Growing varieties tolerant to leaf peach curl disease lowers copper usage and improves fruit growing and economic return.
Practical recommendations and information
• HOST PLANTS: peaches and nectarines
• SYMPTOMS:
o On leaves: symptoms appear about two weeks after leaves emerge from buds, deformations, blisters, thickened curling leaves, and white, yellow to red leave discolorations (Pictures 1 and 2); affected leaves may dry up and fall off
o On fruits: Blistered fruit tissue, later wrinkling
• DAMAGE:
o Infections on fruits make the surface corky and cracked, and affected fruits fall off
o When trees are severely affected, the disease can strongly reduce yield and fruit quality
o If significant premature leaf drop occurs, trees will be susceptible to drought stress and winter injury
• DISEASE TRANSMISSION:
o The fungus overwinters in bark and bud scales
o The infection of buds happens in early spring during bud swelling (Picture 3)
o When temperatures reach above 10°C, infections are possible as early as January
o Humid weather promotes the growth and spread of the disease
o Additional spores form on the surface of diseased tissue, and these spores cause new infections if the weather remains mild and wet
• PROTECTION:
o PREVENTIVE MEASURES: Thin out and remove infested shoots by mid-May, thin fruit if the crop load is heavy, and apply copper in the fall after leaf drop
o DIRECT MEASURES: From bud swell to bud break during humid weather and temperatures above 10-12°C treat with copper; in case of persistent humid weather, repeat the treatment 1-2 weeks later
• Check records of growing degree hours +7°C (sums of active temperatures about 7°C; SAT+7) from the beginning of the year (from January 1st) at meteo-stations in or near your orchards
• The first movements of the bud scales are visible when the SAT+7 reaches the value of 800
• Ordinarily, the first treatment by copper is recommended at the value of 1100-1200 SAT+7, but it is advisable to start mostly already at the value of 1000 SAT+7 (in central Europe)
• Grow tolerant varieties to leaf peach curl disease, however fully resistant varieties do not exist
• Varieties described as the most tolerant: Bella di Roma, Catherine Sel.1, Golden Jubilee, Redhaven, Hardired, Filip, Frumoasa litoralului, Stark Saturn, Creola.; Peach varieties: Bénédicte, Belle de Montélimar and Reine des Vergers are traditional in France
• Nowadays, the offer of peach varieties is large, but the lack of reliable data concerning their suitability to organic systems makes the choice difficul