Botrytis cinerea is the fungus that causes Botrytis fruit rot (BFR). Its spores are ubiquitous and readily dispersed through the air, with disease pressure largely influenced by weather conditions. Each year we conduct trials to determine the efficacy of fungicides against BFR). In order to have a successful trial, we need rainfall to coincide with … Continue reading Botrytis fruit rot management under dry and warm conditions

Why should I care? Are you seeing dying strawberry plants with brown color marbling when you cut open the crown? Do you see strawberries with black sunken lesions? If yes, it could be due to anthracnose. We are receiving an increasing number of samples positive for anthracnose. Anthracnose of strawberry is a fungal disease that … Continue reading What do you know about strawberry anthracnose?

The Strawberry Center’s diagnostic service has experienced another record breaking year for samples received. Between Jan 1 and Dec 31, 2025, 411 samples were submitted for pathogen detection. For comparison, there were 201 and 132 samples in 2024 and 2023, respectively. This year, 51% of submitted samples were from the Santa Maria district, 27% from … Continue reading Strawberry Center Diagnostic Service – Summary of 2025 Results

Powdery mildew is a common disease that affects strawberries and is caused by a fungus called Podosphaera aphanis. It thrives on dry leaf surfaces when weather is mild (between 60° to 80° F) and humidity is high. What does it look like? Early in its development, powdery mildew can be easily overlooked. Infections usually start … Continue reading When mildew evolves: Understanding strawberry powdery mildew’s secret weapon

The Strawberry Center’s diagnostic service is on track for another record-breaking year. As of June 15, over 150 plant samples have been submitted for pathogen screening—surpassing the pace of previous years. For comparison, we reached 150 samples in late August of 2024 and received a total of 123 samples throughout all of 2023. This year, … Continue reading Strawberry Center Diagnostic Update – Spring 2025

The nematode species most commonly associated with California strawberries is the northern root-knot nematode (N-RKN), Meloidogyne hapla (Fig. 1). At the Strawberry Center’s Disease Diagnostic Service, we observed an increase in submitted samples with root-knot nematodes present. Four of these nematode samples were submitted to the CDFA diagnostic lab for confirmation of the species. They performed … Continue reading Root-knot nematode diagnostic update

Drs. Adaskaveg, Michailides, and Eskalen of the University of California just published the latest edition of "Fungicides, Bactericides, Biocontrols, and Natural Products for Deciduous Tree Fruit and Nut, Citrus, Strawberry, and Vine Crops in California, 2025." Center Director Dr. Holmes and Field Research Manager Kyle Blauer collaborate with these authors on the Strawberry tables found … Continue reading New UC fungicide efficacy table published

We posted last March about angular leaf spot and it's back this year for a repeat performance. We got about two inches of rain yesterday afternoon and last night. This morning, the angular leaf spot showed so much bacterial ooze that it looked like someone with a bad sinus infection sneezed on the underside of … Continue reading Prime time for angular leaf spot

As 2024 comes to a close, the Strawberry Center Pathology Lab reflects on all of the projects, grants, and student successes this year. One of the highlights is our ongoing diagnostic plant service provided to California strawberry growers at no fee, funded by the California Strawberry Commission. As of November 15, we've received 185 plant … Continue reading Cal Poly Strawberry Center Diagnostics

A team of scientists at the University of Florida, Corteva Agriscience and Syngenta Crop Protection recently published a meta-analysis using data from 25 field trails conducted in Florida from 2005 to 2021. The analysis showed that Captan applications significantly improved marketable yields and reduced Botrytis fruit rot (Fig. 1) and anthracnose fruit rot incidence. They … Continue reading “Old but Gold”: Meta-analysis shows the value of Captan in strawberries

Figure 1. Strawberry plants dying from Macrophomina root rot. Because the pathogen attacks the crown and roots, above-ground symptoms are similar to other root pathogens (i.e., wilting, necrosis and death) and accurate diagnosis requires laboratory assays. A paper just published in Phytopathology by Pennerman, Dilla-Ermita and Henry (https://doi.org/10.1094/PHYTO-05-23-0154-R) reports that the host range of Macrophomina … Continue reading Macrophomina’s host range was exaggerated

