Journal of Nematology Feed

Description of Deladenus longicaudatus n. sp. (Sphaerularioidea: Neotylenchidae) from Mazandaran province, northern Iran: A morphological and molecular phylogenetic study

Thu, 07 May 2026 00:00:00 GMT

Deladenus longicaudatus n. sp. was recovered from decaying wood of a broad-leaf forest tree in the forests of Javaherdeh, Mazandaran province, northern Iran, and is herein described and illustrated based upon morphological, morphometric, and molecular characters. The new species is mainly characterized by its small to medium body size of free-living mycetophagous females (523–682 µm long) with an elongate conical tail (c = 9.3–11.0 and c′ = 3.9–5.3), a relatively anterior vulval position (V = 84.5–89.0%), the pharyngo-intestinal junction at the level of the nerve ring, the secretory–excretory pore (S–E pore) posterior to the nerve ring, and at the same level as the hemizonid. It is further characterized by seven incisures in the lateral fields, a short stylet (5.0–6.5 µm), small lateral vulval flaps, and absence of a postvulval uterine sac (PUS). By having similarities in tail shape, c′ ratio greater than 3, posterior position of the S–E pore and hemizonid to the nerve ring, and lack of PUS, the new species is comparable to four known species of the genus, namely, D. gilanica, D. hyrcanus, D. zyzyphus, and D. parvus. It is furthermore typologically comparable to mycetophagous phase of Hexatylus vigissi. In molecular phylogenetic analyses using partial small and large subunit (SSU and LSU D2-D3) rDNA sequences, the SSU sequences of the new species formed a moderately supported clade with sequences of Howardula spp. In LSU phylogeny, the newly generated sequences of the new species formed a clade with corresponding sequence of D. hyrcanus.

A new actinolaim, Egtitus invaginatus n. sp. (Nematoda: Actinolaimidae) from South Korea

Wed, 06 May 2026 00:00:00 GMT

Egtitus invaginatus n. sp. isolated from litter soils sampled around a dead black pine was characterized using morphometrics and DNA barcodes. Egtitus invaginatus n. sp. is characterized by a medium sized body 1.67–2.12 mm long, lip region expanded, 2.1–2.5 times as wide as high, anteriorly truncate, with rounded to angular sides, offset by a depression, odontostyle 19.0–21.0 μm long or as long as the lip region diameter, pars refringens vaginae with two irregularly ovoid to D-shaped pieces, vulva flush with body contour in lateral view, a transverse slit in ventral view, vulva opening equatorial to slightly post-equatorial; one to three ventral cleft-like invaginations present at 4.0–6.0 μm posterior to anal opening, forming papilla-like outgrowth, tail straight or slightly curved ventrad, 12.5–17.5 times anal body diameter; spicules 46.5 μm long, seven spaced ventromedian supplements and male tail conoid to broadly rounded. The phylogenetic relationships among species were reconstructed using 18S-rRNA and 28S-rRNA gene sequences. The two phylogenies showed that E. invaginatus n. sp. is genetically similar to the only gene sequences of the genus available in GenBank database.

Papaya seed extract for management of Radopholus similis on Anthurium

Tue, 05 May 2026 00:00:00 GMT

Anthurium cut flowers are an economically important ornamental crop in Hawai’i, but their production is threatened by the burrowing nematode, Radopholus similis, which reduces yield and increases production costs. This study evaluated the nematicidal potential of crude extract from ground papaya seed (PGS CE), a local agricultural by-product that contains glucosinolates that hydrolyze into benzyl isothiocyanate, active against R. similis. Greenhouse trials demonstrated that monthly drenches with 0.5 or 1.0% PGS CE significantly reduced R. similis population densities in both roots and cinder media, decreased root lesion severity, and increased leaf production without phytotoxicity or adverse effects on free-living bacterivorous nematodes. While 1.0% PGS CE slightly reduced plant biomass, 0.5% PGS CE improved plant growth and flower production. Regression analysis supported the link between nematode suppression and enhanced anthurium health. Thus, PGS CE presents a sustainable, locally available, and effective biofumigant for nematode management in anthurium, warranting further optimization and future field-scale validation.

