Plant-parasitic Nematode Populations Research Articles

Management of plant parasitic nematodes in Okra by Bio-fumigation

A pot culture study was carried out to assess the effect of two bio-fumigants viz. Cabbage and Cauliflower leaves on plant parasitic nematode population infecting okra. The experiment resulted in reduction of root knot nematode (40.7%), lance nematode (40.8–80.1%), spiral nematode (49.1–79.7%) and stunt nematode (40.8–81.3%) with improvement of plant growth parameters like shoot length (23.3–54.6%), root length (14.1–46.5%), fresh shoot weight (28.4–81.9%), fresh root weight (22–38.7%), dry shoot weight (11.6–85.7%) and dry root weight (24–39%) of okra plant as compared to untreated control. Both cabbage and cauliflower leaves were found to be at par with respect to reduction of nematode population and enhancement of plant growth parameters. However, Cabbage leaf @ 88 g/kg soil (5.0 kg/m2) exhibited better performance in all above aspects. It reduced the population of root knot nematode, lance nematode, spiral nematode and stunt nematode by 50%, 52.4%, 61.2% and 50.9%, respectively. The enhancement of shoot length, root length, fresh shoot weight, dry shoot weight, fresh root weight and dry root weight to the tune of 49.3%, 46.5%, 79.3%, 78.5%, 38.7% and 39.5%, respectively were observed with this treatment.

Nematicide effects on non-target nematodes in bermudagrass.

In turfgrass systems, nematicides are a valuable tool for managing plant-parasitic nematode populations, but few studies have examined nematicide effects on non-target nematodes. The study evaluated effects of turfgrass nematicide formulations of abamectin (Divanem SC), fluopyram (Indemnify), furfural (MultiGuard Protect EC), and fluensulfone (Nimitz Pro G) on non-target nematode populations in bermudagrass (Cynodon spp.). Nematicides were applied at labeled rates every four weeks as a summer treatment program from June 7, 2016 to August 30, 2016 and April 24, 2017 to July 18, 2017. Samples were collected before the initial treatment and 2 d, 14 d, 56 d, and 238 d after the final treatment in both years for nematode community analysis. Data from each nematicide treatment were compared to the untreated at each sample date using analysis of covariance with initial population counts serving as the covariate. Abamectin had moderate impact and fluopyram had substantial impact on the non-target nematodes. Furfural and fluensulfone had minimal impact on non-target nematodes. The results of this study suggest nematicides can impact non-target nematode densities in bermudagrass.

Evaluation of non-fumigant chemical and biological nematicides for strawberry production in Florida

In Florida, strawberry is an economically important horticultural crop. Plant-parasitic nematodes present a significant obstacle for strawberry growers in the sandy soils found in this state. Historically, nematodes have been controlled through the application of soil fumigants; however, there is interest in exploring the use of non-fumigant nematicides that can provide similar levels of control and at the same time be more environmentally friendly than fumigants. Using two field experiments, the effects of non-fumigant chemical and biological nematicides on plant vigour and fruit yield, populations of plant-parasitic nematodes, and populations of free-living nematode feeding groups were evaluated. In experiment 1, soil fumigation with metam potassium, as well as all non-fumigant chemical nematicides (fluopyram, fluensulfone, fluazaindolizine) failed to increase plant vigour, fruit yield, or suppress populations of plant-parasitic nematodes. In experiment 2, fluopyram increased fruit yield and suppressed Belonolaimus longicaudatus populations by the end of the growing season. Biological nematicides (Dazitol®, Majestene®, and Nemakill®) did not enhance crop establishment or suppress plant-parasitic nematode populations. Soil fumigation with 1,3-dichloropropene + chloropicrin provided consistent enhancement of plant vigour and fruit yield, as well as suppressed populations of B. longicaudatus; however, populations of free-living nematodes were also reduced. Overall, soil application of fluopyram shows potential to be a component of an integrated pest management strategy for the control of B. longicaudatus populations on strawberry in Florida.

