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1.  Population Characteristics and Dosage Trajectory Analysis for Mesocriconema xenoplax in California Prunus Orchards 
Journal of Nematology  2004;36(4):505-516.
The Mesocriconema xenoplax population increased exponentially in a newly planted peach orchard. The rate of increase was greater on Nemaguard than on Lovell rootstock and was reduced by postplant nematicides. Population levels were more stable in an established almond orchard on Nemaguard rootstock. All life stages of the nematode were present year round; lower ratios of juveniles to adults in summer suggested adverse effects of temperature and dry soil. Also in summer, there was a smaller proportion of the population in the upper 30 cm of soil than at greater depths. Nematode dosage, average nematode density multiplied by accumulated degree-days (physiological time) of the sampling interval, was useful in quantifying nematode stress on trees and as an indicator of the nematode management effectiveness. The annual trajectory of the nematode dosage could be determined by two samplings, one in spring and one in fall. A nematode predator, the parasitic fungus Hirsutella rhossiliensis, did not regulate ring nematode populations in the newly planted orchard; a recovery period was necessary for increase in the prevalence of parasitism.
PMCID: PMC2620792  PMID: 19262832
bacterial canker; Mesocriconema xenoplax; nematicides; nematode management; population regulation; Prunus; rootstocks; stress dosage
2.  Do Organic Amendments Enhance the Nematode-Trapping Fungi Dactylellina haptotyla and Arthrobotrys oligospora? 
Journal of Nematology  2004;36(3):267-275.
Soil cages (polyvinyl chloride pipe with mesh-covered ends) were used to determine how the quantity of two organic amendments affected the nematode-trapping fungi Dactylellina haptotyla and Arthrobotrys oligospora, which were studied independently in two different vineyards. Each cage contained 80 cm³ of field soil (120 g dry weight equivalent), fungal inoculum (two alginate pellets, each weighing 1.9 mg and containing assimilative hyphae of one fungus), and dried grape or alfalfa leaves (0, 360, or 720 mg equivalent to 0, 4,500, or 9,000 kg/ha) with a C:N of 28:1 and 8:1, respectively. Cages were buried in the vineyards, recovered after 25 to 39 days, and returned to the laboratory where fungus population density and trapping were quantified. Dactylellina haptotyla population density and trapping were most enhanced by the smaller quantity of alfalfa amendment and were not enhanced by the larger quantity of alfalfa amendment. Arthrobotrys oligospora population density was most enhanced by the larger quantity of alfalfa amendment, but A. oligospora trapped few or no nematodes, regardless of amendment. Trapping and population density were correlated for D. haptotyla but not for A. oligospora.
PMCID: PMC2620777  PMID: 19262815
Arthrobotrys oligospora; biological control; Dactylellina haptotyla; Heterodera schachtii; Steinernema glaseri
3.  Repulsion of Meloidogyne incognita by Alginate Pellets Containing Hyphae of Monacrosporium cionopagum, M. ellipsosporum, or Hirsutella rhossiliensis 
Journal of Nematology  1996;28(2):133-147.
The responses of second-stage juveniles (J2) of Meloidogyne incognita race 3 to calcium alginate pellets containing hyphae of the nematophagous fungi Monacrosporiura cionopagum, M. ellipsosporum, and Hirsutella rhossiliensis were examined using cylinders (38-mm-diam., 40 or 72 mm long) of sand (94% <250-μm particle size). Sand was wetted with a synthetic soil solution (10% moisture, 0.06 bar water potential). A layer of 10 or 20 pellets was placed 4 or 20 mm from one end of the cylinder. After 3, 5, or 13 days, J2 were put on both ends, on one end, or in the center; J2 were extracted from 8-ram-thick sections 1 or 2 days later. All three fungal pellets were repellent; pellets without fungi were not. Aqueous extracts of all pellets and of sand in which fungal pellets had been incubated were repellent, but acetone extracts redissolved in water were not. Injection of CO₂ (20 μl/minute) into the pellet layer attracted J2 and increased fungal-induced mortality. In vials containing four randomly positioned pellets and 17 cm³ of sand or loamy sand, the three fungi suppressed the invasion of cabbage roots by M. javanica J2. Counts of healthy and parasitized nematodes observed in roots or extracted from soil indicated that, in the vial assay, the failure of J2 to penetrate roots resulted primarily from parasitism rather than repulsion. Data were similar whether fungal inoculum consisted of pelletized hyphae or fungal-colonized Steinernema glaseri. Thus, the results indicate that nematode attractants and repellents can have major or negligible effects on the biological control efficacy of pelletized nematophagous fungi. Factors that might influence the importance of substances released by the pellets include the strength, geometry, and duration of gradients; pellet degradation by soil microflora; the nematode species involved; and attractants released by roots.
