Biology Reference
In-Depth Information
at the base of trees before the tops show more
than a slight yellowing or lack of vigor; but if
soil is removed from the root crown, many
lateral roots are found dead, and often the
taproot is also gone. Infection starts at some
point on the lateral roots, spreads to the base of
the tree, and then to other roots. Sometimes
there is gumming at the crown extending
upward on the trunk. Mycelial fans or sheets
are present between bark and wood; the clus-
ters of mushrooms developing at the base are
similar to those of
Armillaria
,buttheblack
shoestring rhizomorphs are lacking. Instead,
there are sometimes black, hard stromatic out-
growths from fissures in bark of infected roots.
The fruiting clusters develop in fall, from mid-
September to December. The caps are light tan
to honey-colored, 2 to 3 1/2 inches in diameter.
The rot is most prevalent on land cleared of
oaks and other hardwoods, also on sandy, well-
drained land subject to drought.
Control
Citrus trees on sour orange stock are
quite resistant. Surgical treatment for fruits and
ornamental trees is often quite successful.
Remove the soil at least 2 or 3 feet from the
trunk, working carefully to avoid injuring healthy
roots. Cut off all dead roots, flush with the root
crown and remove any infected oak or foreign
roots in the vicinity. Cut out dead and infected
bark at the root crown or the base of the trunk,
being sure to collect all chips (on heavy paper
placed under exposed roots) for burning. Paint all
exposed surfaces with a pruning wound com-
pound and fill in partially, disinfesting the soil
with bordeaux mixture. The root crown can be
left exposed to aeration and drying or, if too large
a proportion of the root system has been lost, new
roots can be stimulated by mounding the soil
around the base to a height of several inches
above the partial girdle. The new roots will
come from callus formed at the margin of living
bark.
Trenches 2 or 3 feet deep will aid in
preventing spread to healthy trees. Fallow soil
can be treated with carbon disulfide;
Clitocybe
Armillaria
tabescens
).
Mushroom Root Rot
,
Clitocybe
Root Rot
of citrus, pecan and other fruits and
many ornamentals.
tabescens (see
▶
Colletotrichum
▶
Anthracnose
.
Colletotrichum acutatum
Bitter Rot
of apple
fruit; fruit rot of grape.
Colletotrichum capsici
Ripe Rot
of pepper,
Boll
Rot
of Cotton.
Colletotrichum circinans
Onion Smudge
,
surface rot, also on shallot, garlic and leek.
Bulb or neck has a dark green or black smudge,
often covered with stiff bristles of the acervuli of
the fungus. Smudge is more prominent in white
onions; it is confined to the neck of colored
bulbs. The fungus winters on mature onions, on
sets or in soil. It develops in the field at
a fairly high temperature and soil moisture with
most of the damage just before harvest. Cure
rapidly after harvest; rotate crops; clean up
debris; change to colored onions if the rot is too
serious on white.
Colletotrichum coccodes
Root Rot
and
Wilt
of
greenhouse tomato.
Colletotrichum gloeosporioides
Fruit Rot
of
grape and pepper.
Colletotrichum gloeosporioides (formerly
Colletotrichum nigrum
).
Fruit Rot
of pepper,
probably general on pepper in South and East.
The fungus is a wound parasite on pepper pods.
The spots are irregular, indefinite, depressed,
blackish. Numerous acervuli with stout setae are
scattered over spots.
Colletotrichum lilii
Black Scale Rot
of
Easter lily,
Brown Scale
. First noticed in Louisi-
ana in 1937, the rot immediately threatened the
lily industry in that section. Bulbs are brown to
nearly black when dug, with outer scales most
affected. Young lesions start as irregular light
brown areas, then become black and sunken
owing to collapse of epidermal cells and subepi-
dermal layers. Oldest lesions are nearly
black, with tissue dry and shriveled. Stems
and roots are not affected. The acervuli are
Armillaria
▶
mellea
.
Clitocybe monadelpha (see
Armillaria
▶
tabescens
). On privet, apple.
