Foliar Fungicide

Issue 8
June 1997
Decision Aid Helps Assess Foliar Fungicide Treatments

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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.

A foliar fungicide decision aid created several years ago by University of Minnesota extension plant pathologist Roger Jones, and funded by checkoff dollars administered by the Minnesota Wheat Research and Promotion Council, may help in determining whether to apply foliar fungicides to control leaf diseases.
There are several points to keep in mind, however: Each field should be evaluated separately, at flag leaf emergence (Feekes 8.0). The decision aid applies only to spring wheat. Bear in mind that some varieties are more susceptible to leaf diseases and thus may respond better to foliar fungicide treatments than others.
For example, Verde and Hamer are moderately resistant to foliar diseases; Marshall and Sharp are moderately susceptible; and Butte 86, 2375, Russ, and Grandin are varieties which are susceptible.
Note also that the model does not apply to scab, which develops under different conditions and requires different treatment measures than those used for foliar diseases.
Benlate, Tilt, and Folicur are effective in suppressing scab when applied to wheat at early-flowering. Tilt and Folicur may receive Section 18 exemptions from the Environmental Protection Agency this growing season, which would allow post-heading treatment for scab suppression.
Although the following decision model should not be used to determine scab treatments, it may be valuable in helping growers to weigh foliar diseases such as tan spot, Septoria, and powdery mildew against primary treatment factors, including market price, previous crop, yield potential, and weather conditions.

Foliar Fungicide Decision Aid
Note: Each field should be evaluated separately at flag leaf emergence.

1) MARKET PRICE OF WHEAT
$2.00 - $2.50/bu. or less: 1 suggested point (s.p.)
$2.51 - $3.00/bu: 3 s.p.
$3.01 - $4.00/bu: 5 s.p.
$4.01/bu. or more: 7 s.p.

2) PREVIOUS CROP
Wheat: 4 s.p.
Barley: 1 s.p.
Other: 0 s.p.

3) LEAF SPOT* OR POWDERY MILDEW
DEVELOPMENT AT FLAG LEAF EMERGENCE
Leaf Spot Powdery Mildew
Upper leaves (F-1, F-2): 4 leaf spot (l.s.), 6 powdery mildew (p.m.)
Middle leaves (F-3, F-4): 3 l.s., 4 p.m.
Lower leaves (F-5,F-6): 2 l.s., 2 p.m.
None: 0 l.s., 0 p.m.
*Tan Spot or Septoria Only

4) YIELD POTENTIAL**
40 bu./ac. or less: DO NOT SPRAY
40-50 bu./ac.: 0
50-60 bu./ac.: 2
60-70 bu./ac.: 4
70 bu./ac. or more: 6
**Do not spray fields heavily stressed or damaged due to factors other than diseases (especially drought stressed fields).

5) TEMPERATURE/MOISTURE CONDITIONS -- Based on the past two weeks and a one-week forecast, select the suggested point value most closely associated with the appropriate average temperature/moisture conditions. Temperature selected should be average daytime temperature.
1)Leaf Spot Moisture (Dry/Average/Wet)
2)Powdery Mildew Moisture and RH (Dry/Avg to Wet)***

Temp: 50-60F 1) 0/ 0/ 0 2) 1/ 3
Temp: 60-70 1)0/ 1/ 3 2) 2/ 4
Temp: 70-80 1) 0/ 2/ 4 2) 1/ 3
Temp: 80 or more 1) 0/ 1/ 2 2) 0/ 0
*** If moisture is the result of extremely heavy rainfall, deduct 2 points from the avg/wet assessment in this category.

6) TOTAL NUMBER OF ASSESSED POINTS
Total the number of points assessed for each factor and follow recommendation given below.

RECOMMENDATION
A) 12 points or less Do Not Spray
B) 13-15 points Spray may be beneficial
C) 16 points or more Apply 4 fluid ounces Tilt or two pounds mancozeb for leaf spot. Apply 4 fluid ounces Tilt for powdery mildew. If applying mancozeb, reassess field 10 days after first application and determine if point value has gone down below 16. If so, then DO NOT SPRAY second application.

