The pacific shoot‐gall nematode ( Anguina pacificae ) is a serious pest of annual bluegrass ( Poa annua ) putting greens in coastal Northern California. Until recently, there have been relatively few effective plant protectant compounds against this endoparasitic nematode that infects shoots. This study evaluated the efficacy of cyclobutrifluram, which targets the mitochondrial succinate dehydrogenase complex of nematodes and fungi. Three studies were conducted from 2021 to 2024 at TPC Harding Park Golf Course in San Francisco, CA. Cyclobutrifluram was applied alone at a rate of 125, 250, or 500 g a.i. ha −1 or in combination with abamectin applied at 360 g a.i. ha −1 (3.9 g L ha −1 of product). Fluopyram applied at 500 g a.i. ha −1 (1.25 L ha −1 of product) was included as a standard. Cyclobutrifluram significantly improved turfgrass visual quality and reduced nematode injury compared to the untreated control, and overall effects were comparable to fluopyram. Tank mixtures or rotations with abamectin did not increase efficacy unless nematode pressure was high. These findings suggest that cyclobutrifluram is an effective plant‐protectant compound for managing pacific shoot‐gall nematodes.

California is the primary US producer of processing tomatoes. After decades-long excellent protection against the common tropical Meloidogyne spp. M. incognita, M. javanica, and M. arenaria (root-knot nematode: RKN) by Mi-resistant tomato cultivars, resistance-breaking RKN populations are spreading throughout the San Joaquin Valley. For some time, nematicidal crop management tools have diminished under CA State regulatory pressure. In recent years, new non-volatile compounds have been developed with novel modes of action. In this project with susceptible processing tomato grown on an M. incognita-infested site, the efficacy of three fluorinated nematicides was evaluated in 10 field trials from 2011 to 2021. Seven trials included fluensulfone, six included fluazaindolizine, and five included fluopyram. On average, tomato root-galling (0 - 10 scale) at harvest was reduced by 3.2, 2.3, and 2.5 by fluazaindolizine, fluensulfone, and fluopyram, respectively, compared to the untreated control. These reductions in root-galling corresponded with estimated yield gains of approximately 21%, 14%, and 15%, respectively, over the untreated control. The reproduction of RKN during the tomato crop was not affected by the nematicides. The tested compounds have a very low acute mammalian toxicity and are more target-specific than previous generations of nematicides. However, there is considerable concern about the persistence of synthetic per- and polyfluoroalkyl substances (PFAS) in the environment, including pharmaceuticals and pesticides containing fluorine with the C-F3 functional group.

Root-knot nematodes were discovered in severely declining creeping bentgrass putting greens at a golf course in Indian Wells, Riverside County, California. The exhibited disease symptoms included chlorosis, stunted growth, and dieback. Based on morphological examination and measurements of J2 females and males, it was suggested that the causal pathogen was Meloidogyne marylandi. This identification was confirmed by analysis of the D2-D3 expansion segments of 28S rRNA and COI gene sequences. The host status of 28 plant species was evaluated in greenhouse trials. All tested monocots, except rye and Allium species, were found to be hosts, while no reproduction occurred on dicots. Temperature-tank experiments helped determine that the life cycle of M. marylandi was completed between 17-35 °C, with a base temperature of 8.3 °C and a required heat sum of 493 degree-days (DD). In greenhouse trials in pasteurized soil and near-ideal growing conditions, M. marylandi did not cause significant growth reduction of creeping bentgrass cv. Penn A-4, even at very high J2 inoculation densities. It is highly probable that other biotic and abiotic factors contributed to the observed putting green damage.

