Mesocriconema Xenoplax Research Articles

First report of Mesocriconema xenoplax (Nematoda: Criconematidae) in Greece and first record of Viburnum sp. as a possible host for this ring nematode

Abstract In 2005, root and soil samples were collected from the rhizosphere of Viburnum sp. plants in the yard of a house in Kifissia, Attica, Greece. The plants showed symptoms of yellowing and declining and all were dead within, approximately, one year. The roots were infected with the fungus Rosellinia necatrix. Several specimens of a ring nematode were recovered from soil and identified as Mesocriconema xenoplax based on morphological and morphometrical analysis of females. The nematode had been previously found on grapevines in Samos and Crete islands. This is the first report of M. xenoplax in Greece and the first record of Viburnum sp. as a host for this ring nematode. Additional information regarding distribution of this nematode in Greece is needed.

Preplant Biofumigation with Sorghum or Methyl Bromide Compared for Managing Criconemoides xenoplax in a Young Peach Orchard.

Sorghum as a preplant green manure biofumigant management system of Criconemoides xenoplax was investigated from 1998 to 2003. The study was conducted on a site infested with C. xenoplax and having a previous history of peach tree short life (PTSL). Plots consisted of five preplant treatments: (i) nonfumigated soil without tarp and urea, (ii) nonfumigated soil with tarp and urea, (iii) sorghum as a green manure without tarp and urea, (iv) sorghum as a green manure with tarp and urea, and (v) preplant methyl bromide fumigation. Sorghum as a green manure with and without tarp was comparable with methyl bromide fumigation in suppressing the population of C. xenoplax in the early stages of this experiment. Nematode population densities were suppressed 11 months longer in sorghum with tarp and urea plots than in sorghum without tarp and urea plots. However, nematode population densities in sorghum with tarp and urea plots were not suppressed as long as in fumigated methyl bromide plots (19 versus 24 months, respectively).

Plant-Parasitic Nematodes Infecting Grapevine in Southern Spain and Susceptible Reaction to Root-Knot Nematodes of Rootstocks Reported as Moderately Resistant.

Incidence and nematode population densities of plant-parasitic nematodes were determined in 64 samples of soil and grapevine roots collected from commercial vineyards in southern Spain between October 2003 and May 2005. In addition, a histopathological study was done of root-stock roots naturally infected by root-knot nematodes (Meloidogyne spp.). Nematodes infecting the rootstocks were identified according to conventional procedures, and the Meloidogyne spp. were furthermore identified by sequence characterized amplified region-polymerase chain reaction (SCAR-PCR) and isozyme esterase analyses. The most important plant-parasitic nematodes detected, in order of decreasing frequency of total soil infestation and root infection (percentage of samples), were Mesocriconema xenoplax (34.4%), Meloidogyne incognita (26.6%), Meloidogyne javanica (14.1%), Xiphinema index (12.5%), Xiphinema italiae (10.9%), Pratylenchus vulnus (6.3%), and Meloidogyne arenaria (1.6%). No disease symptoms were observed on aboveground plant parts of the infected grapevines, except for plants in some fields where soil was infested with the virus-vector nematodes X. index and X. italiae. Those grapevines showed a yellow mosaic pattern in leaves early in the growing season and the internode shortening characteristic of infections by Grapevine fanleaf virus. Rootstocks infected by root-knot nematodes (Meloidogyne spp.) showed distorted feeder roots and large- to moderate-sized root galls, present either singly or in clusters. Histopathology of galled roots showed a typical susceptible response to infection by root-knot nematodes: cellular alterations were induced in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and severe distortion of vascular tissues. Most Meloidogyne egg masses ocurred on the surface of the galled root tissues, a position that could facilitate dispersion of the nematode eggs and juveniles and the occurrence of secondary infections. Some of the grapevine rootstocks surveyed in this study (Paulsen 1103, Richter 110, Rupestris du Lot, and SO4) had previously been reported to be resistant to Meloidogyne spp.; however, the population densities of these nematodes found in soil and roots sampled in the present study, as well as the compatible host-parasite relationship revealed by histopathology, indicate a susceptible response to Meloidogyne spp. from southern Spain.

