Fungicide Updates/Northern Corn Leaf Blight

Clarke McGrath

Fungicide Applications may be more profitable this year according to ISA info. Click here.

And a few thoughts from Dr. Mueller, Dr. Robertson and me. Click here.

And to make things more interesting, we are seeing some Northern Corn Leaf Blight start to show in our area, here is an article about that.

Now for local observations… field visits, phone calls, texts and emails this week have me thinking we are on the front end of the disease issues in SW/WC IA. There seems to be Northern Corn Leaf Blight (NCLB) out in many fields- but at low levels so far; but it is early, and favorable disease conditions look like they are back for the next week or better. So… when thinking about what fungicide product to use, some scouting can help guide product choices. If there is NCLB (or Gray Leaf or other fungal disease managed by fungicides) present, you’ll want to consider the preventative/curative products rather than just the straight preventatives. The NCLB link above has a link to product choices, they are numerous.

Goss’s wilt

What I am finding so far is pretty sporadic- I’ve only seen it in a few fields, and it was at pretty low levels (you had to really hunt for it). That doesn’t mean it isn’t out there in force somewhere, but so far it seems that most of our area is at pretty low levels. It can ramp up pretty quickly on susceptible hybrids though, begging the question of “what can we do about it?”. Goss’s wilt is bacterial- so fungicides do absolutely nothing to it. There are a few bactericides out there… but we have little solid information to go on.

What I wrote a couple years ago still probably holds true on Goss’s in season management-

Procidic is advertised as a broad-spectrum fungicide and bactericide with citric acid as an active ingredient. Research we are familiar with reports on the effect of citric acid on fungal pathogens of horticultural crops, but no reports of results against bacterial diseases, and no reports on corn. Procidic is labeled for use in Iowa to control Goss’s wilt, and Iowa State University plant pathologist Alison Robertson is in the process of evaluating it in depth for Goss’s management.

Another product that has been suggested for use to manage Goss’s wilt is Kocide. At last check, while Kocide was labeled for field corn, it wasn’t listing Goss’s as a target pest; this is a gray area where you will want to check with your local dealer. Since it may be labeled in the future, several Midwest universities are looking at it. Preliminary work from University of Nebraska was inconclusive.

A third product we are often asked about is a copper-based product called Intercept. There is very little information available on this product. Apparently it has been used successfully to control citrus canker, which is caused by a bacterium. But there is no published information on the efficacy of Intercept against Goss’s wilt or citrus canker. Research will likely be done on this product as well.

As we look at how similar products are used in citrus and vegetable crops, it becomes evident that it will be challenging to find the right fit for products like these against Goss’s. These products don’t “cure” bacterial diseases; rather, they are more effective as preventatives with some suppressive capabilities. Multiple applications are mentioned in the label language of some of the products, so scouting after treatment is a must and if the Goss’s continues to be an issue, you’ll have to consider another pass.

This of course raises the question, why don’t we have the updated information on these bactericides on Goss’s? Many Midwest Land Grants tried to do Goss’s research (including pretty extensive efforts both years by ISU)… Mother Nature didn’t play ball, though. Trials done in ’12 and ’13 had little to no disease due to the dry weather not completing the disease triangle (pathogen present at problematic levels, susceptible genetics, and proper weather for sustained infection). Research is being conducted this year; so far it looks like we may have the triangle completed so we can get some relevant data on the few products submitted for testing.

The good news is that many (probably the majority) of our hybrids planted in WC/SW are pretty tolerant/resistant to Goss’s Wilt. So, have customers check with their seed supplier and find out which, if any, of the hybrids they planted need to be watched more closely for Goss’s. If it is showing up in the field at levels you are uncomfortable with and the weather looks like it will be favorable for continued infection… your only choices are to leave it and see what happens, or to take a shot at managing it with products we have little experience with. I would like to provide a better answer, but that is our reality with Goss’s at this point in time.

Source : iastate.edu