Identifying and Characterizing Summer Diseases on ‘Babygold’ Peach in South Carolina
2006
Schnabel, Guido | Chai, Wenxuan | Cox, Kerik D.
Summer diseases can cause significant yield losses in processing peach varieties, such as the ‘Babygold’ lines. In this study we identified and characterized the pathogens responsible for disease outbreaks in two orchards (PH and JC) located in the northern ‘Piedmont’ area of South Carolina. Three pathogens, Geotrichum candidum, Colletotrichum acutatum, and Botryosphaeria dothidea, the causal agents of sour rot, anthracnose, and Botryosphaeria fruit rot disease respectively, were identified on fruit from orchard PH using symptomology, culture and spore morphology, and ribosomal DNA analysis. G. candidum and C. acutatum were also isolated from symptomatic fruit from orchard JC. The QoI fungicide azoxystrobin and a mixture of pyraclostrobin and boscalid were evaluated for their in vitro efficacy against five isolates of each of the three pathogens to investigate their possible usefulness in designing management strategies. Azoxystrobin inhibited mycelial growth of C. acutatum isolates (EC₅₀ values of 0.01 to 0.55 mg/liter) but was ineffective against mycelium of G. candidum and B. dothidea isolates (EC₅₀ values >300 mg/liter). The pyraclostrobin-boscalid mixture was highly effective against mycelium of C. acutatum (EC₅₀ values of 0.01 to 0.05 mg/liter) and B. dothidea isolates (EC₅₀ values of 0.02 to 0.03 mg/liter), but only marginally effective against mycelium of G. candidum (EC₅₀ values 15.79 to 39.03 mg/liter). This study provides a diagnostic guide of pathogens that can cause summer diseases on ‘Babygold’ peaches and reports their in vitro sensitivity to registered respiration inhibitor fungicides.
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