The continuing wet humid weather has many growers asking questions about foliar applications of a fungicide on tasseling corn. Most labels dictate that applications be made between VT and R1 stages. The labels I reviewed also require that adjuvants NOT be used after corn has reached the V8 stage. However some offer this option on fully tasseled corn. Recent Agronomy Journal Publications have shown the formation of beer can ears as a result of adjuvants applied near VT. The wet weather has aloud for ideal uniform emergence of silk and tassel applications between VT and R2(blister) are the key times to apply the fungicides. Below are some considerations to better make a decision to treat or not. Many growers may be tempted to add additional products to the tank while going over the field. Most labels allow for the inclusion of insecticides but caution that growers only apply approved tank mixes and observe the most restrictive labeling.
Finally on some products there is a 30 day harvest restriction for forage and grain so bare this in mind early forage harvest might need to be delayed should an application be made. This is not a straight forward recommendation on corn and growers should look at each field and best determine its needs. We have a bumper crop in the making right now and this application on many fields would really make the most difference in preserving potential yield!!
Fungicide Selection– There are numerous options to select to manage foliar diseases. In 2014(figure 1), Dr Collins and I conducted a test of 5 different fungicides on corn and applied product at the V6 and Tassel stage as well as two applications one at V5 and followed by a R2 stage of various fungicides. In 6 out of the 10 treatments, there was a significant response exceeding 11bu/acre overall to the application of a fungicide. In all cases there was a response but not all due to the treatment. The decision is not as much which product to use but rather whether the hybrid will respond to an application. The hybrid in our trial last year was susceptible to leaf diseases. This data supports some Mid Western data showing the response of hybrids over several fields. This link will take the reader to an article and chart for the various options and what disease different products control and their PHI. I recommend one print this off as a reference. Fungicide Efficacy Comparisons
B. High yield history: High yield fields are more likely to show an economic response.
2. 5-10% visible disease
If you go through these simple questions and more than one meets lends the field to infection spraying might be a profitable venture.
One other comment here. It would be beneficial to know how the 2 week future forecast would play into this decision as temperature and humidity play such a key role in the progression of disease