In 2021, an effort began to determine which of the four major soilborne pathogens of strawberry in California – Macrophomina phaseolina, Fusarium oxysporum f. sp. fragariae, Verticillium dahliae, and Phytophthora spp. – are most common. Pathogen surveys of strawberry fields in the three major growing districts of California were proposed: Watsonville-Salinas, Santa Maria, and Oxnard. … Continue reading Which soilborne pathogens are most common in California strawberry fields? Part 2 – Santa Maria district

We are seeing quite a bit of angular leaf spot (ALS) in our fields and getting some calls about it in other areas of the state. Angular leaf spot is a bacterial disease caused by Xanthomonas fragariae. It typically shows up this time of year when rains are more frequent. The optimum temperature of the pathogen … Continue reading Angular leaf spot showing up

The results of two fungicide trials conducted in 2022 and published in Plant Disease Management Reports in 2023 are presented here. In these trials, 20 unique products were evaluated for performance against Botrytis fruit rot (Fig. 1). After 5 weekly applications (Fig. 1), fruit were evaluated in the field (at-harvest) and postharvest after storage at … Continue reading JUST PUBLISHED: Fungicide performance against Botrytis fruit rot

Our most economically important fruit disease is Botrytis fruit rot (BFR). BFR thrives under cool, wet conditions. Temperatures between 60F and 75F and wetness lasting over 16 hours are ideal for infection and disease development. These conditions are most likely to occur during the winter and early Spring, when fruit supply is low and prices are high. This … Continue reading It’s Botrytis fruit rot season 🙁

Figure 1. Botrytis fruit rot often starts beneath the calyx where moisture can get trapped, along with petals, where it will persist long enough for the pathogen to germinate and infect the fruit. (photo by G. J. Holmes) A recently published paper in Phytopathology by Naegele et al. adds to the work done by Cosseboom … Continue reading New publication confirms trends in fungicide resistance

https://strawberrycenterblog.com/2024/04/25/which-soilborne-pathogens-are-most-common-in-california-strawberry-fields-part-2-santa-maria-district This blog article is Part 1 of a two-part series. Part 2 article is available @ https://strawberrycenterblog.com/2024/04/25/which-soilborne-pathogens-are-most-common-in-california-strawberry-fields-part-2-santa-maria-district/ In the California strawberry industry, it's widely accepted that there are four major diseases caused by soilborne pathogens: Macrophomina root rot (caused by Macrophomina phaseolina) (Fig. 1), Fusarium wilt (caused by Fusarium oxysporum f. sp. fragariae), Verticillium … Continue reading Which soilborne pathogens are most common in California strawberry fields? Part 1 – Watsonville/Salinas district

Some strawberry varieties are genetically resistant to the Fusarium wilt disease. For example, Fronteras, Portola, and San Andreas are Fusarium wilt-resistant varieties from the University of California. A description of disease resistance for currently available varieties is on the California Strawberry Commission web site. All Fusarium wilt-resistant varieties have the same resistance gene, called “FW1”. Until … Continue reading FW1-resistant varieties with Fusarium wilt in Oxnard, CA

A recent publication by Mello et al. reports that strawberry powdery mildew (SPM) was reduced by nighttime application of UV-C to field plots at 200 J m-2 . Disease reduction was equivalent to that provided by weekly fungicide applications in CA and superior to that provided by twice weekly fungicide applications in FL.  No negative … Continue reading New publication reports efficacy of UV-C against powdery mildew in FL and CA

Figure 1. A grower field affected by Macrophomina crown rot. About the plant disease diagnostic service Soil-borne pathogens such as Macrophomina phaseolina are challenging strawberry production as they become increasingly prevalent across California (Fig. 1). Accurate disease diagnosis is the cornerstone of integrated pest management. The Strawberry Center's disease diagnostic service has been serving California … Continue reading Cal Poly Strawberry Center Disease Diagnostic Service

We usually see Zythia leaf blotch (caused by Zythia fragariae) during the early spring when plants are small and the weather is cool and wet. With summer planting in Santa Maria occurring in May, especially in fields close to the coastline where fog and heavy dews are common, the same conditions exist (i.e., small plants … Continue reading Off-cycle Zythia leaf blotch

In the vast majority of seasons, powdery mildew (PM) (caused by Podosphaera aphanis) is the most economically important foliar disease of strawberries in California. Many growers have observed that PM is particularly destructive in glasshouses and under plastic tunnels. This could be due to the difference in temperature and relative humidity or to filtering UV … Continue reading Tunnel plastics, UV and powdery mildew