Agriculture Reference
In-Depth Information
than sixty years, his research is still being used in predictive models. Studies on
inoculum densities in orchards and how inoculum densities vary with each rain
through the primary season have been very helpful in understanding differences in
scab severity among orchards.
There is, however, a need for more research in several areas. Probably the
greatest need is for a standard reproducible method for measuring wetness periods.
Direct or indirect methods are needed for monitoring the wetness duration of leaves
and fruit and of overwintering leaves on the ground. Then, wetness-driven predictive
models could be tested and used reliably in different apple regions. Such a system
would be widely applicable because wetness periods govern the progress of many
plant diseases. There is also a lack of understanding of the extent that dry weather or
prolonged periods of low humidity in spring interrupt ascospore maturity and
discharge. Current predictive models for estimating ascospore maturation are based
on temperature, while in nature maturation is often limited by the lack of moisture.
Also, the revised Mills criteria and other scab forecasting systems need to be
validated in several countries using a standard protocol. Additionally, more
information is needed on factors that affect the overwintering of inoculum, the
relationship between inoculum density and the potential for infection and the
relationship between ascospore discharge, deposition and infection. In order to make
more use of information on inoculum density, a simple but suitable procedure is
needed for pest managers to monitor inoculum levels.
ACKNOWLEDGEMENT
Appreciation is extended to Dr. Turner B. Sutton (Department of Plant Pathology,
North Carolina State University, Raleigh) for review of the first edition of this
manuscript.
REFERENCES
Aylor, D.E. (1993) Relative collection efficiency of Rotorod and Burkard spore samplers for airborne
Venturia inaequalis
ascospores.
Phytopathology,
83
, 1116-1119.
Aylor, D.E. (1995) Vertical variation of aerial concentration of
Venturia inaequalis
ascospores in an
apple orchard.
Phytopathology,
85
, 175-181.
Aylor, D.E. (1996) Comparison of the seasonal pattern of airborne
Venturia inaequalis
ascospores with
the release potential of
V. inaequalis
ascospores from a source.
Phytopathology,
86
, 769-776.
Aylor, D.E. (1998) The aerobiology of apple scab.
Plant Disease,
82
, 838-849.
Aylor, D.E. and Anagnostakis, S.L. (1991) Active discharge distance of ascospores of
Venturia
inaequalis
.
Phytopathology,
81
, 548-551.
Aylor, D.E. and Kiyomoto, R.K. (1993) Relationship between aerial concentration of
Venturia inaequalis
ascospores and development of apple scab.
Agricultural and Forest Meteorology,
63
, 133-147.
Aylor, D.E. and Qiu, J. (1996) Micrometeorological determination of release rate of
Venturia inaequalis
ascospores from a ground-level source during rain.
Agricultural and Forest Meteorology,
81
, 157-
178.
Aylor, D.E. and Sutton, T.B. (1992) Release of
Venturia inaequalis
ascospores during unsteady rain:
relationship to spore transport and deposition.
Phytopathology,
82
, 532-540.
Becker, C.M. and Burr, T.J. (1994) Discontinuous wetting and survival of conidia of
Venturia inaequalis
on apple leaves.
Phytopathology,
84
, 372-378.
