This rot is known to every housewife who has bought a basket of peaches for canning and had to wait a
day before getting to it, and to any gardener who has a peach, cherry, or
plum in the backyard. Rotting fruits are covered with grayish cushions of
spores and later wrinkled, dried, mummied fruit is left hanging on bare
trees (Figure 44A). Some mummies fall to the ground, and if they are
kept moist over winter send up apothecia which eject spores to infect
blossoms overhead. Mummies on the trees produce a fresh crop of conidia
in spore cushions, and these are blown by wind or splashed by rain to
blossoms and young fruits, with secondary infection going from fruit to
fruit. The fungus often enters through wounds made by plum curculios
or oriental fruit moths.
Control. Pick mummies off trees, rake up and bury deeply fallen mummies. The standard spray schedule calls for wettable sulfur, at the rate
of 6 pounds per 100 gallons, applied at pink bud, blossom, and shuck
fall, repeated in 2 or 3 weeks and again 2 to 4 weeks before fruit ripens.
Sulfur dusts, applied somewhat more frequently, can be used for dwarf
trees. Phygon has been used for brown rot, and the new organic fungicides captan (Orthocide 406) and Manzate seem promising for practical
lontrol. Spraying to control insects making wounds on fruit will reduce
CROWN ROT, SOUTHERN BLIGHT (Pellicularia (Sclerotium) rolfsii),
mustard seed disease appearing on hundreds of plant species all
over the country in warm, humid weather. The fungus has at least two
strains, possibly species. We call the effect produced by the northern strain
"crown rot" and the other "southern blight," but the signs are the same.
White wefts or fans of mycelium spread up the stem from the base
(Figure 44C) and over the ground in wet weather. Small, roundish
sclerotia, first white then reddish tan or light brown, resembling mustard
seed, are formed in the mycelium. They may be numerous enough to
form a reddish crust over the soil for several inches around the stem, or_
they may be sparse. They can be formed as far down in the soil as
roots go, and they are equipped with a hard coat which lets them survive
a year or two in the soil after host plants die.
Plants wilt because of rotting at the crown. Delphiniums, very susceptible, often break over near ground level. Phlox, ageratum, and a great
number of ornamentals are subject to crown rot, even hosta. Ajuga melts
down to nothing in the first warm spell. In the South, vegetables-
tomatoes, beets, carrots, and plants with fleshy roots-are hard hit. Bulbous plants, iris and narcissus, succumb, and sometimes azaleas and other
shrubs are affected though the disease is more common on herbaceous
rather dian woody plants.