Foliar Health Basics: Understanding the Disease Triangle

Healthy soybean plants with immature pods.

A multi-year, multi-trial comparison shows the value of Aproach® brand fungicides for supporting cereal crop yields.
Three factors create the potential for yield loss due to plant disease: the pathogen, the host and the environment. Together they form the Disease Triangle. An essential fourth factor is the time required for the pathogen to infect the plant and produce disease symptoms.

  • Pathogens that typically cause diseases in plants include fungi, bacteria, viruses and nematodes. Fungi are the most common. Pathogens are often present in fields and can overwinter on residue.
  • The host plant is invaded by the pathogen as a food source.
  • Environments that favor diseases typically involve moisture. Moderate temperatures and frequent rainfall create high humidity and extended dew periods, which promote growth of many plant pathogens. A cool, wet environment also can slow plant growth, making it more susceptible to certain diseases.

Factors Affecting Plant Diseases

These three factors combine to determine whether disease will affect crops.

Aproach® Prima: Higher Soybean Yields (2010-2015)

Side-by-side trials across six years show the yield advantage of using Aproach® Prima provides to control disease.

Aproach® Brands Cross-Trial Analyses: Cereal Yields (2013-2015)

A multi-year, multi-trial comparison shows the value of Aproach® brand fungicides for supporting cereal crop yields.

Manipulating any of the three factors in the Disease Triangle can minimize disease impact. For example, choosing a hybrid or variety with genetic resistance to disease or one well-suited to expected growing conditions can reduce potential for plant stress, since healthy plants are better able to withstand disease.

Changing the environment is more difficult, although managing soil fertility can improve plant growth and reduce disease effects. Adjusting plant populations, row spacing and irrigation schedules can change microclimates within fields to make them less favorable for pathogens.

It’s difficult to eradicate a pathogen from a field, although removing or burying infected plant residue can reduce an infestation, as will planting the field to a non-susceptible host for several years, says Bond McInnes, fungicide technical manager, DuPont Crop Protection.

Fungicides are an important tool for managing many key crop diseases. They inhibit growth or reproduction of a fungus, he explains. “Fungicides work best when applied before disease develops.

For corn, an application of DuPont™ Aproach® fungicide made between V4 and V7 stages provides early season protection and improved plant health. An application of DuPont™ Aproach® Prima fungicide, which has two modes of action, near tassel provides preventive and curative activity on yield-robbing corn diseases, including northern corn leaf blight, gray leaf spot, southern corn leaf blight and common rust.” An application at VT to R1 typically provides the greatest return on investment, but controlling disease as soon as it appears helps protect green leaf area to fuel photosynthesis and, consequently, grain fill.

Aproach® Prima is effective in controlling soybean rust and brown spot in soybeans to help avoid yield loss due to disease.

Aproach® Prima also controls downy mildew, rusts, tan spot, Septoria leaf blotch and glume blotch in wheat to protect yield potential.

DuPont Aproach® Prima fungicide is not registered in all states. See your DuPont retailer or representative for availability in your state.
The information provided on this website is for reference only. Always refer to the product labels for complete details and directions for use.
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