Anthracnose is a fungal disease that causes dark, sunken lesions on the leaves, stems, and fruit of a wide range of plants. It’s one of the most common plant diseases in home gardens and landscapes, affecting everything from shade trees like sycamores and maples to food crops like strawberries, beans, and grapes. The disease is caused by fungi in the genus Colletotrichum, which includes at least 14 recognized species, each with preferences for different host plants.
What Anthracnose Looks Like
The hallmark of anthracnose is sunken, discolored spots. On leaves, these appear as irregular brown or tan patches, often following the veins. On fruit, lesions start as small, water-soaked spots that darken to brown or black and sink into the surface as they expand. In humid conditions, you may notice pink, salmon, or orange-colored masses forming inside the lesions. Those masses are millions of fungal spores, sticky to the touch.
Under dry conditions, the look changes. Lesions become darker and more deeply sunken, and infected fruit can dry out entirely into shriveled, mummified husks. On trees like sycamores, anthracnose can kill expanding leaves and young twigs in spring, giving the canopy a scorched, ragged appearance. California sycamore is so susceptible that repeated infections can twist its entire growth habit over time.
Symptoms typically appear 4 to 13 days after the fungus first lands on and penetrates the plant tissue, though in cool weather the infection can sit dormant inside the plant without showing any visible signs.
Which Plants It Affects
Anthracnose hits an unusually broad range of plants. Among landscape trees, sycamore, ash, oak, maple, and evergreen elms are the most visibly affected. American sycamore and Modesto ash are especially vulnerable and worth avoiding if anthracnose is common in your area. Some London plane tree cultivars (‘Bloodgood,’ ‘Columbia,’ ‘Liberty’) have been bred for better resistance.
In the garden and on farms, anthracnose targets strawberries, grapes, beans, peppers, tomatoes, spinach, and many other crops. It also attacks turfgrass, where it yellows and thins the lawn in irregular patches. Different species of the fungus specialize in different hosts: one species favors corn, another targets beans, another hits soybeans, and so on. But the disease cycle, symptoms, and management approach are similar across all of them.
How the Fungus Spreads and Survives
On deciduous trees, the fungus overwinters inside small cankers on infected twigs or in dead leaf litter on the ground. On evergreen species like Chinese elm and coast live oak, it can persist on leaves and twigs year-round. When spring arrives and conditions turn wet, the fungus produces huge numbers of microscopic spores. Rain splash and irrigation water carry these spores to new leaves, shoots, and fruit, where they germinate and penetrate the plant tissue.
Moisture is the single biggest factor driving anthracnose. The fungus needs high humidity to grow and infect. Rainfall droplets are its main taxi service, splashing spores from old infections to fresh tissue. In dry weather, the disease stalls. Hot temperatures also slow it down considerably: growth stops entirely above about 95°F (35°C). The sweet spot for infection is between roughly 68°F and 77°F (20°C to 25°C) with sustained wet conditions. Below about 45°F (7°C), the fungus can still get inside the plant but tends to sit quietly as a latent infection, waiting for warmer weather to trigger visible symptoms.
How to Tell It Apart From Other Diseases
Several leaf spot diseases can look similar at a glance, but anthracnose has a few distinguishing features. The lesions follow leaf veins more than most other fungal spots, creating angular or irregular shapes rather than perfect circles. On fruit, the sunken texture is a strong clue, since bacterial spots and sunscald tend to stay flat or raised. The sticky, brightly colored spore masses (pink, orange, or salmon) that appear in wet weather are close to a smoking gun for anthracnose. No other common garden disease produces quite that look.
If you’re still unsure, your local cooperative extension office can examine a sample under a microscope. The fungus produces distinctive dark, hair-like structures called setae on its spore-producing bodies, which confirm the diagnosis.
Prevention Through Plant Care
Because anthracnose depends so heavily on moisture, the most effective prevention strategies center on keeping foliage dry. For garden plants and small fruit, avoid overhead watering. Drip irrigation or soaker hoses deliver water to the roots without wetting the leaves. Space plants far enough apart so air circulates freely through the canopy, which helps leaves dry faster after rain.
Pruning matters too. Remove dead or infected twigs from trees during dry weather to eliminate overwintering sites. For deciduous trees, raking up and disposing of fallen leaves in autumn removes a major source of spores for the following spring. In vegetable gardens, rotating crops so you don’t plant the same family in the same spot year after year helps break the disease cycle, since the fungal species involved tend to be host-specific.
Choosing resistant varieties is the simplest long-term strategy. If you’re planting a new shade tree and anthracnose is a known problem in your area, select a resistant cultivar rather than a highly susceptible species. The same principle applies to strawberries, beans, and other crops where resistant varieties are widely available.
Fungicide Options
For high-value crops and turf, fungicides can help, but timing is critical. Preventive applications, starting two to four weeks before symptoms normally appear, work far better than spraying after the disease is already visible. Copper-based fungicides are the most widely available option for home gardeners and are approved for organic use. Chlorothalonil is a common synthetic contact fungicide used on turf and ornamentals.
On large landscape trees, fungicide sprays are rarely practical or necessary. Most established trees tolerate anthracnose without lasting harm. The disease looks alarming when a sycamore drops half its leaves in spring, but healthy trees push out a second flush of growth once warm, dry weather arrives. The tree may look thin for a few weeks, but it recovers. Repeated severe infections year after year can weaken a tree over time, but for most homeowners, good sanitation (pruning and leaf cleanup) is enough to keep anthracnose manageable without chemical treatment.