Studies on dieback of buffel grass (Cenchrus ciliaris) in central Queensland

TLDR: This is the first multifaceted study of buffel grass dieback (BGD), describing the plant and field symptoms, determining factors responsible for plant death, and determining the method of spread.

Abstract: Buffel grass (Cenchrus ciliaris) is an introduced, summer growing, perennial tufted tussock grass which is used extensively in improved pastures in the grazing industry. Since 1993 there has been an increasing level of dieback in buffel grass in districts of Central Queensland districts, involving red leaf symptoms and occurring in roughly circular patches. There is a potential for this condition to destroy large areas, ultimately resulting in loss of production for beef, dairy and sheep farmers who use this grass in improved pastures. This is the first multifaceted study of buffel grass dieback (BGD). Areas showing signs of dieback have previously been the subject of extensive testing for soil fertility factors, soil chemistry, nematodes and phytoplasmas, with few conclusive results. Therefore, one of the aims of this project was to find the cause of buffel grass dieback. Specific objectives included describing the plant and field symptoms, determining factors responsible for plant death, and determining the method of spread. A complete description of the symptoms was made at plant, patch and paddock levels. Symptoms of Buffel Grass Dieback (BGD) presented as a reddening of the leaves starting from the tip and progressively moving towards the ligule. The red symptoms range from bright red, to dark red, to bronze (RHSPCC red group 45: A, B; 46: A, B; greyedorange group 166: A; 177; A) (The Royal Horticultural Society, 2001). Symptoms first appeared on the tips of the older leaves and progressively moved down the leaf. The next oldest leaf then showed symptoms, and so on, with the youngest leaf showing symptoms last. Any tillers followed the same pattern, regardless of whether symptoms on the primary shoot had progressed past the point at which the tiller was produced. The amount of time from new growth to the appearance of the red symptoms seemed to be directly proportional to the amount of rainfall. That is, the more rain, the longer it took for symptoms to develop. The amount of subsequent rainfall seemed to influence the time it took for plants to succumb to the condition. That is, when there was adequate water and lush growth plants grew faster than the spread of the condition. When plants became water stressed, the condition overtook growth and the plants succumbed.