Effect of Application Timing of Oxamyl in Nonbearing Raspberry for Pratylenchus penetrans Management

In 2012, theWashington raspberry (Rubus idaeus) industry received a special local needs (SLN) 24(c) label to apply Vydate L (active ingredient oxamyl) to nonbearing raspberry for the management of Pratylenchus penetrans. This is a new use pattern of this nematicide for raspberry growers; therefore, research was conducted to identify the optimum spring application timing of oxamyl for the suppression of P. penetrans. Three on-farm trials in each of 2012 and 2013 were established in Washington in newly planted raspberry trials on a range of varieties. Oxamyl was applied twice in April (2013 only), May, and June, and these treatments were compared to each other as well as a nontreated control. Population densities of P. penetrans were determined in the fall and spring postoxamyl applications for at least 1.5 years. Plant vigor was also evaluated in the trials. Combined results from 2012 and 2013 trials indicated that application timing in the spring was not critical. Oxamyl application reduced root P. penetrans population densities in all six trials. Reductions in P. penetrans population densities in roots of oxamyl-treated plants, regardless of application timing, ranged from 62% to 99% of densities in nontreated controls. Phytotoxicity to newly planted raspberry was never observed in any of the trials. A nonbearing application of oxamyl is an important addition to current control methods used to manage P. penetrans in raspberry in Washington

Distribution and Longevity of Pratylenchus penetrans in the Red Raspberry Production System

One of the major constraints on the production of red raspberries in the Pacific Northwest is the presence of the rootlesion nematode Pratylenchus penetrans. Current management of this nematode relies heavily on preplant soil fumigation; however, regulations have made the practice more difficult and expensive. Additional issues with soil fumigation include lack of efficacy at deeper soil depths and potential inability to penetrate raspberry root material that remains in the field during fumigation which may harbor P. penetrans. To address these issues, two field experiments were conducted in northwestern Washington. In the first experiment, the residency time of P. penetrans in root material from the previous raspberry crop, which was terminated with or without the use of herbicides, was monitored over time. Pratylenchus penetrans was found in root material from 6 to 8 mon after the crop was terminated, and herbicide application did not reduce P. penetrans residency time compared to untreated root material. In a second experiment, the vertical distribution of P. penetrans at three different times during the field establishment process (pre- and postfumigation, and at planting) was determined at two locations. Both locations had detectable prefumigation P. penetrans populations at all depths. However, postfumigation populations showed a different distribution pattern between locations. The location with coarser soil had populations located mainly at shallower depths with a maximum of 44 P. penetrans/100 g soil at 16 to 30 cm deep, whereas the location with finer soil had populations located mainly at deeper depths with a maximum of 8 P. penetrans/100 g soil at 76 to 90 cm deep. At planting, distribution tended to equilibrate among depths at both locations, but the overall population pattern across depth at each location was similar to that observed at postfumigation. Understanding more about the residency time and distribution of this nematode may provide growers with information that can be used to more effectively target P. penetrans

Potential of an alkaline-stabilized biosolid to manage nematodes: case studies on soybean cyst and root-knot nematodes

The use of treated biosolids for pest management and soil nutrient augmentation is not a new practice, but it has increased in the last two decades, primarily in the United States (22). In the late 1970s, the first land application regulations were formulated by the U.S. Environmental Protection Agency (USEPA) in response to the Clean Water Act (44). Land application of sewage sludge for soil amendment and land reclamation has increased over time as a result of the ban on ocean dumping of wastewater residuals (Ocean Disposal Ban Act of 1988). The Act also minimizes other disposal options, such as land-filling or incineration. In 1993, the Standards for the Use or Disposal of Sewage Sludge (Code of Federal Regulations Title 40, Part 503) was created (45,46). Part 503 (as it is commonly called) set pollutant limits, operational standards for human/animal pathogen and vector-attraction reduction, management practices, and other provisions intended to protect public health and the environment from any reasonably anticipated adverse effects from chemical pollutants and pathogenic organisms. In 1995, the EPA promoted the terminology “biosolids” rather than “sewage sludge” and defined biosolids as “the primarily organic solid product yielded by municipal wastewater treatment processes that can be beneficially recycled as soil amendments and meets the standards of Part 503”. Although the term is sometimes controversial (33), we will use biosolid in reference to the product tested in this research

Comparison of Meldola’s Blue Staining and Hatching Assay with Potato Root Diffusate for Assessment of Globodera sp. Egg Viability

