Plant Pathogenic Nematodes Research Articles

Eradication of plant pathogens and nematodes during composting: a review

The effects of temperature–time combinations and other sanitizing factors during composting on 64 plant pathogenic fungi, plasmodiophoromycetes, oomycetes, bacteria, viruses and nematodes were reviewed. In most cases pathogen survival was determined by bioassays of unknown sensitivity and minimum detection limits of 5% infection or more. For 33 out of 38 fungal and oomycete pathogens, all seven bacterial pathogens and nine nematodes, and three out of nine plant viruses, a peak temperature of 64–70°C and duration of 21 days, were sufficient to reduce numbers to below the detection limits of the tests used. Shorter periods and/or lower temperatures than those quoted in these tests may be satisfactory for eradication, but they were not always examined in detail in composting systems. Plasmodiophora brassicae (clubroot of Brassica spp.), Fusarium oxysporum f.sp. lycopersici (tomato wilt) and Macrophomina phaseolina (dry root rot) were more temperature‐tolerant, as they survived a peak compost temperature of at least 62°C (maximum 74°C) and a composting duration of 21 days. Synchytrium endobioticum (potato wart disease) survived in water at 60°C for 2 h, but was not examined in compost. For Tobacco mosaic virus (TMV), peak compost temperatures in excess of 68°C and composting for longer than 20 days were needed to reduce numbers below detection limits. However, TMV and Tomato mosaic virus (TomMV) were inactivated over time in compost, even at temperatures below 50°C. Temperatures in excess of 60°C were achieved in different composting systems, with a wide range of organic feedstocks. The potential survival of plant pathogens in cooler zones of compost, particularly in systems where the compost is not turned, has not been quantified. This may be an important risk factor in composting plant wastes.

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

WOOD CHIPPING ALMOND BRUSH AND ITS EFFECT ON THE ALMOND RHIZOSPHERE, SOIL AGGREGATION AND SOIL NUTRIENTS

Greenhouse Screening of Commercial Products Marketed as Systemic Resistance and Plant Growth Promotion Inducers

Six greenhouse trials of five commercial products marketed as systemic resistance (SR) and plant growth promotion (PGP) inducers were evaluated on tomato (Lycopersicon esculentum Mill.) over a 21-month period. The effect of the inducers on treated plants was measured by monitoring plant growth and disease suppression after inoculation with either plant pathogenic bacteria or nematodes. The commercially available SR/PGP inducers included a bacterial suspension [Companion (Bacillus subtilis GB03)], two plant defense elicitors with nutrients (Keyplex 350DP plus Nutri-Phite, and Rezist with Cab'y), natural plant extracts (Liquid Seaweed Concentrate and Stimplex), and a synthetic growth regulator (Actigard 50W). Growth enhancement was noted in some trials, but the parameter of growth affected often varied with trial. Response to Actigard treatment included significant suppression of bacterial spot [Xanthomonas campestris pv. vesicatoria (Xcv)] in three of the six trials. Companion, Keyplex 350DP plus Nutri-Phite, Rezist and Cab'y, and seaweed products induced only partial disease suppression of bacterial spot in inoculated tomato plants. The alpha-keto acids plus nutrients (Keyplex 350DP plus Nutri-Phite) increased plant growth by 14.3% and improved root condition compared to the untreated control following exposure to nematodes. Results are encouraging, if not consistent, and with a greater understanding of the SR system and the conditions related to product efficacy, such materials may become effective tools for production agriculture.

