growing in size, although the
infection may not be noticeable until later. These infected areas, even
though they are small and not numerous enough to cause the leaf to fall,
seriously impair the functioning of the leaf out of all proportion to
the area directly affected. Should the infection be so severe as to
cause premature defoliation, the damage will be great even though only a
small percentage of the leaves falls. The disease of eastern Mack walnut
known as leaf spot, or anthracnose, is one of these defoliating diseases
that causes untold damage from poorly filled nuts in the current crop
year, and results in a small crop or none at all the following year. The
development and spread of these diseases is gradual, and unsuspecting
growers do not realize the damage they cause.

On other hand, the injuries caused by such insects as the webworm, the
walnut caterpillar, the pecan leaf case-bearer, the Japanese beetle, and
others are somewhat spectacular in that the leaves may be partly or
completely consumed on portions of the trees. The injury caused by the
walnut aphis, the walnut lace bug, the pecan black aphis, and others, on
the other hand, is less conspicuous; but the end result is far more
serious than it usually is with the leaf eating insects, because the
damage caused is more widespread, almost all of the leaves on a tree
being affected. These sucking insects are small in size and may be
overlooked until premature defoliation takes place. If nut trees are to
bear satisfactory crops of well filled nuts, the diseases and insects
that attack and cause injury to the leaves must be controlled. Under
normal conditions the size of the crop produced, the regularity of
bearing, and the quality of the nuts harvested is proportional to the
leaf area of normal leaves carried by the tree from early spring until
freezing-weather in the fall.

+Second growth of the trees:+ Certain of our nut trees, such as pecan and
walnuts, under some conditions have two or perhaps more periods of shoot
growth during the same growing season. The first, or main period of
growth, starts at the time of foliation in the spring and ends soon
after the shoots flower. The second period of growth, if it occurs, may
begin any time after the nuts are set, and may end any time later. This
second growth seriously affects the filling of the nuts, in that food
materials are consumed in producing this second growth rather than in
the growth and filling o