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Project Leaders: William Turechek and
Marvin Pritts, Cornell University
Cooperators: Alan Lakso, Catherine Heidenreich,
and Mary Jo Kelly, Cornell University
Type of Grant: Monitoring, forecasting,
and economic thresholds
Project Location: All of NY.
Abstract
Leaf scorch, leaf spot, and leaf blight are foliar
diseases of strawberry encountered commonly in perennial plantings in
New York. The extent of direct losses attributable to these diseases
is not known, but high levels of disease reduce the area of photosynthetically
active foliage, weakening the plant and affecting winter hardiness and
yield in subsequent seasons. Many growers do not manage foliar disease
after harvest because the economic benefits of doing so are unclear.
To begin to assess the value of foliar disease management, we measured
the impact of disease on photosynthesis on individual leaves. For leaf
scorch and leaf spot, photosynthesis decreased linearly with increasing
disease severity beginning with very low levels of incidence. Mutisya
and Sullivan (1994) showed that appreciable yield reductions occurred
when leaf scorch severity reached approximately 45% by seasons end.
In our study, leaflets with 45% leaf scorch suffered approximately a
50% reduction in photosynthesis; our preliminary analysis suggests that
this reduction is achieved with 30% leaf spot. This could indicate that
when photosynthesis is reduced by 50%, whether it is by leaf scorch,
leaf spot, leaf blight, or any other foliar pathogen, yield is affected.
We are currently conducting field studies to validate these laboratory
results.
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