Plant protection module 5
   Apple scab prognosis according to Welte

• Software module for the subsequent processing of climatic data to the apple scab prognosis according to Welte
• Determination of the infection curve with consideration of the development of spores
• Extensive parameters for evaluation according to previous year infestation, sort susceptibility, sprouting property etc.

• 30490

The Welte scab module represents an additional module to the software UK_TOSS, that determines an apple scab prognosis on the basis of the meteorological data registered with the standard version according to the model of Dr.sc.agr. Herbert Welte (D – Tettnang).

Models / parameters
The hourly values of the climatic parameters air temperature, relative humidity, precipitation and leaf wetness are the design fundamentals.
For specifying the apple scab prognosis however still further factors are consulted, like the infestation of the previous year, sort susceptibility, the sprouting property and above all the development of spores. Thus the critical phases can be limited and the user is given an aid during the optimization of the spray application.
The calculation begins with the start of the flight of Asco-spores. A set of parameters (ripeness time, ejection after rains, day / night) allows the watching over the development of Asco-spores. The potential of available spores at Asco-spores or later at Konidien represents the basic condition for the determination of the infection potential for an apple scab infection. The duration of leaf wetness necessary for an infection can be determined alternatively according to the tables of

• Mills

• MacHardy

• Jones

• Schwabe

All parameters are freely definable and are exactly described in an extensive help function.

The graphical representation of some important parameters (like temperature/ duration of leaf wetness for an infection, drying time, development of Asco-spores, fruit susceptibility...) serves the illustration of the connections and enables the classification of the influence of the parameters on the scab prognosis.

 An auxiliary function serves the determination of the incubation period, in order

1. to determine at the point when lesions occurred the point of infection or

2. to calculate at the point of infection, when the appropriate lesions will occur.

From the meteorological data and the defined parameters the scab infection is determined. In the primary season (Asco-spores) additionally the concentration of ripe spores as well as the concentration of the ejected spores are determined. These result curves can be represented graphically separate or parallel, or be put one above the other for comparisons.
The prognosis of the scab infection represents the probability of appearance of an infection in per cent. If the infection index exceeds 100% there is to expect an easy, at 130% a middle and at 200% a heavy infection. The end of one infection period is achieved after a defined number of drying hours, i.e. of hours in those no leaf wetness occurred and so 50 % of the spores are en-dried.