NAME:                   Erysiphe necator (Primary Infection)
                        
VERSION:                1-004

DATE:                   2016/02/24

AUTHOR:                 dr. Hlaszny, Edit
                        
SHORT DESCRIPTION:      Powdery mildew of grapevine is the most enduring and 
                        persistent disease problem in Vitis vinifera vineyards. 
                        The impact powdery mildew infection has on a vineyard 
                        often depends on the timing of the first infection. 
                        
                        Early fruit infections cause stunted berries, scarring,
                        and off-flavors in wine. Powdery mildew also reduces the
                        storage life of table grapes and can affect the rate of 
                        photosynthesis, thus reducing berry sugar content.
                        
                        Powdery mildew can affect all suculent tissues on a 
                        grapevine, including teh stem, fruit, and leaves, all of 
                        which can show charecteristic symptoms. 
                        
KEYWORDS:               grapevine powdery mildew, fungus, Erysiphe (Uncinula) necator
                        
INPUT:                  BBCH
                        avg_daily_air_humidity
                        avg_daily_air_temperature
                        current_air_temperature 
                        current_date
                        current_leaf_wetness    
                        current_wind_speed      
                        daily rain precipitation 
                        no_protection_done
                                                    
OUTPUT:                 spraying_should_be_done

PROCESSING STEPS:

//
//  evaluating critical phenological growth stage (BBCH)
//  (from budburst to flowering ~ means 1,5-2 months)
//
IF (BBCH >= 9  AND BBCH < 69
   )
THEN
    LET critical_phenological_growth_stage      IS TRUE
ELSE
    LET critical_phenological_growth_stage      IS FALSE
END-IF

//
// is the weather suitable for spraying
//
IF ( current_air_temperature >= 5 Celsius       AND
     current_air_temperature < 25 Celsius       AND
     current_wind_speed      < 6m/sec           AND
     current_leaf_wetness    < 46%              AND
     critical_phenological_growth_stage         IS TRUE
   )
THEN
    LET weather_is_suitable_for_spraying        TRUE
ELSE
    LET weather_is_suitable_for_spraying        FALSE
END-IF

//  
//  Mills-condition ("wet period") 
//      in the last 5 days back to the current date min. 1 row from the Mills-
//      table should semi-continuously be fulfilled, with max. 4h interruption.
//  
//  The "wet-periods" can be merged.
//  
//  The following Mills-table defines the valid combinations of incidence 
//  of the ascosporal infection 
//
//  avg daily      min. time-intervall [h] in that
//  air temp [C]   the rel. air humidity > 90 %
//
     5.6           40.00
     6.1           34.00
     6.7           30.00
     7.2           27.30
     7.8           25.30
     8.3           23.30
     8.3           23.30
     8.9           20.00
     9.4           20.00
    10.0           19.30
    10.6           18.00
    11.1           17.30
    11.7           16.70
    12.2           16.00
    12.8           16.00
    13.3           14.70
    13.9           14.70
    14.4           14.00
    15.0           14.00
    15.6           13.30
    16.1           13.30
    16.7           12.70
    17.2           12.00
    17.8           12.00
    18.3           12.00
    18.9           12.00
    19.4           12.00
    20.0           12.00
    20.6           12.00
    21.1           12.00
    21.7           12.00
    22.2           12.00
    22.8           12.00
    23.3           12.00
    23.9           12.00
    24.4           12.70
    25.0           14.00
    25.6           17.30 

//  (1) primary infection has not yet been detected, but the first
//      2,5 mm rain precipitation (has been fallen from 2 weeks 
//      before stage of BBCH 9) facilitates the swallowing of
//      the wall of the casmotheciums, so can the ascospores 
//      escape from there
//
//  (2) primary infection has not yet been detected, but the first
//      2,5 mm rain precipitation (has been fallen from growth stage 
//      BBCH 9 to growth stage BBCH-9 + 2 weeks) can also facilitates the 
//      swallowing of the wall of the casmotheciums
//        
//  (3) Mills Condition should be fulfilled in the BBCH interval of 9-69: 
//      
IF ( ( (minimal 2,5 mm rain precipitation has been 
        detected from 2 weeks before stage of BBCH 9)  OR              --  (1)
       (minimal 2,5 mm rain precipitation has been 
        detected from 2 weeks after stage of BBCH 9)                   --  (2)
      )                                                AND
      Mills_Condition                                  IS   FULFILLED  --  (3)
   )
THEN
    LET infectionCanStart IS  TRUE ;        --  in all likelihood   
ELSE
    LET infectionCanStart IS  FALSE ;                                   
END-IF 
    
IF ( no_protection_done                                  IS  TRUE   AND
     weather_is_suitable_for_spraying                    IS  TRUE   AND
     3 days after infectionCanStart has already been set to  TRUE
   )
THEN
    spraying_should_be_done ; 
END-IF     

REMARKS:                The asco stage casues the primary infection (contrasting
                        with the secondary infections,- the last ones are caused 
                        by the condial stage).
                        
KNOWN PROBLEMS:         The following factors were not taken into considerations:
                            heavy_powdery_mildew_infection_was_previous_year,
                            mild_winter_weather,
                            variety_susceptibility_to_powdery_mildew.

REFERENCES:             (1) http://www.apsnet.org/publications/apsnetfeatures/pages/UCDavisRisk.aspx

                        (2) http://www.ipm.ucdavis.edu/DISEASE/DATABASE/grapepowderymildew.html

                        (3) Gadoury, D. M., Cadle-Davidson, L. , WILCOX, W. F. , 
                            Drym I. B. , SEEM, R. C. and Milgroom, M. G. (2012): 
                            Grapevine powdery mildew (Erysiphe necator): 
                            a fascinating system for the study of the biology, 
                            ecology and epidemiology of an obligate biotroph. 
                            MOLECULAR PLANT PATHOLOGY (2012) 13(1) , 1-16 DOI : 
                            10.1111/J .1364-3703.2011.00728.X
