Proper application key to maximizing fungicides

There’s a mountain of available data showing that the proper application of fungicides results in higher yields, higher bushel weights, better grain quality and lower disease losses in wheat and barley. Properly applied fungicides have also proven to be cost effective and improve the returns per acre.

The key words here are: “proper application.” In order to reap the many benefits of fungicides, it’s critical that the right product is applied, in the right concentration, with the right equipment, during a narrow application window. Improper product choice, poor application equipment and/or practices, or spraying at the wrong time can render fungicides ineffective, decrease margins and can even decrease grain quality.

Step One: Understand what fungicides actually do

Step one in proper fungicide use is to remember that fungicides are not the same as herbicides. Herbicides are curative tools — you see a problem, you apply herbicide, problem solved. Fungicides are primarily preventive tools. By the time you see signs of disease, yield loss is already occurring and fungicides will not solve the problem — they can only prevent spores and mycelia from continuing to infect the plant, for a while at least. With fungicides you have to have a proactive approach.

Step Two: Understand the disease

Know what diseases can be a problem, assess the risk of outbreak (field history and current environmental conditions) and know which fungicides control the diseases you want to protect against.

Wheat and barley diseases that are most troubling for Canadian growers are rust diseases, especially stripe rust; leaf spot diseases such as tan spot and spot blotch; and head diseases, particularly fusarium head blight (FHB). Many of these diseases are seed borne, which is why the first fungicide application many farmers make every year comes in the form of treated seed. But later season infection can still occur via fungal spores in crop residue and soil, or by blowing in from neighbouring fields.

Growers also have to consider the resistance package for the cereal variety they’re growing and whether environmental conditions are conducive to disease development. If you plant a variety with excellent disease resistance and conditions are hot and dry, a fungicide application is not as critical as when you plant a susceptible variety and experience humid or wet conditions.

If you want fungicides to work, always follow label instructions for rate, timing, water volumes, number of applications allowed in a season and pre-harvest intervals, especially if you’re applying the fungicide at heading.

Step Three: Timing

It has been a common practice to apply half rate fungicide (along with a herbicide) at herbicide timing. Kelly Turkington, research scientist with Agriculture and Agri-Food Canada in Lacombe, AB, questions that. He notes there’s typically little disease around when herbicides are applied, and if you delay the herbicide application until disease appears, the potential loss from weed competition is greater than the savings in disease prevention.

An exception is stripe rust. Turkington says growers should scout for stripe rust at herbicide timing since it can appear very early. If it is present, he recommends a full rate of fungicide should be considered, along with a herbicide, at herbicide timing.

Many growers are applying fungicides at the flag leaf stage. Research has proven that protecting the flag and penultimate leaves — which are primarily responsible for grain fill — from infection is often economically beneficial, even when disease pressure is low. However, this timing provides no protection against head diseases.

If you need to protect against FHB, or other head diseases, the application window at heading is very narrow. It is important to note that application at head timing will still provide protection against leaf diseases. Ideally you should spray wheat when 15 per cent of the crop is flowering, which occurs shortly after heading is completed.

In barley, flowering begins before the head is fully out of the sheath. Optimal spray windows can come and go very fast — less than a week in most cases and in as little as a day, if conditions are right. So if you are spraying at heading, you must scout daily, have your sprayer ready to go and be prepared to cover all acres in a very short time period.

Bayer has conducted over 100 side-byside field trials over the past eight years across the prairies to determine the best fungicide application timing in cereals. To see trial results specific to your area, go to »

Step Four: Equipment

Your sprayer must be specifically set up for a fungicide application because the product has to penetrate a four- or fivefoot plant canopy and, because fungicides don’t have the same translocation properties that herbicides do, thorough plant coverage is critical to disease control. And that’s not easy when you’re looking to make contact with vertical (heads and stems) and horizontal (leaves) plant parts through a thick canopy.

Tom Wolf, a spray technology specialist and self-described “Nozzle Guy”, has done extensive research into best practices for fungicide application in cereals. On, he writes that while application timing is key, water volume is the most important application parameter when it comes to achieving good coverage. Increasing water volumes has a greater affect on fungicide performance than droplet size or spray pressure.

Other variables like nozzle type, nozzle spacing, travel speed, droplet size, flow rate, spray angle, boom height and spray pressure can all differ depending on the disease you want to control and crop conditions. The one constant is that you need to pay attention to all of them if you’re going to get the full benefit of spraying a fungicide. Check out