Abstract
Shoot blight of suckers of common lilac plants (Syringa vulgaris) was found in an apartment garden in Daegu, Korea. The causal organism was a species of Phytophthora, which was homothallic with paragynous antheridium. Oogonia were globose and measured 21.5-34.0 $\mu\textrm{m}$ with an average of 29.7$\pm$3.2 $\mu\textrm{m}$ in diameter. Oospores in oogonia were round, light orange brown when mature, mostly plerotic, and measured an average of 25.6$\pm$3 $\mu\textrm{m}$ in diameter. Antheridia were ovoid and around 11.7$\times$7.8 $\mu\textrm{m}$. Sporangia seldom formed on agar media but formed abundantly in water. Sporangia that formed in water were semipapillate, ovoid obpyriform, non-caducous, and 23.4-66.3$\times$17.6-37.1 $\mu\textrm{m}$ in dimension with I/b ratio of 1.46. The causal organism was identified as Phytophthora citricola Sawada on the basis of morphological characteristics. This is the first report of shoot blight caused by P. citricola Sawada in lilac suckers in Korea.