Application Timing and Preharvest Intervals for Wheat Fungicides

Application Timing and Preharvest Intervals for Wheat Fungicides

July 2, 2008

Double Check the Restrictions for Your Fungicide

Photo of wheat scab.
Figure 1. Septoria leaf blotch in wheat.
Photo of Septoria leaf blotch in wheat
Figure 2. Fusarium head blight (scab) in wheat.

The 2008 growing season has been unusually wet especially in south central, eastern, and even southwestern Nebraska. The wet weather favored many diseases. The major diseases were Fusarium head blight (scab, Figure 1) and Septoria leaf blotch (Figure 2). Foliar and head diseases of wheat caused by fungi can be controlled by applying fungicides. However, proper timing of fungicide application is critical in achieving maximum efficacy and meeting legal requirements. This growing season there have been a few instances where fungicides apparently were applied later than they should have been. This article provides information on rates, application timing, number of sprays per season, and preharvest intervals for the most commonly used wheat fungicides in Nebraska (Table I).

NDA Reminds Producers About Fungicide Restrictions
To maximize efficacy of fungicides, it is essential that their application is timed properly according to label instructions. In wheat, as in other crops, fungicide application timing often is tied to crop growth stage. Timing also may be dependent on occurrence of environmental conditions favorable to disease development. Always adhere to label restrictions. In general, fungicides are most effective if applied before disease development or soon after disease detection. For suppression of Fusarium head blight (scab), fungicide should be applied at early flowering.

In wheat, fungicide application for optimal control of fungal foliar diseases usually is timed to protect the flag leaf. However, for early season diseases such as powdery mildew and tan spot, if conditions are favorable to disease development early in the season, it may be beneficial to apply a fungicide for early season disease suppression and follow up with a second application at flag leaf emergence. If a decision is made to apply two or more sprays, be careful not to exceed the maximum product rate for a single growing season. Also adhere to restrictions regarding the interval between two sprays and the pre-harvest interval.

Wheat Treated Too Close to Harvest

If wheat was treated with a fungicide which has a preharvest interval extending beyond the expected harvest date, wait as long as practical before harvesting. Postponing harvest allows more time for fungicide residue to degrade, which reduces grain contamination.

If you have questions, contact the Nebraska Department of Agriculture at 1-877-800-4080.

Stephen Wegulo
Extension Plant Pathologist

Table 1. Application timing and preharvest intervals for wheat fungicides.

Product*
(Company)

Rate/Acre

Application timing for optimal disease control

Max. no.
of sequential applications

Max.
rate/acre/
season

Pre-harvest interval
(growth stage)
Apply no later than

Pre-harvest interval
(days)

Headline
(BASF)

6 – 9 fl oz

Prior to disease development; immediately after flag leaf emergence (Feekes 8)

2

18 fl oz

Feekes 10.5
(beginning of flowering)

14 days for hay or feed green-chopped wheat

Quadris
(Syngenta)

4 – 12 fl oz;
7.5 – 11 fl oz for powdery mildew control

Prior to disease development; starting at Feekes 6 (first node of stem visible

2

24 fl oz

Feekes 10.5

14 days for hay; 45 days for grain and straw

Quilt
(Syngenta)

7 – 14 fl oz for early season suppression;
14 fl oz for control of leaf diseases

When the flag leaf is 50% fully emerged

2
(Min interval: 14 days)

20.5 fl oz

Feekes 10.5

45 days for grain or straw

Stratego
(Bayer)

10 fl oz

Preventively when conditions favor disease development

2
(Min interval: 14 days)

20 fl oz

Feekes 9 (ligule of flag leaf just visible)

30 days for forage;
35 days for grain; 45 days for hay

Proline
(Bayer)

4.3 – 5.7 fl oz (Fusarium head blight)
4.3 – 5.0 fl oz (leaf and stem diseases)

Feekes 10.51 (15% flower)

2

9.37 fl oz

Feekes 10.52 (50% flower)

30 days for grain

Folicur

4 fl oz

Rusts: at first sign of disease
Scab: Feekes 10.51 or beginning of flowering

1

4 fl oz

Feekes 10.51 (beginning of flowering)

6 days for forage; 30 days for grain and straw

Caramba

Diseases other than scab: 10 – 14 fl oz;
Scab suppression:
14 – 17 fl oz

Diseases other than scab: Prior to disease development; immediately after flag leaf emergence (Feekes 8)
Scab: beginning of flowering

2
(Min interval: 6 to 8 days)

34 fl oz

30 days for grain; no livestock feeding restrictions

Tilt
(Syngenta)

2 – 4 fl oz for early season suppression; 4 fl oz for control of foliar diseases

At first appearance of disease; at Feekes 8 (flag leaf emergence)

2

4 fl oz

�Feekes 10.5

30 days for forage;
40 days for grain and straw; 45 days for hay

PropiMax EC
(Dow)

4 fl oz

At first appearance of disease; at Feekes 8

1

4 fl oz

Feekes 10.5 (heading)

40 days for grain and straw

Dithane DF
(Dow)

2.1 lb

At first appearance of disease in the tillering to jointing stage

3
(7-10 day interval)

6.3 lb

Feekes 10.5
(heading)

26 days for grain and straw

Manzate 75 DF
(Griffin)

2.1 lb

At first appearance of disease in the tillering to jointing stage

3
(7-10 day interval)

6 lb

Feekes 10.5
(heading)

26 days for grain and straw

*No endorsement is intended for products listed nor is criticism meant for products not listed.