HOW TO USE AU-PECAN, A WEATHER-BASED SYSTEM FOR CONTROLLING PECAN SCAB

Paul Bertrand
Tim Brenneman
Department of Plant Pathology
The University of Georgia

A. EQUIPMENT

1. Plastic rain gauge that will measure 0.1" of rain located in each orchard.
2. Access to a weather forecast giving  % chance of rain each of the next five
 days.  This is available on some TV weather forecasts or on the internet. The
 internet weather forecast is at www.awis.com. Look for AU-PECAN or use AU-PNUT.
 The table that comes up will give the % chance of rain for each of the next
 five days and a 5-Day Average for several South East regions.  Use column
 headed 5-Day Average as the AU-PECAN rain forecast.

B. SETTING A PROTECTION INTERVAL

Choose as a protection interval the spray interval known from experience to
 provide scab control.  It may be fixed through the season or changeable at
 various points in the season.  The protection interval will be the minimum
 interval between sprays.  In the AU-PECAN project a protection interval of
 10-14 days pre pollination and 14 days post pollination was used for Desirable.
 If  a tighter spray interval is used in wet years compared to dry years, use
 the wet year interval and allow AU-PECAN to detect dry periods where the
 schedule can be expanded. In orchards requiring more than one day to spray the
 protection interval begins on the FIRST day of spraying.

C. SPRAYING BY AU-PECAN

Operation of AU-PECAN is based on recorded rain events and the 5-day average
 forecast of more rain.  A rain event is 0.1" of RAIN in a 24 hour period or FOG
 forming before 8:00 p.m.  To spray by AU-PECAN begin recording rain events and
 checking the rain forecast on the last day of the protection interval. Any rain
 events during the protection interval prior to the last day are not counted.
 When the  protection interval since the last fungicide application has passed
 a spray is advised when:

1. No rain has occurred but the 5-day average = 50% or greater.
  OR
2. One rain event has been recorded and the 5-day average is 40% or greater.
  OR
3. Two rain events have been recorded and the 5-day average is 20% or greater.
  OR
4. Immediately after three rain events.

D. TIMING FIRST / LAST SPRAY:

1. Begin tracking rain events at bud break and spray when model is satisfied if
 average temperature (avg. of daily min/max) is 57?F or greater. Cold weather
 is not favorable for scab development and sprays are not advised when
 temperature is below 57?F.
  OR (BUT)
2. Make a protective treatment at parachute stage regardless of weather and
 begin AU-PECAN protection interval model here.	
  AND
3. Scab sprays are not advised after shell hardening.			

E. AU-PECAN LIMITATIONS:

1. AU-PECAN is best suited to operations that can be sprayed in 5-7 days
 or less.

2. AU-PECAN is not recommended for operations requiring >7 days to spray over.

3. Scheduling labor may be a problem in some cases. Once protection interval
 has passed operations for the day depend on the rain gauge and forecast.

4. Integrating other pest management needs.

5. AU-PECAN is not a substitute for management. It is critical to know what is
 happening in the field so that protection intervals can be adjusted as needed.
  
AU-PECAN, like any fungicide scheduling program, will be most successful when
tempered with good judgement.


REFERENCES:

1. Bertrand, P.F. and T.B. Brenneman 1998.  Results of a pilot project on
 control of pecan scab with weather based fungicide programs.  Proc. S.E. Pecan
 Growers Assoc. 91:38-41.

2. Bertrand, P.F., T.B. Brenneman, F. Connelly, B. Mitchell, and T. Otts. 1999.
 Results of a pilot project on control of pecan scab with weather based
 fungicide programs.  Proc. S.E. Pecan Growers Assoc. 92:69-72.

3. Brenneman, T. B. and P.F. Bertrand. 2000. Update on development of spray
 advisories for pecan scab. Proc. S.E. Pecan growers Assoc. 93:59-62.

4. Graves, C.H., W.W. Neel and R.C. Coates. 1973. Concentrate spray application
 for pecan disease and insect control. Proc. S.E. Pecan Growers Assoc.
 66:97-100.

5. Jacobi, J.R., P.A. Backman, D.P. Davis, ans P.M. Brannen. 1995.  AU-PNUTS
 advisory I: development of a rule based system for scheduling peanut leafspot
 fungicide application.  Plant Disease 79:666-671.

6. Sparks, D. 1995. Pecan scab control: a climatic approach, hypothesis and
 epidemiological validation. Northern Nut Grower Ann. Rept. 86:85-97.