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NC State Extension

Development of Anthacnose and Botrytis Strawberry Fruit Infection Risk Models

Anthracnose (Colletotrichum acutatum) and Botrytis (Botrytis cinerea) Strawberry Fruit Rot Risk Models

To predict and forecast strawberry fruit infection risk by Colletotrichum acutatum (anthracnose fruit rot) and Botrytis cinerea (Botrytis fruit rot) in North Carolina, two models have been implemented for each pathogen. The first model set is based on the models used by the Florida Strawberry Advisory System (FLSAS) developed by W. Pavan et al. The FLSAS based models have been evaluated in both Florida and North Carolina for the past several years, and have performed well. The second model set is based on a simple general infection model (GIM) developed by R. D. Magarey et al. The GIM models are currently under evaluation. Both sets of models are based on the same experimental data (Botrytis cinerea study by M. A. Bulger et al. and Colletotrichum acutatum study by L. L. Wilson et al.), but use different equation forms (see below).

The FLSAS and GIM models require air temperature and leaf wetness duration data. Weather data are currently available on a minute time step for 33 ECONet stations located across North Carolina. The stations and data are maintained by the State Climate Office of North Carolina. Leaf wetness duration is calculated based on readings from a Decagon leaf wetness sensor located at each station. National Weather Service (NWS) hourly forecast data are used by the models to predict the risk of infection events in the next 5 to 7 days. Leaf wetness duration for the forecast period is estimated using a modified version of the CART model developed by M.L. Gleason et al. Forecast data for temperature, relative humidity, wind speed, precipitation probability and amount are used by the CART model. ECONet station data and NWS forecast data are updated hourly to provide near real-time infection risk predictions for current events and forecast events.

Infection risk periods start with the onset of rain or dew. For both strawberry fruit pathogens, an infection risk period is terminated by a minimum dry period of four hours. Only the temperatures during the time of leaf wetness are used to calculate the average temperature for the infection risk period.

Note that the risk level displayed for each station on the application map is based on the highest risk index calculated by any of the four models for the 72-hr time period from midnight yesterday through midnight tomorrow. For details about the risk level calculated by each model for each disease and for fungicide recommendations, you must click on the marker for the station of interest.

FLSAS Models

Infection Risk Index:
LWD – leaf wetness duration (hours)
T – average temperature (oC) during wet period

Colletotrichum acutatum (anthracnose fruit rot):

anthracnose fruit rot FLSAS formula
Low risk:          infNdx < .15
Moderate risk: .15 <= infNdx < .50
High risk:         infNdx >= .50

Strawberry Fruit Anthracnose temp graph

Strawberry Fruit Anthracnose leaf wetness graph

Botrytis cinerea (Botrytis fruit rot):

FLSAS Botrytis formula
Low risk:          infNdx < .50
Moderate risk: .50 <= infNdx < .70
High risk:         infNdx >= .70

Strawberry fruit Grey Mold Rot temp graph

Strawberry fruit Grey Mold Rot leaf wetness graph

GIM Models

GIM formula2
LWD – leaf wetness duration (hours)
T – average temperature () during wet period

GIM risk curve

Colletotrichum acutatum (anthracnose fruit rot):

Tmin: 7(oC)
Topt: 27.5(oC)
Tmax: 35(oC)
LWDmin: 6 hrs
LWDmax: 36 hrs

GIM model_Anthracnose_Leaf Wetness

GIM model_Anthracnose_temp

Botrytis cinerea (Botrytis fruit rot):

Tmin: (oC)6
Topt: (oC)20.5
Tmax: (oC)40
LWDmin:   8 hrs
LWDmax:   18 hrs

GIM Botrytis_leafwetness graph

GIM gray mold_temp graph

References

Bulger, M. A., Ellis, M. A., Madden, L. V. 1987. Influence of temperature and wetness duration on infection of strawberry flowers by Botrytis cinerea and disease incidence of fruit originating from infected flowers. Phytopathology 77:1225-1230.
https://www.apsnet.org/publications/phytopathology/backissues/Documents/1987Articles/Phyto77n08_1225.PDF”>https://www.apsnet.org/publications/phytopathology/backissues/Documents/1987Articles/Phyto77n08_1225.PDF

Gleason, M. L.; Taylor, S. E.; Loughin, T.C.; Koehler, K.J. Development and validation of an empirical model to estimate the duration of dew periods. Plant Disease, v.78, p.1011-1016, 1994. http://www.apsnet.org/publications/plantdisease/backissues/Documents/1994Articles/PlantDisease78n10_1011.PDF

Magarey, R. D., Sutton, T. B., and Thayer, C. L. 2005. A Simple Generic Infection Model for Foliar Fungal Plant Pathogens. Phytopathology 95:92-100.
http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-95-0092

Pavan, W., Fraisse, C. W., and Peres N. A. 2012. The Strawberry Advisory System: A Web-Based Decision Support Tool for Timing Fungicide Applications in Strawberry. Department of Agricultural and Biological Engineering, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida publication AE450.
https://edis.ifas.ufl.edu/pdffiles/AE/AE45000.pdf

Wilson, L. L., Madden, L. V., and Ellis, M. A. 1990. Influence of temperature and wetness duration on infection of immature and mature strawberry fruit by Colletotrichum acutatum. Phytopathology 80:111-116.
https://www.apsnet.org/publications/phytopathology/backissues/Documents/1990Articles/Phyto80n01_111.PDF

Links to other sources

Florida Strawberry Advisory system: http://agroclimate.org/tools/Strawberry-Advisory-System/

National Weather Service Digital Forecast Database: http://graphical.weather.gov/xml/

NC ECONet: http://climate.ncsu.edu/econet

State Climate Office of North Carolina: http://climate.ncsu.edu/