DISEASES OF LEMON TREES.

Taranaki Daily News, 27 November 1920, Page 3

DISEASES OF LEMON TREES.

(To the Editor.) Sir, —Perhaps in no previous year since lire introduction of lemon trees into Taranakl has there been so many complaints of the trees failing to bear fruit, and of many of the trees dying in a few months. Having recently examined tlrree dozen dead and halfdead lemon trees in the neighborhood of New Plymouth, possibly some remarks on the failure of the trees to bear fruit, and the causes of their premature death, may be acceptable to some of your readers. Excepting during the summer and autumn .months, when tliei foliage of lemon trees are sometimes attacked by the lemon scale-Insect and a species of aphis, both Introduced, the chief c.iuso of tl-e destruction of these valuable fruit trees is due t<. the ravages of two native species of tree-boring larvae, that tunnel the , stems, thus preventing the natural circulu- ! tlon of the sap required to fully nour'sli the trees. In the earlier stages of their growth the larvae generally attack the alburnum, or the softer layer of wood nearer the bark. When their horny jaws develop ttey begin to eat into the inner or solid wood of the trees. The impairment of il,e health and rate of decay of tho trees depends on the number of larvae tunnelliiithe:r stems. As the trees decay they ate ; assailed by several spede-i of parasitic fungi that sap the juice from the liurk, ano i also hasten their decay. The larvae, or i grubs, causing the destruction of the trees j belong lo two distinct groups of insects. Tic large uliite gTub, with horny head and jaws. Is that of the so-called puriri moth. It also tunnels the stems of many' other species of both indigenous and Introduced and forest trees. Of the 93,000 species of butterflies and moths known to ] science this large Inseet, which may be seen almost anv night hovering around the electric arc lights In the streets, is the largest and most beautiful green moth in the world. The second larva is .that of a species of "scorpion." by which name they are known to school children. They are generally known uS the weta. They are very destructive when boring the outer soft wood of fruit and forest trees, utile the perfect Insect may often bo found In decayed hollow logs, IJotli species generally attack the stems of lemon trees near the base of the stem. In most species of fruit trees It is of great, advantage to train them up with several feet of clear stem. To obviate the attacks of Insects the stems could be bound round tightly with sacking or other material. Spraying the stems and thicker parts of the branches Willi almost any slightly ndl'csive strong solution acts as a deterrent to these insects. With fruit at the enormously •high cost ruling at present, owners of largo or small orchards should endeavor by every means to render their trees healthy and as fruitful as possible.—l am, etc., x- wws New Plymouth, 23rd Nov.