The Fruit Growing Industry.

Motueka Star, Volume I, Issue 25, 5 November 1901, Page 4

The Fruit Growing Industry.

In the imparting ; and dissemination of inforn ation pertaining to fruitgrowing, especial study is given by the Government Pomologist to investigations on ihe diseasi s of fruit order to obtain an accurate knowledge concerning the cause, life history, and their determination, as well as the conditions which are favorable for the production of the disease, a correct knowledge thus obtained, enables the devising of intelligent means to combat, either by restriction, or by complete eradication of the disease. Perhaps no plant malady has puzzled scientists, or caused greater* controversy amongst fruit growers, in regard to its exact nature and cause, than the following disease, concerning which Mr J. C. Blackmore has kindly furnished us with particulars.

An Obscure Disease.—Root Gall or Root Kxot of the Peach, Almond, Raspberry, and other Fruit Trees.

It is characterised by rough knott}* growths at the surface of the ground. This growth usually encircles the entire stem or main root at this point, and smaller knots frequently appear on the lateral roots deeper in the ground. They all have an irregular granularsurface, somewhat resembling, when young at least, the callous growth at the end of a cutting. The excrescences and enlargements upon the root and stem of the affected part vary in size, even occurring upon small roots, and less frequently upon the stem, at some distance above the ground. Although this disease has been prevalent, and well known for a long time both in Europe and America, its true cause was, until quite recently, unknown. In Germany the disease is known as warzelkropf, and is frequently believed to he the result of injury to the roots, received in cultivation or some other way. The disease has been noticed in New Zealand by the writer for some 3-ears past, on the roots of various fruit trees, as -well as the raspberry, but it does not seem to have spread much as yet. In the neighborhood' of Auckland peach trees have been reported as affected with this disease, anil very erroneous statements made in regard to its introduction and spread by the imported peach pips from California. Recent experiments, however, do not verify the statements made that the disease can be introduced through the agency of peach pips in the manner indicated. In some experiments carried out in America, it was found that the root gall trouble became communicated from diseased raspberries to peach trees set in the plantation. The cause of root knot (deudrophagus grobosus) has been under c< ndderation and inve t'g; tio 1 f >r some years, and the ultimate disposition of it by Professor T umay, as related in h s bulletin on the sul J 3C J , which gives the results of his studies, are that he has found that the merismatic cells of the gall or knot'are filled with the substance of a very delicate parasitic organism extremely difficult of detection owing to a great similarity, when in the active stage, to the natural protoplasm of the host plant. Organic bodies of this character are known as plasmodia, and are not usually parasitic, the only other well authenticated case being that of plasmodiophora, which produces the

club root in cabbages and other cruciferous plants. Professor Toumay has been able to follow the organism throout its life history, to observe the formation of the fruit, the production of the spores, and to demonstrate their innoculating power.

Since it is known that a slime mould fungus is the cause; of root knot, and that the disease may be transmitted and communicated to healthy tree roots by the agency of the galls, it is essential to the prevention and introduction and spread of tl e disease that the trees or plants should not be obtained from nurseries where the disease does exist. But it is not always possible to do this. The next best thing is to burn every tree found to be affected. Nurserymen can btsfc serve their interests, as well as their patrons, by destroying all such plants, and by taking every possible precaution to prevent the spread of the disease amongst nursery stock. Remedial Treatment,

On old trees that aie very badly infested, has not, in the main been very satisfactory. It may be well therefore, to completely destroy As regards those which, it is hoped, may be saved by treatment, by way of remedy it is suggested that the earth around the bole of the affected tree be removed of sufficient depth to enable an inspection to be made of the roots. Remove all signs of the disease with a clean cut : then apply a strong solu : tion of Bordeaux mixture to the wound caused by the removal of the affected portions; the earth removed around the collar replaced within a day or two. In order not to convey the disease to healthy trees, by the medium of tools used, disinfect the instrument employed in a strong solution. Another class of rocJt knot, or galls, which infests peach trees in the nurseries, is caused by nematodes, or eel worms. These parasitic worms are also destructive upon cucumbers under glrss, owing to a great extent, that nemotodes are often present in sod or decaying matter. Generally, the only effective remedy against eel worms, as regards the cucumber-, cbnsistsun steaming, or so heating the soil "'prior to putting out the plants, that the parasi ties will be destroyed. In cases where young peach trees are found infested with the minute worms, which produce the galls, and which are very easily distinguished from the root knots, previously described, they may be easily destroyed by freezing. Therefore in a very cold district the pest is not likely to be troublesome. When young peach trees are received infested with this pest, intended to be planted in districts with comparatively mild climate, it is a wise precaution to at once destroy the trees.