PMCID: PMC2619688  PMID: 19277129
alginate; behavior; biological control; chemotaxis; Hirsutella rhossiliensis; Meloidogyne incognita; Meloidogyne javanica; Monacrosporium cionopagum; Monacrosporium ellipsosporum; nematode; nematophagous fungi; Steinernema glaseri
4.  In Vitro Parasitism of Rotylenchus robustus by Isolates of Hirsutella rhossiliensis 
Journal of Nematology  1995;27(4):486-489.
We tested the hypothesis that isolates of Hirsutella rhossiliensis from host nematodes in the family Hoplolaimidae (Rotylenchus robustus and Hoplolaimus galeatus) would be more virulent to R. robustus than would isolates from host nematodes not in the Hoplolaimidae (Heterodera schachtii and Criconemella xenoplax). Nematodes were touched to 10-20 spores of different isolates and incubated at 20 C in 4.5 mM KC1; the percentage of nematodes colonized (filled with hyphae) was determined after 2, 5, 10, 20, and 30 days. The hypothesis was rejected because isolates from H. schachtii and C. xenoplax were equivalent or better at parasitizing R. robustus than were isolates from R. robustus and H. galeatus. In addition, the R. robustus and H. galeatus isolates were as pathogenic to C. curvata as they were to R. robustus, but produced fewer spores per colonized nematode (H. schachtii) than did the other isolates.
PMCID: PMC2619640  PMID: 19277317
biological control; endoparasite; fungus; Hirsutella rhossiliensis; host specificity; parasitism; Rotylenchus rotmstus; virulence
5.  Effect of Lime on Criconemella xenoplax and Bacterial Canker in Two California Orchards 
Journal of Nematology  1994;26(4S):606-611.
In a peach orchard with an initial soil pH of 4.9, preplant application of 0, 13.2, 18.2, 27.3, or 54.2 kg lime/tree site altered soil pH (range after 1 year = 4.8-7.3) but did not affect numbers of Criconemella xenoplax or tree circumference. Liming also failed to reduce the incidence of bacterial canker, which affected 17% of the trees by the sixth year after planting. Four years after planting, numbers of C. xenoplax exceeded 400/100 cm³ soil, regardless of treatment. Trees with higher densities of C. xenoplax had a higher incidence of canker. The nematophagous fungus Hirsutella rhossiliensis was not detected until the fourth year. Thereafter, the incidence of H. rhossiliensis and percentage C. xenoplax parasitized by H. rhossiliensis increased, but the increases lagged behind increases in numbers of nematodes. In an almond orchard with an initial soil pH of 4.6, preplant application of 0, 6.4, 12.8, or 25.0 kg lime/tree site altered soil pH (range after 1 year = 4.7-7.1). Numbers of C. xenoplax remained low (<20/100 cm³ soil), whereas numbers of Paratylenchus sp. increased to high levels (>500/100 cm³ soil), regardless of treatment. Low levels (<20/100 cm³ soil) of H. rhossiliensis -parasitized Paratylenchus sp. were detected. No bacterial canker occurred, but tree circumference was greater after 6 years if soil pH was intermediate (6.0-7.0).
PMCID: PMC2619565  PMID: 19279934
almond; biocontrol; biological control; Criconemella xenoplax; Hirsutella rhossiliensis ; lime; nematode; Paratylenchus sp.; peach; Prunus dulcis; Prunus persica; soil pH
6.  Parasitism of Nematodes by the Fungus Hirsutella rhossiliensis as Affected by Certain Organic Amendments 
Journal of Nematology  1994;26(2):152-161.
Experiments were conducted to determine whether the addition of organic matter to soil increased numbers of bacterivorous nematodes and parasitic activity of the nematophagous fungus Hirsutella rhossiliensis. In a peach orchard on loamy sand, parasitism of the plant-parasitic nematode Criconemella xenoplax by H. rhossiliensis was slightly suppressed and numbers of C. xenoplax were not affected by addition of 73 metric tons of composted chicken manure/ha. In the laboratory, numbers of bacterivorous nematodes (especially Acrobeloides spp.) and fungivorous nematodes increased but parasitism of nematodes by H. rhossiliensis usually decreased with addition of wheat straw or composted cow manure to a loamy sand naturally infested with H. rhossiliensis. These results do not support the hypothesis that organic amendments will enhance parasitism of nematodes by H. rhossiliensis.