Nematophagous Hyalorbilia spp. isolated from Heterodera schachtii in California parasitize Heterodera glycines

Tue, 28 Apr 2026 00:00:00 GMT

The goal of this study is to test whether parasitic Hyalorbilia spp., isolated from sugarbeet cyst nematodes (Heterodera schachtii) in California, could also suppress soybean cyst nematodes (H. glycines). Three H. oviparasitica clade strains, DoUCR50, HsImV27, and ARF18-L, were cultured in powdered peat for use in greenhouse nematode suppression tests. Soils were amended with 500 CFU/cm3 of each fungal strain or autoclaved peat inoculum as a control, seeded with soybeans (Glycine max cv. Williams 82), and 3 weeks later, inoculated with 250 J2 of H. glycines. After 1,260 degree days, cysts and females were collected by flotation sieving and enumerated. DoUCR50, HsImV27, and ARF18-L reduced cysts and females of H. glycines by 73, 87, and 0%, respectively. Egg parasitism was tested by incubating eggs of H. schachtii and H. glycines on water agar cultures of DoUCR50 and HsImV27. Individual eggs of H. schachtii or H. glycines were parasitized by DoUCR50 at rates of 15 or 13%, respectively. Eggs placed in pairs were parasitized at 38 and 43%, while eggs placed in groups of four were parasitized at 70 and 63%, respectively. HsImV27 parasitized fewer than 10% of eggs of either nematode, regardless of egg group size. Both DoUCR50 and HsImV27 were observed to parasitize white females of H. glycines and H. schachtii in tissue culture.

Description of Pristionchus endotocus n. sp., a new obligately bagging androdioecious species from the Philippines

Tue, 28 Apr 2026 00:00:00 GMT

Pristionchus pacificus is an important model organism with a well-developed suite of molecular tools and a genomic dataset. Studies that integrate population genetics, ecology, and evo-devo in P. pacificus are supported by an extensive and robust phylogeny consisting of more than 50 Pristionchus species and close to 3,000 strains. Asia by and large has emerged as the biodiversity hot spot of the genus, becoming the focus of recent sampling efforts for Pristionchus isolates. Here, we describe a new androdioecious species of Pristionchus discovered in recent samplings in the Philippines based on a combination of molecular markers, morphological and morphometric data, and mating experiments. All strains of the new species were collected from Scarabeoid beetles in the Philippines and are basal to a sub-clade of the maupasi clade. Pristionchus endotocus n. sp. exhibits constant bagging and a strong bias toward the stenostomatous morph under laboratory conditions and might therefore provide an additional reference point for life history trait studies in Pristionchus.

Growth and defense enzyme responses of grafted cucurbit crops to varying initial populations of Meloidogyne incognita

Tue, 28 Apr 2026 00:00:00 GMT

Root-knot nematode (Meloidogyne incognita) is among the most serious constraints to cucurbit crop production worldwide. This study evaluated the effects of different initial population densities (0, 1,000, 2,000, 4,000, and 8,000 second-stage juveniles [J 2]/plant) on nematode development, reproduction, plant growth, and defense-related enzyme activities in watermelon (Citrullus lanatus, cv. Aswan F1) and sweet melon (Cucumis melo, cv. Faransawy) hybrids, their grafted combinations, and the resistant rootstocks 6001 F1 and BS F1. Plants were grown in sterilized sandy-loam soil under greenhouse conditions, and nematode parameters, including gall index, females per root system, egg masses per root, final population (Pf), reproduction factor, penetration rate, and reproduction rate were assessed 60 days after inoculation. Both host genotype and inoculum density significantly (P < 0.001) affected nematode reproduction and plant growth traits. Resistant rootstocks and their grafted scions consistently exhibited lower Pf/Pi ratios, fewer galls, reduced shoot weight losses, and significantly higher peroxidase and polyphenol oxidase activities compared to susceptible cultivars. These findings demonstrate that combining resistant rootstocks with grafting can effectively suppress M. incognita multiplication and associated growth losses, while enzyme activity profiling provides a useful biochemical indicator of partial resistance in cucurbit breeding and management programs.

