What do you know about strawberry anthracnose?

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 can have a significant impact on strawberry plants and fruit. The disease is primarily caused by two main Colletotrichum species complexes. It is primarily considered a pathogen that is transmitted through transplants. Severe outbreaks of the disease have occurred in the main strawberry-growing areas in the past, including California.

What are the causal agents?

The two main Colletotrichum species complexes contributing to strawberry anthracnose are Colletotrichum acutatum complex (CAC) and the Colletotrichum gloesporioides complex (CGC). CAC has 40 known species, and CAG has 50 known species. CAC causes anthracnose fruit rot, petiole blight, and root necrosis (Fig. 1), and CAG causes anthracnose crown rot (Fig. 2). The main CAC species in strawberries are C. nymphaeae, C. fioriniae, and C. acutatum sensu stricto, and the main CAG species in strawberries are C. siamense (Fig. 3), C. fructicola, and C. theobromicola (Fig. 3). Based on strawberry isolates collected over a 23-year period from six different states, Wang et al. (2019) determined C. nymphaeae as the dominant species in the United States. Which species complex is common in California currently is to be determined.

**Figure 1.** Anthracnose fruit rot and petiole blight caused by *Colletotrichum acutatum* complex.

**Figure 2.** Anthracnose crown rot caused by *Colletotrichum gloeosporiodes* complex (photo by G. Holmes).

**Figure 3.** Two CAG complex species in culture (Courtesy: Natalia Peres and Marcus Vinicius, University of Florida).

How to diagnose the two species complexes?

Anthracnose fruit rot, in general, can be detected on the fruit and petioles as sunken lesions. After a few days of incubation in a moist chamber, you can see the salmon pink color of sporulation. While conidia characteristics help identify the different Colletotrichum species, DNA-based analysis would give the most reliable identification. We use a quantitative PCR analysis method called high-performance melt curve analysis to detect the pathogen using the methods published by the University of Florida. All samples submitted to the Strawberry Center disease diagnostic service get tested for CAC and CGC (Table 1).

Table 1. Detection of CAC and CAG in diagnostic samples at the Strawberry Center disease diagnostic service.

Year	CAC^a (Colletotrichum acutatum complex)	CAG^b (Colletotrichum gloesporioides complex)
2024	1.5%	10%
2025	1%	8%
2026	7%	30%

^a,b Does not indicate the number of individual sites.

**Figure 4.** High-performance melt-curve analysis to detect CAC and CGC (Wang et al. 2021).

How can you manage the disease?

Clean transplants are the main method of disease management. If the disease is present in the field, roguing, minimizing overhead sprinker irrigation will slow down the spread. The pathogen can survive on plant debris. Therefore, field sanitation is important. Cal Poly Strawberry Center evaluated cultivar resistance to CAC in 2019 and 2020. Fungicide efficacy trial conducted at the Cal Poly Strawberry Center showed that Switch 62.5 WDG and Zivion were highly effective for controlling plant mortality on Monterey and Portola cultivars (Cosseboom et al. 2017; Haack et al. 2018). Based on a recent study conducted by the University of Florida, Switch 62.5 WG + Captan Gold 80 WDG has been shown to be one of the most effective fungicide treatments for anthracnose fruit rot among several other effective ones (Rebello and Peres, 2026).