Journal of nematology最新文献

The small hive beetle (SHB), Aethina tumida Murray (Coleoptera: Nitidulidae), has become a ubiquitous, invasive, and highly destructive pest of western honeybee (Apis mellifera Linnaeus) hives worldwide. Beekeepers often attempt to control this beetle chemically. Still, ineffective registered control options and rampant off-label chemical use in the beekeeping industry have driven research toward alternative pest management strategies. Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae have been established as potential biocontrol agents against soil-dwelling insect pests. However, studies are needed to determine the most appropriate EPN species to control SHB. In this study, an LD₅₀ of ~700 infective juveniles (IJs) of EPN per SHB larva was determined through dose-response experiments. This application rate was used to compare the virulence of the following seven species of EPNs against SHB larvae: Heterorhabditis bacteriophora (VS), H. floridensis (K22), H. georgiana (Kesha), H. indica (HOM1), Steinernema carpocapsae (All), S. rarum (17C+E), and S. riobrave (355). Steinernema carpocapsae (All) and H. floridensis (K22) were found to cause 100% larval mortality of SHB at 14 days post-inoculation. Assays for the persistence of virulence of H. floridensis (K22) and S. carpocapsae in the soil over several weeks from a single application found that both species maintained efficacy, causing 96% mortality of SHB larvae by week 6 post-inoculation. We recommend that S. carpocapsae (All) and H. floridensis (K22) due to their superior virulence for the control of small hive beetles.

Entomopathogenic nematodes (EPNs) have a specialized infective juvenile stage (IJ) that is mobile and has the capability to seek insect hosts to penetrate their haemocoel. EPNs are primarily applied to soil as biological control agents; thus, the IJs must move through the soil to find and infect a host. Soil characteristics are known to be an important factor that can affect the efficiency of EPN movement behavior. Previous research has shown that exposure to ascaroside pheromones can enhance EPN movement and infectivity in soil. The ability of pheromones to enhance EPN efficacy was recently demonstrated under field conditions in a pecan orchard. However, prior to our research, it was unknown whether different soils have differential effects on pheromone enhanced EPN efficacy. In different soils, we tested the biocontrol efficacy of Steinernema carpocapsae, Steinernema feltiae and Heterorhabditis bacteriophora in soil columns with and without pheromone exposure. All nematodes were evaluated in separate columns filled with oven dried commercial play sand and two different soils from pecan orchards (from Byron, GA and Tifton, GA). The soils differed substantially in several aspects such as field capacity, organic matter, nutrients, and nematode movement capacity. Efficacy was determined by baiting the bottom section of each column with larvae of the yellow mealworm (Tenebrio molitor L.). Results indicated that pheromones enhanced EPN efficacy for all EPN species and soils tested compared to treatments without pheromones. The magnitude/extent that pheromones boosted EPN movement in all EPNs regardless of soil type did not differ. Soil did not affect EPN efficacy for H. bacteriophora but did affect S. carpocapsae and S. feltiae. For both S. carpocapsae and S. feltiae efficacy was highest in the sandy field soil (Tifton soil) followed by that of the loamy sand (Byron soil) and pure sand (commercial play sand). When comparing the efficacy of EPN species to each other, we observed that H. bacteriophora killed more bait insects exposed to soil in the bottom of the soil column than other EPNs. Our findings suggest that pheromones can be used to enhance EPN efficacy in diverse soils. Future research may explore pheromone effects on EPNs in additional substrates.

Meloidogyne floridensis was first described in Florida, USA, in 2004 but has since been reported in California, South Carolina, and Georgia. Our objective was to determine the galling and reproduction differences between two isolates of M. floridensis, Mf3 and MfGNV14, on culinary herbs. A duplicated study was performed where both isolates were inoculated separately to nine culinary herbs (basil, catnip, chicory, dill, fennel, marjoram, parsley, sage, and thyme). Tomato was used as a susceptible reference. Regardless of the isolate, chicory and marjoram had the lowest gall indices (1.85 and 1.00, respectively) and egg mass indices (1.25 and 0.90, respectively). The reproduction rate of Mf3 was greatest under catnip (959 eggs/g fresh root) and thyme (701 eggs/g fresh root), followed by sage (549 eggs/g fresh root) and parsley (501 eggs/g fresh root). Catnip (2,151 eggs/g fresh root) stood out for number of eggs among all tested herbs, followed by tomato (1,153 eggs/g fresh root) and sage (847 eggs/g fresh root) for MfGNV14. Marjoram was a non-host, chicory, fennel, and thyme were poor hosts, and catnip, parsley, and tomato were good hosts to both M. floridensis isolates. Basil, dill, and sage responses were isolate-specific, i.e., resistant to Mf3 but susceptible to MfGNV14.

