light
prevalent at the present season in the different walnut growing
sections. Again, the immunity from blight of a particular tree for one
season may be followed by more or less prevalency of blight on the same
tree the next season. The degree of resistance must be tested out
through a number of years before any variety can be pronounced resistant
to this disease. The observations must also be carried out in different
localities as certain varieties seem to behave differently on different
soils and when growing under different climatic conditions.

Some varieties seem to avoid the blight the majority of the seasons but
really have little or no resistant qualities when the seasonal
conditions and the growth of the plant happen to coincide with the most
favorable time for the spread of the disease. An example of this is seen
in the Eureka variety the present season. While this variety has
maintained a reputation during a majority of seasons for freedom from
blight, during the present year the Eureka is badly diseased in certain
sections of Orange County. This may, perhaps, be explained by the
prevalence of damp, cloudy weather for about a week or ten days during
the first of May when this variety was in full bloom. In one grove under
observation the trees were thought to have lost at least 50 per cent of
their blossoms soon after blooming. At the present time on these same
trees, 32 per cent of the nuts are afflicted with more or less blight.
To be sure, some of these will likely mature, but the appearance of
blight on nearly one third of the crop shows that this variety has very
little resistant power against walnut blight. Its freedom from disease
in the past has no doubt been due largely to its dormancy during the
most favorable weather conditions for the spread of blight.

The field for the selection of blight resistant varieties must
necessarily be in the badly blighted sections. A tree with only 10 per
cent blighted nuts in an orchard having an average of 70 per cent to 80
per cent may really be more resistant to blight than a variety which
appears to be positively free from the disease when growing among trees
which are only 15 per cent to 20 per cent blighted. In making
observations and selections, therefore, it is quite as important to know
the amount of blight on the surrounding trees and the grove, as a whole,
as it is to know the prevalence of blight on the selected individual.
The extreme variation of diff