Description and molecular characterization of Coslenchus iranicus n. sp. (Rhabditida: Tylenchidae) from Iran

Mon, 27 Apr 2026 00:00:00 GMT

Coslenchus iranicus n. sp., recovered from the rhizosphere of soapwort in South Khorasan province, Eastern Iran, is described based on morphological and molecular data. The new species is characterized by its cuticle with 18 longitudinal ridges excluding lateral lines, lateral field with three incisures, lip region unstriated, stylet 9.4–12.0 µm long, spermatheca filled with sperm, post-vulval uterine sac absent, vulva with large vulval flaps, and tail mostly with a pointed terminus, though in a few specimens with a finely rounded tip. Based on general characterization, C. iranicus n. sp. is closely similar to C. areolatus, C. franklinae, C. japonicus, C. leiocephalus, and C. maritus. The phylogenetic relationships of the new species with representatives of the family Tylenchidae were reconstructed and discussed using partial sequences of the small subunit, D2–D3 expansion segments of the large subunit, and internal transcribed spacer regions of ribosomal DNA based on Bayesian inference. In the SSU rDNA and LSU rDNA phylogenetic trees, sequences of the new species formed clades with corresponding sequences of C. polonicus and C. leiocephalus with different levels of relatedness, respectively.

Beech leaf disease symptom detection using deep learning and computer vision tools

Mon, 27 Apr 2026 00:00:00 GMT

Beech leaf disease (BLD) has rapidly emerged as a significant threat to forests across the eastern United States and Canada, and early detection is a major challenge. Current surveillance relies on visual identification of characteristic leaf banding, a method that can miss early infections. To address this limitation, we developed deep learning models capable of distinguishing between BLD symptomatic leaves and asymptomatic leaves. A primary dataset of symptomatic and asymptomatic leaves collected in Maryland (Dataset I) was used for model development, and an independent set of images collected in North Carolina, Ohio, and New England (Dataset II) provided real-world validation. In Dataset I model testing, EfficientNetV2-Small was the most accurate model (100%), followed by ResNet50 (99.32%), MobileNetV3-Large (97.95%), and InceptionV3 (94.88%). Independent testing on Dataset II also identified EfficientNetV2-Small as the most accurate model (96.55%). Grad-CAM visualizations confirmed that EfficientNetV2-Small focused on banded regions of BLD leaves that are a main characteristic of the disease. These findings demonstrate the potential of deep learning and computer vision approaches to support more efficient monitoring of BLD in forested regions.

Characterization and reproduction of Paratylenchus enigmaticus from chrysanthemum in Korea

Fri, 24 Apr 2026 00:00:00 GMT

Paratylenchus enigmaticus is a recently described pin nematode species with a broad host range, but its occurrence and pathogenicity on chrysanthemum remain poorly understood. During a survey of spray chrysanthemum (Chrysanthemum × grandiflorum) fields in Icheon, Korea, populations of pin nematodes were detected in the rhizosphere and subsequently identified as P. enigmaticus through detailed morphological observations and molecular analyses of LSU D2–D3 and internal transcribed spacer (ITS) rRNA regions. Phylogenetic analyses confirmed a close relationship between the Korean population and previously described P. enigmaticus sequences from Canada and Spain. Pathogenicity assays revealed density-dependent reproduction on the chrysanthemum cultivar “Milky Star.” The reproduction factor (RF) was highest at the lowest inoculum density (Pi = 100; RF = 3.59 ± 0.54), declined at Pi = 1,000 (RF = 1.49 ± 0.69), and further decreased at Pi = 10,000 (RF = 0.37 ± 0.09). Plant growth parameters showed numerical variation among treatments but no significant differences. A host response assay using five chrysanthemum cultivars demonstrated successful reproduction of P. enigmaticus in all cultivars, although variation in RF was observed. Among them, “Pretty Purple” was classified as a poor host (RF ≤ 1), while the others were considered susceptible hosts (RF > 1). Our results document the first occurrence of P. enigmaticus in Korea, detected from a spray chrysanthemum field in Icheon, and demonstrate that it can utilize spray chrysanthemum as a host. However, its economic importance and potential to cause damage remain unclear, warranting additional investigations.

Enhanced acid fuchsin staining for visualization of foliar nematodes using brightfield and fluorescence microscopy

Fri, 24 Apr 2026 00:00:00 GMT

Foliar nematodes are economically important plant pathogens affecting a wide range of hosts, including food crops, ornamentals, and forest trees. Among these, Litylenchus crenatae (family Anguinidae), the causal agent of beech leaf disease (BLD), poses a growing threat to American beech forests. Traditional nematode staining methods, such as acid fuchsin staining, have been widely used for plant-parasitic nematodes found in roots, but their application to foliar tissues remains limited due to differences in tissue structure and stain permeability. In this study, we optimized two acid fuchsin-based protocols for brightfield and fluorescence microscopy to improve the visualization of L. crenatae in symptomatic beech leaves. The improved staining methods provided high-resolution visualization of L. crenatae at the surface and within the leaf tissues using both dissected and whole-mount samples. These enhanced visualization methods offer a practical tool for investigating the spatial distribution and dynamics of foliar nematodes within distinct layers of the leaf.

