year.  The percentages which follow the varieties named were determined by counting at least 100 nuts on a tree just before the blighted nuts began to drop.  In a seedling grove in the Whittier district about 300 trees were examined and 100 nuts counted on each tree.  The individual trees varied from 2 per cent to 85 per cent blighted nuts, while the grove as a whole averaged 25 per cent.  There were at least a dozen or fifteen trees in this grove which were blighted less than 10 per cent, although some of the nearby trees were blighted as high as 60 per cent or 70 per cent.

Another seedling grove in Orange County which was counted in the same way, averaged 47 per cent blighted nuts during the second week in June.  In making this determination 105 trees were examined.  In this same grove, there were, however, at least three trees which averaged less than 6 per cent blighted nuts.

It is interesting to know that the Placentia variety, growing within a stone’s throw of the aforementioned seedling grove and under identical cultural conditions, was blighted to the extent of 71.9 per cent on the same date.

Observations of the Prolific (Ware’s) in the vicinity of the above mentioned grove, showed less than 1 per cent blighted nuts on the trees and practically none of the nuts have dropped to the ground at the present time, yet in the past this variety has not had a reputation for disease immunity.  The original Chase tree was observed during this time and showed a percentage of 37 per cent blighted nuts.  These examples are given neither in support of any particular variety nor to discredit others, but are noted merely to call attention to the wide variation, and this variation is a great source of encouragement in our endeavors to produce a disease resistant variety.

Of course blight immunity is not the only factor to be considered in selecting a variety of walnut.  A profitable yield of good commercial nuts is the real test of the superiority of any variety.  A very heavy yielding tree with a small amount of blight may prove more profitable than a light yielding variety that is totally immune to this disease.

The production of a medium grade nut which would grade only as a seedling No 1, might prove more profitable if the tree is at least partially blight immune than the production of such a high grade nut as the Placentia with its susceptibility to blight.  These things must be considered and weighed carefully by the growers who are planting walnuts in the blight sections.  The various areas where walnut blight is not a factor might profitably sacrifice heavy production to superior quality.

From our present knowledge it is very apparent that the disease resistance of individual trees varies considerably from year to year and under different soil and climatic conditions.  The thorough testing of resistant varieties will require considerable time.

Nut Characteristics