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Wheat - Foliar Fungicides and Thresholds

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--Rick Cartwright and Gene Milus, Arkansas Cooperative Extension Service

Diseases Fungicides Active Ingredient Rates/A Comments
Leaf Rust Tilt 3.6EC* propiconazole 4 fl oz Do not apply after Feekes GS 10.5*. Do not
Glume Blotch1 Propimax EC* propiconazole 4 fl oz apply more than 4 fl oz per acre per crop per
Septoria Leaf Quilt azoxystrobin + 14 fl oz season. Do not graze or feed treated wheat for
Blotch propiconazole forage, hay, green chop, or silage. Check 24(c)
label for days to harvest restrictions.
Powdery Mildew Quadris 2.08 SC azoxystrobin 6.4 fl oz Do not apply after Feekes GS10.5. Do not
Tan Spot2 (8.5 fl oz for harvest treated wheat for forage. Do not apply
Stripe Rust powdery within 14 days of harvest for hay or 45 days
mildew) for grain or straw. See label for other
Quilt azoxystrobin + 14 fl oz label recommendation rates down to 10.5 fl oz if
propiconazole disease pressure is low. Current label does not allow
applications after Feekes GS 8 (flag leaf emerging) -
be sure to check for future labels prior to use season.
Tank mixes with certain herbicides and fertilizers may
result in crop injury - see label for all restrictions.
Stratego 250EC trifoxystobin + 10 fl oz Do not apply after Feekes GS 10.5.
Please refer to 24(c) label for all restrictions.
Headline pyraclostrobin 6-9 fl oz Do not apply after Feekes GS 10.53 (end of
flowering) See label for all restrictions
*Section 24C Special Local need Label for Arkansas - label must be in possession of user at time of application. GS10.5 is headed but prior to flowering.
Fungicides are beneficial only if certain diseases are present at high enough levels and early enough in the season to cause yield and quality losses.
The more important times for application of foliar fungicides are usually between GS8 (flag leaf emergence) and GS10.5 (full heading).
In most years, GS10 (full boot) is considered the ideal timing for a single fungicide application to control leaf rust and Septoria leaf blotch.
Finally, the higher the yield potential of the field, the more likely an economic return from fungicide use.
The following threshold system is a general guide for whether or not there is adequate disease pressure to justify fungicide use.
The relative susceptibility of the variety, favorable weather conditions during the spring, and location in Arkansas should also be considered.
Check the weekly Wheat Disease Newsletter - published during March, April and May each year - for current information on these factors.
The Newsletter is available through the local Cooperative Extension Office.
Feeke’s stage Disease Indicator Leaf Treatment Threshold
GS 8 Leaf Rust F-3 and above 1 pustule/leaf
Septeoria tritici leaf blotch F-2 and above 25% of indicator leaves infected
Powdery Mildew F-2 and above 5 pustules /leaf
Strip Rust3 Any Leaf Any infected plants in the field
GS 9 - GS 10.5 Leaf Rust, Strip Rust3 F-2 and above 1 pustule/leaf
Septoria tritici leaf blotch F-2 and above 25% of indicator leaves infected
Powdery Mildew F-1 and above 5 pustules/leaf
1Glume blotch is more effectively controlled by seed treatment fungicides because it is primarily seed-borne under Arkansas conditions and foliar symptoms are difficult to scout for in the spring.
See Wheat Seed Treatment Table for details.
2Tan spot is rare in Arkansas. Fields with lots of infected residue (no-till wheat) are more likely to have the disease, however, the identity of the disease should always be confirmed before
a fungicide is considered since tan spot symptoms can be confused with herbicide injury and other non-disease problems.
3All fields with active hot spots should be sprayed if found prior to Feeke’s GS 10.5.
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