Biology Reference
In-Depth Information
Arsenical Injury
Black Root
Leaves of peaches, apricots, and other stone fruits
are readily spotted or burned with lead arsenate
unless lime or zinc sulfate is added as a corrective.
There may be similar leaf spotting and defoliation
when these tender fruits are grown in old apple land
that has accumulated a residue of lead arsenate over
a period of years. Even apple trees can be severely
injured by arsenical sprays under some conditions.
Defective soil drainage and accumulation of
toxins are associated with black roots, but so too
are soil fungi and root nematodes.
Blasting
Blasting of influorescence and failure to produce
seeds. These symptoms seem associated with
extremes of soil moisture, too wet or too dry, at
blossom time. Onion Blast, prevalent in the Con-
necticut Valley, appears within a few hours after
bright sunshine follows cloudy, wet weather.
Leaf tips are first white, then brown.
Baldhead
In beans this is loss of the growing point, due to
mechanical injury in threshing seed.
Bitter Pit
Blindness
On apples this is called stippen or Baldwin spot
and is characterized by small, circular, slightly
sunken spots on fruit, increasing in storage, espe-
cially at warm temperatures, most frequent on
varieties Jonathan, Baldwin, Spy, Rhode Island
Greening. It seems to be related to fluctuation of
the moisture supply in soil and increased by
abundant rainfall shortly before harvest. On
pear, bitter pit is sometimes associated with mois-
ture deficiency; in olives, with overnutrition.
Blindness of tulips and other bulbs. Failure to
flower may be due to Botrytis blight or other
disease, but it may come from root failure in dry
soil or from heating of bulbs in storage or transit.
Too early forcing may result in blindness.
Blossom-End Rot
Very common on tomatoes, also on pepper,
squash, watermelon. The tissues at the blossom
end of the fruit shrink, causing a dark, flattened or
sunken, leathery spot, which may include nearly
half the fruit (see
Fig. 1
). The disease is most
common on plants that have had an excess of
rainfall in the early part of the season, followed
by a period of drought. There are, however, var-
ious contributing factors, the most important
being a deficiency of calcium, which is needed
for synthesis of rigid cell walls of the tomato.
Adding calcium oxide to the soil or spraying
with 1 % calcium chloride has reduced the dis-
ease. For home gardens, deep soil preparation,
use of a complete balanced fertilizer, and
mulching to conserve moisture should help.
Black End
In pear, the whole blossom end of the fruit may turn
black and dry; the disease appears when oriental
pear rootstocks are used in poor soil. In walnut,
black end of nuts is probably drought injury.
Black Heart
In beets, this is generally boron deficiency (see
below); occasionally it is potassium or phospho-
rus deficiency. In apple wood it may be freezing
injury; in potatoes, lack of oxygen; in celery,
fluctuating soil moisture.
