Plant disease forecasting

Plant disease forecasting is a management system used to predict the occurrence or change in severity of plant diseases. At the field scale, these systems are used by farmers to make economic decisions about disease control treatments. Often the systems ask the farmer a series of questions about host plant susceptibility and incorporate current and predicted weather conditions to make a recommendation. A recommendation is usually made as to whether disease treatment is necessary.

Prediction systems are based on assumptions about the interactions of the pathogen with the host and the environment. The goal is to accurately predict when the three factors-host, environment, and pathogen-will interact in such a way that a disease may occur and cause economic losses.

Prediction systems can use one of several parameters to calculate disease risk, or a combination of factors. One of the first prediction systems developed for Stewart's wilt (Pantoea stewartii) on corn was based on the winter temperature index, since low temperatures would kill the vector of the disease so that there would be no outbreak.

A rational method of predicting disease should be based on the following factors:

1. Factors (microclimatic) affecting the initial occurrence and subsequent spread of the inoculum.


2. Thorough knowledge of the life cycle of the pathogen.


3. The way the pathogen spreads.


4. Rough estimate of the quantities of inoculum expected to be spread via propagules, soil, air, vectors, etc.


5. Mechanism of host infection.


6. Knowledge of the susceptibility of the host plant at different growth stages.


7. Meteorological data (macroclimatic conditions) of the area.