Recent work in Western Australia also provides some thought-provoking results on herbicide-disease interactions.
The use of Roundup rather than SpraySeed as a knockdown herbicide (up to 24 hours) before sowing lupins resulted in higher incidence or severity of rhizoctonia root disease, or lower stand density of lupins. This effect of Roundup was greater when a cultitrash type disc machine was used for sowing than when crops were sown with a tined machine.
However, Simazine had no such effect on root rot of lupins caused by Pleiochaeta setosa. The same was true of the use of post-emergence herbicides applied for weed control in wheat, and the incidence or severity of rhizoctonia root rot of wheat.