PMCID: PMC2619489  PMID: 19279878
bacterivorous nematode; biocontrol; biological control; Criconemella xenoplax; density-dependent parasitism; fungivorous nematode; Hirsutella rhossiliensis; nematode; nematophagous fungus; organic amendment
7.  Parasitism of Heterodera schachtii and Meloidogyne javanica by Hirsutella rhossiliensis in Microplots over Two Growing Seasons 
Journal of Nematology  1993;25(3):427-433.
Numbers of cyst and root-knot nematodes and percentage parasitism by the nematophagous fungus Hirsutella rhossiliensis were quantified in microplots over 2 years. The microplots contained either sugarbeets in loam infested with Heterodera schachtii or tomatoes in sand infested with Meloidogyne javanica. The fungus was added to half of the microplots for each crop. Although H. rhossiliensis established in both microplot soils, the percentage of nematodes parasitized did not increase with nematode density and nematode numbers were not affected by the fungus. The results indicate that long-term interactions between populations of the fungus and cyst or root-knot nematodes will not result in biological control.
PMCID: PMC2619392  PMID: 19279790
Beta vulgaris; biological control; Heterodera schachtii; Hirsutella rhossiliensis; Lycopersicon esculentum; Meloidogyne javanica; microplot; nematode; nematophagous fungus; root-knot nematode; sugarbeet cyst nematode; tomato
8.  Influence of Potassium on Spore Germination in the Nematophagous Fungus, Hirsutella rhossiliensis 
Journal of Nematology  1990;22(4):612-613.
PMCID: PMC2619068  PMID: 19287767
Criconemella xenoplax; biological control; spore germination; potassium
9.  Effects of Carbendazim on the Nematophagous Fungus Hirsutella rhossiliensis and the Ring Nematode 
Journal of Nematology  1990;22(3):418-419.
PMCID: PMC2619048  PMID: 19287739
biocide; biological control; Criconemella xenoplax; fungicide; nematicide
10.  Association of Verticillium chlamydosporium and Paecilomyces lilacinus with Root-knot Nematode Infested Soil 
Journal of Nematology  1990;22(2):207-213.
Population densities of Meloidogyne incognita and the nematophagous fungi, Paecilomyces lilacinus and Verticillium chlamydosporium, were determined in 20 northern California tomato fields over two growing seasons. Paecilomyces lilacinus was isolated from three fields, V. chlamydosporium was isolated from one field, and both fungi were isolated from 12 fields. Verticillium chlamydosporium numbers were positively correlated with numbers of M. incognita and P. lilacinus. Paecilomyces lilacinus numbers were positively correlated with V. chlamydosporium numbers, but they did not correlate with M. incognita numbers. The correlation coefficients were low (R < 0.5) but significant (P < 0.05). All P. lilacinus and V. chlamydosporium field isolates parasitized M. incognita eggs in vitro. In a greenhouse study, numbers of V. chlamydosporium and P. lilacinus increased more in soils with M. incognita-infected tomato plants than in soil with uninfected tomato plants. After 10 weeks, the Pf/ Pi of second-stage juveniles in soils infested with P. lilacinus, V. chlamydosporium, and M. incognita was 47.1 to 295.6. The results suggest V. chlamydosporium and P. lilacinus are not effectively suppressing populations of M. incognita in California tomato fields.
PMCID: PMC2619028  PMID: 19287711
biological control; Lycopersicon esculentum; Meloidogyne incognita; Paecilomyces lilacinus; tomato; Verticillium chlamydosporium
11.  Meloidogyne incognita Survival in Soil Infested with Paecilomyces lilacinus and Verticillium chlamydosporium 
Journal of Nematology  1990;22(2):176-181.
Meloidogyne incognita-infected tomato seedlings were transplanted into sterilized soil or unsterilized soil collected from 20 California tomato fields to measure suppression caused by Paecilomyces lilacinus, Verticillium chlamydosporium, and other naturally occurring antagonists. Unsterilized soils Q, A, and H contained 35, 39, and 55% fewer M. incognita second-stage juveniles (J2) than did sterilized soil 1 month after infected tomato seedlings were transplanted to these soils and placed in a greenhouse. Three months after infected seedlings were transplanted to unsterilized or sterilized soil, unsterilized soils K, L, and Q had 97, 62, and 86% fewer J2 than the corresponding sterilized soils. Unsterilized soils of M. incognita-infected seedlings that were maintained 1 month in a greenhouse followed by 1 or 2 months of post-harvest incubation contained J2 numbers equal to, or greater than, numbers in the corresponding sterilized soil. The most suppressive of the unsterilized soils, K and Q, were not infested with V. chlamydosporium. Paecilomyces lilacinus and V. chlamydosporium increased in colony forming units in unsterilized soil of all bioassays, but they were not associated with lower numbers of J2.
