Lateblight Help

Simulation

Begin New resets all the variables to their last-saved values and starts the simulation over again. Begin New may be selected at any time.

Exit terminates the simulation and closes Lateblight. You may exit Lateblight at any time during the simulation.


Potato

Resistance Level gives you the choice of different potato cultivars with Low, Moderate, or High levels of resistance to Phytophthora infestans.

Harvest Season allows you to simulate different potato cultivars with differing rates of maturation by selecting Early, Mid, or Late season maturity.

Yield opens a window in which you can enter the maximum yield (in the absence of late blight) in cwt/acre or kg/hectare to simulate different potato cultivars with different yield potentials.


Environment

Length of Season... opens a window to let you set the number of days from median emergence of the potato vines to harvest.

Emergence Date... opens a window to let you set the calendar date on which median emergence of the vines occurs.

Weather gives you the selection of one of five possible weather data sets: cool and wet, hot and dry, moderate temperatures and dry, moderate temperatures and moderate rainfall, and moderate temperatures and high rainfall.


Inoculum

In Lateblight, there are two independent sources of inoculum--sporangia and infections, which can be set individually or in combination with the other to initiate an epidemic.

The Sources of Sporangia are a cull pile (potatoes discarded from a packing line) and a neighboring unsprayed field. To account for dispersal losses, the distance of the field being managed from each of these inoculum sources can be set. Enter the maximum sporangia per day released at the source. In the case of the cull pile, the number of sporangia released each day will decrease exponentially from this maximum as the season progresses. A typical value for this maximum is 100-1000 sporangia/day. In the case of the unsprayed field, the number of sporangia released per day will increase logistically as the season progresses. A typical value for this maximum is 1000-10,000 sporangia/ha. 10 meters is a reasonable distance from the field for either of these sources.

The Sources of Infections are infected seed tubers and volunteer potatoes in the field being managed. Enter the numbers of infections per hectare or per acre present at plant emergence. A typical value is 10-100 infections/ha.


Management

The Weather Report includes actual temperature and rainfall data from the previous day as well as a forecast of temperature and chance of rainfall for the current day and the next two days. As in the real world, there is a degree of chance in the forecasts. They are based on the weather data that will actually be used in coming days, with a random component to reflect the inherent difficulty of predicting the weather.

Spray Systemic... applies a fungicide that is absorbed by the plant tissues and is therefore not subject to weathering by subsequent rains. The systemic fungicide also acts to suppress infections that are already established. The spray will be applied on the day following the day on which the command was given. Enter the dose of the active ingredient in kg/hectare or lb/acre. Click on "Spray" to apply the fungicide on the date given or on the "Close" button in the top right corner to exit the dialog box without applying the spray. A warning is given if the spray will be applied in the rain. A spray applied while it is raining will not leave the full residue of fungicide on the foliage.

Spray Protectant... applies a fungicide that interacts with the fungus only on the plant surface. To be effective, it must be applied prior to infection, and its residues must be maintained on plant surfaces by frequent applications. The spray will be applied on the day following the day on which the command was given. Enter the dose of the active ingredient in kg/hectare or lb/acre. Click on "Spray" to apply the fungicide on the date given or on the "Close" button in the top right corner to exit the dialog box without applying the spray. A warning is given if the spray will be applied in the rain. A spray applied while it is raining will not leave the full residue of fungicide on the foliage.

The order to Kill Vines immediately defoliates the crop and stops tuber development.


Economics

Costs... allows you to establish the costs of potato production before the start of the season (before Begin New is selected). For each of the items, enter the cost per acre or per hectare. When all of the items show the desired values, click "Save".

Price... allows you to enter the market price per cwt. or per kg. for the current season's potato crop.

Show Report displays a full accounting at the end of the season.


Measure

You may select either American units of measure (pounds, acres, etc.) or metric (kilograms, hectares, etc.). The default is metric units. Your selection here makes the appropriate adjustment throughout the program. The program is designed to set the units before starting the simulation with Begin New. A change made during the course of the simulation may not work properly.

View

Refresh restores the portions of the graph that are obliterated by opening and closing a large menu. The rest of the View menu allows you to turn on and off the display of the different simulation variables on the graph as the season progresses. Click on a variable to toggle it on or off, and click Refresh to make it appear on the graph.

Log

Show Log displays the output of the simulation in text form. It can be highlighted, copied, and pasted into a text editor for subsequent editing to prepare a report. (Security considerations do not permit the browser to write directly to a file.)

Help

Show Help displays this page.