Laboratory-based methods to test egg viability include staining with Meldola's Blue and/or juvenile (J2) hatching assays using potato root diffusate (PRD). These two methods have not been tested under identical conditions to directly compare their assessments of Globodera egg viability. Using two bioassay strategies, cysts from a Glabodera sp. population found in Oregon were subjected to both viability assessment methods. In strategy one, intact cysts were first stained with Meldola's Blue (primary staining) and eggs were then transferred to PRD (secondary hatching). In the second strategy, intact cysts were exposed to PRD (primary hatching) and then unhatched eggs were transferred to Meldola's Blue (secondary staining). Two different cohorts of cysts were evaluated using these experimental strategies: cohort I was comprised Of cysts produced on potato in the greenhouse that exhibited low hatch when exposed to PRD and cohort 2 consisted of field-collected cysts whose eggs yielded significant hatch when exposed to PRD Percentage viability was calculated and is expressed as the number of hatched J2 or unstained eggs/total number of eggs within a cyst. With field-produced cysts, primary staining with Meldola's Blue and hatching with PRD produced similar viability estimates, with averages of 74.9% and 76.3%, respectively. In contrast, with greenhouse-produced cysts the two methods yielded much lower and unequal estimates 32.4% to 2.2%, respectively for primary hatching and staining methods. In addition, J2 hatch from Unstained (viable) greenhouse-produced eggs was 13.7% after secondary exposure to PRD compared to 61.5% for field-produced eggs. The majority of eggs remaining unhatched after primary exposure to PRD (> 87%) stained with Meldola's Blue regardless of cyst cohort. Staining with Meldola's Blue provided a conservative assessment of egg viability compared to hatch assay with PRD regardless of diapause.Keywords: egg hatch, juvenile, Globodera, Meldola’s Blue, method, potato root diffusate, cyst nematod

Spatial Distribution of Plant-Parasitic Nematodes in Semi-Arid Vitis vinifera Vineyards in Washington

The most commonly encountered plant-parasitic nematodes in eastern Washington Vitis vinifera vineyards are Meloidogyne hapla, Mesocriconema xenoplax, Pratylenchus spp., Xiphinema americanum, and Paratylenchus sp.; however, little is known about their distribution in the soil profile. The vertical and horizontal spatial distribution of plant-parasitic nematodes was determined in two Washington V. vinifera vineyards. Others variables measured in these vineyards included soil moisture content, fine root biomass, and root colonization by arbuscular mycorhizal fungi (AMF). Meloidogyne hapla and M. xenoplax were aggregated under irrigation emitters within the vine row and decreased with soil depth. Conversely, Pratylenchus spp. populations were primarily concentrated in vineyard alleyways and decreased with depth. Paratylenchus sp. and X. americanum were randomly distributed within the vineyards. Soil water content played a dominant role in the distribution of fine roots and plant-parasitic nematodes. Colonization of fine roots by AMF decreased directly under irrigation emitters; in addition, galled roots had lower levels of AMF colonization compared with healthy roots. These findings will help facilitate sampling and management decisions for plant-parasitic nematodes in Washington semi-arid vineyards.This is the publisher’s final pdf. The published article is copyrighted by the Society of Nematologists and can be found at: http://journals.fcla.edu/jon/indexKeywords: Spatial distribution, Plant-parasitic nematodes, Management, Washington, Vitis vinifera, Semi-arid, Arbuscular mycorrhizal fungi colonizatio

Identification of candidate effector genes of <i>Pratylenchus penetrans</i>

Pratylenchus penetrans is one of the most important species of root lesion nematodes (RLNs) because of its detrimental and economic impact in a wide range of crops. Similar to other plant‐parasitic nematodes (PPNs), P. penetrans harbours a significant number of secreted proteins that play key roles during parasitism. Here, we combined spatially and temporally resolved next‐generation sequencing datasets of P. penetrans to select a list of candidate genes aimed at the identification of a panel of effector genes for this species. We determined the spatial expression of transcripts of 22 candidate effectors within the oesophageal glands of P. penetrans by in situ hybridization. These comprised homologues of known effectors of other PPNs with diverse putative functions, as well as novel pioneer effectors specific to RLNs. It is noteworthy that five of the pioneer effectors encode extremely proline‐rich proteins. We then combined in situ localization of effectors with available genomic data to identify a non‐coding motif enriched in promoter regions of a subset of P. penetrans effectors, and thus a putative hallmark of spatial expression. Expression profiling analyses of a subset of candidate effectors confirmed their expression during plant infection. Our current results provide the most comprehensive panel of effectors found for RLNs. Considering the damage caused by P. penetrans, this information provides valuable data to elucidate the mode of parasitism of this nematode and offers useful suggestions regarding the potential use of P. penetrans‐specific target effector genes to control this important pathogen