Fungous diseases of ryegrasses in New Zealand

Open Access
Publisher Website
Google Scholar
Abstract
Twelve fungous diseases infecting foliage of ryegrasses (Lolium species) in New Zealand are discussed and their economic importance is noted. Puccinia coronata Corda incites the most important disease of ryegrass and causes much leaf damage and reduction in numbers of tillers and roots over summer and autumn. Heavily infected pastures may contain more than 5,000,000 urediniospores per g dry weight of herbage. Control measures are discussed. Helminthosporium dictyoides f. sp. perenne Braverman & Graham is also of economic importance on ryegrass, causing herbage loss throughout the year, especially in long swards of Lolium perenne L. The fungus can cause leaf yellowing in winter, and this symptom is sometimes mistakenly attributed to a deficiency in nitrogen. Rhynchosporium orthosporum Caldwell causes the most important disease of ryegrass during winter and early spring. Leaf symptoms may be confused with frost or wind damage. “Grasslands Ariki” ryegrass is very susceptible to this disease and sheep avoid grazing heavily infected plants. This is the first record of this disease in New Zealand. Fusarium nivale (Fr.) Ces. has not been previously recorded on ryegrass in New Zealand. It is sometimes common in autumn-saved pastures but is usually not of great economic importance. Ramularia pusilla Unger. Puccinia graminis Pers.. Colletotrichum graminicola (Ces.) Wils., and Helminthosporium siccans Drechs. cause diseases which are generally not serious but can be of minor importance at certain periods of the year in some localities. Septoria tritici var. lolicola Sprague & A. G. Johnson, Ascochyta sorghi Sacc., Spermospora subulata (Sprague) Sprague, and Septogloeum oxysporum Bomm., Rouss., & Sacc. are probably of little or no economic importance on ryegrass. All four diseases are recorded for the first time in New Zealand. In addition, this appears to be the first record of S. subulata and S. oxysporum attacking Lolium species.