Cyst nematodes of the genus Heterodera comprise 87 nominal species of economically important plant parasites, with the Avenae-group one of the largest, consisting of 12 species. Samplings for cyst nematode studies were carried out from multiple locations in Greece from 2013 to 2021. Cysts of the genus Heterodera were recovered from potato fields, athletic stadium turfgrass and a garlic field. The recovered populations were identified using sequences of 28S, ITS1 and ITS2 rRNA, mitochondrial COI, and nuclear Hsp90. Using integrative taxonomic approaches, the recovered isolates were identified as H. filipjevi (from potato fields and turfgrass), H. hordecalis (from potato fields) and H. mani (from a garlic field), representing new records for Greece. Population diversity within each species was investigated using statistical parsimony of ITS rRNA and mtCOI, revealing haplotypes of the Greek populations and their relationships to others found in the Mediterranean basin and worldwide.

Meloidogyne floridensis is a recently described species of root-knot nematode (RKN) that is very closely related to many other tropical RKN species, including M. incognita. Despite its close phylogenetic relationship, M. floridensis is distinctive from its close relatives in both its meiotic mechanism of reproduction and its documented virulence on many of the most common RKN resistance genes in cultivated peach, tomato, and pepper. To further characterize the virulence profile of M. floridensis, we conducted replicate screens using this nematode to infect a panel of pepper lines that carry different sets of known RKN resistance genes. We found that M. floridensis was virulent against all the most common RKN resistance genes, including N, Me1, and Me3. We also found that two of these lines, PA 136 and PM 217, were highly resistant to M. floridensis. PA136 was previously considered to be universally susceptible to all other RKN species. Further testing of an F1 hybrid of this line confirmed this result and indicated that PA 136 contains a yet uncharacterized and potentially dominant source of species-specific resistance against M. floridensis. These surprising results provide additional data on the differences between M. floridensis and its close relatives, and identify new sources of resistance that could be used by pepper breeding programs to develop new cultivars with resistance against this nematode.

Root-knot nematodes (RKN), particularly Meloidogyne enterolobii, pose a significant threat to agriculture, with current management heavily reliant on agrochemicals due to a scarcity of resistant crop varieties. This study explores orchid mycorrhizae, specifically Waitea circinata, as a sustainable biocontrol method to mitigate nematode infestation in tomato plants. The research aimed to compare different application methods and dosages of mycelial suspensions to reduce nematode reproduction and enhance plant health. Two application methods, root immersion for 24 hours and soil drenching, were tested with mycelial suspension concentrations ranging from 5 to 25 g.L^-1. Results showed that a 15 g.L^-1 suspension significantly reduced nematode reproduction factor (RF) by 53.4% and nematode density (DENS) by 49.4% while increasing root fresh weight (RFW) by 53.8% in drenching. In subsequent experiments, soil drenching with 15 g.L^-1 mycelial suspension again reduced RF by 32.41% and DENS by 28.52%, with increases in shoot length (SL) by 26.31%, RFW by 20.42%, and shoot fresh weight (SFW) by 22.20%. Enzymatic analysis revealed that plants treated with W.circinata and inoculated with nematodes (Wc+Me) showed a substantial decline in RF (71.13%) and DENS (76.96%). Additionally, there was a marked increase in peroxidase (POX) and catalase (CAT) activity, with Wc plants displaying a 180% increase in POX and a 112.5% increase in CAT at root colonization onset. By day 21, Wc+Me plants exhibited further enzyme activity increases, with POX up by 128% and CAT by 67.6%. This study emphasizes the potential of W. circinata in enhancing plant resistance and reducing nematode impact, presenting a promising alternative to chemical control.

A new species of the genus Ditylenchoides, D. agaricivorus n. sp., collected from coconut fiber used as growing media for staghorn ferns and intercepted during import quarantine, is described and illustrated herein based on morphological and molecular studies. The new species is characterized by a body length of 728 (612-846) μm and 641 (511-720) μm in female and male, respectively, delicate stylet 8.0 (7.4-8.4) μm long, six lines in the lateral field, median bulb of esophagus well-developed, muscular with crescentic valve, post-vulval uterine sac well-developed, 36 (22-52) μm long, female tail elongate-conoid with finely rounded terminus. The results of phylogenetic analyses based on sequences of the D2D3 expansion region of 28S rRNA and ITS confirmed the close molecular relationship between D. agaricivorus n. sp., and other Ditylenchoides species such as D. africanus, D. arachis, D. destructor, D. halictus, D. myceliophagus and D. persicus. Ditylenchoides agaricivorus n. sp. was successfully reared on the Rhizoctonia solani and Agaricus biporus. However, D. agaricvorus n. sp. did not reproduce when culturing on Lentinula edodes, Pleurotus erungii, Volcariella volvacea, A. bitorquis, nor on callused carrot disks, and alfalfa seedlings.

