A bed raked clean of last year's spotted leaves starts the new season far cleaner than one left buried in old debris. Anthracnose overwintering takes place in plant matter, not in bare soil. The fungus rides out winter inside infected leaf litter, dead twigs, and bark cankers. Pull that material away and you take most of next year's disease with it. Leave it in place and you hand the fungus a head start the moment spring warms up.
The spores do not really live free in the dirt the way some garden pests do. They cling to dead and diseased tissue from the plants they hit last year. That is why a thick mat of fallen leaves under a sick tree is the real problem, not the ground beneath it. The same goes for a tomato bed. The fungus stays on the old vines and dropped fruit you forgot to clear out.
So how long does it last? On infected twigs and in cankers, the fungus can survive a full winter. It wakes back up when warm, wet weather returns in spring. The pathogen also has a sneaky trick for fungal survival. It can enter a quiet, dormant phase called a quiescent state. This pause lasts anywhere from a few days to several months. The pause lets the fungus wait out dry or cold spells without dying off. This is a big reason anthracnose overwintering is so hard to stop on its own.
Loose spores are tougher than you might think too. Research shows anthracnose spores can stay alive up to 48 hours even without the leaf wetness they need to infect a plant. They just sit and wait for the next rain or a round of overhead watering. Once water splashes them onto fresh growth, the whole cycle starts over. A single wet week in spring can launch a new wave of spots from debris you never cleaned up.
This is the big reason old debris is so dangerous. Those dead leaves and fallen twigs are the main source of the spores that attack your plants the following season. Never toss this material on your compost pile. Most home compost heaps do not get hot enough to kill the fungus, so you would just brew a fresh batch of spores and spread them right back into the garden.
Because the fungus lives in plant tissue, you should not waste time trying to treat the soil itself. There is no spray that scrubs the ground clean of anthracnose. Your strongest tool by far is good sanitation. Rake up and bag every spotted leaf in fall, then clear out the fallen twigs around any plant that showed symptoms. Do not let that infected leaf litter sit over winter where the spores can ride out the cold and splash back up in spring.
On trees and shrubs, take the cleanup a step further and prune out the cankers. Cut about four inches below any sunken, dead patch on a branch so you remove the live edge of the infection. Wipe your tool blades with rubbing alcohol between cuts so you do not move the fungus from one branch to the next. Bag or burn what you remove rather than letting it pile up nearby.
Do this same cleanup every fall and you starve the disease of the home it needs. Add a layer of fresh mulch under cleaned-up trees to bury any spores you missed. The mulch keeps them from splashing back up onto new leaves. Sanitation will not give you a spotless garden overnight. But it cuts the spore load each year, and that is what keeps anthracnose from building up season after season.
Read the full article: Anthracnose Disease: Identify and Stop It
