Development of disease symptoms and fungal pathogens on shoot bases in continuous winter wheat, and effects of fungicides

Abstract

Field plots in three consecutive crops of winter wheat were sampled at approximately 2‐week intervals from April to July in 1989, 1990 and 1991. Culm and stem bases were examined for symptoms of eyespot, sharp eyespot and brown foot rot. The W‐type and R‐type of Pseudocercosporella herpotrichoides, P. anguioides, Fusarium culmorum, F. avenaceum and Microdochium nivale grown from this plant material on agar were identified. Eyespot was most severe in 1991, when plant development was least rapid following cool weather in late winter and the summer was relatively cool and wet. Sharp eyespot was most severe in 1990, which had a warm summer with moderate rainfall. The other warm summer, 1989, was drier and these conditions favoured late development of brown foot rot, associated mainly with F. culmorum which was scarce at other times. Sharp eyespot sometimes increased where prochloraz, which decreased eyespot, was applied. Distinct symptoms of more than one disease occurred less frequently on the same stem than expected from the individual total occurrences, but co‐occurrences of different fungi were often more frequent than expected. In July 1990, Fusarium spp. co‐occurred with R‐type, but not W‐type, P. herpotrichoides more frequently than expected, and in July 1990 and 1991 M. nivale and both W‐type and R‐type co‐occurred more frequently than expected. Fusarium spp. and M. nivale were more frequent, especially in the earlier samples, on nodes than on internodes, whilst P. herpotrichoides normally infected at the internodes. The results suggest that stems weakened or altered by a primary colonizer are often a suitable substrate for a secondary colonizer, often a Fusarium sp., which may begin infection at a distance from the original lesion and often not cause distinct symptoms itself.

The Role of the Preceding Crop and Weed Control in the Transmission of Rhizoctonia Cerealis and R. Solani to Winter Cereals

“…Nicholson et al (2002) and Ray et al (2006) found that the amount of DNA of R. cerealis, in relation to total DNA obtained from the plant, was increasing at successive development stages of wheat. Similarly in the present research, many more isolates of R. cerealis and R. solani were obtained at the end of the plant vegetation period than at the cereals seedling phase, which also coincides with the reports by Bateman (1993).…”

Characterisation of New Zealand Fusarium populations using a polyphasic approach differentiates the F. avenaceum/F. acuminatum/F. tricinctum species complex in cereal and grassland systems

“…F. avenaceum and F. culmorum are associated with crown rot in more temperate regions overseas, such as the United Kingdom (Bateman 1993), France (Colbach et al 1996), the USA (Windels & Wiersma 1992) and Victoria, Australia (Backhouse & Burgess 2002).…”

Fusarium culmorum: causal agent of foot and root rot and head blight on wheat

“…FRR by F. culmorum is severe when wheat is grown in warm areas, where the host plant is more subject to water stress (Bateman, ; Cariddi and Catalano, ; Chekali et al ., ; Colhoun et al ., ; Inglis and Cook, ; Papendick and Cook, ; Parry, ; Prew et al ., ). Drought conditions increase the susceptibility of the plant rather than the virulence of the fungus.…”