The higher incidence of winter rust fungus (Puccinia abrupta var. Partheniicola) on the invasive weed Parthenium (Parthenium hysterophorus L.) in central Ethiopia is related to greater average rainfall, cloud cover and relative humidity in 2020.
Parthenium hysterophorus L. is an aggressive weed found in over 40 countries including Ethiopia. One of its natural enemies is the winter rust fungus Puccinia abrupta var. partheniicola. There was an outbreak of the winter rust fungus on parthenium in Ethiopia in 2020. A survey at six locations in central Ethiopia indicated a mean per cent score of winter rust fungus infection ranging from 76 ± 10% to 96 ± 6%. In 2020, for July August and September, the average rainfall (370 mm), cloud cover (65%) and relative humidity (81%) were greater than in previous years. The conditions in 2020 were ideal for germination and development of the winter rust fungus.