Nothing beats a ripe peach! However, peach growers in central Illinois face a variety of challenges in the quest for this delectable fruit of summer.
In most years, the threat of a late spring frost is one of the biggest worries. Lower temperatures during flowering have the potential to freeze blooms, killing delicate reproductive parts and eliminating the year’s crop in a matter of hours. From the peach trees I’ve inspected this spring, it appears we have dodged this bullet in most areas of central Illinois. Flowers seem to have survived and are now progressing toward fruit set.
Now that leaves have emerged and are nearly fully developed, a new threat to peach production may rear its ugly face. Peach leaf curl is a common fungal disease that infects leaves, as well as twigs and fruits at times. While this pathogen is rarely deadly, it is certainly unsightly. In addition, trees with substantial infections rarely produce fruit.
Although we can most likely breath a big sigh of relief with respect to spring frosts, now is the time to keep an eye out for the development of symptoms on leaves.
Peach leaf curl is caused by the fungal pathogen Taphrina deformans. Infection results in unsightly deformation of peach leaves as they develop in spring. In general, the leaf will become thicker, leather-like and deformed at infection sites. These spreading deformations develop raised areas that are pink, reddish or purple, bumpy and contorted, becoming quite noticeable as the infection expands with leaf development.
Eventually, symptomatic leaves will drop from the tree as the season continues, often turning yellow before falling to the ground. Severely infected plants can lose nearly all their leaves by summer. While this disease is rarely fatal, it can severely stress the tree, making the plant more susceptible to other disease, insects or environment stresses. In many cases, the tree will produce a new flush of leaves in midsummer as a response to earlier leaf drop. This second flush of leaves takes significant energy investment and can serve to further lower the plant’s energy reserves and defenses.
Right now is the time to scout for peach leaf curl and other foliar infections on fruit trees. If your peach tree has the tell-tale symptoms of peach leaf curl right now, the best step you can take is to wait and watch what plays out.
Unfortunately, infection of leaves occurred much earlier in spring, during leaf out, when weather was much cooler and wetter. The pathogen overwinters on buds and bark plants waiting to infect swelling buds in early spring. When conditions are cooler (between 50 and 70 degrees) and wetter in early spring, this fungus releases spores which infect the developing buds and newly emerged leaves on peach trees. Later in the spring, as leaves fully emerge, the symptoms become noticeable, although all infection on the plant has already occurred, and no further infection will happen as temperatures get above 70 degrees. So, there is no preventative treatment that can be done now, but it is important to monitor leaf loss as the season continues.
Take note of how much canopy is lost in the coming month, and watch for new leaves later in summer. While fruit will likely be aborted, a healthy peach tree can bounce back just fine from a single defoliation. As it leafs out, the amount of canopy the tree is able to fill back in can be a sign of the disease’s impact. If your tree produces a full, new canopy, it’s safe to assume it has bounced back and will regain most of the energy lost from its new leaves. However, if your tree cannot mount a full response and has a thin canopy this year, that is a sign it’s struggling.
Treatment for peach leaf curl requires a dormant spray, done after leaf drop. A fungicide must be applied to buds and twigs to kill the overwintering fungus before spring bud break and subsequent infection of leaves. However, if your tree has adequately leafed out after this spring’s infection, I usually recommend just observing next year. Peach leaf curl is highly dependent on cool, wet conditions in spring, and next year’s spring may prove less conductive to infection.
Trees showing signs of stress or that are unable to leaf out adequately a second time this summer are good candidates for treatment in winter. Most products labeled for control of peach leaf curl are quite effective if applied correctly, making this disease easily controlled when necessary.
For any tree infected this year, it is a good idea to do some of the basics in boosting health, such as mulching, watering during drought and potentially fertilization if soil tests indicate a nutrient deficiency.
Ryan Pankau is horticulture extension educator with University of Illinois Extension serving Champaign, Ford, Iroquois and Vermilion counties.