As of June 30th, 19.3% of Western Iowa is considered abnormally dry and according to the forecast will continue to get drier. During the normal course of
growing, corn and
soybean plants photosynthesize and with the exchange of CO2
and O2 through the stomata the plants give off water vapor in a
process called transpiration. In fact, according to the USGS an
acre of corn can transpire 3,000-4,000 gallons of water each
day. Transpiration rates are affected by many things including
temperature, humidity, sunlight intensity, precipitation, soil
type and saturation. In a normal year plenty of water falls in
Iowa and little thought is given to this process. Conversely, in a
year where water is at a premium anything that can be done to
help the plants conserve water can translate into yield gains.
The question has come up should one continue to invest in a crop if it is going turn off hot and dry and
will the fungicide help in water conservation? The answer to this question is undoubtably yes. The
strobilurin chemistries have for a long time been known to help plants reduce transpiration and the
same goes for the new SDHI chemistries, Solatenol in Trivapro fungicide and Adepidyn in Miravis Neo fungicides=.
Several studies were then conducted to
see if these new fungicides provided
the same or more plant health benefits
as some of the older strobilurin
fungicides. One of those studies was
conducted by J. Leipner and published
in ASM Biology Research in 2015 (figure
3) and showed that transpiration was
reduced by up to 40% compared to the
untreated check and did NOT affect
photosynthesis. That means that the
plant had the best of both worlds by
staying at peak photosynthesis while conserving water. Additionally, Leipner found out this was rate dependent. Meaning that maximum water conservation occurred at the highest rate studied.
Another way to measure stress on a plant is to use a hyperspectral analyzer or Lab Spec 4.
This tool measures different wavelengths of light that cannot be seen with the naked eye.
One of the things that it can measure is plant water content. In figure 4 the Lab Spec 4 was
used to take readings on drought stressed plants that were treated and untreated with different fungicides. In this case Quilt Xcel (combination of a strobilurin and triazole fungicides) and Adepidyn (SDHI fungicide) which is found in Miravis Neo were studied. The study showed significantly better vegetative index in both fungicide treated plants compared to the untreated.
What does this mean to the average grower? Fungicides not only help protect the plant from disease they will also help maintain proper growth and function within the plant during times of water stress which will in turn lead to yield protection.
Dean Grossnickle, Agronomic Service Representative
Randy Kool, Agronomic Service Representative Western Iowa
Zach Trower, Agronomic Service Representative Eastern Iowa