Spray shoots as they come up in spring with Fermate (1 ounce in 4
gallons water) or bordeaux mixture, repeating for a month or so at 10-day
intervals. Fermate dust can be used.
TULIP BOTRYTIS BLIGHT (Botrytis tulipae),
tulip fire, a general problem.
Plants from infected bulbs are often stunted, with buds blasted;
leaves sometimes have large light patches resembling frost injury (Figure
13B). When gray mold forms on affected parts, spores are splashed by
rain to nearby tulips, causing myriads of small white spots on colored
petals, brown spots on white flowers. In another day or two such a flower
is covered with its own mold, ready to infect more and more tulips. Small
black sclerotia are formed in leaves and petals as they rot into the ground,
and also on bulbs.
Control. Practice strict sanitation. Inspect bulbs before planting; discard
those showing sclerotia. When a whole plant is blighted in spring, dig
out immediately. Cut fading flowers into a paper bag instead of letting
petals rot on ground. Cut foliage at ground level as soon as it ripens and
turns yellow. Spraying weekly, before blooming, with Fermate or Zerlate
v somewhat helpful. If this disease has been present for some years in
your garden, plant new healthy bulbs in a different location.
Early blight (Cercospora apit) is characterized by small
yellow leaf spots which change to large irregular ash-gray regions.
The spores are splashed by rain or carried on tools or gardener's trousers
through the patch. In late blight (Septoria apii and 5. apii-graveolentis)
the spots on leaves and stalks are covered with small black dots, fruiting
bodies of the fungus.
Control. Unless seed is 2 years old, tie in cheesecloth and treat with
calomel. Spray or dust with Dithane Z-78, Parzate, Zerlate, or with a
fixed copper, starting in the seedbed. Rotate crops; clean up all refuse at
end of season.
FIRE BLIGHT (Erwinia amylovord).
This is a serious bacterial disease of
pear, quince, apple, and related species, including hawthorn, mountain-ash, pyracantha, and cotoneaster. Many pear orchards have been
wiped out. Blossoms and leaves of infected twigs suddenly turn dark
brown to black, shrivel and die, but remain attached to twigs. Blighted
branches thus appear to have been scorched by fire.
The bacteria survive the winter in holdover cankers on the limbs. These
are slightly sunken areas with a definite margin at the base of branches.
In spring, drops of bacterial ooze appear, to be carried by rain and insects
to blossoms, leaves, and fruit.