Cost of root disease on white clover growth in New Zealand dairy pastures

Abstract

The cost to clover growth of soil-borne root disease was measured in ten New Zealand dairy pasture soils. The average increase clover growth (weight) after soil pasteurisation was 28.5 %, but ranged from a 64 % increase (Whataroa soil) to a decrease of 11.9 % (Ruakura soil). The economic cost of reduced clover growth was determined using the Farmax Dairy Pro decision support system. In Southland and Canterbury, clover root disease was estimated to cost $750 and $715 ha −1 year −1 respectively, and in the Waikato region $1506 ha −1 year −1 . DNA-based testing of the soils detected the presence of diverse fungal, oomycete and nematode pathogen populations. A significant linear relationship was found between reduction in clover growth and group F Pythium spp. (P = 0.0177). The DNA-based assay indicated that Aphanomyces trifolii, a root pathogen of subterranean clover, may be present in the dairy-pasture soils. As this pathogen is currently not recognised as present in New Zealand, a definitive determination of its presence is required. Based on the high economic costs of diseases, the control of soil-borne root pathogens in New Zealand pasture is a direct means to increase profitability.

High spatial variation in population size and symbiotic performance of Rhizobium leguminosarum bv. trifolii with white clover in New Zealand pasture soils

“…In these instances, the net effect of deleterious microflora outweigh the importance of beneficial symbionts in these soils. Recent surveys of pathogenic microorganisms and nematodes in New Zealand pastures have revealed surprisingly large impacts of disease on white clover growth [ 32 , 33 ]. The inoculation of soils harbouring these pathogen-enriched communities into clover growth assays can result in poor outcomes for clover seedlings.…”

Effect of land use and soil organic matter quality on the structure and function of microbial communities in pastoral soils: Implications for disease suppression

“…Management of the soil microbial community towards inducing or enhancing disease suppression presents an emerging, and potentially more enduring, approach to disease control in agricultural systems [ 11 ]. Managing or ‘engineering’ the soil microbiome in this way may prove to be particularly important in pastoral grasslands where the control of diverse pathogens is complicated by multi-plant-multi-pathogen interactions [ 2 , 12 ]. To exploit the natural processes that lead to enhanced disease suppression in pastures, and to support farmers in managing pastoral systems towards a more suppressive state, it is important to develop understanding of the occurrence of suppressive microbiota in the field and how these vary spatially, temporally, and with farm management practices.…”

Detection of Invertebrate Suppressive Soils, and Identification of a Possible Biological Control Agent for Meloidogyne Nematodes Using High Resolution Rhizosphere Microbial Community Analysis

“…There are likely a range of reasons for this difference between studies including temporal (the soils were sampled in different years), spatial (diseases, for instance, can be patchily distributed) and the severity of the treatment imposed. In the current study virtually all microbes were eliminated while the Wakelin et al (2016) method was less severe and may have retained some beneficial microbes which then minimized the negative effects of the sterilization treatment. Root length in all soils were greater in Experiment 2 than Experiment 1, with many root systems reaching the bounds of the pot depth (120 mm).…”

“…Skipp and Christensen (1983) recorded the incidence of potential root-rotting fungi on white clover roots during a survey of New Zealand pastures and found that Codinea fertilis predominated in root pieces from two soils in Northland (close to soil 1 in the current study) and that Bimuria novae-zelandiae predominated in soils of Southland (close to the current soil 10). Wakelin et al (2016) found a significant negative association between a Pythium clade and T. repens shoot growth. Whether, these are the causative agents of the root rotting observed in the current study will be clarified by the next generation sequencing results to be carried out on white clover endosphere samples which will be reported in a future paper.…”

“…Wakelin et al (2016) used microwaving to sterilize a range of New Zealand soils and found that of 10 soils they tested all but one gave a significant positive response in T. repens growth in sterilized soil. Over all soils they found that control soil produced 28.6% more T. repens shoot weight than sterile soils.…”