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Brown Rot (fungus - Monilinia sp.): Only the blossom blight phase of brown rot has been observed in Texas and it is of minor importance. Brown rot may become more prevalent as mayhaws are commercialized.
Cedar-Quince
Rust (fungus - Gymnosporangium clavipes): Cedar- Quince Rust is the
most destructive disease on mayhaw. Infection takes place in spring. Fungal
spores for infection on mayhaw come from orange jelly-like growths on cedar
limbs - Eastern red cedar primarily (Photo).
These spores are windblown from up to a mile away, indicating the alternate
host for cedar-quince rust does not have to be in close proximity. Mayhaw fruit
is more susceptible than young twigs. Leaves are seldom infected. After colonizing
fruit the fungus erupts through the epidermis forming tubular orange structures
full of spores Photo) that
can only infect cedar or some similar alternate host. Infectious cankers on
cedar are perennial. Therefore, yearly re-infection of cedar is not necessary
to keep the disease active. Heavily infected mayhaw fruit does not ripen properly
and is of no value. Fungicide protection up to four weeks after bloom or until
fungal eruptions on cedar cease is essential for control. Fungicides are being
developed but are not currently available.
Fire
Blight (bacterium - Erwinia amylovora): The bacterium is spread by
wind, rain and insects during bloom. Infected blooms die. Invading bacteria
progress into tender shoots causing a shoot blight. The bacterium becomes inactive
in hot weather. This is a spring and early summer disease that is generally
not encountered every year.
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