WALNUT-BLIGHT.

New Zealand Journal of Agriculture, Volume XXVII, Issue 1, 20 July 1923, Page 25

WALNUT-BLIGHT.

INTRODUCTION OF IMMUNE VARIETY BY THE DEPARTMENT.

Horticulture Division.

The ravages of the bacterial disease of walnuts (Pseudomonas juglandis} has rendered walnut-growing very precariousso much so, indeed, that the Department does not think it wise while the present conditions obtain to encourage the extensive planting of the tree for the production of nuts.' The present condition of the noted walnut-groves at Akaroa is well known. A few years ago these groves were a good source of income to their owners. During the past few years the blight has attacked the trees, and their production has dwindled to' an almost negligible quantity. . ■

This blight is not confined to New Zealand ; it is a serious pest wherever walnuts are grown. Owing to its bacterial nature spraying is useless, and no other way of controlling it on affected trees has yet been discovered. The hope for the future appears to be in working the desired varieties on stocks immune to the bacterial disease. It has long been known that in California the native black - walnut (Juglans Hindsii) is - used for the purpose; This species is a very strong grower, makes a very handsome tree, and is the favourite avenue tree in California. It is immune to the bacterial disease, and has been proved to be suitable as a stock. The nuts it bears are similar to other walnuts, but are smaller. They, have exceedingly thick shells and only a small amount of meat.

Six years ago the Department sent an order to ■ California for a bushel of these nuts, but in spite of repeated inquiries the nuts were not received till March of last year. On receipt of the nuts arrangements were, made with the Nurserymen’s Association for the nuts to be distributed to leading nurserymen, they agreeing to raise the trees and to use them for working commercial varieties. Under this arrangement a considerable number of trees should be available for purchase in the spring of 1924 or 1925.

The former practice was to raise trees . from nuts. The resultant trees would bear fruit when from nine to. twelve years old, except in cases where the trees, , being in - unsuitable soil, became stunted. They might then bear earlier, . but would never make thrifty trees. Budded trees usually begin to bear nuts at. the third year in fact, nuts were frequently produced by young trees in the nursery rows. It will be seen that it pays to wait even a few years for budded trees.

During the currency of the Panama - Pacific Exposition, at San Francisco, in ' 1915, Mr. E. Clifton, the New Zealand Commissioner, sent us a small parcel of Juglans Hindsii nuts. Trees raised from these nuts are now growing, at . Te Kauwhata Horticultural Station, and in a few years’ time should be a source from which nuts , can be obtained for raising stocks.