Rigitano: nova cultivar de umezeiro para porta-enxerto de pessegueiro

A pesquisa brasileira não havia desenvolvido, até o presente momento, um porta-enxerto clonal para a cultura do pessegueiro com características agronômicas desejáveis, especialmente com relação à resistência a nematóides-de-galha, facilidade de propagação por estacas herbáceas e indução à melhoria da qualidade dos frutos da cultivar-copa. O presente trabalho tem por objetivo apresentar a cultivar Rigitano de umezeiro, selecionada e aprovada para constituir um novo porta-enxerto para a cultura do pessegueiro. Identificada inicialmente como 'Clone 10', a cultivar Rigitano é resultante de um amplo projeto de pesquisa, realizado a partir de 1998 em colaboração com material procedente do Instituto Agronômico de Campinas (IAC), na Faculdade de Ciências Agrárias e Veterinárias (FCAV/UNESP), Câmpus de Jaboticabal (SP). Os trabalhos de seleção e multiplicação para validação técnico-científica final iniciaram-se com experimentos de propagação por estacas herbáceas, cujos resultados indicaram viabilidade do método nas quatro estações do ano, nas condições climáticas de Jaboticabal (SP). A enxertia com o pessegueiro 'Aurora-1', borbulhia em escudo ou escudo modificado, demonstrou ser viável em porta-enxertos de maior diâmetro (± 10 mm). Em condições de campo, 'Rigitano' revelou-se o menos vigoroso dos clones de umezeiro testados. Além disso, 'Rigitano' é resistente a Meloidogyne javanica e M. incognita, entretanto é suscetível a Mesocriconema xenoplax. Os resultados de campo, como porta-enxerto da cv. Aurora-1 de pessegueiro, revelam boa produtividade e frutos com boas qualidades pomológicas e tecnológicas. Os resultados de pesquisa obtidos revelam amplas possibilidades de sucesso da cv. Rigitano em sua validação como novo porta-enxerto de pessegueiro, bem como seu uso visando à redução do espaçamento de plantio e à produção de frutos de melhor qualidade.

Influence of Ring Nematode Infestation and Calcium, Nitrogen, and Indoleacetic Acid Applications on Peach Susceptibility toPseudomonas syringaepv.syringae

ABSTRACT Two field experiments were conducted to study the effects of added nitrogen, calcium, and indoleacetic acid, in the presence or absence of ring nematodes (Mesocriconema xenoplax), on susceptibility of peach to bacterial canker. When noninfested soil was inoculated with ring nematodes, peach tree susceptibility to bacterial canker infection caused by Pseudomonas syringae pv. syringae was dramatically increased after a period of 2 years. However, no evidence was found that ring nematode infestation increased tree water stress or, in turn, altered plant calcium uptake. Soil fumigation with methyl bromide prior to planting in a commercial orchard significantly reduced both nematode populations and peach tree susceptibility to bacterial canker infection when compared with nonfumigated treatments. In both experiments, tree susceptibility, as measured by canker length following inoculation of stems with P. syringae pv. syringae, was negatively correlated with plant tissue nitrogen content and positively correlated with tissue calcium content. A principal components analysis showed that tissue nitrogen and calcium levels were negatively correlated, and that high-nitrogen, low-calcium tissues were less susceptible to bacterial canker than low-nitrogen, high-calcium tissues. These results indicate that the increased susceptibility of peach to P. syringae pv. syringae under nematode infestation conditions is mediated by both nutritional effects (primarily nitrogen) and nutritional-independent effects, but do not support previous reports of beneficial effects of calcium for reducing bacterial canker.

Association of Meloidogyne partityla with Nickel Deficiency and Mouse-ear of Pecan

Pecan [Carya illinoinensis (Wangenh.) K. Koch] trees exhibit nickel (Ni) deficiency in certain orchard situations. The symptoms are manifest as either mouse-ear or replant disorder and in certain situations are associated with nematode parasitism. A field microplot study of pecan seedlings treated with either Meloidogyne partityla or Criconemoides xenoplax or both found that parasitism by M. partityla can result in enhancement in the severity of mouse-ear symptoms and a reduction in foliar Ni concentration. The Ni threshold for triggering morphological symptoms in young developing foliage was between 0.265 and 0.862 μg·g–1 dry weight, while the threshold for rosetting was between 0.007 and 0.064 μg·g–1 dw. Results indicate that parasitism by M. partityla is a contributing factor to the induction of Ni deficiency in pecan and raises the possibility that nematode parasitism and Ni nutrition can be contributing factors to many plant maladies.

