Should Hail-Damaged Corn be Treated With Foliar Fungicides?

Should Hail-Damaged Corn be Treated With Foliar Fungicides?

June 27, 2008

With the frequent hail events that have pounded Nebraska corn fields, many have questioned whether a foliar fungicide should be applied to protect the remaining injured foliage from infection by pathogens.

Photo of hail-damaged corn plant.
Figure 1. Hail-damaged corn.

Many of the diseases favored by wounding are not controlled with foliar fungicides, such as those caused by bacteria, (especially Goss's wilt and blight), and common smut and stalk rots. Furthermore, foliar diseases that can be managed with foliar fungicides, such as gray leaf spot and southern rust, do NOT require wounds for infection. The development of some of these diseases following a hail event might more likely be attributed to the rain and increased relative humidity that accompanied the storm rather than the hail itself.

A study conducted in Illinois last year at a single location evaluated the effects of fungicide applications in simulated hail-injured corn on gray leaf spot severity and yield. In that study, fungicide applications did not statistically increase yield when applied on tasseling corn that was damaged the previous day (Table 1) to simulate hail injury.

Table 1. Effect of simulated hail damage and foliar fungicides applied at tassel emergence on gray leaf spot severity and yield of a susceptible corn hybrid near Champaign, Illinois, in 2007.(Bradley and Ames, 2008. Foliar Fungicides in Corn Production: A Look at Local and Regional Data. Proceedings of the 2008 Illinois Crop Protection Technology Conference.)

Simulated Hail1

Fungicide

Rate/Acre

GLS Severity2

Yield (bu/ac)

No
Untreated
 
57
174
 
Headline®
6 fl oz
33
179
 
Quadris®
6 fl oz
42
170
 
Quilt®
14 fl oz
40
155
Yes
Untreated®
 
62
141
 
Headline ®
6 fl oz
48
144
 
Quadris®
6 fl oz
47
142
 
Quilt®
14 fl oz
35
140
 
 
LSD 3
12
11
1 Hail was simulated by damaging corn plants with a weed-eater type string mower.
2 Gray leaf spot severity (0-100% scale).
3 Fisher's protected least significant difference (? = 0.05).

There is no strong consensus among plant pathologists regarding this topic due to the limited research data that are currently available, so additional research is needed to better determine the potential for foliar fungicides to protect hail-damaged corn. For those considering pre-tassel applications of foliar fungicides this year, be advised that some company recommendations have changed, particularly for the use of tank mixes and adjuvants with fungicides to prevent potential plant injury and are summarized in Foliar Fungicides on Corn: Label Changes and Potential Phytotoxic Effects in the March 7, 2008 issue of CropWatch.

Tamra Jackson
Extension Plant Pathologist