TomatoPM: A Spray Forecast Model of Tomato Powdery Mildew
by R. A. Guzman-Plazola, R. M. Davis, and J. J. Marois, University of California, Davis, in conjunction with the UC Statewide IPM Program
Before using TomatoPM: This model is based on research sponsored by the California Tomato Research Institute and California Tomato Board and conducted by R. M. Davis, R. A. Guzman-Plazola, and J .J. Marois from 1993 through 1996. The model is based on results from experiments under controlled conditions (growth chamber) and field monitoring of disease and weather data. A linear discriminant function was generated to classify daily environmental conditions of tomato canopies according to their conduciveness for disease. Cross-validation of the discriminant function and tests with independent data sets yielded percentages of correct classification of 74-96% and 87%, respectively.
The model was tested during two consecutive years (1995 and 1996) in ten tomato fields (fresh market and processing) in the northern San Joaquin and southern Sacramento valleys of California. After following the recommendations of the model, it was possible to save 2 to 5 fungicide sprays with no significant impact on fruit yield and quality. Disease levels at harvest time in plots managed according to the model have been equal to or only slightly higher than that of plots where fungicide applications were made every 14 days.
While these results are very promising, remember that
You can download TomatoPM, a working version of this model prepared for use with Microsoft Excel 5 and 97/98 for Windows or for Macintosh. (Add Excel as a helper application in your browser for files with extension ".xls" before downloading.) Below is information to help you collect the required data and use it to run the working version of the model.
Hardware and software requirements. This working version requires Microsoft Excel 5 or 97/98, running under Windows 3.1 or 95 or on a Macintosh computer. As this initial version is improved, new versions will be posted here. Send e-mail to webmaster to get on a mailing list for future updates.
TomatoPM is a computer representation of the spray forecast model for tomato powdery mildew developed by R. Guzman-Plazola, R. M. Davis, and J. .J. Marois at University of California, Davis. This computer version was developed by Joyce Fox Strand, Statewide IPM Program, UC Davis.
TomatoPM is an Excel 5 workbook (file) which includes a prepared worksheet and macros that
The TomatoPM spray forecasts and the model calculations for each day can be printed, and the daily calculations can be used to create charts or for further analysis.
collection for input into the model
Placement of the sensors. Proper placement and calibration are critical for reproducing the research results.
T and RH. Each set of sensors for T
and RH should be kept together (they are usually parts of a single
probe) and protected by a shield to avoid direct exposure to the sun
and water, but the shield must allow good air flow around the sensor.
LW. Leaf wetness sensors must be placed on the top of the canopy and relocated periodically according to the dynamics of plant growth.
Output variables. The datalogger should make several measurements from each sensor during an hour, to be averaged over the hour. Measurements reported more often than each hour must be summarized into hourly values for input into this working version of the model.
The data values required by the model, and their units, are listed
in the following table.
TomatoPM expects to find the data in a worksheet in an Excel 5/97-98 workbook. You may download a sample data file "stockton.xls" (for Windows or Mac) to use to try out TomatoPM. Data in this file start at Julian day 225 and end on day 267.
The worksheet should be in the following format:
If you have only one sensor for T, RH, or LW, TomatoPM expects to find the data in the column labeled for sensor 1 and the sensor 2 column left BLANK.
All hours must have a value. If you have missing data, fill in from hours on a similar day, use data from a similar station, or in some other way fill in the gaps. If you cannot fill the gaps, you will need to start a new sheet and enter a starting date that falls after the gap as the beginning date.
TomatoPM prepares one worksheet for each field/weather station location you plan to enter. The program then takes the data you have prepared in the data workbook and uses it to generate a forecast on the highlighted area of the TomatoPM worksheet.
The buttons to the left of the highlighted area of the TomatoPM worksheet
allow you to:
Getting started: set up a location sheet
Open the TomatoPM workbook in Excel. Note that one of the sheet tabs on the bottom of the screen says Set_up. This worksheet is the main template for the model. To generate forecasts, you must ADD a new sheet for each location for which you are generating forecasts.
A new worksheet will be created and labeled with the location name you supplied. This is the worksheet on which the forecast will be generated for data from that location.
Updating a new forecast from new data
TomatoPM will search the data workbook/worksheet for values for the requested days, copy the data to the TomatoPM location sheet, calculate the daily values and values for the evaluation period, then display the forecast, recommendations, and a data summary in the highlighted area on your screen.
Interpreting the forecast
The forecast display includes the following information:
Press the Print Forecast button to print a copy of the forecast display. Press the Print Data button to print a copy of the detailed daily and period evaluations.
Note: The spray forecast and recommended action provide you with additional guidance to use in making a decision about when (and if) to spray a fungicide to control powdery mildew in your field. The applicability of the forecast to fields where no weather data are being collected is unknown; reliability will depend on the similarity of micrometeorological conditions between the field where the weather is monitored and other fields to which you are attempting to apply the data and forecast.
This model assumes the following:
Effect of sprays on the forecast
When you spray a fungicide, enter the date on which the spray is made. The model assumes that fungicide sprays can reduce infection in progress and provide effective protection for a 10-day period, where the first day is the date of the spray.
As you update the weather data and the forecast, the display will always inform you of the conditions for each day and the disease risk without fungicide protection. However, the forecast will also indicate whether the crop is protected by a recent spray.
To make it available for the 1997 season, a few shortcuts have been taken in preparing TomatoPM. These will be corrected through better error handling in a future version.
The following conditions produce known errors:
Avoidance is the easiest way to solve these errors: close your data file and don't move it after you've designated it as a TomatoPM location. However, if you do get the error, the most straightforward way to fix either of these errors is to close TomatoPM without saving changes, fix the problem with the Weather Data file, and restart TomatoPM.
As other problems are known, information about them will be posted here.
Questions about TomatoPM? Please send e-mail to webmaster and we'll do our best to help.
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Regents of the University of California. All rights reserved.