By Angie Peltier
After the Wind and Hail: Corn and Soybean Recovery and Yield Potential. The severe weather that rolled through several counties in Western Illinois in the early morning hours of June 22 makes one think long and hard about how wind- and hail-damaged corn and soybean crops might fare and whether there is anything that can be done to help to preserve remaining yield potential (Figures). Recent University of Illinois Pest and Crop Management Bulletin articles featured pictures of the damaged crops and discussed the effect of hail on both corn and soybean yield potential.
Some disease is favored by hail damage. While disease caused by some plant pathogens can be favored in hail-wounded tissue, many of these pathogens cannot be managed with fungicides. Most of the fungi that cause foliar disease in corn and soybean are able to directly penetrate leaf tissue and do not require wounds or natural openings in order to infect leaves. However bacterial diseases such as Goss's wilt in corn and bacterial blight in soybean are favored by violent weather events such as hail. Unlike foliar fungicides that can be used in-season to protect plant tissue from fungi, there are not really in-season tools to manage bacterial disease. This is one reason why careful disease diagnosis is essential.
Foliar Fungicides on Hail Damaged Corn and Soybean. While many researchers have taken advantage of naturally occurring hail events to compare yields of hail-damaged corn and soybean in plots that were either treated or not treated with a foliar fungicide. While these experiments are important, as mother nature is unlikely to leave random areas of experimental fields untouched by hail, these experiments are unable to compare the effect of foliar fungicides on disease severity and yield between hail-damaged plots and undamaged plots.
Three recent articles summarize research that took place in Illinois and Iowa on corn and in Iowa on soybean.
Illinois-Corn (Bradley and Ames, 2010.). Former University of Illinois Extension Plant Pathologist Dr. Carl Bradley and Research Specialist Keith Ames used a gas-powered weed whipper to simulate hail damage in corn at the twelve-leaf (V12) growth stage in both 2007 and 2008. They then either did not apply a foliar fungicide or applied fungicide active ingredients azoxystrobin or pyraclostrobin to corn at tasseling (VT). Disease severity ratings were collected from each plot 3 weeks after fungicide treatment.
They found the following: 1) that simulated hail damage significantly reduced yield in both years, 2) that in one year simulate hail damage increased grey leaf spot severity, 3) that in one year foliar fungicides reduced disease severity, 4) when compared with untreated control plots, foliar fungicides did not significantly improve grain yields in either undamaged or simulated hail-damaged plots.
Iowa-Corn (Sisson et al., 2016a.). Plant pathologists and economists from Iowa State University conducted research trials in 2012, 2013 and 2014 in which they simulated hail damage using either a weed whipper or an ice propelling machine on corn at the tasseling (VT) or blister growth stages (R2). They then applied the foliar fungicide active ingredients pyraclostrobin and metconazole within 3 or 8 days after injury. Disease severity ratings were collected from plots when plants reached the dent (R5) growth stage.
They found the following: 1) that compared with uninjured plants, simulated hail significantly decreased yield, 2) that although overall severity was low, contrary to Illinois results, hail-injured plants had lower disease severity than uninjured plants, 3) when compared to untreated plots, foliar fungicides did not reduce disease severity in hail-damaged plots, 4) when compared to untreated plots, foliar fungicides did not significantly increase yield in hail-damaged plots, 5) there were positive economic returns when corn injured at tasseling was treated with fungicides 8 days after injury.
Iowa-Soybean (Sisson et al., 2016b). Plant pathologists and economists from Iowa State University conducted research trials in 2012, 2013 and 2014 in which they then simulated hail damage using an ice propelling machine at either beginning flowering (R1) or full pod growth (R4) stages. They then applied either a foliar fungicide (pyraclostrobin) alone or in combination with an insecticide (alpha-cypermetrin) at the beginning pod (R3) growth stage. They then assessed the upper and lower canopy for foliar disease.
They found the following: 1) simulated hail caused significant yield loss compared to uninjured plots, ) there were no consistent differences in disease severity between injured and uninjured soybeans, 3) there were no differences in foliar disease severity between treated and untreated plots, 4) there were significantly higher yields in two of the six site-years when R1-injured soybeans were treated with insecticide or insecticide plus fungicide, 5) when compared with fungicide alone, fungicide plus insecticide was more likely to result in a positive economic return in hail-damaged soybean.
Conclusions and Recommendations. The authors of each of these three articles suggested that factors other than hail-damage (such as disease pressure) should be used to make foliar fungicide decisions.
From Bradley and Ames (2010),
"Results from our research trials indicated that foliar fungicides provided very little benefit to corn injured by simulated hail; thus, growers should consider factors other than hail damage when making fungicide application decisions for corn."
While they state the limited scope of their research, Sisson et al. (2016a) state:
"Our findings that yield of corn plants receiving hail midseason is not significantly affected by Headline AMP application, and that foliar disease risk is reduced in hail-injured plants, could decrease unjustified pesticide applications and save farmers money during an already difficult growing situation."
From Sisson et al. (2016b),
"Based on our results, R3 fungicide application to soybean injured by hail at R1 or R4 will likely provide little yield-preserving or disease-limiting benefits when foliar disease severity is low."
Source:.illinois.edu