Deladenus coreanus n. sp. (Rhabditida: Neotylenchidae), a new species from South Korea

Mon, 20 Apr 2026 00:00:00 GMT

A new species of the genus Deladenus isolated from the outer wood and bark layers of a dead red pine tree (Pinus densiflora f. erecta) was characterized using morphological and morphometric data, as well as DNA sequences. Deladenus coreanus n. sp. is characterized by the medium sized body of mycetophagous female abruptly narrowing behind vulva, lateral fields with four incisures, pharyngeal corpus without a distinct median bulb and lacking a chamber, pharyngo-intestinal junction immediately behind the nerve ring, hemizonid 13.0–37.0 μm posterior to nerve ring, excretory pore at level with hemizonid, vulva with prominently protuberant lips and with no lateral vulval flaps, post-uterine sac absent, vulva–anus distance approximately equal to tail length, tail conoid, gradually tapering to a broadly or narrowly rounded terminus, or subcylindrical and clubbed, males with slender spicules, 19.0–21.0 μm long and bursa reaching tail tip. The phylogenetic relationships were reconstructed using partial 18S rRNA, 28S rRNA, and COI gene sequences. The newly generated 18S rRNA and 28S rRNA sequences appeared as independent lineages in corresponding trees, and the new COI gene sequence formed a clade with the corresponding gene sequence of Deladenus brevis with moderate (87) Bayesian posterior probability.

From muscle to gland: The reorganization of the terminal bulb within the symbiotic Stilbonematinae (Nematoda, Desmodoroidea)

Wed, 15 Apr 2026 00:00:00 GMT

The Stilbonematinae live in symbiosis with ectosymbiotic bacteria covering their cuticle, which evidently constitute their food. In different Stilbonematinae genera, two pharynx types are found, depending on the arrangement of the bacterial coat. Species descriptions show that most Stilbonematinae species with a thick multilayer of symbionts have a two-part pharynx with a predominantly muscular posterior bulb. In contrast, in cases of a thin monolayer of bacteria, the nematodes predominantly show a three-part pharynx with a distinctly swollen muscular corpus at their anterior end. This indicates a shift of the main pumping structure from the terminal bulb to the anterior corpus. Consequently, the amount of contractile filaments in the terminal bulb should decrease. Using phalloidin staining in combination with confocal laser scanning microscopy, light microscopy, and transmission electron microscopy, we measured and compared the filamentous actin (F-actin) volume in the posterior bulb in several Stilbonematinae species representing both pharynx types. Two-part pharynges had a larger relative F-actin volume in the terminal bulb than three-part pharynges. In the latter, prominent gland tissue occupied most of the space between the reduced muscles. This supports our hypothesis of two distinct feeding modes: ingestion of large amounts of food in species with a two-part pharynx (“gourmands”) requiring a muscular terminal bulb vs discriminant grazing on a thin bacterial coat in species with a three-part pharynx (“gourmets”).

Small Samples, Big Problems, Statistical Tests in Nematology Research Need Power

Mon, 02 Feb 2026 00:00:00 GMT

In nematology research, hypothesis testing is a fundamental method and is typically supported by statistical significance (e.g., P-value <0.05). However, our review of recent publications in nematology reveals frequent issues, including unjustified sample size and unclear reporting of statistical methods, which undermines the validity and reproducibility of the results. To address these issues, we recommend researchers to conduct a priori power analyses to estimate adequate sample sizes and report key descriptive statistics (e.g., effect size). These practices not only strengthen the reliability of research, but can also help answer a central question for investigators: How many samples are needed to detect a “truly” statistically significant difference in an experiment?

