According to fruit pathology specialist Dr.
Steve Ries, peach leaf curl is now at epidemic levels
throughout most of Illinois. On every infected tree that
Ries has seen, all of the leaves have been infected.
Confirmations of the disease have come from local
homegrowers in Champaign as well as from the CES educator in
DeWitt County, Pat Toohill.
Peach leaf curl occurs on peach, nectarine, and some
ornamental Prunus species. It also occurs, although rarely,
on cherry and plum. Leaf distortion and blisterlike growths
or puckering of the leaves is common. The leaves are often
thickened and almost crisp; they turn downward and inward
and may become red or purple.
The causal fungi (Taphrina) survive over winter in buds and
twigs. They infect leaves and flowers in the cool, moist
weather of early spring, from bud swell to bud opening.
Infected trees may show early leaf drop, but generally the
life of the tree is not threatened. Repeated yearly
infection may weaken a tree and predispose it to other
problems. Fruit growers are often concerned because of
reduced fruit quality. Ries said that peach trees showing
leaf infection will also have infected fruit.
Why is the disease so prevalent this year? Ries suggests two
reasons. First, the typical control for this disease on a
peach tree is a dormant fungicide spray that cannot be
applied after the tree breaks dormancy. The spray can be
applied any time after fall leaf drop and before spring bud
swell. Bud swell this year was a full three weeks earlier
than usual, which may have caught many growers off guard,
resulting in a missed application. The second reason for
increased disease is likely the fact that peach buds took a
long time to open due to cool temperatures after budbreak,
which allowed the window of opportunity for fungal infection
to be left open longer than usual.
The good news is that peach leaf curl is a monocyclic
disease&there is no secondary infection. The leaves will
pucker and curl, spores will form on the leaves and fruit
(peach fruit), and leaves will fall. Peach fruit will be
shriveled and drop early. Then infected species will form
new leaves that will not be infected. Growers and homeowners
can help their trees by applying a 12-12-12 or similar
fertilizer now. Do not overfertilize: Ries recommends no
more than 2 to 3 pounds of 12-12-12 per tree. The idea is to
help the tree produce new leaves and allow it to go into
dormancy in late summer.
The heavy infection this year means inoculum levels will be
high for next year. Peach growers should mark their
calendars now to remind them to apply a dormant fungicide
spray (Bravo, Carbamate, Ziram, Bordeaux, copper hydroxide,
or copper oxychloride) in the first week of February 1998.
Spraying now will do nothing to stop peach leaf curl or leaf
For more information on leaf curls and blisters, consult
Report on Plant Diseases No. 805, Peach Leaf Curl and Plum
Pockets, or No. 663, Oak Leaf Blister.