Mycorrhizal fungi enhance nutrient uptake but disarm defences in plant roots, promoting plant-parasitic nematode populations

Arbuscular mycorrhizal (AM) fungi are ubiquitous components of the soil biota which live symbiotically with terrestrial plants. Plant-parasitic nematodes are an important group of soil-dwelling invertebrates that inflict considerable damage to crops, representing a serious threat to food security. The effects of the AM symbiosis on plant-parasitic nematodes can be variable, and the mechanisms driving such variability remain ambiguous.We tested the impacts of inoculation with AM fungi on the root metabolic profile and nutritional chemistry of two varieties of wheat (Triticum aestivum), and how this affected populations of the plant-parasitic nematode Pratylenchus neglectus.AM fungi reduced plant biomass by almost 24%, yet increased root concentrations of phosphorus, potassium and zinc by 50%, 15% and 16%, respectively. Contrary to our predictions, nematode populations were 47–117% higher on AM inoculated plants, depending on variety. Untargeted metabolomic profiling revealed significant effects of mycorrhizal colonisation on certain markers of biological interest, these compounds were the benzoxazinoid glucoside defence compounds DIBOA-Glc, HMBOA-Glc and HDMBOA-Glc. Overall, mycorrhizae reduced abundances of these defence metabolites, which were potentially driving AM fungi – nematode interactions; although for DIBOA-Glc this was dependent on wheat variety. Moreover, there was a negative correlation between total AM colonisation and DIBOA-Glc concentrations.Our results demonstrate AM fungi can reduce plant biomass and supress root defence compounds associated with plant resistance to invertebrate pests, while still providing nutritional benefit to the host plant. This highlights that mycorrhizal colonisation of wheat varieties can have simultaneous positive and negative effects on different plant traits which drive plant-herbivore interactions. In working towards effective exploitation of the AM symbiosis in sustainable plant production, the context dependent outcomes of mycorrhizal-plant-nematode interactions is a key challenge. Untargeted metabolomic profiling offers the ability to reveal some of the driving mechanisms underpinning such complex tripartite interactions in the soil.

Effect of the entomopathogenic nematode-bacterial symbiont complex on Meloidogyne hapla and Nacobbus aberrans in short-term greenhouse trials

Meloidogyne hapla and Nacobbus aberrans are plant-parasitic nematodes that form galls in the roots of infected plants and cause important economic losses. Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis infect and kill insects via toxins produced by their symbiotic bacteria. EPNs have shown to have an antagonistic effect on different plant-parasitic nematode species in field and greenhouse trials. The aim of the present work was to evaluate, in tomato plants in greenhouse, the effect of the application of three Argentine EPN isolates, their symbiotic bacteria and cell-free supernatants, on a population of M. hapla and two populations of N. aberrans. Sixty days after inoculation, the number of galls and egg masses, the nematode reproduction factor (RF) and plant biomass were calculated. With a few exceptions, biomass was not affected by the different treatments. None of the plant-parasitic nematode populations was reduced by infective juvenile inoculation of the different EPN isolates. Bacterial action differed among populations; M. hapla was the most susceptible one, with a significant reduction in the number of galls, egg masses and RF caused by the application of the three bacterial strains. The most significant effect was produced by the cell-free supernatants on nematode RF, with reductions of 62–90%, caused by bacterial metabolites. The different inoculation alternatives of the EPN-bacterial symbiont complex tested in the present work (infective juveniles, bacteria and cell-free supernatant) are compared for the first time for plant-parasitic nematode species.

Nematodes in the soil and roots of spring barley grown in crop rotation and long-term monoculture

Background. Species structure of plant parasitic nematode populations from the rhizosphere of spring barley grown in an 18-year-old crop rotation and in a 48-year-old monoculture were analyzed and compared. Material and methods. Plots were established in fields of spring barley grown in an 18-year-old crop rotation and in a 48-year-old monoculture. Four 1 m2 plots were located in each corner of each field. Four soil samples from each 1 m2 plot were taken by a pedestrian cane of a 3 cm section at a depth of 40 cm in the vicinity of the barley roots at start (BBCH 09) and a day after harvest (BBCH 99). Each soil sample weighed 1 kg and contained 50 g of fresh roots and spikes. The sample from each of the four 1 m2 plots was a replicate (and at the same time, the combination of the soil + roots + stems), hence the isolated nematode from each part of the sample was a set of nematodes associated with the host on 1 m2. Results. Populations of dominating species such as Bitylenchus dubius, Merlinius microdorus, Pratylenchus neglectus and Heterodera avenae became higher in the monoculture than in the crop rotation. H. avenae eggs and larvae were infected by pathogenic fungi in 50% of samples from the monoculture (vs. 60% of the cysts from the crop rotation), and 18–35% of Pratylenchus specimens were colonized by bacteria, mainly by Bacillus penetrans. Conclusion. The results illustrated nematological changes occurring in long-term cropping systems and provided additional information necessary to fight dangerous viral vectors for the examined cereal.

