By The Certis Team
As California growers know all too well, June Gloom isn’t just a weather phrase—it’s a seasonal shift that can quietly impact crop health across the state. With cooler temperatures, overcast skies, and elevated humidity, June Gloom can create ideal conditions for plant disease to thrive, especially in high-value specialty crops like grapes, strawberries, tomatoes, leafy greens, and brassicas.
Understanding how this weather pattern affects your crops—and how to respond with smart, sustainable protection—is key to managing risk and maintaining yield.
What is June Gloom?
"June Gloom" refers to the marine layer-driven overcast and cool weather that settles over California’s coastal and inland valleys during late spring and early summer. While it may be a relief from scorching heat, the consistent morning fog, high humidity, and lack of sun can lead to conditions that support fungal and bacterial diseases, including:
Why It Matters for Crop Health
The biggest threat June Gloom brings isn’t visible—it’s moisture retention. Prolonged leaf wetness, poor airflow, and reduced evaporation. This creates an environment where pathogens can flourish, especially in tight canopies or shaded row areas. If left unchecked, these diseases can reduce quality, yield, and storability, hitting both organic and conventional growers hard.
What to Watch For
During June Gloom, be alert to early signs of:
✅ Regular scouting during foggy, humid mornings is essential—especially in grape vineyards and coastal strawberry blocks, where Botrytis and powdery mildew thrive under these conditions.
How Certis Biologicals Can Help
Biologicals offer powerful, flexible protection during periods of intense disease pressure—especially when weather limits spray opportunities or residue concerns are top of mind. Certis Biologicals delivers proven control while offering convenience, including lower use rates and packaging designed for ease and efficiency in the field.
Activates Systemic Acquired Resistance (SAR) in the plant, helping crops defend themselves against pathogens like downy mildew and bacterial leaf spots—with zero residue and excellent fit for integrated programs.
A broad-spectrum biofungicide and bactericide that thrives under humid conditions. Effective on Botrytis, powdery mildew, and leaf spots, it’s a top choice for grapes, strawberries, and other crops during foggy spells. The low use rate of 10 ac/case compared to competitors and flexible compatibility make it easy to work into rotational programs.
A low-load copper soap fungicide that offers excellent surface protection with reduced phytotoxicity—ideal for early intervention under wet conditions without excessive copper load concerns.
This next-generation biofungicide delivers both preventive and curative control of diseases like Botrytis, powdery mildew, and Alternaria—frequent threats during June Gloom. With strong residual activity, no MRL concerns, and broad tank mix compatibility, Howler EVO is built for season-long use in grapes, strawberries, and vegetables. Plus, its concentrated formulation means fewer pounds per acre and easier handling, making it a go-to option for sustainable disease control with fewer logistical headaches.
Proactive Tips for Growers
While June Gloom may feel like a break from California’s dry heat, it’s anything but a break for growers. Stay ahead of crop disease with timely scouting, smart application planning, and proven biological solutions from Certis Biologicals. With the right tools, you can turn foggy challenges into clean, productive harvests.
About Certis Biologicals
Certis Biologicals is the leading developer, manufacturer, and distributor of biological innovation such as biofungicides, bioinsecticides, bionematicides, bioherbicides, and plant health-promoting products, servicing the agriculture, turf, greenhouse, home, and garden markets globally. With a proven, broad portfolio of products and a continuous pursuit of new solutions for conventional and organic production, Certis Biologicals is a leader and partner in sustainable crop production trusted by farmers in the U.S. and more than 50 countries across the world. To learn more about Certis Biologicals and their portfolio of proven solutions, visit CertisBio.com.