Impact of floor vegetation on the abundance of nematode trophic groups in vineyards

Abstract

This study examined the effect of two floor vegetation management strategies on the abundance of nematode trophic groups in two Australian vineyards (one cool and one warm climate) for three consecutive years. Throughout the grape growing season floor vegetation was managed either as a perennial sward by regular mowing/snipping (permanent sward) or eliminated by spraying herbicide (spray/bare soil). Soil from both treatments was inhabited by five nematode trophic groups namely bacteria feeders, predators, omnivores, fungal feeders and plant parasites. Of these, bacteria feeder nematodes were predominant, comprising 60–70% of the total population in each site. Predators and plant parasites comprised ca. 3% and 17% of the total population respectively at Wagga Wagga, and ca. 17% and 4% at Tumbarumba. In the sward plots by the end of the experiment, the populations of non-plant parasitic ‘beneficial’ nematodes (bacteria feeders, predators, omnivores and fungal feeders) had generally increased linearly with time whereas plant parasitic nematode populations had decreased. On the last sampling date, the total bacteria feeder nematode populations were ca. 3–4-fold and ca. 2–3-fold greater in the sward than the spray plots at Wagga Wagga and Tumbarumba vineyard respectively. Over three years, the omnivore nematode (primarily Dorylaimidae) populations were also significantly increased by ca. 2–6-fold and 3-fold in the sward plots compared to the spray plots at Wagga Wagga and at Tumbarumba vineyard respectively. Similarly, predatory nematodes in the sward plots were ca. 32–57% higher at Wagga Wagga and ca. 60–164% at Tumbarumba compared to the spray plots. In contrast, plant parasitic nematodes were ca. 4-fold greater in inter-row sward plots than the spray plots at Wagga Wagga but 3-fold lower at Tumbarumba. The plant parasitic nematode populations were decreased consistently over time for both treatments and soil layers until at the termination of the experiment when its populations were reduced below 100 m −2 in undervine soil in the Tumbarumba vineyard. Therefore, the overall results from this study showed that non-plant parasitic ‘beneficial’ nematodes were increased generally in plots with permanent swards, which in turn suppressed pest nematodes.