er injury on
May 10, 1951. By August 3, leaf scorch was evident on trees in certain
treatments and the trees were scored for leaf scorch. At this time it
was found in certain treatments that the trees that had not shown any
appreciable amount of scorch heretofore had some severely necrotic
leaves on them. Careful examination revealed many fruiting bodies of one
or more fungi in these necrotic areas. Each tree was, therefore, scored
for the presence of this disease, which has been tentatively identified
by Paul L. Lentz, of this Bureau, as being caused by _Labrella coryli_.
The data on leaf scorch, winter injury, and the fungus disease are given
in table 2.

Table 2. Relation of magnesium deficiency in filbert leaves to leaf
scorch, winter injury, and disease caused by _Labrella coryli_

______________________________________________________________________

Ratio Scorch[1] Winter[2] Scorch[1] Disease[1]
Treatment Mg (percent) score injury score score score
K (percent) (1950) (spring, 1951) (1951) (1951)
______________________________________________________________________
1. Nitrogen .151 1 4 7 9
2. Phosphorus .210 1 3 1 11
3. Potassium .094 21 22 24 3
4. Complete .112 2 5 8 11
5. Nitrogen
and potassium .073 13 19 9 5
6. Check .167 14 6 6 8

Note 1: Total plot score for 12 trees; highest possible score 36.
The scale for scoring was 0, none; 1, light; 3, severe.

Note 2: Total plot score for 12 trees; highest possible score 48.
The scale for scoring winter injury was 0, full leaf, no injury; 1,
few dead twigs; 2, half of buds not growing; 3, very large amount
of dead twigs; 4, only a few buds growing.

Trees that had received potassium alone had the most severely scorched
leaves and more of them on August 15, 1950, followed by those that had
received nitrogen plus potassium. The trees that had received nitrogen
or phosphorus alone showed practically no scorch, each having a total
score of 1; and the complete fertilizer trees a total score of only 2,
while those in the check had a total score of 6. These scores indicate
that scorch is related to