PMCID: PMC2619027  PMID: 19287707
bioassay; biological control; Meloidogyne incognita; Paecilomyces lilacinus; Verticillium chlamydosporium
12.  Suppression of Cyst Nematode by Natural Infestation of a Nematophagous Fungus 
Journal of Nematology  1989;21(4):505-510.
Penetration of cabbage roots by Heterodera schachtii was suppressed 50-77% in loamy sand naturally infested with the nematophagous fungus Hirsutella rhossiliensis. When Heterodera schachtii was incubated in the suppressive soil without plants for 2 days, 40-63% of the juveniles had Hirsutella rhossiliensis spores adhering to their cuticles. Of those with spores, 82-92% were infected. Infected nematodes were killed and filled with hyphae within 2-3 days. Addition of KCl to soil did not increase infection of Heterodera schachtii by Hirsutella rhossiliensis. The percentage of infection was lower when nematodes were touched to two spores and incubated in KCl solution than when nematodes naturally acquired two spores in soil.
PMCID: PMC2618957  PMID: 19287645
biological control; Brassica oleracea; cabbage; Criconemella xenoplax; Heterodera schachtii; Hirsutella rhossiliensis; nematophagous fungus; peach; sugar beet cyst nematode; suppressive soil
13.  An Assay for Hirsutella rhossiliensis Spores and the Importance of Phialides for Nematode Inoculation 
Journal of Nematology  1989;21(2):229-234.
A spore assay was developed to measure the relative density of spores of the nematophagous fungus Hirsutella rhossiliensis in soil. Orchard soil containing H. rhossiliensis-parasitized Criconemella xenoplax was placed in vials and incubated for 0-120 days before the addition of probe nematodes, Heterorhabditis heliothidis juveniles. After 18 hours, H. heliothidis were extracted from the soil and examined for adhering spores of H. rhossiliensis. No spores were detected when H. heliothidis were added to freshly mixed soil, but the percentage of H. heliothidis with spores increased rapidly if soil was incubated undisturbed. Because mixing soil detaches spores from phialides, the results indicate that spores must be attached to phialides to adhere to nematodes. The spore assay was compared with a plate assay that measures the population density of H. rhossiliensis-parasitized C. xenoplax. Results from the two assays were highly correlated, suggesting that spores occur in three phases: reserves in nematodes that may be converted into spores; spores on phialides and therefore capable of adhering to nematodes; and spores detached from phialides and thus incapable of adhering to nematodes.
PMCID: PMC2618927  PMID: 19287601
biocontrol; Criconemella xenoplax; entomogenous; Heterorhabditis heliothidis; Hirsutella rhossiliensis; nematophagous; phialide; ring nematode
14.  Reproduction of Meloidogyne javanica on Plant Roots Genetically Transformed by Agrobacterium rhizogenes 
Journal of Nematology  1988;20(4):599-604.
Reproduction of Meloidogyne javanica was compared on several Agrobacterium rhizogenes-transformed root cultures under monoxenic conditions. M. javanica reproduced on all transformed roots tested; however, more females and eggs were obtained on potato and South Australian Early Dwarf Red tomato than on bindweed, Tropic tomato, lima bean, or carrot. Roots that grew at moderate rates into the agar and produced many secondary roots supported the highest reproduction. Numbers of females produced in cultures of transformed potato roots increased with increasing nematode inoculum levels, whether inoculum was dispersed eggs or juveniles. Females appeared smaller, produced fewer eggs, and were found in coalesced galls at the higher inoculum levels. The ratio between the final and initial population decreased sharply as the juvenile inoculum increased. The second-stage juvenile was preferred to dispersed eggs or egg masses for inoculation of tissue culture systems because quantity and viability of inoculum were easily assessed. Meloidogyne javanica reared on transformed root cultures were able to complete their life cycles on new transformed root cultures or greenhouse tomato plants.
PMCID: PMC2618848  PMID: 19290260
Agrobacterium rhizogenes; bindweed; carrot; gnotobiotic; hairy root pathogen; inoculum level; lima bean; Meloidogyne javanica; monoxenic; nematode Stage; potato; root-knot nematode; tissue culture; tomato
15.  Criconemella spp. in Pennsylvania Peach Orchards with Morphological Observations of C. curvata and C. ornata 
Journal of Nematology  1987;19(4):420-423.
