How It Spreads

• Leaves and twigs of the sycamore are the main sites where the fungi responsible for anthracnose occur, according to the University of California Integrated Pest Management Program. The fungi spend the winter in a dormant state in any infected twigs and/or infected leaves fallen from the tree. These fungi produce microscopic spores that move from leaf to leaf and branch to branch when spring rains commence. The raindrops splash on the spores, which moves them about the sycamore where they can infect any new growth. A damp springtime is a perfect scenario for the spread of anthracnose.
  
  

Importance of Temperature

• In addition to rainfall, a key factor in how severe each year's infestation of anthracnose will be is the temperature. Temperatures that hover between 50 and 55 degrees F during early springtime, when new leaves emerge, are very conducive to anthracnose spreading, reports the University of Delaware Cooperative Extension. However, temperatures above 60 degrees result in a much slighter infestation. Anthracnose activity stops during the hot summer, when hot weather brings about dry conditions.
  
  

Symptoms

• Twigs are susceptible to anthracnose even before the leaves emerge on the tree, developing cankers that can kill them. Cankers are sunken areas that inhibit the flow of water and nutrients, effectively killing the twigs. The new leaf shoots crinkle up when infected by the spores, turning brown. Mature leaves infected with the ailment may develop odd-shaped dead, brown spots; these infected leaves often die and fall from the tree. These dead regions typically show up along the large veins of the sycamore leaf.
  
  

Effects

• Years when anthracnose infestation is severe can result in an entire sycamore losing all its leaves. While new leaves grow in by the start of summer, this can bring about stress to the sycamore and leave it open to attacks by other diseases. Repeated loss of leaves year after year and the development of cankers on twigs, branches and the sycamore's trunk are more serious, sometimes causing the trunk to become hollow and the tree to die.
  
  

Management

• By raking and getting rid of any fallen leaves and twigs during the sycamore's growing season and the fall months, you reduce the chances of infection the following year. Look for any infected branches and prune them off during the winter so they cannot precipitate infection in the spring. By taking out branches, you increase the circulation of air, helping the leaves dry more quickly, making them less likely to fall victim to the malady. Spraying the emerging leaf buds with fungicides like chlorothalonil and thiophante-methyl can help prevent anthracnose infection, states the Colorado State University Extension.