Nematodes as soil indicators: functional and biodiversity aspects

Since it has become appreciated that soil nematode assemblages are abundant, diverse and contribute to soil nutrient turnover, they have been increasingly used as indicators of soil condition. Use of nematodes as functional indicators relies on the allocation of nematodes to feeding groups and reproductive strategies; in both cases groupings are uncertain. Species within feeding groups vary in their food resources and response to environmental variables, as shown by the difficulties in managing plant-pathogenic nematodes. Therefore species-level discrimination is necessary to permit further advances in understanding the role of nematodes in soil processes and thus in ecosystem resilience. Analysis of published nematode lists shows that among the bacterial-feeding nematodes Cephalobidae are often the most abundant group in soils; Rhabditidae may increase following a resource pulse; in stressed, natural environments Plectidae may be important. To be comparable with other biota, nematode biodiversity assessment requires species-level identification. In many jurisdictions such identification will be difficult due to inadequate systematic knowledge of the nematode fauna.

Abstracts, The Canadian Phytopathological Society, annual meeting, Montreacute;al, Quebec, 1999

Abstracts, The Canadian Phytopathological Society, annual meeting, Montreacute;al, Quebec, 1999

Biological control of plant-parasitic nematodes in pigeonpea field crops using neem-based products and manurial treatments

The paper presents an account of a field plot experiment to investigate the influence of soil applications of neem-based (Achook and Suneem G) and crop fertilizer (urea and cattle manure) treatments, separately and in combination on free-living, and plant-pathogenic nematode populations and crop productivity. All the treatments significantly decreased the number of plant-parasitic nematodes with increasing doses. Combinations of both neem-products with urea were most effective in reducing plant-parasitic nematode populations. The neem products and product combinations with urea significantly decreased numbers of free-living nematodes compared to controls; however, numbers increased in the cattle-manure-treated plots. The growth of pigeonpea ( Cajanus cajan L.) was improved in all the treatments, in part due to the control of plant-parasitic nematodes and in part due to manurial effects. Urea was phytotoxic at 330 kg N/ha applied alone; however, it was not phytotoxic at this rate in combination with the neem-based products.

Impact of animal manures on verticillium wilt, potato scab, and soil microbial populations

This study examined the effect of chicken, liquid swine, and solid cattle manures on verticillium wilt and potato scab incidence at two commercial farms near Alliston, Ontario. The manures (chicken, 66 t/ha; swine, 55 hLJha; cattle, 100 t/ha) were spread in the spring of 1996 and incorporated with a Rototiller to a depth of 15 cm. Survival of Verticillium dahliae microsclerotia (MS) was determined by burying nylon mesh bags containing MS in the plots. After 4 weeks, the MS were plated on agaz medium. Soil samples collected after incorporation of manures were brought back to the laboratory and used for concurrent laboratory experiments. Ten-gram amounts of soil were placed into test tubes, bags of MS buried in the soil,and survival measured under controlled conditions. Potatoes were planted in the field 1 month after amendment. Potatoes were planted in 1997 and 1998 without any further treatment. verticillium wilt incidence was determined by isolation of V.dahliae from petioles. Scab incidence was determined from visual estimation of lesion coverage on tubers. Changes in soil chemistry, in soil microbiology, and in populations of plant pathogenic nematodes were also determined. Chicken manure reduced scab and wilt incidence and nematodes to near zero levels at both sites. Swine manure reduced scab incidence at both sites but reduced wilt and nematode populations at one site only. Cattle manure application caused a small reduction in wilt at one site. Disease incidence in the second crop was similaz for all treatments except for swine manure at one site where a lower scab incidence was observed and chicken manure at both sites where wilt incidence remainded below that in untreated plots. Scab incidence in the third crop was reduced at one site treated with swine manure, but one of the chicken manure treated plots had a higher scab incidence than the untreated plot. The viability of MS was similar for identical treatments in the field and laboratory assay and predicted which treatments decreased verticillium wilt. Reductions in viability of MS were found to be manure and soil specific.

