Incidence of powdery mildew and scab in different cultivars of commercial pear orchards in Rio Negro valley

LUTZ, M. C.; VERA, L.; SOSA, M.C.

PHYTOPATHOLOGY

AMER PHYTOPATHOLOGICAL SOC

Lugar: St. Paul, Minnesota; Año: 2022 vol. 112

0031-949X

During 2018/2019 an outbreak of scab (Venturia pirina, Vp) and powdery mildew (Podosphaera leucotricha, Ple) affected pear trees in the Alto Valle de Rio Negro. Here, we report the incidence of Vp and Ple on Williams (W), Packham?s (P) and d?Anjou (D) pear cultivars from 3 commercial orchards in Ingeniero Huergo, Rio Negro, Argentina. Vp and Ple incidence (%) was evaluated i) in November (30-45 mm diameter, fruit development) on 50 plants/row (6, 3, and 3 rows for W, P, and D, respectively), and ii) in January (harvest), on 2115 W, 1557 P and 997 D fruits. In November, Vp incidence (plant with at least one affected fruit) was 20% (60/300) for W, 2% (3/150) for P, and 5.3% (8/150) for D plants. In turn, Ple incidence (plant with at least one affected sprout) was 50% (150/300) for W, 18% (27/150) for P, and 95% (142/150) for D plants. Among affected plants by Ple, 10% of W and 18% of P presented also at least one affected fruit. At harvest, the incidence of Vp and Ple was 14.4% and 15.4% in W fruit, 1.7% and 6.8% in P fruit, and 0.5% and 4.1% in D fruit, respectively. Besides, 6.5% of W fruits showed symptoms of both diseases. Thus, both in the orchard and atharvest, Williams cv fruits showed the highest susceptibility to Vp infection, whereas Ple affected mainly d?Anjou sprouts and W and P fruits. These data are relevant to implement effective control strategies against Vp and Ple in the main pear cultivars grown in the region.