Abstract:
Weed resistance to herbicides present one of the greatest current economic challenges to agriculture. Herbicide
resistant ryegrass (Lolium spp.) is a serious problem in Western Cape grain-producing areas. Morphological and
pathogenic analyses were performed on ryegrass samples. Morphologically, 50% of specimens were classified
as rigid ryegrass, 48% as a hybrid, namely L. multiflorum L. perenne and 2% as perennial ryegrass. Fusarium
pseudograminearum (cause of Fusarium crown rot) was isolated from six localities. Pathogencity tests confirmed
that F. pseudograminearum isolates obtained from ryegrass and wheat are pathogenic on both crops, indicating
that ryegrass can act as an alternative host and a source of inoculum of this important soilborne pathogen. Grass
weed infestation can favour the disease, and grass weed control is therefore recommended as part of an integrated
strategy to manage crown rot. Knowledge on morphological differences among ryegrass may be important to guide
differential weed management of ryegrass. Smother cropping, as part of conservation farming, should receive more
prominence to suppress herbicide-resistant ryegrass and simultaneously reduce the occurrence of crown rot.
