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Friday, Jun. 19th 2015

Bacterial Spot of Peach

bacterial spot of peach

This bacterial disease is a common disease in Kansas but rarely causes extensive losses in fruit quality or production. The disease affects leaves, fruit, and occasionally twigs. Leaf infections first appear as small, pale green to yellow angular spots. These spots normally are more prevalent near the leaf tip and are surrounded by a yellow halo. Eventually, the lesions turn dark brown, separate from healthy tissue, and drop out, giving the leaf a shot- hole appearance. On susceptible cultivars, 1 or 2 leaf lesions can cause a complete yellowing of the leaf and result in premature defoliation. 

Fruit infections are mostly superficial but more serious infections can cause pitting and cracking of the fruit surface.

Peach cultivars vary in their susceptibility to bacterial spot, although no variety is immune. Those cultivars showing tolerance to the disease include Belle of Georgia, Biscoe, Candor, Comanche, Dixired, Earliglo, Early-Free Red, Emery, Encore, Garnet Beauty, Harbelle, Harbinger, Harbrite, Harken, Late Sunhaven, Loring, Madison, Norman, Ranger, Redhaven, Redkist, Redskin, Sentinel, and Sunhaven.

Cultivars most susceptible to bacterial spot are Autumnglo, Autumn Lady, Blake, Elberta, Halehaven, July Elberta, Jersey Queen, Jerseyland, Kalhaven, Suncling, Suncrest, Sunhigh, Ran Cocas, Redcrest, Rio-Oso-Gem, and Sweet Sue. Most apricot and nectarine cultivars are susceptible to bacterial spot.

Excessive fertilization can predispose peaches to severe bacterial spot infections. On the other hand, proper fertilization is necessary to maintain tree vigor and to prevent the development of Cytospora canker. Monitoring the fertility needs of trees is best accomplished through soil and leaf analysis.

Since this disease is cause by a bacteria, fungicides found in fruit tree sprays are ineffective. 

(Ward Upham)

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