As of today, no downy mildew has been detected in Ohio sentinel plots, according to the most recent update from 7/3/2025. These sentinel plots, designed for early crop disease detection, are located at:
Fremont (North Central Agricultural Research Station, Sandusky County)
Huron (Huron County)
Wooster (Wayne County)
Pike County (Piketon Research Station)
Figure 1. Cucurbit sentinel plot locations. Image Credit: Andres Sanabria-Velazquez
Weekly scouting and spore-trap monitoring are ongoing at all four locations. Despite favorable conditions and outbreaks in neighboring states, these Ohio plots remain negative so far for Pseudoperonospora cubensis activity.
Figure 2. Field visit to a cucurbit sentinel plot in Piketon, Ohio, for early detection of downy mildew and other vegetable diseases. From left to right: research team members conducting disease scouting and environmental monitoring. Image Credit: Andres Sanabria-Velazquez
However, powdery mildew has been observed in cucurbit crops across the state, and Phytophthora capsici has been confirmed in pepper plantings. Growers should maintain regular scouting and utilize pathogen-free seed, proper irrigation, and effective fungicide rotations as needed.
Figure 3. Early symptoms of powdery mildew on a cucurbit leaf. Image Credit: Francesca Rotondo
Figure 4. Advanced symptoms of powdery mildew on Zucchini leaf. Image Credit: Andres Sanabria-Velazquez
Figure 6. Microscopic view showing characteristic structures of powdery mildew. Image Credit: Francesca Rotondo
Figure 5. Typical symptoms of Phytophthora blight caused by Phytophthora capsici on pepper stem tissue. Image Credit: Francesca Rotondo
Diagnostic Confirmation: Submit suspect samples to the OSU Plant and Pest Diagnostic Clinic, directed by Dr. Francesca Rotondo. Early confirmation allows for timely interventions (https://ppdc.osu.edu/).
Samples may be mailed:
C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic
Ohio State CFAES Wooster Campus
c/o Dr. Francesca Rotondo
234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691
Samples may be hand-delivered:
Requires coordination with Dr. Rotondo: (330-263-3721) | rotondo.11@osu.edu