Reaction of Grape Rootstocks to Ring NematodeMesocriconema xenoplax

The reaction of grape rootstocks to the ring nematode <i>Mesocriconema xenoplax</i> was studied in glasshouse experiments and in a vineyard trial. Growth of one Oregon population of <i>M. xenoplax</i> differed among 20 rootstock and self-rooted cultivars grown in the glasshouse for eight months. The reproductive factor, Rf (final nematode density divided by initial nematode density), was ≤0.5 for 420A Mgt rootstock and ≤2.4 for 101-14 Mgt and 110R rootstocks; Rf values ≤1 indicate high nematode resistance. Other rootstocks had Rf values between 6.9 and 52.5. Root dry weights of all varieties except 420A Mgt were reduced by <i>M. xenoplax</i>. In another glasshouse experiment, 420A Mgt and 101-14 Mgt were found to be resistant to one Washington State and four Oregon populations of <i>M. xenoplax</i>, although both were moderately susceptible to a California population. A root-stock trial was planted in 1997 in a vineyard infested with <i>M. xenoplax</i>. After six and seven years, population densities of <i>M. xenoplax</i> were lowest in vines on 420A Mgt (≤0.08 g⁻¹ soil) and 101-14 Mgt (≤0.24 g⁻¹ soil) rootstocks. Population densities on other rootstocks ranged from 1.25 to 4.57 g⁻¹ soil. 420A Mgt produced good vine vigor and yield and showed the highest degree of <i>M. xenoplax</i> resistance. Rootstock 101-14 Mgt, which is widely used in Oregon, was also resistant but produced only average vigor and yield. Other common Oregon rootstocks, Riparia Gloire, 3309C, and self-rooted Pinot noir, were highly susceptible to <i>M. xenoplax</i> and were among the least vigorous vines.

Reação de clones de umezeiro (Prunus mume Sieb. et Zucc.) e cultivares de pessegueiro [Prunus persica (L.) Batsch] ao nematóide anelado Mesocriconema xenoplax (Nemata: Criconematidae)

Com o objetivo de avaliar a reação de clones de umezeiro (Prunus mume Sieb. et Zucc.) e cultivares de pessegueiro [Prunus persica (L.) Batsch] ao nematóide anelado Mesocriconema xenoplax (Raski) Loof &amp; de Grise, realizou-se o presente estudo em casa de vegetação do Departamento de Fitossanidade da FCAV/UNESP, Câmpus de Jaboticabal-SP. As plantas foram mantidas em vasos de cerâmica com 6 litros de capacidade, contendo uma mistura de solo e areia (1:1, v/v), previamente autoclavada a 121°C e 1kgf.cm-2 por 2 horas. Cada planta foi inoculada com 10mL de uma suspensão de 200 M. xenoplax por mL. Com os resultados obtidos, após 105 dias da inoculação, pode-se concluir que os Clones 05; 10 e 15 de umezeiro e as cultivares Okinawa e Aurora-1 de pessegueiro são suscetíveis a M. xenoplax. A cultivar Aurora-1 apresentou maior Fator de Reprodução (93,06).

Control of plant-parasitic nematodes with extracts of Quillaja saponaria

AbstractAqueous extracts of the tree Quillaja saponaria Molina, containing triterpenoid saponins, polyphenols, salts and sugars, were tested against the most important plant-parasitic nematodes present in Chile: Xiphinema index, X. americanum s.l., Meloidogyne hapla, M. ethiopica, Pratylenchus thornei, Tylenchorhynchus sp., Criconemoides xenoplax and Helicotylenchus sp. Three different products were tested in the laboratory: i) QL 1000® (whole extract containing saponin and non-saponin fractions); ii) QL ULTRA® (saponin fraction); and iii) QL NS® (non-saponin fraction). The results showed that QL 1000® had important nematicidal effects at economically attractive doses (e.g., 100 ppm). When used separately, QL ULTRA® and QL NS® had minimum nematicidal effects. However, the combined use of both products gave similar results to QL 1000®, suggesting a synergy between the saponin and non-saponin fractions. Based on this, QL 1000® was tested in commercial vineyards and table grapes in the Central region of Chile. The use of 30 l ha−1 showed a similar control and fruit yields to synthetic chemical nematicides.

