Biology Reference
In-Depth Information
Gnomonia caryae
Hickory Anthracnose
,
Leaf
Spot
, widespread. The disease is common in
eastern states, causing defoliation in wet seasons.
Large, roundish spots are reddish brown on upper
leaf surface, dull brown underneath. The fruiting
bodies are minute brown specks, and the fungus
winters in dead leaves on the ground.
Gnomonia leptostyla (
Marssonina juglandis
).
Walnut Anthracnose
,
Leaf Spot
, general on but-
ternut, hickory, and walnut. Spring infection
comes from ascospores shot from dead leaves
on the ground, secondary infection from conidia.
Irregular dark brown spots appear on leaflets in
early summer; if these are numerous, there is
defoliation. An unthrifty condition of black wal-
nuts and butternuts is often due to anthracnose.
Monographella opuntiae (formerly
Mycosphaerella opuntiae
).
Cactus Anthracnose
on Cereus, Echinocactus, Mammillaria, and
Opuntia. The curved spores of the anamorph
state (
Microdochium lunatum
) form light pink
pustules on the surface of moist, light brown rotten
areas. Cut out and destroy diseased segments.
Pezicula
Ascomycetes, Helotiales
This is one of the discomycetes, cup fungi. The
apothecia, formed on living plants, are fleshy,
bright-colored with a peridium of dark cells
forming a pseudoparenchyma. Spores are hya-
line, fusoid.
Pezicula malicorticis (formerly
Neofabraea
malicorticis
).
Northwestern Apple Anthracnose
on apple, crabapple, pear, quince, chiefly in the
Pacific Northwest, where it is a native disease,
serious in regions with heavy rainfall. Cankers are
formed on younger branches - elliptical, dark,
sunken, up to 3 or 4 inches wide and 10 to 12 inches
long, delimited when mature by a crack in the bark.
Conidia of the anamorph state (
Gloeosporium
malicorticis
) are formed in cream-colored cushions,
which turn black with age, in slits in the bark.
Young cankers, reddish brown, circular spots
appear on the bark in late fall. Fruit is infected,
usually through lenticels from either ascospores or
conidia in pustules on bark, but the disease may not
show up until the apples are in storage.
Control
Cut out diseased limbs or excise can-
kers, burning all prunings and dead bark. Spray
with bordeaux mixture before fruit is picked and
fall rains start; repeat after harvest, and again
about 2 weeks later.
Microdochium
Deuteromycetes, Coelomycetes
Hyaline, two-celled spores are formed in acervuli
without setae. Spores are rounded at ends and are
formed in pale to black masses on leaves.
Microdochium panattonianum (formerly
Marssonina panattoniana
).
Lettuce Anthrac-
nose
. Small, dead, brown spots appear on blades
and petioles, centers often falling out leaving
black margined shot holes. Spots progress from
older to young inner leaves; outer leaves are
broken off and blown around by wind. The dis-
ease is important only during prolonged periods
of wet weather, when it may cause heavy losses.
Sanitary measures and treating seed before plant-
ing suffice for control.
Monographella
Ascomycetes, Dothideales
Phlyctema
Deuteromycetes, Coleomycetes
Perithecia immersed in substratum, not beaked,
not setose, paraphyses lacking; spores hyaline,
two-celled. The genus contains more than 1,000
species, many destructive to plants, with conidial
stages in many genera.
Pycnidia dark, separate or sometimes cofluent,
developing in or under the epidermis or bark.
Conidiophores simle or forked; conidia hyaline,
