Can reniform nematode (Rotylenchulus reniformis) in Australian cotton be managed by crop rotations?

Abstract

Reniform nematode is an important pest in cotton production in Central Queensland. No reniform resistant cultivars are commercially available. Rotation to resistant or non-host crops is used overseas to manage this pest. The potential of non-hosts to reduce the population density of reniform nematode was investigated in a replicated strip trial over two seasons on a commercial farm in Theodore, Qld. A sorghum plant with biofumigation properties, grain sorghum, and two corn varieties were investigated. In the second year the effect of previous crop on soil population of reniform post-harvest was determined.

In the 2014/15 season the four non-hosts significantly reduced soil nematode populations, with reductions of 98% compared with cotton in the top 15 cm of soil post-harvest. Deep coring showed that high populations of reniform were present at depth after cotton, confirming they survive deep in the soil profile. It is possible that re-colonisation of the planting zone could occur by drawing upon this population reservoir.

In the 2015/16 season, pre-plant populations in the non-host plots were significantly lower than the cotton plots. Post-harvest however, reniform populations were extremely high in the top profile for all treatments. Fumig8tor forage sorghum was the only crop that significantly reduced the population in the top 15 cm compared to cotton. Soil populations under Fumig8tor were significantly lower than commercial corn 606.

Researchers overseas have shown that a single rotation with a non-host may only suppress nematode populations, with economic thresholds being reached again by the end of the next cotton crop. Two successive rotations with a non-host crop are therefore recommended for improved production sustainability in such circumstances. Data from trial concurs, as large populations were observed after cotton for all treatments hence two years out of cotton is not sufficient to manage this pest.