Introduction:
Apple scab is the primary apple disease of concern in the early
season. If not managed, the disease can cause extensive losses
following cool and wet weather conditions during the spring months.
Direct losses result from fruit infections and indirect losses
from defoliation, which can reduce tree vigor, winter hardiness
and subsequent yield. Pennsylvania apple growers must apply synthetic
fungicides on a regular basis to prevent infection. Over the last
several growing seasons there have been very few new fungicides
developed with different modes-of-action. This results in the
continued reliance of growers on the same fungicides to prevent
apple scab year after year. Experience has taught growers that
the continued use of a material, no matter how effective initially,
has resulted in the eventual loss of the fungicide through the
development of fungal resistance to the fungicide.
The risk for fungicide resistance is compounded in 2005 due to
the high level of apple scab on leaves in the orchards in the
fall of 2004. Apple scab on fallen leaves is at record levels
in Pennsylvania apple orchards this winter. There is the expectation
of high initial apple scab disease pressure in the spring of 2005
that will require regular applications of the most effective fungicides
that are also more prone to resistance if applied repeatedly.
Recent research trials at the Fruit Research and Extension Center
(FREC) have indicated that there are some effective alternative
materials to synthetic fungicides to control apple scab on limited
greenhouse and laboratory trials at the FREC research facility.
Effective alternatives do exist but must be identified and developed
for use in PA apple orchards.
Objective: The objective of this proposal was to identify,
evaluate and begin refining the use of alternative materials and
microbial organisms to control apple scab under Pennsylvania orchard
conditions.
