Data on the occurrence of deadheads in wheat have been collected in agronomy trials In Victoria over many pars. The main points arising from this data are- 1. No consistent differences in the susceptibility of many commonly grown Australian varieties. 2. No positive relationship between a root rot index and the number of deadheads. 3. A significant reduction in deadhead numbers with the use of superphosphate in half the fertilizer trials where counts were made. In other trials, where superphosphate had no significant effect, the general trend was still a reduction in deadheads where superphosphate was used. 4. In several trials, deadheads increased after a pasture period. Barley grass was a prominent species in many of the pastures and, in others, legume species were an important component. In some trials there were more deadheads where barley was included in the rotation and, in others, less deadheads where oats were included. 5. In general, there was an increase in deadheads when fallowing was delayed, especially if the initial working was not done until just before sowing. 6. Burning stubble, when the land was winter-fallowed, did not significantly, affect the number of deadheads.

Microplots containing soil, naturally infested with the cereal cyst nematode (Heterodera avenae) were left fallow or sown to one of nine cereal cultivars or grass species for five consecutive years. Wild oat (Avena fatua) was the most efficient host and, after three plantings, the nematode reached a potential increase ceiling of 42.2 eggs/g soil. Of the cereal cultivars tested, wheat (cv. Olympic) and barley (cv. Prior) were the most efficient hosts and levels of approximately 40 eggs/g were reached after five plantings. Barley grass (Hordeum leporinum) was less efficient than Wimmera ryegrass (Lolium rigidum) which maintained a ceiling population of about 10 eggs/g. Under fallow, populations declined to 0.5 eggs/g after 4 years. The most inefficient cereal hosts were the oat, cv. Avon, and cereal rye, cv. South Australian. The low populations maintained under continuous cropping with these cereals suggested that a rapid selection of a resistance-breaking biotype is unlikely to result from the continued use of inefficient hosts. Growth and yield of a subsequent wheat crop on all plots reflected the relative levels of nematode populations. At the low levels of infestation, grain yields were more than double those on heavily infested plots.

No abstract

Field trials in a sandy mallee soil in Victoria have shown that large increases (up to 323%) in grain yield are obtained by soil fumigation or the application of nematicides. Development of the plants was enhanced by control of soil-borne root pathogens. The occurrence of both cereal cyst nematode (H. avenae) and Rhizoctonia solani in patches of poor wheat in a field trial in South Australia indicate a possible association between these two pathogens. Glasshouse studies showed that the effects of H. avenae and R. solani on wheat were greater when both pathogens were together than with each individually.

Two hundred and seventy cereal species and cultivars (wheat, barley, oats, rye, and Triticales), were field tested for resistance to the cereal cyst nematode (Heterodera avenae Woll.) in Victoria. Tests were made in the Wimmera District at Natimuk (1952-1954) and in the Mallee District at Walpeup (1953), and Sea Lake (1966-1969). Some species and cultivars were tested at all sites, but most were tested at one site only. All wheats tested were susceptible or very susceptible, and all Triticales were susceptible. Two barley cultivars, Morocco and Marocaine 079 were resistant, and two others were moderately resistant. The oat species, Avena sterilis and A. strigosa were resistant and fifteen cultivars of A. sativa were moderately resistant. Rye, CV. South Australian, possesses a high degree of resistance in contrast to European ryes.