Associação de Alternaria dauci e A. alternata com sementes de coentro e eficiência do tratamento químico

Abstract

Association of Alternaria dauci and A. alternata with coriander seeds and efficiency of chemical treatments Twelve lots of coriander seeds were evaluated for the presence of Alternaria spp., using 600 seeds per lot in the blotter test. Two Alternaria species were detected, A. dauci (AD) in eight lots and A. alternata (AA) in six lots. A sample of 400 seeds was sown in styrofoam trays and the incidence of spots on cotyledons was evaluated 21 days after sowing. Only lesions caused by AD were observed on leaves. The seed lot with higher incidence of AA and AD was treated with fungicides (thiram, benomyl, captam and iprodione) and 400 seeds in each treatment were placed in four gerbox boxes with sterilized wet filter paper. Seeds were observed under stereoscopic microscope for presence of AD and AA. The best treatment was the mixture of thiram + iprodione resulting in 0.5% and 0% incidence of AA and AD, respectively. Treated seed samples were sown in styrofoam trays to verify transmission of Alternaria spp. from seeds to seedlings. Plants resulting from non treated seeds presented 13% of infection with AD. Plants from seeds treated with the mixture thiram + iprodione were not infected by AD. The results demonstrated the efficacy of thiram + iprodione mixture for treatment of coriander seeds against A. dauci and A. alternata.