Wheat - Foliar Fungicides and Thresholds

Jan 29, 2007 2:23 PM


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
				restrictions.
	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.

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

Wheat - Foliar Fungicides and Thresholds

Latest Jobs

Browse Print Issues

Additional Resources