The Effects of Adjuvants on Steinernema Carpocapsae Efficacy Against Chrysodeixis Includens and Suspension Stability

Sat, 31 Jan 2026 00:00:00 GMT

Chrysodeixis includens is a major soybean pest in the southern United States and has developed resistance to many insecticides. Entomopathogenic nematodes (EPNs) are potential alternative control tools. Above ground EPN applications are limited by environmental stresses; thus, we evaluated adjuvants to improve the performance of Steinernema carpocapsae. Laboratory assays showed that Xanthan & Tween enhanced EPN efficacy at 24 hr post application across all four exposure durations, whereas Barricade did not improve efficacy at the 1 hr exposure compared with EPNs without adjuvants. At 72 hr post application, adjuvant treatments achieved >90% mortality beginning at the 4 hr exposure duration, whereas EPNs without adjuvants reached >90% only at 24 hr. Greenhouse trials indicated efficacy improvements with Xanthan & Tween under some conditions, whereas Barricade did not. Optimization tests demonstrated that adding Tween to Barricade significantly improved EPN performance. Both Xanthan & Tween and Barricade & Tween reduced nematode sedimentation. Overall, adjuvant enhanced formulations increased EPN efficacy and stability, supporting their potential as a biological management tool for C. includens.

Independent Evaluation of Rootstock Resistance and Endophytic Bacteria for Managing Citrus Nematode

Sat, 31 Jan 2026 00:00:00 GMT

Tylenchulus semipenetrans, a destructive root-parasitic nematode, causes slow decline and significant yield losses worldwide in citrus. Developing resistant cultivars/rootstocks remains an important strategy for the sustainable management of plant-parasitic nematodes in integrated pest management (IPM) systems. Controlling the citrus nematode is challenging due to its wide host range and high adaptability. Although commonly used, chemical nematicides increase production costs and pose risks to human health and the environment. In this study, we separately evaluated the response of five commonly used citrus rootstocks, Citrus paradisi (M.) × Poncirus trifoliata (L.) Raf. (Citromelo), P. trifoliata (L.) Raf. (Poncirus), Citrus jambhiri Lush (Rough lemon), C. volkameriana Ten. & Pasq. (Volkamer lemon), and Citrus aurantium L. (Sour orange), to T. semipenetrans infection. In parallel, we evaluated the biocontrol potential of two bacterial strains, Bacillus safensis Q.en and Pseudomonas chlororaphis P.en, on the susceptible ‘Sour Orange’. The results showed that T. semipenetrans exhibited the highest reproduction on ‘Volkamer lemon’ (275 females/g root and 1,150 second-stage juveniles [J2s]/200 g soil), whereas ‘Citromelo’ showed the strongest resistance (8 females/g root and 220 J2s/200 g soil). Application of the bacterial agents to ‘Sour Orange’ significantly reduced the number of females on roots and juveniles in the soil, while also improving plant growth parameters compared to untreated controls. Our findings demonstrate the individual potential of using resistant rootstocks or biocontrol agents as economical, effective, and environmentally safe components for managing T. semipenetrans. The resistant genotypes identified may also be useful in future breeding programs.

Two New Reported Species of Longidorus spp. and Xenocriconemella spp. from Mainland Greece

Wed, 14 Jan 2026 00:00:00 GMT

Nematode sampling was conducted to identify ring and needle nematodes in forests of central and northern Greece. Two species of the genus Xenocriconemella, X. iberica and X. paraiberica, and three species of Longidorus, L. aetnaeus, L. intermedius, and L. iranicus, were identified based on integrative taxonomy. To our knowledge, this is the first report of X. iberica and X. paraiberica in Greece, and the first time these species have been documented outside the Iberian Peninsula. Similarly, L. aetnaeus and L. intermedius are reported from Greece for the first time. This study expands the known geographic distribution of Xenocriconemella and Longidorus species in Greece and the broader Mediterranean Basin. Molecular characterization confirms that two morphologically distinct species, L. intermedius and L. piceicola, despite differences in lip region width, odontostyle and body lengths, exhibit high similarity in the D2–D3 expansion segments of 28S and internal transcribed spacer 1 (ITS1) rDNA regions. This close molecular affinity underscores the need for further investigation using additional nuclear (e.g., hsp90) and mitochondrial (e.g., COI) markers to clarify the extent of genetic divergence between these two needle nematode species.

Evaluation of Meloidogyne chitwoodi Race 1 and Pathotype Roza in Arabidopsis thaliana and Tomato Plants

Wed, 14 Jan 2026 00:00:00 GMT

Meloidogyne chitwoodi, commonly known as the Columbia root-knot nematode (CRKN), is a major threat to potato production in the Pacific Northwest (Idaho, Oregon, and Washington) of the United States. The nematode damages both roots and tubers, significantly lowering tuber market value. In Washington and Oregon’s Columbia Basin, the two main M. chitwoodi populations are race 1 and a pathotype of race 1 known as Roza. While resistance to race 1 is present in the potato breeding line PA99N82-4, this resistance is ineffective against Roza. To assess virulence differences, both populations were tested on Arabidopsis thaliana and tomato roots. Results showed that Roza was more virulent on these two susceptible hosts. Furthermore, infection assays on tomatoes carrying the Mi-1.2 resistance gene revealed that both populations can overcome this resistance, indicating that Mi-1.2 does not confer protection against either M. chitwoodi race 1 or Roza.

