Biology Reference
In-Depth Information
widespread in Florida and occurs frequently in
California. Leaves are unusually large and dark
green, or very small and quickly shed, on twigs
that die back, with a reddish brown gummy dis-
charge. Citrus fruits are bumpy and drop, or have
insipid flavor and dry pulp. Application of copper
sulfate to the soil corrects the deficiency, but
often spraying trees once or twice in the spring
with bordeaux mixture provides sufficient copper
indirectly. Spraying almonds with a copper che-
late has prevented shriveling of kernels. Muck or
peat soils in New York, formerly unproductive,
now grow normal crops of onions and lettuce
with the addition of copper sulfate. On copper-
deficient Florida soils, many truck crops fail to
grow or are stunted, bleached, and chlorotic.
DDT Injury
Foliage of some plants - cucurbits particularly,
roses occasionally - turns yellow or orange, often
with stunting. Certain camellia varieties have
been injured when shrubs are under trees sprayed
with DDT. Continued spraying with DDT builds
up a residue in the soil which may eventually
have a toxic effect on the root system, the effect
varying with the type of soil and plant.
Dieback
This is due to deficiency or excess of moisture,
nutrients; winter injury; also cankers, nematodes,
borers.
Copper Spray Injury
Drought
Some fixed copper sprays are less injurious than
bordeaux mixture, but all coppers may be harm-
ful to some plants under some conditions. Foliage
spots are small, numerous, reddish, sometimes
brown. In peach leaves the centers of the spots
may fall out, leaving shot holes. Rosaceous plants
follow spotting with yellowing and dropping of
leaves. Even mild coppers may be injurious if the
temperature is below 55
F, or the weather con-
tinues rainy or cloudy. Treated leaves are often
harsher than normal and more subject to frost
injury. Dwarfing and stunting are important
symptoms on many crops, especially cucurbits.
Tomato flowering is injured or delayed; apple and
tomato fruits are russeted. Tree roots are injured
by overflow from pools treated with copper for
algae.
The effects of a prolonged dry period may be
evident in trees and shrubs for two or three
years thereafter.
End Spot
End Spot of avocado. Unequal maturity in both
ends of the fruit seems to be a factor in withering,
spotting, and cracking at lower end. Pick
promptly, instead of leaving on trees.
Exanthema
Copper deficiency, in fruits.
Cork
Frost Injury
Boron deficiency, in apple.
This injury is caused by low temperature after
plants have started growth in spring or before
they are dormant in fall (see
Winter Injury
for freezing during the dormant period). Yellow
color of some leaves in early spring is due
to temperatures unfavorable for chlorophyll
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Cracked Stem
Boron deficiency, in rhubarb, celery.