Examining trophic-level nematode community structure and nitrogen mineralization to assess local effective microorganisms’ role in nitrogen availability of swine effluent to forage crops

Culturing and using effective microorganisms from locally derived microorganisms has become a common practice employed by farmers throughout Central America as well as parts of South America and Southeast Asia to control foul odors and flies around compost piles and livestock facilities. These local, effective microorganisms (LEM) are applied in a concentrated solution fermented from carbohydrate-rich substrates inoculated with locally-sourced, actively decomposing leaf litter. Despite its growing prevalence among small-scale farmers in some parts of the world, there is little published research that explores the beneficial or detrimental effects of changing the biome of animal-based nutrients and the soils to which LEM are applied. The objectives of this study were to evaluate the effect of combining LEM with swine effluent to fertilize annual ryegrass (Lolium multiflorum) on plant-available nitrogen, nematode community structure, and forage productivity. Forage performance was good across all of the treatments – with relative feed quality (RFQ) values above 200 and 100 in the March and May harvests respectively. In the first, second and third sampling dates, soils from 0 to 5 cm depth showed more nitrogen mineralized in LEM-treated soils than in control soils (p = 0.178, p < 0.0001 and p = 0.027) respectively. After nutrient applications, soil-nematode community structure (0–10 cm) at the trophic group level changed over time. Most changes were similar between treatments, however, plant parasitic nematode populations were found to be significantly higher in LEM-treated plots in all but one of the sampling dates. LEM is gaining popularity as a natural amendment and although we have shown that it does increase N availability and changes trophic-level nematode community structure, more research is needed to optimize the potential of these benefits.

Effect of soil temperature and moisture on population dynamics of phytonematodes infesting sugarcane

In India, phytonematodes are reported to cause about 10-40 %yield loss in sugarcane. In India, Uttar Pradesh is the major sugarcane growing state, contributing about 48% of the area and 40% of the production. The present study was undertaken to record biodiversity, to correlate the soil major edaphic factors (temperature &amp; moisture). The study was also centered on to reveal the edaphic factors affecting sex ratio fluctuation of the dominant phytonematodes. Soil temperature, which changes constantly, is a major factor influencing nematode development. Temperature is an important environmental factor for organisms. Different organisms have their own optimal temperatures for normal activities and high and low temperature limits they can tolerate. Diurnal fluctuations in temperature vary in extent and depend upon soil type, texture, moisture, atmospheric conditions, latitude, elevation, season and soil cover. Cool climate species often develop slowly in winter and become more active when temperatures rise in spring season and in this season plant parasitic nematodes population decrease. Moisture plays an important role in the movement of the soil organism. The findings indicated that during winter period when moisture and humidity is high in soil environment conditions. Populations of plant parasitic nematodes were highest in this season.

SCREEN HOUSE ASSESSMENT OF NEEM-FORTIFIED CASSAVA PEEL POWDER FOR CONTROLLING NEMATODES AND YIELD IMPROVEMENT OF SUGARCANE (SACCHARUM OFFICINARUM)

Screen house trials for the assessment of Neem-fortified cassava peels for control of plant-parasitic nematodes and yield improvement of sugarcane (Saccharum officinarum) were conducted in Moor plantation, Ibadan, Southwest Nigeria. Cassava peel powder (CPP) solely and in combination with Neem Leaf Powder (NLP) or Neem Seed Powder (NSD) at 100gCPP/10 Litre soil, 90gCPP+30gNSP/10 Litre soil, 80gCPP+20gNSP/10 Litre soil, 70gCPP+30gNSP/10 Litre of soil, 90gCPP+10gNLP/10 Litre soil, 80gCPP+20gNLP/10 Litre soil, 70gCPP+30gNLP/10 Litre soil were incorporated into potted naturally infested soil in the screen house, at 14 d before planting. All treatments significantly (p&lt;0.05) reduced plant-parasitic nematode population. Soil treatment with Cassava Peel Powder in combination with Neem Leaf Powder at 70gCPP+30gNLP/10 Litre of soil recorded the most effective control for soil and root nematodes associated with sugarcane in the two screen house trials. The soil amendment also supported the good vegetative growth and yield of sugarcane, which is an indication of its capability to improve soil fertility.

