Should You Make a Wheat Foliar Fungicide Application?

Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist April 26, 2014 15:35

Should You Make a Wheat Foliar Fungicide Application?

We have reached the time of year when automatic foliar fungicide applications are suggested for wheat. As most would suspect, I am a firm believer that fungicides provide the most economic response when used on varieties that are reported to be susceptible to the more damaging foliar diseases (e.g., stripe rust). At present, stripe rust has not been identified in a commercial wheat field. However, last night I was able to identify minimal stripe rust infection on some volunteer wheat growing under the MSPB-funded rainout shelter in Stoneville. I suspect the infection occurred in the fall. Interestingly enough, telia had started to form on some of the leaves, which suggests the environment under the plastic covering of the rainout shelter is no longer conducive for stripe rust development (too hot). Wheat in the vicinity of the rainout shelter is not infected. I suspect this is an isolated incident and certainly not cause for concern. Moreover, volunteer wheat is normally more susceptible to foliar disease. I’m not suggesting a fungicide application needs to be made to wheat simply because I found 10 leaves containing stripe rust.

Firstly, I do not remember ever seeing such a clean wheat crop in the years I have had wheat responsibilities (going on 10 years). But, with that in mind, there are quite a number of fields that have received some form of drift from a local herbicide application. Keep this in mind when scouting for foliar diseases present. Paraquat will produce a tear

Paraquat injury on wheat leaves will produce a teardrop type lesion.

Paraquat injury on wheat leaves will produce a teardrop type lesion.

drop shaped lesion with a bleached center.

When considering a fungicide application in wheat there are several key characteristics to consider. Growth stage is important since the majority of fungicides have a specific pre-harvest interval (PHI) that likely cuts off at heading complete (Feekes 10.5), which immediately precedes the observation of flowers (Feekes 10.5.1). For the specific fungicide products labeled for application in wheat and their respective PHI see the associated table (NCERA 184 Wheat fungicide table).  See: http://www.mississippi-crops.com/2014/03/20/identifying-wheat-growth-stages-using-the-feekes-scale/ for more information regarding growth stages in wheat.

Yield

In MS we have an extremely limited data set regarding the “plant health” fungicide applications, in the absence of disease, which are now quite commonplace. The majority of the time when I conduct wheat fungicide trials I am managing a disease present in the field (see: http://www.mississippi-crops.com/2013/03/11/fungicide-applications-in-wheat-targeting-disease-to-prevent-yield-loss/ ) on an extremely rust-susceptible wheat variety because I am interested in the specific response of the fungicide. However, over the past few years I have been privy to data sets from other states and have had numerous conversations with other plant pathologists that conduct fungicide trials in wheat regarding plant health applications as well as the different responses of susceptible versus resistant varieties to fungicide applications. Similar to the plant health situation in corn production systems, plant pathologists have not observed large yield increases following a timed fungicide application especially to foliar disease resistant wheat varieties.

In general, fungicide applications provide the most consistent benefit when applied in situations either before disease occurs or after disease has been observed in a field of a susceptible wheat variety. Stripe rust resistant wheat varieties have not responded near as well to fungicide applications in adjacent states. In the years when I have conducted fungicide applications in response to stripe rust, I have observed a substantial yield response (see the below link regarding fungicide trials conducted during the 2012 wheat season). In addition, test weight has also been greater following the fungicide application in the presence of disease with some fungicides, but not all.

In the attached pdf file, yield response was either minimal or non-existent during the 2013 wheat season since no observable foliar disease (either leaf or stripe rust) was present in the sprayed trials (2013 Foliar fungicide wheat trial data from Western MS).

Test weight

The resulting test weight following a fungicide application appears to be similar situation to the yield response. In years where I have made fungicide application trials in response to foliar disease such as stripe rust, the response of the fungicide with regards to test weight has varied by fungicide product (e.g., Headline and TwinLine versus Priaxor (Table 2)) (see: http://www.mississippi-crops.com/wp-content/uploads/2013/03/wheat-fungicide-tables1.pdf). In the attached tables, note that test weight was not influenced by a fungicide application in the absence of foliar disease during the 2013 season in either of the two wheat varieties treated (see the above link to the pdf).

The answer

Based on my observations this season, with little to no foliar disease present in the wheat crop (and a Fusarium head blight (scab) predictive model that continues to suggest the environment in 98+% of the state hasn’t been conducive for scab to develop), I would forego making a fungicide application to wheat. However, I leave that type of a decision up to each of you. In my opinion, the wet, cold winter has appeared to reduce the threat of foliar disease this season.

Print Friendly
Tom Allen, Extension Plant Pathologist
By Tom Allen, Extension Plant Pathologist April 26, 2014 15:35
Write a comment

No Comments

No Comments Yet!

Let me tell You a sad story ! There are no comments yet, but You can be first one to comment this article.

Write a comment
View comments

Write a comment

Your e-mail address will not be published.
Required fields are marked*

Subscribe to receive updates

  • Soybean Harvest Aids

    Several calls have come in over the last week regarding soybean harvest aid options for various scenarios. In some cases, fields have been observed with varying degrees of maturity. In ...
  • Sugarcane Aphid Control with Falling Temperatures

    In 2014 we saw two brief time periods of less than satisfactory control with Transform on sugarcane aphids in grain sorghum across a broad geography. At the time we were mixing a ...
  • Pheromone Trap Counts, August 28. 2015

    Bollworm trap catches remained similar to last week, which is somewhat lower than average for this time of year. Tobacco budworm trap catches were somewhat higher this week. As most ...
  • Pheromone Trap Counts, August 21, 2015

    Bollworm moth trap catches were slightly higher in most counties this week but are generally lower than average counts for this time of year. Tobacco budworm moths continued to be ...
  • Defoliating Caterpillars in Peanuts

    We have had numerous calls over the last 2 weeks about caterpillars in peanut from all around the state. In every case, the calls have involved a complex of multiple species including bollworm/tobacco budworm, cutworms, armyworms, saltmarsh caterpillar, loopers, and rednecked peanut worm. ...
  • 3rd Annual Mississippi Sweetpotato Field Day Program- August 27th

    Mississippi State University will host its 3rd Annual Sweetpotato Field Day Thursday August 27 at the Pontotoc Ridge-Flatwoods Branch Experiment Station (8320 Hwy 15 S., Pontotoc, MS 38863).  Registration is ...

More Info By