Characterization of Benomyl Resistance in Mycosphaerella fijiensis, Cause of Black Sigatoka of Banana, in Costa Rica.

Sixty-eight and eighty-six percent of monoascosporic isolates of Mycosphaerella fijiensis from two banana plantations in Costa Rica, in which benomyl was used for ≈10 years to control black Sigatoka, were resistant to benomyl in February and November 1994, respectively. No resistance to benomyl was detected in isolates collected during February 1994 from farms with no history of benomyl use that were located ≈50 km from the nearest banana plantations. Only 1% of isolates was resistant to benomyl in a sample taken during November 1994.

Reaction of Four Musa Genotypes at Three Temperatures to Isolates of Mycosphaerella fijiensis from Different Geographical Regions.

Two tetraploid banana hybrids, FHIA1 and FHIA2, with resistance to black Sigatoka, and two highly susceptible, naturally occurring triploids, Grand Naine and False Horn, were evaluated at three temperatures for their resistance to isolates of Mycosphaerella fijiensis from five geographical regions. The youngest open leaf of young plants was inoculated, and plants were incubated at 22, 26, and 30°C in growth chambers. Duration of the incubation period and disease severity were used to evaluate the reactions of the genotypes.