Gary E. Walker

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The distribution pattern of Meloidogyne spp. (root-knot nematodes, RKN) was studied in five vineyards in three locations in South Australia. Nematodes were extracted from soil samples at two depths (0–300 and 300–600 mm) for each of five positions; three along the vine row, one under cover crops and one next to cover crops in the inter-row. RKN were found(More)
This paper provides a brief overview of the Australian grape industry and discusses the distribution and economic importance of its main nematode pests and outlines the management practices (hot water treatment of planting material, nematode-resistant rootstocks and nematicides) that are currently used to minimise losses from nematodes. However, the main(More)
Growth rates of young mandarin (Citrus reticulata cv. Imperial) trees on C. sinensis rootstocks were reduced by foliar sprays or soil drenches with m-d KP Foli-R-Fos (20% a.i. phosphorous acid) at rates of 2 L/100 L water or higher. Foliar sprays caused leaf burn, particularly to new growth. Growth rates of trees treated with soil drenches of Ridomil 50G(More)
Nematode population densities were monitored and carrot yields and incidence of defects were assessed on three farms, one under organic management. The lowest proportion of marketable carrots and the lowest mean carrot weight were observed at the organically managed farm. Initial population densities of most nematodes were higher at the organically managed(More)
The soils of a wheat-field and pine-forest had different mycofloras and supported different populations ofAphelenchus avenae, a mycophagous nematode. The abundance ofA. avenae was correlated with the composition of the mycoflora in these soils; the greater abundance ofA. avenae in wheat-field soil being associated with a more diverse mycoflora.
Xiphinema vuittenezi is reported for the first time in Australia in soil associated with roots of declining grapevines (Vitis vinifera) in a Barossa Valley (SA) vineyard. This nematode may be able to transmit some strains of Cherry leaf roll virus and is the putative vector of Grapevine chrome mosaic virus; hence its finding may have potential significance(More)
Metalaxyl, fosetyl-AI, calcium nitrate and phosphorous acid were tested in field trials against carrot cavity spot. Metalaxyl applied to soil at 1 kg/ha at the three to six trueleaf stage was the most consistently effective treatment, reducing the proportion of roots affected by at least 32%. Additional applications made 9-12 weeks later had no further(More)
A disease complex involving Meloidogyne incognita and Rhizoctonia solani was associated with stunting of grapevines in a field nursery. Nematode reproduction was occurring on both susceptible and resistant cultivars, and pot experiments were conducted to determine the virulence of this M. incognita population, and of M. javanica and M. hapla populations, to(More)
Mycelial growth ofPhytophthora nicotianae var.parasitica in vitro was inhibited by phosphorous and acetyl salicylic acids at 10 ppm; mycelial growth ofP. citrophthora was inhibited by phosphorous acid at 10 ppm and acetyl salicylic acid at 100 ppm. Foliar sprays and soil drenches with these chemicals were compared with soil applications of metalaxyl as(More)