Anthracnose is a group of fungal diseases that cause dark, sunken lesions on the leaves, stems, and fruits of a wide range of plants. It affects everything from shade trees and lawn grasses to tomatoes, strawberries, and peppers. The fungi responsible belong primarily to the genus Colletotrichum, and dozens of species within that group target different hosts. While anthracnose rarely kills established trees outright, it can defoliate them, disfigure fruit crops, and thin out turfgrass if left unchecked.
What Causes Anthracnose
Anthracnose isn’t a single disease but a family of diseases caused by closely related fungi. The most common culprits are species within the Colletotrichum complex. One species, C. siamense, accounts for roughly 57% of anthracnose cases on certain ornamental shrubs and also attacks pecans, strawberries, grapes, and mangoes. Other frequently identified species include C. gloeosporioides, C. fructicola, and C. acutatum, each with its own preferred hosts. A given plant can be attacked by several species at once.
The fungus overwinters in infected leaf debris on the ground or in cankers on branches. When spring arrives, spores form on that old material and spread by wind and rain to newly emerging leaves. Once those fresh leaves are infected, they produce a new generation of spores that keeps the cycle going as long as conditions stay favorable. On some plants, the pathogen can colonize leaves and green tissue without showing any visible symptoms, silently building up before an outbreak becomes obvious.
Conditions That Trigger Outbreaks
Cool, wet weather is the classic trigger. Infection is most severe when temperatures are moderate and moisture is persistent, which is why anthracnose flares up in spring and early summer in most climates. Rain splash is the primary way spores travel short distances, landing on neighboring leaves, fruits, or stems. On turfgrass, mowing equipment and foot traffic also spread spores across a lawn or putting green.
The disease cycle slows once daily temperatures consistently average above 60°F and the weather dries out. Mature leaves are generally more resistant to infection than young, expanding tissue, so plants that leaf out early in a cool spring are especially vulnerable. A second wave can occur in late summer if warm, humid conditions return.
Symptoms on Trees
On shade trees like sycamore, oak, maple, ash, and dogwood, anthracnose typically starts with small dead spots on leaves. Those spots expand into brown, dead areas along leaf veins or large blotches between veins. Sycamore and oak lesions tend to follow major veins, while ash, maple, and willow show more irregular dead patches. If leaves are very young when infected, they can curl, distort, and partially die.
The disease often works from the ground up, defoliating the lower and inner canopy first while leaving a rim of undamaged foliage at the top. Premature leaf drop is common, and in severe years trees can lose nearly all their leaves. Infected young twigs get girdled and killed, and early-season bud killing can look a lot like frost damage. The good news: most hardwoods push out a second flush of leaves quickly enough to avoid lasting harm, provided defoliation doesn’t happen year after year.
Symptoms on Fruits and Vegetables
On tomatoes, anthracnose shows up as dark, bruise-like spots on ripe fruit. You might pick a perfectly healthy-looking tomato and notice sunken brown or black marks within a couple of days. On strawberries, the lesions start as water-soaked spots on green or ripe fruit. Under humid conditions, those spots develop salmon or orange masses of spores visible to the naked eye. In drier weather, the same lesions turn black and sunken, and the entire fruit can shrivel into a dry mummy.
Peppers develop sunken, water-soaked necrotic lesions that expand rapidly in warm, humid conditions. On strawberries, the fungus can also attack flowers and stems. If infection hits shortly after pollination, developing fruit stays small, hard, and misshapen. In transplant trays, the first sign is often patches of stunted plants that eventually collapse and die.
Symptoms on Turfgrass
Anthracnose on lawns and putting greens takes two forms: foliar blight and basal rot. In the foliar phase, leaf blades develop reddish-tan or yellow elongated spots, often with tiny black spore-bearing structures visible in the center of each lesion. Sometimes no discrete spots form at all; instead, older leaf blades simply become water-soaked and collapse. Affected patches range from a few centimeters across to areas larger than a meter wide, and they can appear patchy or diffuse.
Basal rot is more damaging. The fungus colonizes the leaf sheaths at the base of individual grass plants, turning them dark brown to black. The leaf blades above turn orange or yellow but show no lesions themselves because the damage is happening underground at the crown. Creeping bentgrass and annual bluegrass, common on golf courses, are particularly susceptible. Warm, wet periods in early to mid-summer are the peak risk window for turfgrass anthracnose.
How to Prevent Anthracnose
Cultural practices are the first and most effective line of defense. For trees and shrubs, rake up and destroy fallen leaves around susceptible plants, especially those with branches close to the ground. That debris is where the fungus survives winter and produces next year’s spores. Prune out dead branches and twigs to remove canker tissue, and improve air circulation within the canopy so foliage dries faster after rain.
For vegetable and fruit gardens, avoid overhead irrigation. Drip systems or soaker hoses keep foliage dry and reduce the splash that carries spores from plant to plant. Rotate crops so the same spot doesn’t host the same susceptible species year after year. Remove and dispose of infected fruit and plant debris rather than composting it, since home compost piles often don’t reach temperatures high enough to kill fungal spores.
On turfgrass, proper fertility, adequate irrigation (without overwatering), and raising mowing heights during stress periods all reduce susceptibility. Avoid mowing wet turf, which drags spores across the surface.
When Fungicides Make Sense
For most shade trees, fungicide sprays aren’t necessary. If defoliation is mild, doesn’t recur year after year, and the tree isn’t a prized specimen, the tree will recover on its own. When protection is warranted, spraying needs to start at bud break and continue on a weekly or biweekly schedule until daily temperatures average above 60°F. That timing is critical because the goal is to shield young, expanding leaves during the vulnerable window. Once leaves mature, they resist infection naturally. In some cases, a fungicide can be injected directly into a tree’s vascular system, offering protection for more than one season.
For fruit and vegetable crops, preventive fungicide applications before symptoms appear are far more effective than trying to stop an active outbreak. Contact fungicides protect leaf and fruit surfaces from spore germination, but they wash off in rain and need reapplication. Systemic products move inside plant tissue and last longer, though resistance management matters: alternating between different types of fungicides prevents the pathogen from adapting.
Choosing Resistant Varieties
Planting resistant cultivars is the simplest long-term strategy. For dogwoods, Kousa dogwood varieties and certain hybrids offer strong resistance. Cultivars including ‘Steeple’, a clone of ‘Milky Way’, and hybrids like Stardust, Stellar Pink, and Galaxy showed 1% or less leaf area affected in trials and 100% survival through the following spring, with no detectable disease in woody tissue. Native flowering dogwood (Cornus florida) is far more susceptible, so if you live in a region where dogwood anthracnose is common, Kousa types or interspecific hybrids are the safer choice.
For tomatoes and beans, seed catalogs and extension services list cultivars bred for anthracnose resistance. Look for disease resistance codes on seed packets. In strawberries, variety selection combined with good sanitation practices dramatically reduces fruit rot losses. No cultivar is perfectly immune, but resistant varieties give you a much wider margin before conditions overwhelm the plant’s defenses.