by Holly Johnson, Alameda Backyard Growers
Alameda Sun, Thursday, November 8, 2018
While several varieties of peach trees can do well in Alameda, these fruit trees are also susceptible to a fungal disease that makes them look unhealthy and, in fact, weakens their ability to thrive.
The disease, peach leaf curl, is caused by a fungus called taphrina deformans. The fungus can hibernate on the tree trunk and in the dead leaves under a tree during winter and then emerge just as leaves and shoots begin to grow in early spring. It loves periods of cool, wet weather. This fungus can affect peach, almond and nectarine trees. Symptoms include new leaves with spots that soon thicken and pucker, deforming the leaves (giving the fungus its name) and causing them to blacken, dry up and fall off. While it shouldn’t stop fruit production, and healthy leaves do replace the deformed ones that fall off, the infected tree is further weakened by fruit production and therefore more susceptible to the fungus.
There isn’t a cure once a tree reveals a peach leaf curl infection, but the gardener can help the victimized tree get ready for a healthier new year.
Later this month, once the tree is dormant (probably after Thanksgiving), prune the tree to reduce the number of spores overwintering on the tree and remove as many leaves as possible from the scene of the crime. Taphrina deformans spores are hardy, so it is best to keep these affected leaves out of compost by bagging them up and using the grey bin. The disease can spread through leaf detritus. After pruning, spray the naked trees until they are dripping with a copper-based fungicide that coats the tree and kills remaining spores so they will not infect new leaves come spring. Repeat the treatment in early January and again before Valentine’s Day to protect the new leaf buds preparing to emerge in spring. Some winters in Alameda are so short and mild that just two treatments may be enough. A favorite plant nursery will be able to help choose the best spray for your yard.
Some gardeners treat all their peach and nectarines even if they did not show signs of infection the previous year just to prevent contagion.
Should a tree continue to show symptoms of a fungal infection when the new leaves emerge, or if a newcomer to the garden arrives infected, there are a few steps to take to help your tree as much as possible.
Remove the puckered leaves as they curl and keep them from piling up under the tree and releasing spores that will further infect the tree and its neighbors. Thinning the baby fruit to one fruit every five to seven inches will allow the tree to maintain its strength.
If peach leaf curl has gotten you down, remember, you are not alone. Peach leaf curl is very common in this area but does let up as the growing season gets underway. Applying a high-quality fruit tree food once the emerging foliage no longer shows signs of the disease will greatly help reinvigorate a diseased tree. Consult with master gardeners at the University of California at ucanr.edu/Gardening or the friendly experts in the Alameda Backyard Grower community.
Added information: Here’s an excellent article from the UC Master Gardener Program of Alameda County on peach leaf curl. Click here.