Strategy to control Peach Leaf Curl damage (BIOFRUITNET Practice Abstract)

Summary

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 difficult