Epidemiology and chemical control of Fusarium ear and seedling blight of wheat

The aim of the study was to determine a link between the applications of fungicides, ear blight (caused by Microdochium nivale and Fusarium culmorum), grain quality and the subsequent emergence of infected seed. In order to determine this a series of field and glasshouse trials were carried out. In field situations the pathogen causing ear blight symptoms is often unknown. Azoxystrobin is reported to be less effective against F. culmorum (Dardis & Walsh, 2000) and the results from this study agree with this work. The trials concluded that for chemical control in the field a mixture of the fungicides azoxystrobin and metconazole provided the most significant reduction of ear blight severity and grain infection when compared with the control treatments. The emergence trials concluded that the use of a seed treatment (fludioxonil) can significantly improve the emergence of an infected crop. It is known that M. nivale may be present in a seed crop with the absence of visible symptoms on the seed (Hare et al, 1999). For plots drilled with out a seed treatment, the ones that had received an ear spray of azoxystrobin alone or a mixture of azoxystrobin and metconazole showed a higher percentage emergence regardless of the pathogen. The emergence trials proved the infection of seed can be significantly reduced by the use of ear sprays. If the seed is to be saved on the farm, the use of a seed treatment will improve the emergence of the new crop. Trials on the effect of increasing inoculum load on the symptoms of ear blight and the infection of grain. It was found that increasing the inoculum load for F. culmorum either alone or in a mixture of pathogens gave a reduction in yield and thousand-grain weight but this was not so with M. nivale this agrees with Hare et al,(1999) who studies the relationship between wheat seed weight infected with F. culmorum or M. nivale. When grain form these trial was drilled in the emergence trials it was shown that where the seed contained F. culmorum a significant improvement in emergence was seen when a seed treatment of fludioxonil was used. Glasshouse studies were conducted on point inoculation of ears with pathogens and found that there is a relationship between grain infection and seed weight for F. culmorum but not for M. nivale. Thus, grain weight can not be used on farm as a measure of infection when assessing seed health as M. nivale can be symptomless