Anthracnose is an extremely common fungal disease that affects a large number of plant species. Variants of it have been named for the plant species they specialize in, though all are closely related fungi and in many cases are genetically the same across target hosts. Anthracnose is especially troubling as it can attack the plant at any stage in its life.
The most common host plants for the gardener are Anthracnose of tomato, bean, cereal, onion, strawberry and raspberry, cucurbits, and pepper. In addition, anthracnose can affect cotton, banana, mango, and several types of hardwood and some fruit trees – especially citrus.
Anthracnose primarily attacks leaves and stems, but can also manifest on fruits or pods. Symptoms are most often seen on leaves and ripe fruits. It will begin by appearing as small, irregular yellow, brown, or black spots. These will merge to affect large areas. As the fungus spreads, connects, and ages, it turns darker and becomes more prominent.
When on the fruit, the disease usually appears as a boil-like area in a gray or pinkish color, depending on the fruit affecting. Over time, the spots will turn black as the fruit decays from the fungal rot. On tomatoes, for instance, the spots will appear as dimple-like areas on the skin that gradually widen.
On dark-colored fruit such as beans, the spots will appear as BB-sized indentations with dark rings around them. On onions, it appears as “onion smudge” and will often go unnoticed until harvest.
The life cycle of anthracnose is similar to other fungi. It will infect the host, spread as far as possible (even jumping from plant-to-plant in rows, riding the breeze) or during periods of long-term wet, such as with a lot of rain or extended watering times, it may “crawl” across the ground, infecting plant debris such as mulch as it travels. Once ensconced in a host, the fungus will spread rapidly over its leaves, stems and fruits.
It incubates during the winter months or off-season in the soil, often infecting seeds, spore, or leftover plant material after harvest. It will then re-emerge the next year with the warmth of spring.
How Anthracnose Fungal Disease Impacts the Garden
The disease ruins fruits entirely, severely limits the plant’s ability to grow healthy and strong, and stunts overall plant growth and fruit production. The amount of damage the fungus does to the plant depends on which growth stage is initially infected with it. Plants that are infected early, including during the seed and sprouting stage, will not likely survive.
How to Prevent
Proper seed choice, ensuring disease-free seeds, field sanitation, choosing only healthy seedlings for transplant, and the physical removing and destroying of infected parts as soon as they appear are the best ways to prevent the spread of this disease. Crop rotation and good watering technique are a must.
How to Treat Anthracnose
Treating can take the form of plucking and destroying the infected parts of plants – or the plants themselves. If caught early, sprays and fungal remedies can usually work to good effect.
Other Quality Anthracnose Resources:
This YouTube video explains more about Anthracnose.