The Fruit Growing Industry.

Motueka Star, Volume I, Issue 22, 25 October 1901, Page 4

The Fruit Growing Industry.

A Mysterious Disease amongst Fruit Trees in the Motjeteka District. —o — For several yejp-s past apparently healthy fruit trees have soon after growth has commenced in the sprint suddenly wilted and died, especially Epps' seedling- apple trees over twenty years old. With-a view of giving information to fruit growers, the matter has been referred to Mr J. C. Blackmore, the Government Pomologist by the proprietors of the Motueka Star, in order to ascertain the true cause. He has very kindly supplied us with the following very instructive article, in respect of the cause of the disease,life history, and its prevention. The Root Rot Fungus Disease Of Fruit Trees The symptoms of this disease are so very characteristic that no one should have anydifficulty in determining whether it is present or not in the orchard. One prominent symptom of the disease is, the leaves of the fruit tree affected turn yellow during the growing season, or what is more usual wilt very rapidly, and remain on the limbs.' It. is perfectly useless to attempt to restore any tree shewing these symptoms to its normal condition. The disease is caused by several species of toadstools. The underground dark colored strands of these fungi penetrate the. bark of the root, and then produces between the bark and the wood, plates and threads of white miceluim. These threads and plates soon kill the parts with which they come in contact. The dark strands found adhering to the roots are called rhizomorphs, and are the characteristic underground parts of a certain toadstool. Occasionally the toad stool, producing these strands will be found in ciustres about the base of the tree ; though as a rule they do not appear until the tree is quite dead. The toadstool, like all fungi, reproduces by means of spores, and these spores, in the case of the toadstool, are found on the surface of the plates or gills thaffcare produced on the under side of the%ap of the toadstool. Each one of these minute white spores is able, upon germination, to produce some of the velvety white threads already mentioned, and the.-;e white strands may be formed into the long black strands, and these are then able to grow out through the soil to great distances, and when they come in contact with the root of one of the fruit trees, they are able to enter through the bark and then produce the disease ; but an entire orchard may be killed before a single one of the fruiting bodies, commonly called toadstools, appears about the base, of any of the trees. This is due to the fact that each small piece of the white threads produced by the germination of the spores is able to develop into the typical black strands, and infect new trees and from these strands are produced the toadstools. The disease is often very prevalent in those orchards which were planted on cleared timber land owing to the fungi having been at one time common as a parasite, and also a sapprophyte on various trees and shrubs or logs. Hence the decaying roots of trees remaining in the soil are apt to became fertile sources of the infecti >n of the healthy trees planted in that same soil. It follows, therefore, that all stumps and roots, as much as possible, should be removed and burned before the planting cf an orchard. Treatment. From the nature of the disease, the application of any fung'c'de is "of doubtful utility. Fruit trees, that are found diseased should be at once re,m">ved, care beiiig taken t:» burn not lily the trunk but all the larger rootf,

and especially all the diseased ones. It is not advisable to plant trees in holes from which diseased ones have just been removed, unless precautionary measures have been taken to rid the soil of all traces of the micelium of the fungus. When single trees in the midst of the orchard are found to be diseased, it is an excellent plan by way of remedial measures to prevent the further spread ox the disease by the underground strands of the fungus, to dig a ditch, say about one foot wide, and about two feet deep, with vertical walls, about ten feet from the tree, dependant upon the area occupied by its roots ; or a ditch may be dug, sufficient in area, so as to include all the trees in an affected group. As a further precautionary measnre, the burning of brush in the ditch will assist to kill the strands of the fungus, and prevent further spreading. The application of sulphate of iron to the soil about the tree has in some instances, when slightly affected, proved serviceable, but fungicides,, are apt to combine with other things present in the soil, and thus lose their usefulness. In regard to the particular species of fungus, which causes root rot of fruit trees in the colony, very' little careful study has so far been given to the wood destroying fungi which causes root rot of fruit and other trees. In Europe, agaricus melleus, the common honey mushroom, which is edidble, is responsible for the trouble ; also arrnellaria mellea.

In the United States of America, E. Mead Wilcox, Ph. D. Harvard, has recently discribed a rhizomorphs root rot of fruit trees, caused by clitoczbe parasitica, which is edible, and a common parasiti and saprophytic fungus on several species of oaks widely distributed. Root rot fungus of the raspberry, both in New Zealand, and Australia, is due to the fungus hypholoma f ascicularis and agric, very common in Britain. Root rot fungus of fiuit trees is probably due to arrnellaria mellea, so widely distributed over various portions of the world. Other species which may cause rhizomorphs root rot af fruit trees and other trees in this colony are as yet undetermined.

A meeting of fruitgrowers was held in the school room Ngatimoti, on Tuesday evening. Mr John A. Guy being in the chair. Mr J. 0. Blackmore Government Pomologist, gave an instiuctive addsess on general fruit culture. Those present were very much interested, and at the conclusion of the address several questions were asked and satisfactorily answered. Owinoto the limited attendance a desire was expressed that the lecture should be repeated, and Mr Blackmore kindly consented to re-deliver it on Friday week, the Ist of Novembea.