Category: Fungicide Use in Corn

Barley Yellow Dwarf Virus Case Study

Del V0ight – Penn State Extension

Prior to this snow I was asked to field diagnose an issue in Atlantic Barley.  Symptoms were visual and I collected specimens for analysis.  A pattern did not present itself and it was not confined to an area. After collecting samples I took them to SEAREC for analysis.  Suspected BYDV and have sent tissue to the disease lab to confirm. Low pH could also be at play so I will collect 2 inch samples and use a Cornell pH kit to rule that out.

 

pH in top 2 inch is fine

Foliar Applications of Fungicides on Corn.

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


Figure 1 Penn State SEAREC- 2014 Corn Response to Fungicide Applications- D.G. Voight and A. Collins
Questions to ask?
Ask some simple questions to determine the benefit that might come through a foliar application of a fungicide to VT-R1 Corn. We cannot make a decision for you but if you ask some simple questions of yourself to address your fields and also to address your seed representative and seed guides to determine the benefit of an application.
A. Disease history: Low lying fields with a history of disease are more likely to respond to a fungicide.                                                                            
1. No
2. Yes

B. High yield history:  High yield fields are more likely to show an economic response. 

1. Poor
2. Average
3. High yielding
C. Hybrid resistance: The lower the genetic resistance to gray leaf spot, northern corn leaf blight and anthracnose, the more potential for an economic response.
1. Highly resistant
2. Average
3. Poor resistance
D. Crop rotation: Corn following corn tends to harbor more disease inoculum.
1. Following other crops
2. Following corn
E. IPM: Corn diseases are just starting to appear, especially in no-till corn on corn fields. The more presence of disease on the leaf the higher the risk of further development.
1. Less than 5% visible disease

2. 5-10% visible disease

3. 10% or greater disease
F. Fertility: Low K levels and compacted soils could exacerbate disease effects on lodging and yield.    If the field has poor fertility the likelyhood of increased disease invasion is higher.                                                              
1. High fertility
2. Average
3. Poor fertility
 
If you go through these simple questions and more than one meets lends the field to infection spraying might be a profitable venture.