Phylogeny of Criconematina Siddiqi, 1980 (Nematoda: Tylenchida) based on morphology and D2-D3 expansion segments of the 28S-rRNA gene sequences with application of a secondary structure model

AbstractThe suborder Criconematina is a large group of ecto- and endoparasitic nematodes, including several species of major agricultural importance. The D2-D3 expansion segments of the 28S nuclear ribosomal RNA gene were amplified and sequenced from 23 nominal and six unidentified species from the genera Mesocriconema, Criconemoides, Ogma, Criconema, Xenocriconemella, Hemicriconemoides, Hemicycliophora, Paratylenchus, Tylenchulus, Trophonema and Sphaeronema, together with outgroup taxa from Tylenchidae (Aglenchus) and Atylenchidae (Eutylenchus). A sequence alignment optimised using the secondary structure model was analysed using maximum parsimony, maximum likelihood and Bayesian inference approaches under two models. All analyses yielded a similar topology with differences primarily in the position of poorly supported clades. Although some molecular trees differ from the previous morphologically based hypotheses of criconematid phylogeny, maximum likelihood tests did not yield statistically significant differences between some of the tested classical morphological and molecular topologies. DNA data support monophyly for the genera Mesocriconema, Hemicriconemoides and Criconema and reject the hypothesis of a single origin of criconematids with a cuticular sheath or 'double cuticle'. Application of the complex model of rRNA evolution, considering paired nucleotides for the stem and unpaired nucleotides for the loop region, resulted in a majority rule consensus Bayesian tree with unresolved relationships between main clades. This lack of resolution is expected by the low number of independently evolving nucleotides. Sequence divergence in this DNA segment between populations of Mesocriconema xenoplax, M. sphaerocephalum and Hemicriconemoides cocophillus suggest the presence of several sibling species under these taxa names.

Creating a Short Life Site for Prunus Rootstock Evaluation on Land with No Innate Mesocriconema xenoplax Population

Peach tree short life (PTSL) is associated with the presence of ring nematode, Mesocriconema xenoplax, and poor orchard management practices. Finding a noncommercial field site to evaluate rootstocks for PTSL resistance is increasingly difficult. The time needed to create a PTSL test site was investigated. In 1994, a site not planted in peaches for &gt;80 years was identified in Byron, Ga. Analysis of preplant soil samples revealed that there were no M. xenoplax on the site. One-third of the land was planted to peach and infested with 1600 ring nematodes per tree in Spring 1994 (P2) and another one-third in Spring 1995 (P1). The remaining one-third of the land received no trees or ring nematode and served as the control (F2). In Fall 1995, trees were removed from P1 and P2 plots and all treatments were replanted to peach in 1996. In 1997, tree death resulting from PTSL occurred only in P2 (7%). By 2000, PTSL tree death reached 41% in P2, 16% in P1, and 4% in F2 plots. Nematode populations were higher (P &lt; 0.05) in P1 (649 ring nematode/100 cm3 soil) than in F2 (221 ring nematode/100 cm3 soil) plots, whereas populations in P2 (300 ring nematode/100 cm3 soil) plots did not differ from those in P1 or F2 plots. Establishing a PTSL screening site was possible 3 years after M. xenoplax introduction; PTSL development among treatments in the subsequent planting was dependent upon cumulative population exposure of trees to M. xenoplax.

Field Performance of Guardian™ Peach Rootstock Selections

Twelve peach [Prunus persica (L.) Batsch] seedling rootstocks [Lovell, Nemaguard, Flordaguard, 14DR51, five Guardian™ (BY520-9) selections, and three BY520-8 selections] budded with `Cresthaven' were planted in 1994 and evaluated through 2000 to determine performance under commercial management practices. Mesocriconema xenoplax population densities were above the South Carolina nematicide treatment threshold of 50 nematodes/100 cm3 of soil after 1996. However, symptoms of peach tree short life (PTSL) were not observed. Tree mortality was less than 14% through 1999, with most of the dead trees exhibiting symptoms consistent with Armillaria root rot. About 13% of the surviving trees in 1999 were removed in 2000 due to symptoms of phony peach. There were no differences in tree mortality among rootstocks. Tree growth, photosynthesis, and suckering varied among rootstocks, but leaf conductance, internal CO2, and leaf transpiration did not. Foliar calcium, magnesium, iron, and phosphorus varied among rootstocks, but all were within the range considered sufficient for peach trees. Fruit yield varied among rootstocks, but yield efficiency did not, indicating that higher yield corresponded with larger trees. Bloom date did not vary among rootstocks, but harvest date was advanced as much as 2 days for some rootstocks, compared to Lovell. Fruit weight varied among rootstocks but skin color, flesh firmness, and soluble solids content were similar. All rootstocks performed satisfactorily for commercial peach production.

