Biology Reference
In-Depth Information
in greenhouses. Covering the paint with a paste of
dry lime sulfur mixed with lime, flour, and water
reduced the amount of toxic vapor.
Little Leaf
Little Leaf, on almond, apricot, avocado and
other fruits.
Zinc Deficiency.
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Molybdenum Toxicity
Magnesium Deficiency
Cause of whiptail in broccoli and cabbage, chlo-
rosis of citrus in Florida, of grapes in Michigan.
Citrus leaves have large interveinal yellow spots
with gum on undersurface and may fall. Injecting
the trunk with sodium molybdenate has corrected
the condition quickly. On grapes chlorosis of
terminal leaves was attributed to molybdenum
deficiency correlated with nitrogen toxicity and
was corrected by adding 0.01 ppm molybdic acid
to nutrient solutions.
Large areas in the Atlantic and Gulf Coast truck crop
regions are low in magnesium because of natural
lack of magnesium rock, extensive leaching from
heavy rainfall, removal of large quantities in crops,
and use of fertilizers lacking this element. In toma-
toes, veins remain dark green while rest of leaf is
yellow or chlorotic. Cabbages have lower leaves
puckered, chlorotic, mottled, turning white at the
margin and in center. In strawberries, leaves are
thin, bright green, then with necrotic blotches. On
fruit trees, fawn-colored patches are formed on
mature, large leaves, with affected leaves dropping
progressively toward the tip. In flowering plants
there are a greatly reduced rate of growth, yellowing
between veins of lower leaves, sometimes dead
areas between veins, sometimes puckering.
Control by using dolomitic limestone, or with
fertilizers containing magnesium, or with Epsom
salts (magnesium sulfate) around azaleas and
other shrubs in home gardens.
Mottle Leaf
Zinc deficiency.
Nitrogen Deficiency
Symptoms are paleness or uniform yellowing of
leaves, and stems, firing or burning of lower
leaves, sometimes red pigments along veins,
stunted growth, reduced yield with small fruit.
Immediate results can be obtained by side-
dressing with a quickly available nitrogenous
fertilizer, but long-range planning includes use
of legumes in the rotation, green-manure crops,
and balanced fertilizers. Urea is recommended
for turf, one application providing a slow release
through the season.
Manganese Deficiency
Top leaves become yellow between veins, but
even smallest veins retain green color, giving
a netted appearance. Lower the pH below 7 and
add manganese sulfate to the soil.
Marginal Browning
Nitrogen Excess
Potassium deficiency or hopperburn.
Too much nitrogen leads to overdevelopment of
vegetative growth at the expense of flowers and
fruit; to bud drop of roses, sweet peas, and toma-
toes; and, in high concentrations, to stunting, chlo-
rosis, and death. Excessive nitrogen decreases
resistance to winter injury and to such diseases as
fire blight, powdery mildew, and apple scab.
Mercury Toxicity
Roses are extremely sensitive to mercury vapor
and have been gravely injured when paints
containing mercury were used to paint sash bars
