Microplot Experiments On the Effect of Plant Hosts On Populations of the Cereal Cyst Nematode (Heterodera a Venae) and On the Subsequent Yield of Wheat

Abstract

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.