Incidence and Population Density of Plant-Parasitic Nematodes Associated with Olive Planting Stocks at Nurseries in Southern Spain.

Nematode population densities were determined in 259 soil and root samples collected from 18 olive nurseries in Córdoba, Jaén, and Sevilla provinces (southern Spain), between October 1997 and May 1998. The most important plant-parasitic nematodes detected, in order of decreasing frequency of infestation (percentage of samples), were Mesocriconema xenoplax (39.0%), Pratylenchus penetrans (32.1%), P. vulnus (25.9%), Meloidogyne incognita (14.7%), M. javanica (11.2%), and M. arenaria (2.7%). No disease symptoms were noted on aboveground organs of infected plants. However, population densities of Pratylenchus and Meloidogyne spp. were at potentially damaging levels in most of the olive nurseries surveyed. Histopathological studies of galled roots from the naturally infected olive planting stocks showed a susceptible response to root-knot nematode infection. Large numbers of egg masses were present within the galled root tissues that might contribute to secondary infections. Feeding by root-knot nematodes induced the expected cellular alterations in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and the alteration of vascular tissues.

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

PARASITIC NEMATODES ASSOCIATED WITH OLIVE IN COUNTRIES BORDERING THE MEDITERRANEAN SEA

Identification of genetic loci in a rhizosphere-inhabiting, species of Pseudomonas involved in expression of a phytoparasitic nematode ovicidal factor

Pseudomonas sp. BG33R was isolated from peach orchard soil suppressive to the phytoparasitic ring nematode, Mesocriconema xenoplax. Tn 5 transposon mutagenesis was utilized to generate five BG33R mutants 246, 1122, 1233, 1397, and 1917, which lacked ovicidal activity and also exhibited altered fluorescent siderophore and protease production. Southern blot analysis revealed that each of the five mutants contained a single unique Tn 5 insertion. Mobilization of selected BG33R genomic cosmid clones into mutants 246 and 1917 restored egg-kill activity and restored normal protease and siderophore production. Furthermore, a genomic cosmid clone hybridizing to the Tn 5 insertion site in 1122 also complemented mutant 1917. Site-directed mutagenesis of BG33R using the cloned Tn 5 insertion site from mutant 1397 resulted in the loss of ovicidal activity and restoration of the hyperfluorescence phenotype. Sequence analysis was performed on the genetic regions flanking the Tn 5 insertion site in all five egg-kill-negative mutants. Open reading frame analysis and amino acid comparative database searches of the Tn 5 insertion sites in the five mutants revealed a high degree of homology to the vgrG gene, the two-component sensor kinase protein, rtpA ( gacS analog), a UDP-glucose 4-epimerase gene, a siderophore receptor protein, and the 50S ribosomal protein, L21. The involvement of these genes in the production of the egg-kill factor is discussed.

Interactions of Selected Rootstocks with Ectoparasitic Nematodes

The reaction of grape rootstocks on the population growth of three ectoparasitic nematodes was studied in microplots. After 18 months in sandy loam soil, most grape cultivars had grown larger in the presence of <i>Xiphinema americanum</i> than where it was absent. In the presence of <i>Xiphinema index</i>, only Freedom rootstock displayed a significant growth increase, but no grape cultivars received significant damage by its presence. In the presence of <i>Mesocriconema xenoplax</i>, only Schwarzmann rootstock grew significantly larger and most rootstocks were significantly damaged by its presence in sandy soil. Longer exposure periods are necessary for the measurement of tolerance to <i>Xiphinema</i> spp. VR 039-16, Schwarzmann, and Freedom rootstocks were rated as resistant against <i>X. index</i> on the basis of reproduction and vine growth. All other rootstocks were found susceptible to all three nematodes. Resistance to <i>X. index</i> was relatively easy to assess, whereas resistance to <i>X. americanum</i> and <i>M. xenoplax</i> was less clear, perhaps a result of our relatively high nematode inoculation levels.

Preplanting Bahia Grass or Wheat Compared for Controlling Mesocriconema xenoplax and Short Life in a Young Peach Orchard.

