WINETECH Technical Yearbook 2020

FIGURE 1. Close- up view of ring nematodes.

The ring nematode is a plant-parasitic nematode that is associated with grapevine, with it being regarded as the most difficult

(2 627 ± 303) was found to be much higher than that for plum, peach and apricot (160 ± 43.8). To determine whether all the specimens obtained were of the same species, the nematodes were identified morphologically and morphometrically, as well as by using molecular techniques. The results indicate that the species in all the grapevine production areas surveyed were the same. UNIQUE PROBLEMS FACED CONCERNING RING NEMATODE The ring nematode is unique among plant- parasitic nematodes, requiring that a highly specific sugar flotation technique be used for their extraction from the soil. The rings are believed to prevent the nematodes from crawling through a filter and being trapped in water. Unfortunately, the use of the sugar flotation technique compromises the viability of the nematodes concerned, due to the amount of osmotic pressure involved, which prevents their use by researchers as an inoculum for any kind of laboratory or glasshouse experiment. The ring nematodes for use in experiments under glasshouse conditions require inoculation as infected soil. An annual host for the cultivation of the nematodes in high numbers is currently not available. With the minimum agricultural disturbance of the soil involved, all other nematodes in the ring nematode complex that can

nematode to control. INTRODUCTION

The ring nematode, Criconemoides xenoplax , is described as a migratory ectoparasitic nematode that feeds on the roots of plants, mainly those of woody perennials, such as grapevine. They feed by means of a long stylet that they insert into the roots of grapevine plants. The name ‘ring nematode’ has its origin in the unique ring-like ornamentation that covers the body, which is extremely rare in plant-parasitic nematodes (figure 1). The name ‘ring nematode’ applies to a collection of nematodes in the same family, which show great diversity, but which are not necessarily of agricultural importance. Ring nematode occurs throughout the world where grapevine is grown. The ring nematode is regarded, worldwide, as a significant pest in vineyards, with it having become a common soil pest in During a recent survey to determine the occurrence of ring nematode in grapevine and deciduous fruit, ring nematodes were found in 100% of the samples analysed (i.e. 49 samples). The mean number of ring nematodes observed on the grapevine South African production areas. SPECIES IDENTIFICATION

Ring nematode in grapevine – a major problem for producers and researchers

MAY 2020

ANTOINETTE MALAN 1 & SHEILA STOREY 2 : 1 Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch; 2 Nemlab, Klapmuts KEYWORDS: Ring nematode, vineyard pest

WINETECH TECHNICAL YEARBOOK 2020 38