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POSTERS: Biological control

In vitro control of Colletotrichum acutatum isolates from citrus using extract from brown alga Dictyota dichotoma
Carolina Rebello - Gulf Coast Research and Education Center, University of Florida. Levi Pompermayer Machado- UNESP, Rayrah Esperidiăo da Silva- UNESP, Geraldo Silva- FUNDECITRUS, Maria Cândida De Godoy Gasparoto- UNESP

Citrus postbloom fruit drop (PFD), caused by Colletotrichum acutatum, is a sporadic disease in Brazilian orchards, however can cause yield losses up to 85%, resulting in frequent fungicide applications. This situation can decrease commercial products efficacy, cause environmental impacts and have harmful effect on human. Additionally, alternative control of PFD is absent in commercial orchards. The aim of this work was to evaluate the effect of dichlorometane/methanol (2:1 v/v) extract of Dictyota dichotoma in the control of C. acutatum germination in vitro. Discriminatory dose of D. dichotoma (100 or 1000 µg.mL-1) or fungicides (10 µg.mL-1 of trifloxystrobin or triazole) were amended into PDA medium. PDA without extract and fungicides served as control. Aliquots of conidia suspension were deposited on plates with the treatments, in a total of 9 repetitions per treatment. The plates were randomly incubated at 23°C under light for 9 hours and spore germination was calculated. The extract in the highest concentration resulted in inhibition of 97.4% of C. acutatum germination, which was statistically the same obtained by 10 µg.mL-1 of trifloxystrobin. The seaweed extract in a concentration of 100 µg.mL-1 resulted in a lower inhibition in conidia germination than that achieved with triazole, although its effect was better than the control. These previous results demonstrated the potential of seaweed extracts to be used as an alternative control in the management of PFD.