Report for Occurrence of Spring Dead Spot Caused by Rhizoctonia cerealis AG-D on Zoysiagrass During the Fall Season

Jung Han Lee¹ Jeong Ho Kim¹ Chang Wook Jeon² Gyu Yul Shim^1,* YounSig Kwak^2,*

¹Korea Turfgrass Research Institute, Seongnam 13522, Korea
²Institute of Agriculture & Life Science, Gyeongsang National University, Jinju 52828, Korea

Abstract

In October 2018, symptoms of the spring dead spot (Rhizoctonia cerealis AG-D) disease in Kwang-Ju Country Club at Gokseong, Jeonnam province, South Korea were observed on Zoysiagrass (Zoysia japonica Steud.). Spring dead spot symptom commonly appears in spring, however our research showed that the spring dead spot symptom on Zoysiagrass could be shown in autumn. The initial disease symptoms were observed on reddish brown leaves and a decaying, irregular-shape patch of the leaf (30-50 cm), developed by the end of October, as the disease progressive. Aerial hyphae, like spider web on the leaves, were observed in the early morning. The causal agent was isolated and identified as Rhizoctonia cerealis AG-D by morphological and molecular characteristics. Optimal temperature and pH for mycelial growth of Rhizoctonia cerealis AG-D were 20℃ and pH 6.0, respectively. Bud formation from the infected tissue in fall season was considerably reduced compared to healthy lawn in spring. The spring dead spot infection site was a leaf auricle while the big patch was stemmed around the crown tissue. Thus sheath infected large patch was plucked easily than lawn spring dead spot pathogen. This is the first report of an outbreak of the spring dead spot disease on Zoysiagrass in the fall season.

Figures & Tables

Fig. 1. Disease symptoms on zoysiagrass infected by spring dead spot appeared in the fall season in Korea. A: Observed on Oct. 30; A-1: Close-up view of lesion; B: Observed on Nov. 12; B-1: Close-up view of lesion.