magnesium deficiency or unbalance. There was a
close relation between the amount of leaf scorch in August, 1950, and
the amount of winter injury, the coefficient of correlation being 0.97,
which is very highly significant. This coefficient means that 94 percent
of the winter injury sustained could be accounted for by the leaf scorch
present the preceding summer and early fall.

The scorch scores of August, 1951, show that there had been no
consistent improvement from the magnesium-deficiency condition as a
result of the dolomite and Epsom salt applications. The scores for the
disease caused by _Labrella_ show that applications of phosphorus alone
increased the incidence of the disease and those of potassium alone or
potassium plus nitrogen decreased it.

In all cases, the incidence of leaf scorch, winter injury, and disease
were strikingly different on the Reed and Potomac varieties. In the
summer of 1950, the total scorch score of the Reed variety was 26 and
that of the Potomac 18, and in August, 1951, the scores were 36 and 19,
respectively. The total winter injury scores were 46 for the Reed
variety and 21 for the Potomac. Thus, it is clearly evident that under
the conditions of this experiment the Reed variety was much more
susceptible to leaf scorch and to the winter injury resulting from
magnesium deficiency or unbalance between magnesium and calcium plus
potassium than was the variety Potomac. Furthermore, the total score for
the incidence of the disease caused by _Labrella coryli_ on the variety
Reed was 38 as compared with 9 for the Potomac variety. It would,
therefore, seem that the Reed is about four times as susceptible to
infection by this fungus as is the Potomac. Its less vigorous tree
growth, susceptibility to leaf scorch, winter injury, and infection by
_L. coryli_ may be due to the differences between its nutritional
requirements and those of the Potomac variety.

Conclusions and Summary

The preliminary results of the experiment described show that there is a
great difference in vigor, growth, flowering habit, susceptibility to
leaf scorch, winter injury, and infection with a fungus disease
tentatively believed to be caused by _L. coryli_ between trees of the
Reed and Potomac filbert varieties. In all cases the Potomac variety has
been the superior.

It would appear that much of the leaf scorch on filberts experienced in
the past has been due to a magnesium deficiency or to an unbalanced
cond