Peach Leaf Curl – It’s time!

Peach leaf curl, also known as leaf curl, is a disease caused by the fungus Taphrina deformans. Peach leaf curl affects the blossoms, fruit, leaves, and shoots of peaches, ornamental flowering peaches, and nectarines, and is one of the most common disease problems for Texas Peaches. The distorted, reddened foliage that it causes is easily seen in spring. When severe, the disease can even reduce fruit production substantially. If you saw leaves that looked anything like the ones above, you may want to consider treatment.

Leaf symptoms appear about 2 weeks after leaves emerge from buds. The fungus grows between leaf cells and stimulates them to divide and grow larger than normal, causing swelling and distortion of the leaf. Red plant pigments accumulate in the distorted cells as you can see in the picture above.

Why am I writing about this disease now since we won’t see it till spring? Well, this disease has gone through the summer and is on the tree now as ascospores (sexual spores) and bud-conidia (asexual spores) on the tree’s surfaces, such as leaves, buds, bark, etc. As we get into the fall and much cooler temperatures or even a frost the leaves will begin to fall off. This leaf abscission (separation of the leaf from the tree) is actually a wound. When you have a wound, you have a place for these disease spores to enter the tree. Any dew, light rain or even wind can move spores to the wound.

Treatment

So, as the leaves begin falling off or after they have all fallen off, it is time to consider a treatment. Generally, a single early treatment when the tree is dormant is effective, although in areas of high rainfall or during a particularly wet winter, it might be advisable to apply a second spray late in the dormant season, preferably as flower buds begin to swell but before green leaf tips are first visible.

Historically, the most commonly and basically only fungicide for organic growers to use are the fixed copper products (see below for a list). For all copper-containing products, the active ingredient, copper, is listed as “metallic copper equivalent,” or MCE, on the label. Various product formulations differ widely in their metallic copper content. The higher the MCE, the greater the amount of copper and the more effective the product will be. However, other factors such as coverage, use of additives as such stickers and spreaders, and frequency and duration of rain, which can wash off the copper, also will impact product effectiveness. In all cases, the copper is active only when it is wet, when the copper ions are in solution. Thorough coverage is very important but without leaves not that hard. It is really good to get a calm day, lower pressure down, try to get a mist out of your spray tips and make sure the limbs are wet.

Active IngredientTrade NameCompany
copper hydroxideKocide-2000/3000
Champ ION or WG
Certis
NuFarm
copper octanoateCuevaCertis
Copper oxychloride 23.82%  
Copper Hydroxide 21.49%
Badge X2Gowan
copper sulphate (pentahydrate)Cuproxat
Instill O
Troya
NuFarm
Sym Agro
Oro Agri

As I first said, It’s time! It’s time for all you peach growers to get that sprayer back out, purchase your spray product, and SPRAY!

Author: Bob Whitney, Regents Fellow & Extension Organic Specialist

Agriculturalist, extension educator and researcher, organic agriculture enthusiast and promoter, international program developer, Christian, husband, father and friend.

3 thoughts on “Peach Leaf Curl – It’s time!”

  1. Bob,

    What are your thoughts on adding PAA (peryoxycetic acid) into the tank to help sanitize and help with IPM (second mode of action/chemistry)?

    OxiDate can safely be tank-mixed w/ Cueva when following label directions, or it can be used in rotation with other coppers!

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    1. As I was writing this blog I did wonder if there is any work out there with Peach Leaf Curl using some sort of preventative. The issue is that this fungal spore is resistant many organic and conventional fungicides and can stay in the environment a long time. This fungus is only activated when moved to these wounds where there is both plant sap and moisture to cause germination. This is the reason why so many fungicides don’t work on Taphrina deformans. But copper as a metal, sticks around throughout the winter and is available when needed. This is also why Cueva may be a lightweight in this battle because of its low MCE. That said, there is still a distinct possibility that OxiDate could remove enough disease pressure owing to its unique chemistry as compared to typical organic or even conventional fungicides. Peracetic Acid (PAA) is a great sanitizer because it kills spores like this (just talk to the wine makers) and it might take out sufficient numbers on the bark to make the fungus essentially non-pathogenic. Looks like we just need to try it!!

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      1. Bob, thanks for the details on the spread of the spores! In addition to treating the trees themselves, I can see using SaniDate on equipment (same chemistry as OxiDate, different concentrations of PAA and hydrogen peroxide) during any pruning. While this doesn’t help for leaf drop, it’s something else I have our R&D folks look into.

        Sounds like I need to make a trip to the Hill Country and visit with some peach guys to get educated on how things are done by the professionals!

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