---
title: How June Gloom Impacts California Crops—And What Growers Can Do About It
description: Learn how to prevent and manage fire blight in apples and pears using integrated pest management strategies, from early season prep to post-bloom defense.
---

[Certis Biologicals Blog ](https://www.certisbio.com/blog)

# [How June Gloom Impacts California Crops—And What Growers Can Do About It](https://www.certisbio.com/blog/california-june-gloom-0)

 Written by [The Certis Team](https://www.certisbio.com/blog/author/the-certis-team) | Jun 18, 2025 7:13:18 PM

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:

- **Downy mildew****  
  **
- **Botrytis (gray mold)****  
  **
- **Powdery mildew****  
  **
- **Leaf spots and rots**

**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:

- **Lesions or water-soaked spots on leaves and  fruits****  
  **
- **Fuzzy gray mold growth** on berries, stems, or flowers
- **White fungal growth** on the underside of leaves
- **Prolonged canopy wetness** after irrigation or dew

✅ **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.

[**🛡️LifeGard® WG**](https://www.certisbio.com/products/biological-plant-activators/lifegard-wg)

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.

[**🍓Double Nickel®**](https://www.certisbio.com/products/biofungicides/double-nickel-lc)

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.

[**💧Cueva® **](https://www.certisbio.com/products/biochemicals/cueva)

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.

[**🌿Howler® EVO**](https://www.certisbio.com/products/biofungicides/howler)

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**

- **Start early.** Apply preventively, not curatively, when conditions favor disease.
- **Use weather-based forecasting tools** to time applications.
- **Rotate biologicals with conventional chemistry** to avoid resistance and maintain control.
- **Monitor closely** in low-lying or shaded blocks where humidity lingers longer.

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](https://certisbio.com/) 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**.](https://certisbio.com/)

[View full post](https://www.certisbio.com/blog/california-june-gloom-0)

```json
{
  "@context" : "http://schema.org",
  "@type" : "BlogPosting",
  "author" : {
    "@type" : "Person",
    "name" : "The Certis Team"
  },
  "dateModified" : "2025-06-18T19:16:52.435Z",
  "datePublished" : "2025-06-18T19:13:18Z",
  "headline" : "How June Gloom Impacts California Crops—And What Growers Can Do About It",
  "image" : {
    "@type" : "ImageObject",
    "height" : 368,
    "url" : "https://www.certisbio.com/hubfs/Certis%20Blog%20Images%20%283%29.png",
    "width" : 600
  },
  "mainEntityOfPage" : "https://www.certisbio.com/blog/california-june-gloom-0",
  "publisher" : {
    "@type" : "Organization",
    "logo" : {
      "@type" : "ImageObject",
      "height" : 60,
      "url" : "/hs/hsstatic/content_shared_assets/static-1.4092/img/default-amp-logo.png",
      "width" : 60
    },
    "name" : "Certis Biologicals Blog"
  }
}
```