Macrophomina phaseolina (Tassi.) Goid-was isolated from sunflower plants showing typical charcoal rot symptoms. The pathogen causes pre-and post-emergence damping-off at low frequency, but its major damage occurs on mature plants. The disease was most prevalent at Behera and less frequent at Giza, Beni-Suef and Minia.
Pathogenicity of 4 isolates of the pathogen was tested on sunflower plants. The pathogen did not appreciably affect seed germination at the pre- and post-emergence stages, while considerable loss was recorded on 8 weeks-old plants. Slight differences were recorded between the pathogenicity of the tested isolates especially 3 weeks after sowing.
The disease significantly decreased the seed yield per plant in all tested sunflower cultivars by 15.0-52.2%. Head diameter was reduced by 27.1-41.1%. and average weight of 1000 seeds was al3o reduced by 5.3-12.5%. The oil content and the average oil yield per plant were reduced by 3.6-10.8% end 22.4-53.9%, respectively.
These findings indicate the significant economic loss due to this disease on sunflower plants in ARE.