A Comparative Study of Field Nematode Communities over a Decade of Cotton Production in Australia

Oliver Knox,David Backhouse,Vadakattu Gupta

doi:10.3390/agronomy10010123

Abstract

Soil nematode populations have the potential to indicate ecosystem disturbances. In response to questions about nematode interactions with soilborne diseases and whether genetically modified cotton altered nematode populations, several fields in the Namoi cotton growing area of Australia were sampled between 2005 and 2007. No significant interactions were observed, but nematodes numbers were low and postulated to be due to the use of the nematicide aldicarb. Aldicarb was removed from the system in 2011 and in 2015 funding allowed some fields to be resampled to determine if there had been a change in the nematode numbers following aldicarb removal. No significant changes in the total nematode numbers were observed, implying that the removal of aldicarb had little impact on the total nematode population size. However, an increase in plant parasitic nematodes was observed in both fields, but the species identified and the levels of change were not considered a threat to cotton production nor driven solely by altered pesticide chemistry. Additionally, greater numbers of higher order coloniser-persisters in the 2015 samples suggests that the current cotton production system is less disruptive to the soil ecosystem than that of a decade ago.

Highlights

The use of pesticides often courts controversy and remains an issue that often results in political intervention [1,2]
Australian cotton systems have historically been without the nematode related production issues experienced by other cotton producing nations [6], the presence of the reniform nematode, Rotylenchus reniformus [7], in the Theodore production area of Queensland highlights that this status can change
For field in the lower Namoi (field A) and 134.5 g for field B over the period of assessment with no apparent statistical difference between weights with sampling time or field, moisture content varied between 24% and 35%

Summary

Introduction

The use of pesticides often courts controversy and remains an issue that often results in political intervention [1,2]. As a consequence of this, aldicarb was not registered for nematode control, but for early season control of aphids, mirids, jassids, mites, wireworms and thrips that aldicarb’s systemic activity offered whilst retaining beneficial populations [8]. Control of these early season pests following the removal of aldicarb from Australia in 2011 has been provided either through the optional use of neonicotinoids, in the form of Cruiser® (active ingredient (a.i.) thiomethoxam, Syngenta) [9], or through the continued or adopted use of the organophosphates and carbamates, such as phorate

Methods

Results

Conclusion