A severe leaf and stem necrosis disease of Alternanthera philoxeroides (alligatorweed) was examined in the summer of 2011. Symptoms on leaves and stems of A. philoxeroides consisted of round to oval straw colored spots with maroon margins resulting in chlorosis, severe defoliation and withering of stems. The causal pathogen isolated on V-8 agar medium was morphologically identified as Nimbya alternantherae. Pathogenicity of N. alternantherae was proven on healthy A. philoxeroides plants. This is the first report of A. philoxeroides necrosis caused by N. alternantherae in Pakistan.
Alternanthera philoxeroides; Nimbya alternantherae; herbaceous weed; identification