CRITICAL PERIOD FOR APPLE SCAB CONTROL AND EFFECT OF POST HARVEST TREATMENT WITH UREA ON RELEASE OF THE ASCOSPORES OF VENTURIA INAEQUALIS IN THE SÃO JOAQUIM REGION, SC, BRAZIL

A field trial was carried out at the Research Station of São Joaquim, in order to determine the critical period of the apple scab and the effect of urea, spraying under post harvest and before leaf-fall conditions, on the release of the ascospores of Venturia inaequalis.

The ascospores liberation begins in middle of August and extends until middle of November.
The apple bud break at Santa Catarina State is variable and ordinarily occurs in September or October.

The apple is subject to infection by V. inaequalis since the apple bud break, because the ascospores liberation start in August.
Treatments with fungicides, about 5 to 6 applications, from bud break (green tipe stage of apple) until the end of ascospores liberation, were enough to control the apple scab.
The pulverization with urea 2.5%, 5.0%, 7.5% and 10.0% caused an increasing reduction in the number of ascospores released.
It was observed a decrease of 90.0% in the number of ascospores released as well as decrease in the lesions formed on the leaves when a 5.0% urea solution was applied.
It was also observed that most of the ascospores released by the spring were from infected leaves which fall in May and June.

International Workshop on Apple Culture in the Tropics and Subtropics

J.I.d. Bonetti, Y. Katsurayama

https://doi.org/10.17660/ActaHortic.1988.232.33