Criconemella xenoplax and C. curvata, previously associated with decline of peach trees in other parts of the United States, were found in 20 of 25 Pennsylvania peach orchards. Population densities were high in some samples. Morphometrics of juveniles and adult females of Criconemella curvata and C. ornata, are provided. Cuticular crenations were observed on J2 and J3 stages of C. curvata and J2-J4 stages of C. ornata.
PMCID: PMC2618673  PMID: 19290165
Criconemella curvata; C. ornata; C. xenoplax; Hirsutella rhossiliensis; morphometrics; peach decline; ring nematode
16.  Seasonal Population Fluctuation of Xiphinema americanum and X. rivesi in New York and Pennsylvania Orchards 
Journal of Nematology  1987;19(3):369-378.
The population fluctuation and composition of Xiphinema americanum (sensu stricto) and X. rivesi were studied in a New York apple orchard (only X. americanum present), a Pennsylvania apple orchard (both X. americanum and X. rivesi present), and a Pennsylvania peach orchard (X. americanum, X. rivesi, and X. californicum present). Few clear trends in population fluctuation or composition were observed. The adult female was the predominant stage in most sample periods, and the reproductive period was limited to late spring and early summer. Only a few of the females at any sample period were gravid. All stages were present throughout the year, and all stages overwintered. Eggs in soil were not monitored. In the Pennsylvania apple orchard, X. americanum and X. rivesi were easily separated by morphological characteristics; however, the two species did not display differences in population structure or composition. The predominance of adults, the relatively low reproductive rates, and the association of these species with stable habitats suggest that the life strategies of X. americanum and X. rivesi are K-selected as opposed to r-selected.
PMCID: PMC2618643  PMID: 19290157
apple; dagger nematodes; Malus; Nematoda; Prunus; Xiphinema americanum; X. rivesi
17.  Parasitic and Saprophytic Abilities of the Nematode-Attacking Fungus Hirsutella rhossiliensis 
Journal of Nematology  1985;17(3):341-345.
The ability of Hirsutella rhossiliensis to colonize various substrates in sterile and nonsterile soil was measured. Hirsutella rhossiliensis was recovered from 67% and 77% of living, inoculated Criconemella xenoplax incubated in sterile and nonsterile soil, respectively. In contrast, the fungus was recovered from 100% and 18% of heat-killed, inoculated nematodes incubated on sterile and nonsterile soil, respectively. Hirsutella rhossiliensis was readily recovered from inoculated, autoclaved wheat seeds incubated in sterile soil but not from seeds incubated in nonsterile soil. Autoclaved peach roots were a poor substrate for the fungus. Germination of H. rhossiliensis spores incubated on agar disks above soil was about 90% regardless of soil treatment. However, germ tube length was greatly suppressed by nonsterile soil. Our results suggest that H. rhossiliensis is a better parasite than saprophyte and that the fungus may be specialized for attacking nematodes.
PMCID: PMC2618463  PMID: 19294104
biological control; Criconemella xenoplax; Arthrobotrys oligospora
18.  Effect of Soil Water Potential on Growth of Apple Trees Infected with Pratylenchus penetrans 
Journal of Nematology  1979;11(2):165-168.
Malling-Merton 106 apple rootstocks inoculated with Pratylenchus penetrans, or uninoculated, were grown in a growth chamber in pots of loamy sand maintained at two moisture levels, 0 to -0.4 bar or 0 to -10 bars. Either inoculation or low soil moisture suppressed shoot growth and increased root necrosis. However, the nematode-soil moisture interaction was not significant.
PMCID: PMC2617957  PMID: 19305552
root-lesion nematodes; nematode-soil ntoisture interaction
19.  Growth Reduction of Apple Seedlings by Pratylenchus penetrans as Influenced by Seedling Age at Inoculation 
Journal of Nematology  1979;11(2):161-165.
Apple seedlings of different ages (1, 3, and 5 weeks) were inoculated with 6,900 Pratylenchus penetrans per seedling in 10-cm-diam pots in a growth chamber. Rate of growth suppression and total growth suppression of seedlings by P. penetrans were inversely proportional to seedling age at time of nematode inoculation. Younger seedlings were found to contain a higher number of nematodes per gram root.
PMCID: PMC2617956  PMID: 19305551
root-lesion nematodes

Results 1-19 (19)