Josiah Garber found tar spot lurking in one of his cornfields the last week of June. The southeast Pennsylvania corn grower says that was a first for his farm.
“I’d never found it in July before, much less the end of June. I think the pressure this year is going to be intense with all the moisture around,” predicts Garber, who’s based in Lancaster County, Pa.
Tar spot commonly overwinters as spores in plant residue. During the subsequent growing season, rain and high humidity can promote spores which can be splashed onto corn plants and then develop into what is often called homegrown tar spot.
Tar spot spores can also become air-borne in a field and blow into new fields.
How significant tar spot infections become in any given season depends on the disease triangle – the interplay between a susceptible host, a pathogen and the environment.
A Two-Pass Program Is In Place
Garber’s plan to address tar spot – along with any other disease pressure that’s present – is to make two fungicide applications 21 days apart. This year, the first one went on the crop with a ground rig just before tassel and the second application will be made right after tassel, which was underway last week.
“This is the first time we went with a fungicide application this early, but I’m glad we did since we found the tar spot,” Garber says.
For the past five-plus years, he has been investing in two fungicide applications annually, with both made post-tassel.
“We found that that pays, and once we saw that it would pay, it just became part of our program,” Garber told David Hula and Randy Dowdy during their latest Breaking Barriers with R&D podcast, available now on Farm Journal TV. This episode offers farmers some serious actionable insights to help improve ROI.
To achieve good coverage with the ground rig, Garber says he applies a fungicide/water tank mix at 20 to 25 gallons per acre.
“We’ve been working really hard on our applications, trying to cover below the ear leaf to get optimum performance,” he says. “That’s our goal.”
Droplet Size Impacts Coverage And Efficacy
The goal of getting fungicide placed in the crop where plants can readily use it is what Matt Crabbe shoots to achieve with aerial applications. He typically uses 2 gallons of water per acre as the carrier, depending on the products being sprayed.
“I hear a lot of times people talking water, water, water, but a lot of water can go to the ground and take the product with it if you’re not careful,” cautions Crabbe, owner of Crabbe Aviation, with locations in North Carolina and Virginia.
“Because you’ve got bigger droplets with the plane, you’re putting out a little more volume, and it’s not going to necessarily stay with the plant like I found it does with the lower volumes,” he tells Dowdy and Hula.
To help ensure product stays on plant leaves, Crabbe usually applies products like foliar fungicides at 3’ to 8’ above the crop canopy, maintaining a consistent speed of between 150 and 160 miles per hour.
“I try to keep the application in that range, because our test results show that sets up the droplets at the right size for optimum coverage,” he says.
Get As-Applied Maps For Your Records
Dowdy asked Crabbe whether he provides customers with as-applied maps for their reference and records, post product applications.
“You know, there’s a lot of people that want to overlay yield maps, and then some people just want to trust but verify the good old Ronald Reagan way,” Dowdy says.
Crabbe says modern technology is making as-applied maps easier to provide to growers than in previous years.
“If you place an order on my website, I can press ‘done’ when I finish spraying a field and the system will give you a look at the as-applied map,” he explains.
Crabbe recommends farmers ask their aerial applicator directly about their mapping system as many now have digital platforms where you can get a password to access your specific maps and view application details immediately after completion.
Hear more about getting the biggest bang out of your fungicide buck from Dowdy and Hula on YouTube at Breaking Barriers With R&D: Flying High and Digging Deep — Precision Ag from the Sky to the Soil and on AgriTalk, with Host Chip Flory:
Your next read: Is 600-Bu.-Per-Acre Corn in the Cards This Year for David Hula, the Reigning World Record Holder?
