Agriculture Reference
In-Depth Information
dusts or sprays at the beginning of, during, or immediately after rain or other
wetting event.
Table 10.2 will guide you on how much time is available to apply the fun-
gicide. Once lesions develop on the leaves and fruit, you will need to contin-
ue applying the fungicide through harvest to prevent secondary infections
by conidia. Particularly in long-season areas, consider applying post-harvest
fungicides to reduce the amount of pathogens that overwinter. Leaf damage
at this point is less serious than it would be earlier in the season.
Pear Scab
Pear scab is caused by
Venturia pirina,
a pathogen closely related to the one
that causes apple scab. Although pear scab can create serious damage, it is
more of a problem in Europe and Japan than in North America. Pear scab is
sometimes called black spot.
Symptoms.
Pear scab symptoms resemble those of apple scab. Unlike apple
scab, pear scab attacks small stems, creating lesions that produce more
spores and provide overwintering sites for the pathogen. Spores from the
stem lesions and last year's fallen leaves infect developing fruits and are
released over a 2-month period in spring and early summer. Infections on
young fruits usually begin on the blossom ends and move up along the sides
of the fruits. Small, velvety lesions darken to black points and can merge to
form extensive scabs. Infected fruits are often deformed. Leaf infections are
less common than for apple scab and appear as small, brown lesions, usually
on the undersides of the leaves.
Management.
Management methods are similar to those used for apple scab.
While some pear varieties are resistant to pear scab in one area of the coun-
try, they may not be so in other areas due to different strains of the patho-
gen. Keep a record of pear scab problems to help plan management for the
coming year. The same materials used to manage apple scab can be em-
