אסיף מאגר המחקר החקלאי

The performance of potassium phosphite for controlling Alternaria brown spot of citrus fruit

Year:

2006

Source of publication :

Authors :

Volume :

113

Co-Authors:

Yogev, E., Luxembourg Industries (Pamol) Ltd., P.O. Box 13, Tel Aviv 61000, Israel
Sadowsky, A., Division of Citriculture, Extension Service, Ministry of Agriculture and Rural Development, Bet Dagan 50250, Israel
Solel, Z., Departement of Plant Pathology, Agricultural Research Organization, Volcani Center, Bet Dagan 50250, Israel
Oren, Y., Division of Citriculture, Extension Service, Ministry of Agriculture and Rural Development, Bet Dagan 50250, Israel
Orbach, Y., Division of Citriculture, Extension Service, Ministry of Agriculture and Rural Development, Bet Dagan 50250, Israel

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Abstract:

Potassium phosphite (Canon®) was evaluated as a means to control Alternaria brown spot, caused by Alternaria alternata pv. citri, which inflicts severe damage on susceptible citrus cultivars worldwide. Canon®, at concentrations up to 400 μg/ml, did not inhibit germination of conidia of A. alternata pv. citri, but it did inhibit mycelium growth, slightly at 3.12 μg/ml and completely at 50 μg/ml. These concentrations are much higher than those of Sygnum® that gave comparable inhibition. Foliar protection assays revealed that prophylactic spray with Canon® decreased lesion development on leaves, even though it had a negligible effect on spore germination and subsequent mycelium development. Laboratory inoculation assays revealed that fruits and leaves collected after treatment with Canon® were often unprotected, whereas recommended fungicides were effective. In eight experiments conducted in 2001 to 2003 in groves of Minneola or Nova (Yanuv) tangelos and murcott, the effects of fungicides were evaluated according to the number of lesions per fruit. In all the experiments, Canon® significantly increased the proportion of export quality class I fruits (up to five small lesions per fruit), compared with untreated controls, and its performance did not differ from that of the commercial treatment with recommended fungicides on alternating schedules. The proportion of exportable fruits was often 50-100% greater than that in the untreated control. Moreover, the proportion of severely infected fruits (category 3 infections) was sometimes more than 10 times as high in the control than in the Canon® treatment. © Eugen Ulmer KG.

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