Potential release of primary inoculum of Venturia inaequalis in the Osorno Province, X Región of Chile

Ivette Acuña B.1, Paola Riffo F.1 y Cecilia Catalán D.2

The Xth Region of Chile has a great potential for apple production, especially for processing. Nevertheless, one ofthe most important apple diseases, the scab, caused by the ascomycete fungus Venturia inaequalis (Cooke) Winter, is strongly enhanced by the favourable climates predominating in the area during spring and summer. The objective of this research was to determine the ascospore potential release curve of Venturia inaequalis in the Xth Region in order to get a better control of this disease. The field work was carried out from 1989 to 1992 on different apple orchards in the Osorno province. Apple leaves were collected during fall, and allocated on wood frames placed on the borders of the plantation. From August to January, leaf were sampled weekly to determine ascospore potential release by a laboratory technique. The results ofthe study indicated that V. inaequalis ascospore potential release started in mid August, with a rapid increase toward mid September, having its peak between September and October and decreasing significantly in November. No main deviations from this pattern was observed in the different locations evaluated. Spores release started at swollen bud stage in apples, with a peak between pink button and full bloom stages. The refore, this potential release of ascospores must be considered for research as a critical period in apple scab control.

Keywords: plant diseases, Venturia inaequalis, apple scab, epidemiology.
1 Estación Experimental Remehue (INIA), Casilla 24-0, Osorno, Chile.
2 Memorante Departamento Quimica y Alimentos, Instituto Profesional de Osorno, actualmente en actividad privada.