Potato Field

3 Steps to Optimize Fungicide Applications

July 18, 2022 7:30 a.m.


A fungicide can be defined as any substance that destroys, inhibits, or prevents the growth of fungi. Fungal pathogens are notorious for their potential to significantly reduce the yield potential and quality of agricultural crops. Over the last 25 years, the use of fungicides has been a practice that has grown in popularity, where it is now common practice for a pest management program to include seed, in-furrow, and/or foliar fungicide treatment(s). For optimized efficacy and return on investment, there are several aspects of fungicide use that growers and applicators should keep in mind. Here are three steps to optimizing fungicide applications this season:

1. Anticipate and plan your management strategy

    • Cropping history – know the crop rotation history in your field, certain continuous crop situations can lead to a buildup of disease inoculum
    • Tillage practices – conservation tillage can lead to certain pathogens overwintering in the field on crop residue, whereas conventional tillage can promote the breakdown of the residue pathogens rely on at a faster pace
    • Hybrid/Variety used – the disease ratings and natural tolerance present in certain varieties and hybrids will differ, understanding if a certain cultivar is more susceptible to a common disease can help prepare your management plan

2. Understand your fungicides and how they work best

    • Different actives – active ingredients perform differently on different diseases, understand what active ingredient(s) are found in the product you are using and be sure your targeted pest is labelled
    • Systemic vs Contact – systemic fungicides have the capability for translaminar movement, localized leaf movement, and/or upward movement via the xylem. Contact fungicides rely on thorough coverage to form a protective barrier against disease inoculation. Understand the mobility of your product to use it at it’s fullest potential, but regardless of if it is systemic or contact, thorough coverage will always help to optimize any product’s efficacy.
    • Disease spectrum – study the product label of fungicide you choose to ensure that the targeted/expected disease(s) are included in the spectrum of pathogens listed on the label.
    • Preventative vs Curative – fungicides generally perform best when used preventatively, i.e. before significant fungal infection has occurred. Other products like certain active ingredients in the Triazole family will have curative properties. However, most fungicides will perform at their best when used preventatively.

3. Proper application techniques and timing

    • Disease triangle – for disease to occur, 3 things must happen together:
          • 1. A susceptible host must be present (a crop with a low resistance level to a certain pathogen)
          • 2. A conducive environment for infection must be present (generally warm, humid conditions)
          • 3. A virulent pathogen must be present
    • Fungicide timing – know that each crop will have a unique timing where a fungicide offers the most potential for a positive return on investment, for a few of our crops, those timings are as follows:
          • VT/R1 for Corn
          • R1 and R3 for Soybean
          • Flag leaf and heading for wheat


healthy corn plantSouthern Rust in corn plant

An example of fungicide applied preventatively ahead of Southern Rust blowing into the field versus a situation where a fungicide was used after significant disease infection already occurred.

    • Full rates and carrier volume – always use full labelled rates of any product used, apply in the proper carrier volume, and utilize recommended nozzles packages and droplet size

Optimizing Fungicide Applications this Season

MANZATE PRO-STICK is a reliable fungicide that finds a large amount of utility in the IPM programs of potato and sugar beet growers, in addition to a number of other labelled crops. For potatoes, MANZAT PRO-STICK provides control of early and late blights, in addition to black dot and suppression of botrytis when used at 1 – 2 lbs/Ac. Crop size will determine the proper use rate of this protectant fungicide that acts via contact. With a 4 – 6” tall crop, use 1 lbs/Ac, then as vines increase in size, apply 1.5 – 2 lbs/Ac at intervals of 5 to 10 days or 1 lbs/Ac at 3 to 5 days. With sugar beets, MANZATE PRO-STICK provides control of Cercospora leaf spot when used at 1.5 – 2 lbs/Ac with applications beginning when disease infection first threatens and repeated at 7 to 10 day intervals.

For more information on MANZATE PRO-STICK, visit the UPL website.