Three fluorinated, one carbamate nematicide, as well as two biological control agents were tested in greenhouse trials to determine their efficacy against Meloidogyne incognita on tomato plants in three different soils. Each soil was treated with one of the following chemical nematicides at the labelled rate: fluensulfone, fluopyram, fluazaindolizine, and oxamyl. The biocontrol agents used were Metacordyceps chlamydosporia and Pasteuria penetrans. In one additional treatment, a combination of the biocontrol agents was applied. After 60 days, root-knot nematode population data, tomato plant growth, and root galling were assessed. Of the chemical nematicide treatments, fluazaindolizine had the strongest effect on M. incognita J2 in soil, with a 99% reduction relative to the untreated control. More than 99% reduction in the number of eggs per root system was achieved by all three fluorinated nematicides. The strongest effect on M. incognita J2 in soil by a biological control agent was in a combined M. chlamydosporia + P. penetrans treatment that resulted in an 87% reduction. This combined treatment was also the most effective on the eggs per root system, reducing the number of eggs by 69% relative to the untreated control. The different soils affected the efficacy of the biocontrol agents more than the efficacy of the fluorinated nematicides. For example, the percentage reduction in M. incognita J2 by the biocontrol treatments ranged from 40% to 65% for the three soils. For the fluorinated nematicides this range was 96% to 97%. These trials demonstrate the influence of the growth substrate on the efficacy of the biocontrol treatments. Overall, the tested biological control agents did not match the novel nematicides' early protection of tomato transplants.

The nematophagous fungus Hyalorbilia oviparasitica and relatives (Hyalorbilia spp.) are known to parasitize several endoparasitic nematodes. In this project, we hypothesized that indigenous populations of this fungus could be used to predict nematode suppression in agricultural field soils. We quantified Hyalorbilia spp. in soil samples from 44 different sugar beet fields in the Imperial Valley of California. Seven soils harboring Hyalorbilia spp. and two that tested negative for the fungi were examined for nematode suppressive activity. Untreated and autoclaved portions of each soil were planted with cabbage and infested with sugar beet cyst nematode (Heterodera schachtii) juveniles. Females and cysts of H. schachtii were enumerated after 12 weeks. In the seven soils harboring Hyalorbilia spp., females and cysts in the untreated soils were reduced by 61 to 82% compared with the autoclaved controls. Soils with no detectable Hyalorbilia spp. exhibited no nematode suppression. Two novel Hyalorbilia strains, HsImV25 and HsImV27, were isolated from H. schachtii females reared in field soil using an enrichment and double-baiting cultivation technique. Both strains suppressed H. schachtii populations by more than 80% in soil-based assays, confirming that Hyalorbilia spp. are the likely causal agents of the nematode suppression in these soils. This study demonstrated that indigenous populations of a hyperparasite (Hyalorbilia spp.) in agricultural field soils predicted suppressive activity against a soilborne plant pathogen (H. schachtii). To our knowledge, this is the first report to demonstrate this capability. We anticipate that this research will provide a blueprint for other similar studies, thereby advancing the field of soilborne biological control.

The southern root-knot nematode, Meloidogyne incognita (Kofoid and White, 1919) Chitwood, 1949, is one of the most important, yield-limiting pathogens of agronomic and vegetable crops in the United States and worldwide. It was first reported on cotton ( Gossypium hirsutum L.) in Alabama in the United States. Since then, it has been reported in many states across the United States. These reports include detections in greenhouses, nurseries, or home gardens but do not provide information on where this species persists from year to year in field soils. Furthermore, these reports do not provide distribution information within each state in individual counties. This report summarized the distribution of M. incognita on field crops (e.g., agronomic and vegetable crops) by county for each state across the continental United States.

As pest management options, such as nematicides, become more restrictive, developing rootstocks resistant to the citrus nematode is fundamental for citrus production. This study provides an updated methodology to screen for citrus nematode resistance in rootstock-breeding programs. We developed a novel method to extract female citrus nematodes from roots that is suitable for molecular work and a real-time-PCR-based nematode quantification method for Tylenchulus semipenetrans. These procedures allow scaling up screening to high-throughput workflows, increasing the chances of finding rootstock candidates that combine all the desired traits. Our results contribute to the growing literature supporting quantification of nematodes with molecular methods.

