Barbara Shew, Department of Plant Pathology, NC State University
The North Carolina Sclerotinia advisory is a cooperative effort by the State Climate Office of North Carolina and the Department of Plant Pathology at NC State University. The advisory helps to identify periods that are favorable for Sclerotinia blight development so that protective sprays can be applied.
Sclerotinia advisories account for favorable weather only; they do not account for field history. Fields with no history of disease do not need to be sprayed unless a new outbreak is confirmed. In fields with a history of disease, careful scouting should begin the second week in July.
There are two advisories for each location.
Use the advisory for row index = 2 if rows are within 6” of touching.
Use the advisory for row index = 3 if rows are touching.
Sprays normally are not needed if rows are more than 6” apart.
Advisory Details:
Date and station name - ECONET stations are indicated by an abbreviated name; airport stations are indicated by call letters. In general, ECONET stations are more reliable than airport stations. It is a good idea to check advisories for the two closest weather stations.
Daily Sclerotinia index values for the last 5 days. Three index values are given for each day as in this example:
For 2011-07-05: MI=1, TI=1, EI=1
MI - moisture index. MI = 1 is favorable for disease. MI = 0 means that moisture is too low for disease. MI = 1 if
1) RH was 95% or higher for at least 8 consecutive hours; or
2) one-half inch of rain fell in the past 5 days; or
3)1 inch of rain fell in the last 10 days.
The advisory lists all of the reasons that MI=1 on a given day as in this example:
The advisory lists all of the reasons that MI=1 on a given day as in this example:
MI from RH, MI from 5-day rain, MI from 10-day rain
If your rainfall history is different, the advisory may not apply to you
If your rainfall history is different, the advisory may not apply to you
TI - temperature index.
TI = 0 if the day’s 24-hour average temperature was more than 82°F
TI = 1 if 77 to 82°F
TI = 2 if 72 to 77°F
TI = 3 if 72°F or lower
EI - environmental index.
EI = MI * TI. The daily index (not shown on the output) is obtained by multiplying the EI X row index X 3.
Row index –Use the advisory for row index = 2 for rows within 6” of touching. Use the advisory for row index = 3 for rows touching. Conditions usually are not favorable for disease for rows more than 6" apart
setDate - used to calculate the advisory
Five day index – this is the total of the daily index values for the past 5 days. A spray is advised when the five day index is greater than 32.
Last effective spray date (LESD) – A spray is assumed to be effective for 21 days. You do not need to spray if you have sprayed since the LESD.
Advisory – if the advisory is “spray today” conditions are favorable for Sclerotinia blight and you should spray if no Sclerotinia fungicide has been applied in the past 21 days. If the advisory is “do not spray today” a spray is not required.
Disease level - the five day index is used to rate the disease hazard as low (<32), moderate (32-47), high (48-98), or very high (>99).
Growing degree days - for peanuts (base 56) since the LESD and since May 1.
Records count - number of hourly weather observations out of total possible observations. The advisory may not be reliable if there are a lot of missing records.
Most recent hourly observation – should be or 7:00:00 (7 a.m.) on today’s date.
