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Control of Phytophthora palmivora in Papaya Orchards with Weekly Sprays of Chlorothalonil. A. M. Alvarez, Assistant Plant Pathologist, Department of Plant Pathology, University of Hawaii, Honolulu 96822. M. G. Nelson, Research Associate, Department of Plant Pathology, University of Hawaii, Honolulu 96822. Plant Dis. 66:37-39. Accepted for publication 14 April 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-37.

Weekly sprays with chlorothalonil (3.4 kg a.i./ha) for control of Phytophthora palmivora resulted in 2534% fewer diseased papaya trees in sprayed plots in three orchards than in unsprayed controls. A zinc ion-maneb complex sprayed weekly at 1.8 kg/ha was less effective than chlorothalonil in controlling fruit rot and preventing loss of trees. When the interval between sprays of chlorothalonil was increased from 7 to 14, 21, and 28 days, disease incidence increased by about 6% for each interval. Both chlorothalonil and zinc ion-maneb were effective only in protecting trees before trunk cankers developed. After cankers formed, trees continued to die in wet weather regardless of the fungicide used.

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