The Pacific shoot-gall nematode ( Anguina pacificae Cid del Prado Vera & Maggenti, 1984) is a devastating pest on annual bluegrass ( Poa annua L.) putting greens in coastal Northern California, USA. Frequently used plant protection compounds such as fenamiphos and azadirachtin are either no longer registered or very expensive and have often resulted in nematode suppression at best. A new formulation of abamectin (Divanem; Syngenta, Greensboro, NC) was tested at two rates (0.15 and 0.30 kg a.i. ha − 1 ) and two application frequencies (2X vs. 4X) in comparison to fluopyram (Indemnify; Bayer CropScience, St. Louis, MO) applied at the rate of 0.5 kg a.i. ha − 1 on three California golf courses: Pasatiempo, Santa Cruz; Laguna Seca, Monterey; and Del Monte, Monterey. Fluopyram showed the best efficacy regarding from and against the Pacific shoot-gall disease. two applications for season-long applications of the new formulation rate efficacy fluopyram. Overall, represents plant tool offers a treatment alternative for the management of this pathogen. Neither had much effect on populations of soil-dwelling A. pacificae , spiral ( Helicotylenchus spp.), ring ( Criconemoides spp.), and root-knot ( Meloidogyne spp.) nematodes.

This study endeavored to test two hypotheses: (i) Hyalorbilia oviparasitica and related species (H. oviparasitica clade) will be detected in sugar beet fields in California’s Imperial Valley and (ii) the population densities of these fungi will increase in the presence of their nematode host (Heterodera schachtii) and a host plant of this nematode. The H. oviparasitica clade includes potent hyperparasites of sedentary stages of plant-parasitic nematodes, which have the ability to substantially suppress the population densities of several endoparasitic nematode species. In this study, 21 of 25 Imperial Valley soils cropped to sugar beets harbored members of the H. oviparasitica clade. The population densities of these fungi increased, on average, approximately 10,000-fold in the presence of H. schachtii and its host Swiss Chard over one nematode generation. An rRNA ITS sequence analysis showed that members of the H. oviparasitica clade were the dominant group of fungi associated with H. schachtii females derived from these soils. These results provide evidence supporting the hypotheses. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Until the early 1990s, cyst nematodes were abundant pathogens in fields where hosts of Heterodera spp. were frequent members of crop rotations along California’s Central Coast. To mitigate damage caused by Heterodera schachtii and H. cruciferae, the soil fumigant 1,3-dichloropropene (1,3-D) was used by more than 43% of surveyed broccoli growers. Over the last few decades, use of 1,3-D and other nematicides has dramatically diminished, suggesting a decline in nematode disease pressure. The goal of this study was to examine the hypothesis that increased population densities of nematophagous fungi contribute to the low populations of Heterodera spp. in fields frequently cropped to their hosts. In 2016, soil samples were collected from 152 Brassica fields with a broad geographical distribution, from Santa Barbara County to Santa Cruz County. The average number of Heterodera cysts per 250 cm3 of soil ranged from 0.5 to 27.5, with 62% of the soils harboring no detectable cyst nematodes and only a few samples reaching a potentially damaging threshold level. A baiting experiment with H. schachtii and cabbage was performed in a greenhouse to detect nematophagous fungi associated with nematode females as their posterior end emerged and became exposed to the soil’s rhizosphere. An Illumina-based sequence analysis of these H. schachtii females identified several known nematophagous fungi, including members of the Hyalorbilia oviparasitica clade, Pochonia chlamydosporia, certain Fusarium spp., and others. These soils clearly harbor a diverse population of hyperparasitic fungi that could be biologically suppressing cyst nematodes below a damaging threshold. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of Meloidogyne incognita infesting carrots in California, USA. Future research requirements and future developments are also mentioned.