In 2022-2023, a survey of drying coniferous plantations in 5 regions of the Republic of Armenia was conducted. Investigations were carried out in plantations of Scots pine Pinus sylvestris L. and Crimean pine Pinus nigra subsp. pallasiana (Lamb.) Holmboe. A total of 125 wood samples were collected and analyzed. For the first time in the territory of the Republic of Armenia, single individuals of pinewood nematode Bursaphelenchus xylophilus (Steiner and Buhrer 1934) Nickle 1981 were found near Hankavan village (Kotayk Province). The nematodes were found in samples from several trees with signs of browning needles. Identification by morphological features corresponded to the description of nematodes of the genus Bursaphelenchus Fuchs, 1937 of xylophilus group. The results of molecular genetic analysis of a fragment of the mitochondrial cytochrome oxidase I (mtCOI) gene showed 100% compliance with the species B. xylophilus. The phylogenetic analysis showed that the identified nematodes are grouped into one cluster with isolates from China, Korea, Portugal, and Japan. It is necessary to thoroughly examine pine plantations on the territory of Armenia to accurately determine the size of the outbreak of this quarantine species.

Fruit flies (Diptera: Tephritidae) are among the most serious agricultural pests globally, causing significant economic losses in fruit production and posing major quarantine concerns for many countries. Bactrocera zonata, one of the most harmful species in the family Tephritidae, has recently established in Iraq. Entomopathogenic nematodes (EPNs) and potential EPNs can be used as vital tools in integrated pest management (IPM) programs for both organic and conventional production systems. In our study, three species - two native and free-living, and the other, a native EPN - were isolated from various orchards in Iraq. Their pathogenicity was evaluated in laboratory and greenhouse experiments against the soil-dwelling third-instar larvae of B. zonata. In laboratory bioassays, mortality rates varied from 70-98% for Oscheius myriophilus, 12-58% for Acrobeloides saeedi, and 14-56% for Heterorhabditis bacteriophora 12 days post-treatment. The mean lethal concentration (LC₅₀) values, measured by infective juveniles (IJs)/larva, were 7.08 for O. myriophilus, 104.49 for A. saeedi, and 97.74 for H. bacteriophora in data set 1. They were 13.50, 86.04, and 86.67 IJs/larva, respectively, in data set 2. These values were determined for third-instar larvae in laboratory tests conducted 12 days post-treatment at 25°C and 60% relative humidity (RH). Under greenhouse conditions, applications of O. myriophilus, H. bacteriophora, and A. saeedi resulted in 50.00-91.75% mortality in fruit tests at a concentration of 250 IJs/larva, and 33.58-67.82% mortality in soil tests against B. zonata, at a concentration of 1,000 IJs/larva 19 days after treatment. Our results suggest that two presently studied free-living native nematodes are potential EPNs, and together with native isolate of Heterorhabditis bacteriophora, could be integrated into pest management programs against B. zonata in Iraqi orchards.

Many root-knot nematode (RKN) species in the genus Meloidogyne occur in Florida, including M. enterolobii, a species able to overcome RKN resistance genes in many crops. The distribution of these nematodes in horticultural crops is not well known. A RKN survey was conducted in South and Central Florida aiming to: (i) identify RKN infecting vegetables, fruit, and other crops; (ii) document host plants; (iii) determine RKN distribution; and (iv) gain insight on the relatedness of M. enterolobii obtained in this study with other populations from the USA and other countries. A total of 304 soil and root samples were collected from 56 plant species cultivated in commercial vegetable and fruit farms, research farms, horticultural gardens, Asian vegetable farms, and natural landscapes in 12 counties. Meloidogyne species identification was performed using mitochondrial haplotype-based identification, species-specific primers, DNA sequencing and phylogenetic analysis. RKN were detected in 247 out of 304 (81.25%) root samples collected from September 2019 to January 2023. Five RKN species (M. arenaria, M. enterolobii, M. hapla, M. incognita and M. javanica) were identified. The most prevalent RKN were M. incognita and M. enterolobii, which were found in 25% of the samples. Less prevalent were M. javanica, found in 16%, and M. arenaria and M. hapla, found in 8% and 5% of samples, respectively. Mixed populations of M. enterolobii and M. incognita were found in 1% of the samples. Phylogenetic analysis showed low genetic variability among DNA sequences of M. enterolobii populations from Florida, other states in the USA, and other countries. New host records found in this study include: a worldwide host record, Solanum capsicoides (M. enterolobii); new US continental host records, Vigna unguiculata (M. enterolobii), Opuntia cochenillifera (mixed species - M. enterolobii and M. incognita). Additionally, new state host records found were Cannabis sativa, Colocasia esculenta, and Lilium sp. (M. arenaria), Phaseolus vulgaris (M. enterolobii), Cucumis melo (M. hapla), and Lavandula angustifolia and Helianthus annuus (M. incognita). These findings confirm the predominance of tropical RKN species, and especially of M. enterolobii, in Florida. and provide new insights into the distribution, prevalence, and hosts of RKN species in horticultural crops in Central and South Florida.