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Disease Management for a Strong Tomato Crop

June 29, 2023
Fruiting, healthy tomato crop with no sign of diseases

Fruiting, healthy tomato crop

As we move into the latter part of the season, disease threats are likely on most of your minds. We recommend thinking ahead and starting treatments early. While crops may not begin to show signs of disease until later in the season, early action is key to preventing infection.

So, which diseases should you be looking for, what specific issues do they present, and how can you protect your yield potential?

Disease threats

A couple of key diseases are likely to present themselves now, or the carriers of these diseases may begin to move in. Curly top, brought to plants by beet leafhoppers acting as vectors for the disease, can cause real challenges for your crop.  Phytophthora root rot begins to affect tomatoes about a month after planting. However, early blight is the most common disease threat to tomatoes that can arise at any stage of development, driven by Alternaria infections.  The spores of this pathogen spread, like many pathogens, by wind or water splash, surviving between seasons on crop debris in the soil.

Problems posed

Tomato leaf infected with early blight

Tomato leaf infected with early blight

Each disease poses a unique risk to yield potential in tomatoes. They cut off growing plants from nutrients and use them to nurture their own growth, making them stronger than early-emerging plants. Defoliation is another detrimental factor of disease. When there’s less leaf surface available for photosynthesis, growing plants aren’t getting the nutrients needed for a strong, healthy growth. This can cause stunted growth, reduced quality and lower yield potential.

With curly top, infected plants can turn yellow, stop growing and become stiff, potentially killing the plant. The disease gets its name from the first symptom that usually appears: discolored leaves that curl in at the edges. Phytophthora root rot also poses the risk of plant death. Brown lesions might be seen around the base, and eventually the roots can rot away and die, causing plants to grow slowly or wilt.

Early blight degrades the tissue it infects, which causes multiple issues: lost growth means the plant must regenerate, and a reduced canopy may not be able to support as large a crop and can reduce yield. Defoliation in the lower part of the plant leaves the tomato fruit susceptible to sunscald, opening the door to rot.

How to protect your crop

Following through on a sound management plan drives marketable yield in tomatoes. Cultural tactics paired with preventive fungicide applications can help keep crops healthy through harvest, withstanding the pressures of disease.

Cultural practices include:

  • Develop and stick to a crop rotation program.
  • Remove volunteer weeds.
  • Cull infected tomatoes to reduce sources of inoculum and, therefore, disease.
  • Minimize moisture on the plants themselves through the use of drip irrigation.

Preventive treatment also can help preserve marketable yield potential. Adding a fungicide in a mildew or hopper spray can help with early control. We recommend a fungicide with efficacy on Alternaria, such as Aprovia® Top or Miravis® Prime. These products also offer strong residual control on both powdery mildew and early blight.

Like any disease management program, preventive action is foundational to protecting yield and quality potential through the end of the season.

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