it for tall frees. When the lime touches a larva it either kills it or causes it to cast its skin in a hurry, but a second application a few days or a week later, when it cannot again escape in that way, kills it. Common road dust is said to act in the same way, and the writer has found such to be the case in experiments made under glass cases, but it is not so deadly certain as the lime, which does good as well in other respects. By all means get rid of the " tree leach." It is well in* using the kerosene emulsion in summer to avoid making it too strong, as it injures the foliage, and for the saw fly larva a strength of 1 of oil to 25 of water is quite enough. „ Entomologist.