Corn FUNgicides

By Darren Clark, CCA-ON, 4R NMS
Crop Sales Specialist, AGRIS Co-operative - Muirkirk

As tassels are beginning to pop across the countryside in the corn crop, it’s time to begin planning and determining the need for fungicide applications.

Some areas within our trading area have seen excess moisture. This excess in precipitation along with high temperatures and high relative humidity have caused prolonged leaf wetness in the corn canopy.

We need to be aware of prolonged leaf wetness as this is often associated with the onset of foliar leaf diseases and ear rots.

Source: Crop Protection Network

It’s important to understand which products on the market will give us the best protection against foliar leaf diseases and Gibberella ear rots. Below I’ll review a few diseases to keep an eye out for and some preventative control options we have in the toolbox:

Northern Corn Leaf Blight (NCLB)

• The fungus overwinters in corn residue.
• Symptoms usually appear first on the lower leaves.
• Leaf lesions are 1" – 6” long.
• It can be economically damaging when identified near pollination.
• This disease thrives at moderate temperatures and prolonged leaf wetness.
• Some hybrids have resistance to NCLB.

"Cigar-shaped" northern corn leaf blight lesions.
Source: Crop Protection Network. Image: Daren Mueller.

Gray Leaf Spot (GLS)

• The fungus survives in corn residue.
• Symptoms first appear on lower leaves prior to tassel.
• Leaf lesions are up to 2” long, narrow, rectangular and light tan coloured.
• Disease thrives in wet conditions and high relative humidity <90%.

Rectangular gray leaf spot lesions delimited by leaf veins.
Source: Crop Protection Network. Image: Adam Sisson

Tar Spot

• Confirmed in Ontario last year in the five southern counties.
• Small raised black spots scattered across upper and lower leaf surfaces.
• The disease can blow in and overwinter in corn residue.

Characteristic tar spot symptoms and signs on corn leaf.
Source: Crop Protection Network. Image: Kiersten Wise, Bugwood.org

Tools to combat foliar leaf diseases

Delaro® Complete

Bayer Crop Science

• New in 2021.
• Available in a very limited supply.
• Contains three modes of action (3, 7 & 11)
• Applied at pre-tassel to full tassel controlling a wide range of foliar diseases including NCLB, GLS and Tar Spot.

Priaxor®

BASF

• Two modes of action (7 & 11)
• Applied pre-tassel to full tassel.
• Controls a wide range of foliar diseases including NCLB, GLS and Common Rust.

Headline® AMP

BASF

• Two modes of action (3 & 11).
• Applied pre-tassel to full tassel. W
• ill provide control of NCLB, GLS among others and has shown some promise controlling Tar Spot in US trials.

Gibberella Ear Rot

• The fungus overwinters in corn residue.
• Spores are spread by splashing rain and wind.
• Favourable conditions are warm temperatures, high relative humidity and moisture.
• Feeding insects such as Western Bean Cutworm can provide damage favourable for disease development.

Tools to combat ear rots

Proline®

Bayer Crop Science

Caramba®

BASF

• Caramba from BASF is also a group 3 fungicide which is a great tool for reducing DON levels in corn.
• Again, we want to apply to green silks.

The best of both worlds: foliar leaf disease and DON suppression

Headline® AMP + Caramba

BASF

• Topping up Headline AMP with Caramba is an all-encompassing solution for preventative control of foliar leaf diseases but also has great action reducing DON levels in corn.
• Apply from 75% green silks until silks have browned off.

Miravis® Neo

Syngenta

• New from Syngenta in 2020.
• Group 3, 7 & 11 fungicide.
• Miravis Neo controls a wide range of foliar leaf diseases and also suppresses DON levels. Apply from 75% green silks until silks have browned off.

It will be time well spent with your local AGRIS Crop Specialist. There are many other things to consider as we enter fungicide application timing.