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Research and IPMModels: Diseases
Crop: CarrotDisease: Alternaria Leaf Blight
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Model 1 of 3
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Mike Davis and Joe Nunez. Investigations into the Cause and Control of Carrot Root Forking, Cavity Spot, and Leaf Blights. California Fresh Carrot Advisory Board 1995 Annual Report. P. 57-68.
10 cm above soil surface in crop canopy.
Environmental: Air temperature, relative humidity, leaf wetness duration.
Host: Age of carrot field.
The model is based on a weekly summation of daily disease severity values (DSV). DSVs begin to accumulate eight weeks after planting.
To predict disease development one week in advance, multiply weekly DSV by 0.03 and add this to the current week's observed percent disease incidence.
The determination of an action threshold is in progress.
Validation work is being conducted in 1996 and 1997, by Mike Davis and Joe Nunez of the University of California, in Kern County.
The model is still in the validation phase.
To develop an action threshold.
Strandberg, J. O. Spore production and dispersal of Alternaria dauci. Phytopathology 67:1262-1266.
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Model 2 of 3 |
Modifications by Campbell Soup Company.
Pitblado, R .E. 1992. The development and implementation of TOM-CAST: A weather-timed fungicide spray program for field tomatoes. Ministry of Agriculture and Food, Ontario, Canada.
Madden L., Pennypacker, S. P., and McNab, A. A. 1978. FAST, a forecast system for Alternaria solani on tomato. Phytopathology 68:1354-1358.
Not specified.
Environmental: Air temperature, leaf wetness duration.
Calculated: Mean air temperature during the leaf wetness period.
Disease severity values (DSV) are calulated as a function of hours of leaf wetness and average air temperature during leaf wetness. The DSV is based on the FAST early blight model of tomato. After treatment, the DSV accumulations reset to zero. The accumulations of DSVs continues through September.
According to the model, initiate treatments when 35 DSVs have accumulated or by July 5, whichever comes first. Subsequent treatments should occur at the accumulation of 20 DSVs.
Not known.
Campbell Soup Company in MI, OH, NJ, using TOMCAST.
Bolkan, H. A., and Reinert, W. R. 1994. Developing and implementing IPM strategies to assist farmers: an industry approach. Plant Dis. 78:545-550.
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Model 3 of 3 |
Gillespie, T. J., and Sutton, J. C. 1979. A predictive scheme for timing fungicide applications to control Alternaria leaf blight in carrots. Can. J. Plant Pathol., 1: 95-99.
At ground level among the carrots.
Environmental: Forecasted temperature and leaf surface wetness duration (based on forecasts of rain, cloud cover and surface wind speed).
Calculated: Mean air temperature during the leaf wetness period.
Presence of blight symptoms.
This model is based on infection indices derived from the interaction of surface wetness duration and mean air temperature during the wetness period. Surface wetness duration is determined from forecasted weather of the forthcoming 36 hours. See original reference for a table of infection indices.
According to the model, initiate treatments when blight symptoms appear on 1-2% of the foliage. Subsequent treatments should occur based on infection period indices of 2 or 3 (moderate or high risk of infection), after a minimum of a seven- to ten-day spray interval.
Evaluated in CA in 1992.
Gillespie, T. J., and Sutton, J. C. 1979. A predictive scheme for timing fungicide applications to control Alternaria leaf blight in carrots. Can. J. Plant Pathol., 1:95-99.
Not known.
To adapt model according to cultivar susceptibility; To integrate the model with Cercospora forecaster, a model of Cercospora leaf blight of carrot, when appropriate.
Sutton, J. C., and Gillespie, T. J. 1977. Relation of weather variables and periodicities or airborne spores of Alternaria dauci. Phytopathology 67:879-883.
Langenberg, W. J. 1975. Carrot leaf blight (Alternaria dauci) development in relation to environmental factors and fungicide applications. M.Sc. Thesis, University of Guelph. Guelph, Ontario. 119 pp.