Copyright Prairie
Grains Magazine
June 1997

Issue 8 June 1997	Decision Aid Helps Assess Foliar Fungicide Treatments

Library Home E-Mail Back Prairie Grains is the official publication of the Minnesota Association of Wheat Growers, North Dakota Grain Growers Association, South Dakota Wheat, Inc., and the Minnesota Barley Growers Association.	A foliar fungicide decision aid created several years ago by University of Minnesota extension plant pathologist Roger Jones, and funded by checkoff dollars administered by the Minnesota Wheat Research and Promotion Council, may help in determining whether to apply foliar fungicides to control leaf diseases. There are several points to keep in mind, however: Each field should be evaluated separately, at flag leaf emergence (Feekes 8.0). The decision aid applies only to spring wheat. Bear in mind that some varieties are more susceptible to leaf diseases and thus may respond better to foliar fungicide treatments than others. For example, Verde and Hamer are moderately resistant to foliar diseases; Marshall and Sharp are moderately susceptible; and Butte 86, 2375, Russ, and Grandin are varieties which are susceptible. Note also that the model does not apply to scab, which develops under different conditions and requires different treatment measures than those used for foliar diseases. Benlate, Tilt, and Folicur are effective in suppressing scab when applied to wheat at early-flowering. Tilt and Folicur may receive Section 18 exemptions from the Environmental Protection Agency this growing season, which would allow post-heading treatment for scab suppression. Although the following decision model should not be used to determine scab treatments, it may be valuable in helping growers to weigh foliar diseases such as tan spot, Septoria, and powdery mildew against primary treatment factors, including market price, previous crop, yield potential, and weather conditions. Foliar Fungicide Decision Aid Note: Each field should be evaluated separately at flag leaf emergence. 1) MARKET PRICE OF WHEAT $2.00 - $2.50/bu. or less: 1 suggested point (s.p.) $2.51 - $3.00/bu: 3 s.p. $3.01 - $4.00/bu: 5 s.p. $4.01/bu. or more: 7 s.p. 2) PREVIOUS CROP Wheat: 4 s.p. Barley: 1 s.p. Other: 0 s.p. *3) LEAF SPOT OR POWDERY MILDEW DEVELOPMENT AT FLAG LEAF EMERGENCE Leaf Spot Powdery Mildew** Upper leaves (F-1, F-2): 4 leaf spot (l.s.), 6 powdery mildew (p.m.) Middle leaves (F-3, F-4): 3 l.s., 4 p.m. Lower leaves (F-5,F-6): 2 l.s., 2 p.m. None: 0 l.s., 0 p.m. Tan Spot or Septoria Only 4) YIELD POTENTIAL* 40 bu./ac. or less: DO NOT SPRAY 40-50 bu./ac.: 0 50-60 bu./ac.: 2 60-70 bu./ac.: 4 70 bu./ac. or more: 6 Do not spray fields heavily stressed or damaged due to factors other than diseases (especially drought stressed fields). 5) TEMPERATURE/MOISTURE CONDITIONS -- Based on the past two weeks and a one-week forecast, select the suggested point value most closely associated with the appropriate average temperature/moisture conditions. Temperature selected should be average daytime temperature. 1)Leaf Spot Moisture (Dry/Average/Wet) 2)Powdery Mildew Moisture and RH (Dry/Avg to Wet)* Temp: 50-60F 1) 0/ 0/ 0 2) 1/ 3 Temp: 60-70 1)0/ 1/ 3 2) 2/ 4 Temp: 70-80 1) 0/ 2/ 4 2) 1/ 3 Temp: 80 or more 1) 0/ 1/ 2 2) 0/ 0 * If moisture is the result of extremely heavy rainfall, deduct 2 points from the avg/wet assessment in this category. 6) TOTAL NUMBER OF ASSESSED POINTS Total the number of points assessed for each factor and follow recommendation given below. RECOMMENDATION A) 12 points or less Do Not Spray B) 13-15 points Spray may be beneficial C) 16 points or more** Apply 4 fluid ounces Tilt or two pounds mancozeb for leaf spot. Apply 4 fluid ounces Tilt for powdery mildew. If applying mancozeb, reassess field 10 days after first application and determine if point value has gone down below 16. If so, then DO NOT SPRAY second application.
Copyright Prairie Grains Magazine June 1997

Decision Aid Helps Assess Foliar Fungicide Treatments

Copyright Prairie Grains Magazine June 1997

Copyright Prairie
Grains Magazine
June 1997