If red, puckered leaves are seen on peach, nectarine, or almond trees, it’s probably peach leaf curl.
Peach leaf curl can seriously reduce the leaf canopy, cutting the number of leaves available for photosynthesis. This fungal disease is caused by Taphrina deformans and it is estimated to cost U.S. orchardists $2.5-3 million each year.
Fungal spores stay on tree surfaces year round as ascospores. When spring rains or, in my case, bad drainage occur, the spores germinate and form blastospores that attack vulnerable new growth.
Symptoms of peach leaf curl
Red, blistered leaves that tend to twist and curl are a sure sign of peach leaf curl infection. Similar to the initial signs of eugenia psyllid infestation, peach leaf curl damage progresses down twigs and stems, into the trunk of the tree, significantly reducing fruit production.
As infected leaves mature, they become thicker and more rubbery than normal. Leaf color changes from green to purplish-red to white. Infected leaves fall earlier than normal, as well. Red lesions may also be seen on the fruit. If you cut into the wood, the vascular bundle will be discolored, showing where the fungal spores are reproducing.
Peach leaf curl treatment
Once a tree is infected with peach leaf curl, the only thing you can do is treat it with fungicides each fall, after the leaves have dropped. Those leaves should be removed and destroyed. Effective fungicides include fixed copper and Bordeaux mixture. For non-organic growers, chlorothalonil is the only effective non-copper fungicide. Chlorothalonil is a carcinogen that can damage your kidneys, so I don’t recommend it. Heavy infestations may need a second treatment as buds swell, but before leaves are visible.
Unfortunately, long term copper use can result in a toxic build-up in the soil. Treatments should be applied after fall pruning. To help an infected tree during the summer, thin fruit later in the season to minimize points of entry for further infection.
Until recently, it was a common practice to remove the affected leaves in spring. Research has not shown this to be effective or even helpful. Removing too many leaves reduces photosynthesis and can lead to sunburn damage. If you must remove infected leaves, be sure to sanitized your tools between each cut, or you may simply spread the disease. A solution of 1 part bleach and 9 parts water can be used, or you can liberally spray your cutters with bathroom cleaner between each cut. Also, protect exposed limbs by painting them with a 50:50 solution of water and white latex (not enamel) paint.
Severely damaged trees may need additional nitrogen later in the growing season.
You can grow a surprising amount of food in your own yard. Ask me how!