The effects of four preplant ground cover systems as alternatives to chemical control of Mesocriconema xenoplax were investigated from 1991 to 1998. Ground cover establishment was initiated in 1991 in an orchard known to be infested with M. xenoplax and having a history of peach tree short life (PTSL). Ground cover systems included (i) Pensacola bahia grass, (ii) Tifton 9 bahia grass, (iii) winter wheat (Triticum aestivum 'Stacy'), and (iv) naturally occurring weeds that were maintained over the entire orchard floor. Ground cover evaluation was initiated in 1994, when herbicide was applied to the ground cover plots and half the weed plots were fumigated with methyl bromide. Peach trees were planted into all plots in 1995. Fumigation effect on M. xenoplax population density collapsed 25 months after application. Young peach trees grew faster for the first 13 months in killed Pensacola bahia grass sod and fumigated soil, intermediate in Tifton 9 bahia grass and wheat plots, and slowest in unfumigated weed plots. By the end of the experiment, tree growth was greatest in Pensacola bahia grass killed sod and least in the unfumigated weed plots. Preplant wheat was as effective as fallow for 3 years plus a preplant methyl bromide fumigation in increasing tree survival from PTSL.

Increased Susceptibility to Bacterial Spot of Peach Trees Growing in Soil Infested with Criconemella xenoplax.

Young Suwanee peach trees were planted in soil infested or not infested with the nematode Criconemella xenoplax. Five months after soil infestation, the leaves were inoculated with Xanthomonas campestris pv. pruni to measure the influence of nematode infestation on bacterial spot development. Bacterial spot lesions in inoculated leaves were more numerous and covered a greater leaf surface area for trees growing in nematode-infested soil than for those in noninfested soil. When the trees were growing in nematode-infested soil, the leaf area diseased was slightly greater on trees in nonsteamed field soil than in soil treated with aerated steam (57 to 62°C for 75 min) prior to infestation with C. xenoplax. Results indicate that bacterial spot damage may become more severe on peach trees if the soil is infested with C. xenoplax than when nematodes have been suppressed.

Interplanting Wheat Is Not an Effective Postplant Management Tactic for Criconemella xenoplax in Peach Production.

In two orchard experiments, interplanting wheat (Triticum aestivum cv. Stacy) around either newly planted or 4-year-old well-established peach trees did not suppress (P ≤ 0.05) the population density of the ring nematode, Criconemella xenoplax, after 3 years. Furthermore, inter-planting wheat around newly planted trees reduced tree growth, perhaps the result of competition for water and (or) nutrients. Wheat root exudate was not as attractive to C. xenoplax as peach root exudate, but wheat root exudate did not repel the nematode either. Stacy wheat appeared to be more beneficial as a preplant rather than as a postplant ground cover management tool for suppressing the population density of C. xenoplax.

Occurrence of Peach Tree Short Life on a Field Site with No History of Peach Production

Table 1. Soil population density (1985 to 1989) of Criconemella xenoplax (Cx) on Nemaguard peach planted in Dec. 1985 on a site not recently planted with peaches (n = 12). Peach tree short life (PTSL) usually is associated with poor management practices and the continuous presence of the ring nematode [Criconemella xenoplax (Raski) Luc & Raski = Mesocriconema xenoplax (Raski) Loof & de Grisse]. Bacterial canker (Pseudomonas syringae pv. syringae van Hall), cold injury, or both are responsible for the sudden springtime collapse of peach trees associated with PTSL in the southeastern United States (Brittain and Miller, 1978). However, C. xenoplax (Cx) clearly has been identified as the primary biotic factor essential for PTSL to occur (Nyczepir, 1990). Although generally associated with old orchard sites, PTSL can be induced in virgin peach soil in field microplots by inoculation with ring nematode (Nyczepir, 1990). Our objective was to determine if PTSL could occur on land not planted with peaches for ≥75 years. The field site was a loamy sand (86% sand, 10% silt, 4% clay; 1.54% organic matter) located at the Southeastern Fruit and Tree Nut Research Laboratory, Byron, Ga. The site, recently cleared of ≈75-year-old pecan trees, had no known history of peach production. Soil pH was 6.0, so preplant liming was not required. Preplant nematode soil samples revealed no Cx in July 1985. Twenty-four rooted cuttings of Nemaguard were planted at 6 × 6 m in Dec. 1985. Each of 12 cuttings had been inoculated with 10,000 adult and juvenile Cx per 3700 cm soil in Apr. 1985, while the remaining 12 cuttings received nematode-free water extract from the culture medium and served as controls (Nyczepir, 1990). Each nematode-inoculated tree also received 16,000 Cx in the planting hole. Treatments were replicated 12 times and arranged in a randomized complete-block design. Trees were cultured as recommended by the Georgia Cooperative Extension Service. Nematode populations were monitored beneath the canopy of each tree in