Effect of contrasting farm management on vegetation and biochemical, chemical, and biological condition of moist steepland soils of the South Island high country, New Zealand

A question of economic, social, and land-use importance in the predominantly steep South Island high country tussock grasslands of New Zealand is whether these lands can be sustainably farmed by oversowing introduced grasses and legumes and using fertilisers. To help answer this question, we compared vegetation and soil chemical, biochemical, and biological properties on Brown soils (Dystrudepts) on adjacent land areas which have been differently managed since 1978. One area had never been fertilised or oversown. The other had been oversown with grasses and clovers and received about 1100 kg/ha of sulfur-superphosphate between 1979 and 1997. Oversowing and fertilising reduced the amount of bare ground and transformed the vegetation to a species composition dominated by the introduced adventives Anthoxanthum odoratum and Agrostis capillaris. Fertilising raised soil carbon (C) and nitrogen (N) content, increased A-horizon thickness, and raised exchangeable cation values. All of the phosphorus (P) applied to the fertilised area was accounted for in the top 15 cm of soil, but has accumulated in the relatively unavailable organic form. Oversowing and fertilising significantly (P < 0 . 05) increased microbial biomass C, N, and P relative to values in unfertilised soils. The microbial biomass C: N and C: P ratios were significantly (P < 0 . 05) lower in fertilised soils. Fertilised soils had significantly more (P < 0 . 05) mineralised N than unfertilised soils. Populations of 5 groups of soil fauna (Scarabaeidae, nematodes, enchytraeids, rotifers, tardigrades) were higher in fertilised soils. Nematode species parasitic or pathogenic for clovers were present in greater numbers on fertilised soils. A combination of fertility decline (in particular, P immobilisation as organic P) and nematode damage may be the reason for the low clover cover on fertilised sites, and may explain the widely observed clover ‘flush’ and decline common to oversown high country. We conclude that there is no simple measure of ‘soil quality’ that can be used as a sustainability indicator in moist New Zealand high country. Nor can sustainability be judged purely on biological, biochemical, and chemical critieria. Although many of the effects associated with oversowing and fertilising, such as increased organic matter content of A horizons and increased biological activity, are positive, these effects must be balanced against the economic risk associated with being committed to a high-input farming system, the loss of low-producing but resilient native species, and increase of plant-pathogenic nematodes.

Structure elucidation of omphalotin, a cyclic dodecapetide with potent nematicidal activity isolated fromOmphalotus olearius

The structure and absolute configuration of omphalotin, a cyclic dodecapeptide isolated from the basidiomycete fungus Omphalotus olearius and possessing potent and selective activity against the plant pathogenic nematode Meloidogyne incognita, was determined by a combination of spectroscopic and chemical techniques. © 1998 Society of Chemical Industry

Field Pathogenicity Studies of Four Species of Plant-Pathogenic Nematodes on French-American Hybrid Grapevine Cultivars in Michigan

Ten French-American hybrid grapevine cultivars were evaluated for their reactions to four plant-parasitic nematodes : Criconemella xenoplax, Meloidogyne hapla, Pratylenchus penetrans, and Xiphinema americanum. In the spring of 1987, following soil fumigation, ownrooted vines of the cultivars Couderc 1202, Couderc 1616, Couderc 3309, Kober 5BB, Teleki 5A, Teleki 5C, Foch, Seyval, Vidal, and Vignoles were planted into microplots arranged in a completely randomized design with five replications per treatment. The microplots were inoculated with 2,500 M. hapla eggs, 2,500 juveniles and adults of the other three nematode species, or not inoculated. In 1989 and 1990, cane length was measured for each vine, and from 1991 to 1993, vine pruning weights and fruit yields were recorded. The experiment was terminated in the fall of 1993. At least one of the four species of nematodes reduced growth or yield of all the grapevine cultivars tested during 1 year of the study except for Couderc 1202. Yields of cv. Seyval were increased in the presence of all four species of nematodes in at least I year of the study, although vine pruning weight was reduced by M. hapla in 1993. In general, M. hapla was the most virulent of the nematodes studied. Meloidogyne hapla reduced fruit yields at least 1 year compared with the control plots in five of the seven cultivars from which yields were collected. Criconemella xenoplax only reduced yields of Foch, P. penetrans did not reduce yields of any cultivar, and X. americanum reduced yields of Vidal and Vignoles. This study should provide viticulturists with valuable information on nematode-grapevine cultivar interactions for management purposes.

