Small Grains Focus

Efficacy of Early Season Fungicide in Spring Wheat

By Jochum Wiersma
U of M Small Grains Specialist
wiers002@umn.edu

In the past few years more and more producers have looked at the use of fungicides early in the season as a means to further improve the bottom line. Systemic fungicides like Tilt or Stratego can readily be tank-mixed with most any herbicide program, resulting in cost savings.

The past two summers, I have had a research project at the Northwest Regional Outreach Center in Crookston that compares five different fungicide management approaches across four different groups of varieties. The objectives of the research are to evaluate which fungicide management approach is most economical, and whether varieties differ in their response to fungicides.

The five fungicide treatments are listed in Table 1. Stratego was applied at half the labeled rate and Folicur was applied at the labeled rate. In both years, treatment 5 – defined as the treatment in which the decision to spray is dependent on the disease forecasting system from NDSU (www.ag. ndsu.nodak.edu/cropdisease) – resulted in a treatment with 4 oz of Folicur at Feekes 8. Varieties in the study are listed in Table 2, grouped according to susceptibility to leaf diseases and Fusarium head blight (scab).

Table 1: Five different fungicide programs applied at Crookston in 2001 and 2002
Treatment	Feekes 5	Feekes 8	Feekes 10.51
1 (untreated check)	-	-	-
2	5 oz Stratego	-	-
3	-	-	4 oz Folicur
4	5 oz Stratego	-	4 oz Folicur
5	-	4 oz Folicur	-

Table 2: Varieties used in the fungicide management trial in Crookston in 2001 and 2002 and their disease ratings for leaf diseases and FHB
Variety	Group	Leaf disease	FHB
Oxen	1	Susceptible	Susceptible
Russ	1	Susceptible	Susceptible
Alsen	2	Susceptible	Mod. Resistant
P2375	2	Susceptible	Mod. Resistant
Mercury	3	Mod. Resistant	Susceptible
Norm	3	Mod. Resistant	Susceptible
Gunner	4	Mod. Resistant	Mod. Resistant
Parshall	4	Mod. Resistant	Mod. Resistant

In the dry summer of 2001, the groups differed for the total amount of leaf disease over the season (with variety groups 1 and 2 showing more leaf disease over the whole season). However, no significant differences were found between the different fungicide management programs for grain yield.

In 2002, the results were quite different, although it should be stressed that this is single year data and a preliminary analysis. However, the results intrigued me so much that I thought it was worthwhile sharing some of it. First it should be noted that when the really application at Feekes 5 was made, very little if any disease was present in the crop and weather conditions up to that pint had not been favorable for disease development. After this first application was made conditions changed from somewhat to very favorable for leaf diseases. Disease pressure for FHB was light to moderate in 2002.

For the grain yield relative to the untreated check (treatment 1), only treatment 2 did not result in a significant increase in yield across the variety groups (Figure 1). Treatment 4 resulted in the highest increase in grain yield across variety groups at 34%. Statistically speaking, there were no significant interactions between fungicide treatment and the variety groups, but looking at this single year data shows some interesting results for group 2 – an early application of a foliar fungicide did not provide season-long control of the leaf diseases, but the combination of an early season application with an heading application provided the highest increase in grain yield relative to the untreated check at 55%.

Figure 1: Grain yield for each of the fungicide treatments relative to the untreated control for each of the four variety groups in 2002.

It is too early to draw any firm conclusions to which fungicide treatment is most economical, but the results of this study indicate that a single application of a half rate of Stratego early in the season does not provide season-long control, and that the two applications across the season provide the best protection and results in the highest grain yield across varieties.

There is no question that fungicides will suppress disease and increase yield, if weather conditions are favorable for disease development, and treatment is made in a timely manner.  Given the results in 2001 and 2002, it remains unclear whether the use of a half-rate application of Tilt or Stratego early in the season in combination with a second application at heading time is most economical.  It’s too premature to make any firm recommendations.