Crucifer anthracnose

Colletotrichum higginsianum is a devastating fungal pathogen responsible for anthracnose disease in a wide range of cruciferous plants. It is a hemibiotrophic fungus, meaning it initially lives within the host tissues without causing damage before switching to a necrotrophic phase that kills host cells. This switch is central to the development of the characteristic lesions observed in infected fields.

This pathogen has a broad host range, primarily infecting members of the Brassicaceae family. Major economic crops such as Brassica napus (oilseed rape), Brassica oleracea (cabbage, cauliflower, broccoli), and Raphanus sativus (radish) are highly susceptible. The ability of the fungus to infect both wild and cultivated species makes it a persistent threat in various agricultural landscapes.

Clinical signs of infection start as small, water-soaked spots on leaves, stems, or pods. As the disease progresses, these lesions turn tan or brown with a dark border, often becoming sunken. Under high humidity, the characteristic pinkish-orange masses of conidia appear in the center of the spots. In severe cases, the stem tissue becomes girdled, leading to wilting, stunting, or total loss of pod filling.

The fungus thrives in warm, humid conditions, which are ideal for its spore production and dispersal. Colletotrichum higginsianum spreads via rain splashes, wind-borne conidia, and contaminated equipment. It survives between seasons as dormant mycelium or spores on crop debris, in the soil, and on infected seeds, ensuring its recurrence in the following growing cycle.

Management of crucifer anthracnose requires a proactive approach aimed at reducing the primary inoculum and inhibiting its spread:

• Implementing a diverse crop rotation cycle, avoiding crucifers for at least 3 years.
• Removing and destroying infected crop residues post-harvest to reduce the fungal reservoir.
• Using certified disease-free seeds or treating seeds with effective systemic fungicides.
• Maintaining optimal plant nutrition, as nutrient deficiencies can exacerbate plant stress and susceptibility.
• Applying targeted fungicides during weather conditions favorable for disease development, such as prolonged warm, wet spells.