Comparison of Corn and Fescue Rotations on Pathogenic -Nematodes, Nematode Biocontrol Agents, and Soil Structure and Fertility on an Apple Replant Site

Integrated whole farm management systems offer the potential to reduce impacts on the environment and human health by reducing inputs of petrochemicals while increasing net income to the fruit industry through reduced costs. This article reports on the rotation phase of orchard establishment focusing on integration of an alternative rotation crop system (tall fescue) with a conventional orchard establishment practice (m + nematicide). A 5.6-ha (14-acre)orchard has been established at the West Vuginia University Experiment Fann, Keameysville, WV. The site has been divided into six 0.8-ha main plots with each plot randomly assigned one of two rotation treatments. Comparisons between rotation treatments included soil organic matter and fertility, populations of plant pathogenic nematodes, nematode biological control activity, and an economic analysis. When compared with the conventional corn rotation, plots rotated with fescue exhibited increased numbers of nematode biological control organisms, higher soil organic matter, and elevated soil fertility. Economic analysis of the two rotation systems showed that the increase in soil organic matter in the fescue plots was achieved at a lower expenditure than would have been required by compost application.

Corn Rootworm Control with Nematodes, 1983

Abstract * These experiments were conducted in Buffalo County, NE. Experiment 1 was center pivot sprinkler irrigated with 4 replications; Experiment 2 was furrow irrigated with three replications. The entomophagous nematodes, Neoaplectana carpocapsae Weiser (Breton Strain), in Experiment 1 were applied at the rate of 70 million nematodes per acre in liquid fertilizer at time of planting on 5 May. In Experiment 2, 50 million nematodes per acre were applied at planting in liquid fertilizer on 11 May. Granular insecticides were applied at planting time by the cooperating farmer in an 18-cm band. Entomophagous and plant pathogenic nematodes were counted by Dr. Eric Kerr, U-N-Panhandle Research and Extension Center, from 2.5 × 20-cm soil samples taken on 14 Jul. Roots were evaluated on 19 Jul on a 1 to 6 damage scale (1 = no damage; 6 = 3 or more nodes of roots destroyed). In Experiment 1 corn was hand harvested from three, 6-m long sections of row within each treatment. The yield data for Experiment 2 was obtained by the cooperating farmer who harvested corn with a combine from 16 rows, 402 m long.

Effects of oxamyl and carbofuran on nematode populations below 10 grass cultivars

Abstract Ten grass cultivars sown in plots of Horotiu sandy loam were treated with oxamyl and carbofuran for insect control, and a year after sowing were sampled for soil nematodes. There were significantly (P<0.05) fewer nematodes in 0-10 cm soil below 9 of the cultivars, the average reduction being from 2.7 × l06/m2 to 0.6 × 106/m2; below phalaris there was no reduction. Herbage production was increased (10–24%) in all cultivars except prairie grass. The nematode fauna in untreated plots contained less than 1% of any of the recognised plant pathogenic nematode genera. Glasshouse pot trials showed some significant responses to oxamyl and carbofuran, in sieved soil in the absence of insects and in sterilised soil. Field response to these insecticides in this trial may be due to insect control; there may be an element of plant response to the chemicals used, but nematode control is not a factor.

Prospects for the biological control of plant-parasitic nematodes

SUMMARYBiological control is understood here in the classical sense, which is precisely defined by De Bach (1964) as ‘the action of parasites, predators or pathogens in maintaining another organism's population density at a lower average than would occur in their absence’. This account consists of a survey of the principal causes of disease in nematodes, with a summary of the efforts made to use certain pathogens in practise and a discussion of nematode pathology with reference to destruction of plant pathogenic nematodes.