Agriculture Reference
In-Depth Information
you would when managing apple scab. Early-season sprays used to control
scab usually control leaf spot as well. Because older leaves and shoots are
susceptible to infection, you must continue sprays later into the year than
for scab. In Pennsylvania, one fungicide spray applied in June and another in
July are usually sufficient. In more southerly locations, fungicide sprays dur-
ing mid-August and September are also recommended, particularly during
wet weather and on late-ripening varieties such as 'Bosc' pear.
Sooty Blotch and Flyspeck
These are common problems on apples, pears, and quinces in eastern North
America. The diseases are caused by different pathogens, but they are usu-
ally discussed together because they behave similarly and are controlled in
the same ways. These pathogens create superficial symptoms on the fruit
surfaces. Although not damaging to the trees, cosmetic damage reduces the
marketability of the fruit.
Symptoms.
Sooty blotch symptoms include from one to many greenish or
soot-colored colonies on the fruit surfaces. These symptoms may develop in
as little as 3 to 4 weeks after petal fall but more commonly appear in mid-
to late summer. Symptoms may not appear until the fruits are in cold stor-
age. Flyspeck symptoms appear as small, circular patches of up to about 50
black spots on the fruit skin. Infected fruits have one to many such patches.
The timing of infection and appearance of disease symptoms are similar to
those for sooty blotch. Primary infections usually occur 2 to 3 weeks after
petal fall, and secondary infections can develop in mid- to late summer dur-
ing wet years.
The pathogens overwinter on infected twigs on the fruit trees and many
other species of woody plants. Especially common and serious reservoirs
are raspberries and blackberries, which should be removed from hedgerows.
High humidity (greater than 90 percent) greatly increases the occurrence
