Foliar fungicides for corn

Thursday, July 30, 2015

A lot of producers in the area are either considering spraying their corn with fungicide or have already started.

Fungicides can be used to manage foliar diseases of corn and protect yield.

With the volatile markets and with yield potential already taking a knock from late planting and excessive moisture, the use of a fungicide to protect every bushel sounds even more appealing.

Foliar applications of fungicides to corn will not always provide a yield or economic benefit. The main purpose of using a fungicide is to control a disease.

The problem is in the fact that by the time that you know a foliar disease is significant enough to cause economic loss, there is little you can do about it. This leaves the producer in a quandary of trying to outguess the disease situation or to just spray and hope for the best.

The producer can evaluate a corn field's risk of developing a severe foliar disease problem and increase the probability of an economic return on his fungicide dollars.

--Previous crop and tillage practice

When corn was the previous crop and a substantial amount of residue is left on the soil surface, the risk of foliar disease increases.

--Planting date

Late planted corn is more at risk for gray leaf spot.

--Hybrid susceptibility

Hybrids with greater susceptibility are as greater risk.

--Weather and environment

High relative humidity and moisture are important for the development of foliar diseases.

--Disease observations

The earlier that some diseases are apparent, the greater the risk of losing yield.

There are reports of yield increases despite lack of disease pressure. It is true that some fungicide classes, such as strobilurin fungicides can have other impacts on plants beside disease control. One of the most visual effects that can happen to corn plants is a "greening effect". However in replicated trials, this has not always resulted in yield increases.

Overall considering the year and commodity prices there are a few factors that producers need to consider.

What's lost is lost

The weather has already resulted in lost yield potential in many fields. No fungicide application can recover those yields.

If producers are to spray, it would be best to target those fields that have the highest yield potential and any fields or hybrids that might be more susceptible to a disease problem. Fungicide applications to intermediate and susceptible hybrids should be based on disease pressure, forecasted weather conditions and previous crop history.

Uneven plant stand is evident in a lot of corn fields

Growth stages do vary across the fields. Last year, applications of fungicide prior to VT (tasseling) were implicated in deformed ears and reduced yield.

This may or may not be a factor this year, as temperature at the time of application directly affects phytotoxicity of many fungicides. Recent information also indicates that this effect may have been the result of the surfactant and not the fungicide.

--Most fungicide

products registered for corn are effective for 14 to 21 days

Since the grain fill period ranges from 55 to 65 days, timing of fungicide applications will be crucial to ensure maximum effectiveness of the product.

Foliar fungicides can help increase production and profits, if they are used appropriately.