Comportamiento de nematodos fitoparásitos en dos sistemas de cultivo de tomate convencional en Costa Rica

&lt;p&gt;Esta investigación se realizó en los cantones de Grecia (tomate asociado con café) y Heredia (tomate en monocultivo) de la Región Occidental de Costa Rica, durante setiembre del 2012 y febrero del 2013. Los muestreos mensuales consistieron en recolectar suelo y raíces de tomate en monocultivo y áreas agrícolas con café. Mediante el método centrifugación - flotación se extrajeron, identificaron y cuantificaron los nematodos presentes. Los géneros (en suelo y raíces) fueron Meloidogyne, Helicotylenchus, Criconemoides, Pratylenchus, Aphelenchus.&lt;/p&gt;&lt;p&gt;Los primeros meses después del trasplante (DDT) las poblaciones de fitonematodos fueron bajas. A partir del cuarto mes DDT en áreas en asocio, las muestras de suelo sin oxamil, presentaron aumentos en poblaciones de Meloidogyne (48 a 7300 individuos) y Helicotylenchus (234 a 2100), mientras que en áreas con oxamil, las poblaciones de Meloidogyne se incrementaron de 50 a 2800. En raíces de tomate de áreas sin oxamil, se incrementaron las poblacionales de Meloidogyne (1625 individuos a 59200) y Helicotylenchus (2175 a 3800); y en zonas con oxamil, las poblacionales de Meloidogyne aumentaron de 3288 a 68467.&lt;/p&gt;&lt;p&gt;El tomate en monocultivo, a partir del cuarto mes DDT no presentó poblaciones de Meloidogyne en suelo, mientras que Helicotylenchus varía de 97 a 123. En raíces, las poblaciones de Meloidogyne varían de 17 a 52, y para Helicotylenchus de 405 a 392.&lt;/p&gt;&lt;p&gt;La presencia de agallas por Meloidogyne se hace más evidente al asociarse tomate con café, aumentando los niveles hasta el 90%. En áreas de tomate en monocultivo no se presentó agallas ni poblaciones de Meloidogyne.&lt;/p&gt;

Dynamics of plant parasitic and free living nematode populations in sugarcane &lt;i&gt;Saccharum officinarum&lt;/i&gt; in Fiji

&#x0D; &#x0D; &#x0D; Parasitic nematodes are one of the main constraints in the production of sugarcane, Saccharum officinarum, in Fiji and other sugarcane-growing countries. Both plant parasitic and free-living nematodes are associated with roots of the plant, and the level of infestation affects both soil health and cane yield. This study examined the dynamics of plant parasitic and free-living nematode populations in sugarcane crops in Drasa Estate, Lautoka, Fiji. Soil samples to quantify nematode populations were collected ve times during the crop cycle. There was an exponential increase in the plant parasitic nematode population with time after planting (nematode population=64.316e0.0112x; R2=0.56, x=days after planting). However, the increase was not consistent among the different nematode groups. Significant increases in Lesion (P&lt;0.05), Rootknot (P&lt;0.05), Spiral (P&lt;0.01), and Ring (P&lt;0.03) nematode populations were found but not for Reniforms (P&gt;0.05). Populations of free-living nematodes built up 90 days after planting and remained elevated in the ratoon crop. Populations of parasitic nematodes increased with the growth of cane (as measured by cane height) with increases occurring faster in the ratoon than in the plant crop (P=0.001). The number of free-living nematodes may have affected population growth of parasitic nematodes.&#x0D; &#x0D; &#x0D;

Effects of Fertilizer, Nematicide, and Tillage on Plant–Parasitic Nematodes and Yield in Corn and Soybean

