Biology Reference
In-Depth Information
interveinal areas. Terminal growth of twigs is
small, and the shrub or tree is generally stunted.
To obtain a quick response it is possible to
spray leaves with a solution of ferrous sulfate.
More lasting is a soil treatment of a 50-50 mix-
ture of ferrous sulfate and sulfur.
Rather recent is the use of chelated iron, sold
as Sequestrene and under other trade names. In
this form the iron cannot be combined with soil
elements and remains available to the plant even
under alkaline conditions. The solution, prepared
according to directions on the package, is poured
on the soil around the unthrifty bush, and often
the green color returns in a matter of days. Iron
chelates are now extensively used for citrus and
for ornamentals.
Leaf Scorch
Leaf Scorch, of maple, horse-chestnut, beech,
walnut, and other trees. Scattered areas in the
leaf, between the veins or along the margins,
turn light or dark brown, with all the leaves on
a branch affected more or less uniformly. The
canopy of the tree looks dry and scorched; leaves
may dry and fall, with new leaves formed in
summer. Lack of fruiting bodies distinguishes
scorch from a fungus leaf blotch. It appears dur-
ing periods of high temperature and drying winds
and often after a rainy period has produced suc-
culent growth.
Leaf scorch of Easter lilies has been a problem
for years but can be prevented by keeping the pH
of soil near 7.0 with lime, adequate nitrogen, but
low phosphorus. It may have some connection
with root rots.
Leaf scorch of iris has puzzled amateur
growers in the past few years; it is more serious
in the Southwest but has appeared in gardens
elsewhere. Leaves turn bright reddish brown at
the tips in spring before flowering, and in a few
days the whole fan is scorched and withered, and
the roots have rotted with a reddish discoloration
(see
Fig. 4
). Many theories, including nutrition
and nematodes, have been advanced, but there is
no general agreement as to cause.
Fig. 4
Scorch in Iris
Lightning Injury
Trees may be completely shattered or a narrow
strip of bark and a shallow layer of wood torn
down the trunk. Tall trees or those growing in the
open are most likely to be struck. Valuable trees
can be protected with lightning conductors,
installed by a competent tree expert.
Lime-Induced Chlorosis
Plants are sickly, with yellow foliage, in calcare-
ous soils or near cement foundations.
Iron
▶
Deficiency.