Survey of Pulse Crop Field for Plant-Parasitic Nematodes in the Canadian Prairies

Wed, 31 Dec 2025 00:00:00 GMT

The distribution of economically significant plant-parasitic nematodes in pulse crops in the Canadian Prairies is relatively unknown. Reports suggested that Ditylenchus dipsaci in yellow pea export was likely the nonquarantine species D. weischeri, a Canada thistle (Cirsium arvense) parasite. To determine if D. dipsaci is found in pulse plants and understand nematode distribution in the Canadian Prairies, a survey was conducted in commercial yellow pea, lentil and chickpea fields in Alberta, Saskatchewan, and Manitoba. Samples of pulse and thistle plants (flowers or pods, stems and leaves) and soil were collected from 94 fields. Nematodes were identified by morphological features and molecular analyses (species-specific PCR, PCR-RFLP, and sequencing of the partial 18S, 28S and ITS of the rDNA gene). High densities of plant-parasitic nematodes — Pratylenchus, Paratylenchus, Helicotylenchus and Telotylenchinae — were found in several fields. Ditylenchus weischeri, a parasite of thistles and not pulse crops, was recovered from 20 fields across Alberta, Saskatchewan and Manitoba; D. dipsaci was found in pods of one yellow pea field in Manitoba. These results confirm the high prevalence of D. weischeri on creeping thistle in pulse fields and the near absence of the quarantine pest D. dipsaci.

Description of Xiphinema baliense sp. nov. (Nematoda: Longidoridae), a new member of the X. americanum-group from Bali, Indonesia

Mon, 29 Dec 2025 00:00:00 GMT

Xiphinema baliense sp. nov., a member of the X. americanum-group, brevicolle-subgroup, was recovered from the rhizosphere of native vegetation in Bali, Indonesia. Females of the new species are characterized by a moderately long body (2.0–2.4 mm), having a lip region offset by a shallow depression, well-developed odontostyle (106–118 μm), didelphic-amphidelphic equally developed reproductive branches, vulva at 52–55% of body length and a conoid tail (24–31 μm), dorsally convex, ventrally flat with a widely rounded tip. Males were not observed. The alpha-numeric identification codes for the new species are: A5, B23, C2, D2, E3, F-, G2, H2, I2. The new species was morphologically compared with relevant tentative cryptic species in the aforementioned subgroup, including X. brevicolle, X. himalayense, X. paramonovi, X. primum, X. parabrevicolle, and X. purpureum. Molecular data derived from the D2–D3 expansion segments of 28S rRNA, ITS1, partial 18S rRNA, and COI genes were used to reconstruct the phylogenetic relationships of X. baliense sp. nov. with related species within the X. americanum-group using the Bayesian approach, and the resulting topologies were discussed.

Organic mulches and irrigation affect Mesocriconema xenoplax and Pratylenchus penetrans under cherry

Sun, 14 Dec 2025 00:00:00 GMT

Mesocriconema xenoplax and Pratylenchus penetrans are important plant parasitic nematodes of cherry trees, but little is known of how soil and water management practices affect the buildup of either species in cherry orchards. A split-plot field experiment was initiated in 2014 to compare five soil treatments (untreated control, preplant fumigated, compost, bark chip mulch, compost+bark chip mulch) under drip and microsprinkler irrigation. Plant-parasitic nematode populations were monitored through 2023. The population of M. xenoplax was initially detected in only 3% of the 60 plots whereas P. penetrans was initially present in all plots. By 2023, M. xenoplax were detected in 70% of plots with maximum population density among plots of 834 M. xenoplax 100 cm−1 soil. Mesocriconema xenoplax became more abundant in compost plots and fumigated plots than in untreated plots, and more abundant under drip than microsprinkler irrigation. In contrast, P. penetrans were least abundant in compost plots and less abundant under drip than microsprinkler irrigation. The opposing responses of these two nematode species illustrate tradeoffs in pest pressures that can occur with changes in orchard soil and water management practices, obscuring effects of either species on tree growth.