Golf courses in coastal regions of northern California are often faced with severe injury caused by pacific shoot-gall nematodes (Anguina pacificae) on their annual bluegrass (Poa annua) host in putting greens. For years, fenamiphos was used for mitigating disease outbreaks until its registration was withdrawn in 2008. An alternative product containing azadirachtin was intended for nematode suppression. Still, it required repeated applications throughout the year with questionable efficacy, making attempts to lessen the impact of the pathogen costly. This study evaluated fluopyram as a novel nematicide for control of pacific shoot-gall disease. Various application frequencies and rates were tested at several golf courses affected by the nematode. Results revealed that fluopyram applied once at 0.22 lb/acre reduced the number of new shoot-galls and improved annual bluegrass appearance for several months. Increased rates and application frequency occasionally improved the efficacy further. Although the visual quality of turf treated with this plant protection compound was tremendously enhanced, and the number of new shoot-galls was reduced, rarely a significant effect was observed on the population density of several soil-dwelling plant-parasitic nematodes, including pacific shoot-gall nematode. It is hypothesized that fluopyram did not move significantly past the thatch layer and into the soil. However, it effectively reduced the ability of pacific shoot-gall nematode juveniles to induce new shoot galls. Due to its long half-life, it likely protected against both new nematode infections and dissemination of pacific shoot-gall nematode when the shoot-galls decomposed.

Meloidogyne enterolobii, an aggressive plant-parasitic nematode, has been causing great yield loss worldwide in recent years. With no resistant Chinese cabbage cultivar available currently, a biological control strategy is needed to offer an eco-friendly option for sustainable farming. In this study, the nematode suppression efficacy of two newly isolated fungi, Paraboeremia taiwanensis and Samsoniella sp., were evaluated against M. enterolobii and compared to the known biological control agents Hyalorbilia oviparasitica strain DoUCR50 and Purpureocillium lilacinum strain 251 (PL251). Both P. taiwanensis and Samsoniella sp. reduced 29%–63% disease severity as effectively as the commercial product PL251 on Chinese cabbage in greenhouse trails. The in vitro egg infection rate was 47.83% by P. taiwanensis and 47.50% for Samsoniella sp., respectively. A special protocol for scanning electron microscope observation of the fungi-infected nematodes was established in this study, and the egg parasitism of the four fungi against M. enterolobii was further confirmed. For all fungi examined in this study, fungal hyphae were seen apparently penetrating into M. enterolobii eggs without destructive damage of the overall outer eggshell and the hyphae continued to grow within eggs after 6 days of infection. The results of this study imply a similar egg-parasitism mechanism for P. taiwanensis, Samsoniella sp., H. oviparasitica DoUCR50, and P. lilacinum PL251. It further enlightens the application potential of nematophagous fungi as biocontrol agents against plant-parasitic nematodes in vegetable crop management.

Three closely related nematophagous fungi in the genus Hyalorbilia were compared for their ability to parasitize females and eggs of Heterodera schachtii at different developmental stages. DoUCR50, StM, and ARF were originally isolated from Heterodera schachtii, Meloidogyne incognita, and Heterodera glycines, respectively. Phylogenetic analysis and pairwise sequence analysis showed that DoUCR50 and StM are more closely related to each other than they are to ARF. DoUCR50 parasitism suppressed 100% of the J2 hatch from 3-week-old H. schachtii females and 75% of the hatch from 4-week-old females. Eggs within 5-week-old females were resistant to parasitism, and hatch of J2 was unaffected by exposure to DoUCR50. StM and ARF did not reduce the hatch of J2 from H. schachtii females of any age. Eggs removed from females and spread onto water agar cultures of the fungi were mostly resistant to parasitism. DoUCR50 parasitized only 16% of such eggs from 3-week-old females. Extracellular hydrolytic enzyme production by the three fungal strains grown on PDA or parasitized H. schachtii females was evaluated using API ZYM (bioMérieux) test strips. All three fungi produced extracellular hydrolytic enzymes when grown on PDA or H. schachtii females. Trypsin-like protease activity was uniquely detected in DoUCR50 grown on PDA and H. schachtii females, with the highest activity associated with the fungus grown on parasitized females.