Wheat Rust in Australia. 69 



known that here in Australia, where barberry bushes are not native, and 

 where they are comparatively scarce, the rust is particularly bad in certain 

 seasons, so that there must be other causes to account for the prevalence 

 of rust. 



The connexion between wheat-rust and barberry has already been dis- 

 cussed, so need not be further referred to here. There are several possible 

 ways in which the presence of the rust year after year may be accounted for, 

 and it may be worth while to consider some of these. 



1. The uredospores produced in such immense numbers may serve to 

 carry it on. They are very minute and light, easily distributed by the 

 wind, and it has been shown- that they exist in the air and on the ground. 

 They might thus be readily transported and even carried to localities 

 far removed from wheat-growing areas, in some cases by the duststorms 

 which are very prevalent in the northern parts of Victoria. But the mere 

 presence of spores is not sufficient to account for the rust being spread, 

 since they must be capable of germination. I have often tried to germinate 

 uredospores taken from straw that had been left on the ground, but without 

 success. My latest attempt was with uredospores still retaining their 

 colour from a sorus on a dead leaf of Queen's Jubilee wheat on March 25th. 

 The spores^ were kept moist under a bell -jar, but not a single one ger- 

 minated. But the result is different when spores are taken from self-sown 

 wheat growing in the interval between the two crops. (Note 8, p. 75.) 



2. These spores are not only in the air and on the ground, but they 

 are commonly to be found entangled in the bearded tip or " brush " of the 

 grain. In one variety, Queen's Jubilee, this was so common that not a 

 single grain could be found without the uredospores. Dr. Cobb 11 has 

 likewise examined the brush of a number of varieties in New South Wales, 

 and found in about 57 per cent, of the grains examined ithat the spores 

 were in the brush. This is an evident starting-point for the rust, but not 

 the only one, since seed wheat treated with bluestone. formalin, corrosive 

 sublimate, and other fungicides, produced rusty plants, and in fact there 

 was little difference as regards rust between the plants from treated and 

 untreated seed. 



3. It was commonly supposed until recently that the rust could readily 

 pass from one cereal crop to another, and thus it was passed on to the 

 wheat at the proper season. This view was put forward as late as 

 September, 1904, in the Journal of Agriculture of South Australia, by 

 A. Molineux 1 , who states: "I have observed for many years that when 

 ever we have a mild autumn and summer, accompanied with occasional 

 showers, we have complaints of red rust in the succeeding crop j and I have 

 been led to the belief that until the new wheat crops have started, the rust 

 is nursed by the wild oats and other cereals that may always be found 

 growing on the headlands and by the roadsides." Of course, this is a 

 very convenient way of accounting for the presence of rust throughout the 

 year, but Eriksson has shown thaT the spores from oats will neither infect 

 wheat nor barley, nor will the spores from the barley infect wheat or oats. 

 It follows from this that adjacent fields of these crops will not affect or 

 be affected iby each other, so far as this rust is concerned. Probably, 

 however, Molineux' s view is correct, except that it is the self -sown or 

 volunteer wheat growing in our paddocks or on the headlands that carry 

 it over. The system of harvesting practised in Australia with the com- 

 bined harvester, which takes off the heads only and delivers the winnowed 

 grain into bags, necessarily implies the scattering of a certain amount of 

 seed on the ground, and this germinates with the first rain, and is almost 

 always partly rusted, and often badly so. Our hay being la/rgely made 



