Integrated management of cyst nematodes in oilseed rape (PhD)

Abstract

Oilseed rape (OSR) production in the UK has increased markedly since the 1970s. This has led to reduced rotation lengths with potential for increased damage and yield loss by the two OSR cyst nematode species; the brassica cyst nematode (Heterodera cruciferae) and the sugar beet cyst nematode (H. schachtii). This project aimed to: assess the distribution and potential yield losses caused by cyst nematodes in OSR, provide management advice to minimise current and future crop losses and investigate the effect of temperature on H. schachtii development.

A survey for the two cyst nematode species was conducted in OSR-growing areas of the UK, whilst glasshouse and polytunnel experiments were conducted to investigate the host status of five of the most popular UK OSR cultivars (cvs), and the relationship between initial population densities of H. schachtii, H. cruciferae and yield. Water bath and outdoor pot experiments were conducted to investigate the effect of temperature on the life cycle of H. schachtii, and the number of generations completed by H. schachtii on OSR during the growing season.

Cyst nematode species H. schachtii (70%), the cereal cyst nematode (H. avenae complex) (19%) and the potato cyst nematode (PCN) (Globodera pallida) (10%) were detected in 14% of the 221 survey samples, whilst 11% of the samples contained a mixture of both H. schachtii and G. pallida. The population densities were generally low with 85% of the samples having less than 10 eggs g-1 of soil, whilst H. cruciferae was not detected in any of the samples.

The winter OSR cvs Flash and DK Cabernet were more susceptible to cyst nematode damage than cvs ES Astrid, Castille and Catana respectively.

Temperature influenced the development of H. schachtii with the duration of the life cycle ranging between three and six weeks. The optimum temperature for development ranged between 20.5 and 32.2°C, whilst at least two generations of H. schachtii were completed during the growing season.

These results indicate that, given the high potential for nematode multiplication at low population densities and the rising UK soil temperatures, coupled with the low resistance of current OSR cvs, agronomic practices may lead to build-up of high cyst nematode population densities in the future.