Core Ideas Tillage decreased plant–parasitic nematode population densities during portions of the study. Fertilizers did not help manage plant–parasitic nematode population densities. Manure application increased both corn and soybean yields. Soybean response to NPK and NPKS was more positive in a lower yielding environment. Soybean cyst nematode (SCN, Heterodera glycines) is the most damaging pathogen of soybean [Glycine max (L.) Merr.] in the United States and plant–parasitic nematodes such as Pratylenchus (lesion nematode) and Helicotylenchus (spiral nematode) commonly infect corn (Zea mays L.). There are few management options for these nematodes, so understanding how common agronomic practices affect these nematodes is critical. Therefore, a series of 2‐yr experiments were conducted in corn and soybean production. Long‐term conventional tillage (CT) and minimum tillage (MT) treatments were in place at the study site. Fertilizer and granular nematicide—for assessing crop damage by nematodes—treatments were applied: (i) untreated control, (ii) NPK, (iii) NPKS, (iv) liquid swine manure, (v) nematicide without fertilizer, and (vi) NPKS with nematicide. Lesion nematode and SCN densities were greater in MT than CT during portions of the study, but tillage did not affect spiral nematodes. Corn yield was 8% greater in CT than MT in the first phase of the rotation, but tillage did not significantly affect soybean yield. None of the fertilizers—manure, NPK, or NPKS—reduced plant–parasitic nematode densities compared to control. Manure consistently increased corn and soybean yields. The NPK and NPKS were beneficial for corn, but inconsistent for soybean yields. There was some evidence that soybean yield response to fertilizers was greater in more stressed environments, such as with more SCN pressure. Because nematicide efficacy was inconsistent, it was not possible to make a definitive measurement of crop damage by plant–parasitic nematodes in this study.

Development of Plant-Parasitic Nematode Populations on Forage Crops under Field Conditions

The continuous increase in cost and scarcity of mineral fertilizers resultingfrom the use of high-cost energy sources has renewed interests in organic recyclingand biological nitrogen-fixation to improve soil fertility and productivity. Foragelegumes can fix nitrogen from atmosphere which has the merit to offer nitrogen forboth crop production and soil fertility. However, plant-parasitic nematodes (PPNs)interactions with leguminous crops can be agronomically damaging under variousconditions. The present study examined population development of each of thePPN genera Meloidogyne spp., Paratrichodorus spp., Criconemella spp.,Pratylenchus spp., Tylenchorhynchus, and Tylenchus spp. on fourteen legumecultivars (i.e. 'Florida' red clover, 'Nolin' red clover, 'Kenland' red clover, 'Kenstar'red clover, 'Tibbee' crimson clover, 'Dixie' crimson clover, 'Mt. Barker' Subterraneanclover, 'Amclo' arrowleaf clover, 'FL - 77' alfalfa, 'Abon' persian clover, 'Wood ford'big flower vetch, 'Seqrest' ball clover, 'Kondinin' rose clover, and 'Chief' crimsonclover). The nematode initial and final populations varied considerably among thelegume cultivars. Therefore, we adjusted for the rate of nematode multiplication byusing analysis of covariance. However, we could not use one of the statisticalmultiple comparison methods because each treatment had different mean ofsquares for the experimental error. Consequently, a matrix was designed to test thesignificance of nematode populations on the cultivars using the t-test. Using acomputer program, the exact (numerical) level of statistical significance fornematode densities among the cultivars could be established. Relatively lowerpopulations of the nematode genera were found on 'FL-77' alfalfa plants.

The role of plant parasitic nematodes on productivity reduction of banana and tomato in East Kalimantan, Indonesia

Suyadi, Rosfiansyah. 2017. The role of plant parasitic nematodes on productivity reduction of banana and tomato in East Kalimantan, Indonesia. Asian J Agric 1: xxxx. Plant parasitic nematode is one of the most limiting factor of agricultural ecosystem productivity in East Kalimantan, but their occurrence in agricultural field as a crop’s pest generally undistinguished, due to their microscopic size and their existence wrapped in the roots or soil particles. However, plant parasitic nematodes might cause yield loss up to 75%, without showed any disease symptom on crop morphologically. Perennial crop and annual crop under intensive cultivation usually experience high yield loss due to plant parasitic nematodes, if crop protection management was not implemented properly. This research aimed to determine the role of plant parasitic nematodes in reducing crop’s productivity in East Kalimantan, in relation to agricultural practices implemented by farmers. A descriptive research and comparative analyses were implemented to determine the role of plant parasitic nematode on yield reduction of banana and tomato as the indicator of productivity. Based on the field observation related to pest management in East Kalimantan, it was determined that plant parasitic nematode existence was neglected by farmers and no significant effort was implemented to control plant parasitic nematodes population. Therefore, low productivity of agricultural ecosystem in East Kalimantan was reported by Statistical Office, and it was not only caused by soil fertility problems, in some crops it was also the impact of population outbreak of plant parasitic nematodes. The first ranking three genera of plant parasite nematodes observed in East Kalimantan were Meloidogyne, Radhopholus, and Rotylenchulus, respectively. Meloidogyne and Rotylenchulus were major pest on vegetables, and caused yield loss &gt;50% on tomato. While, genus of Radhopholus was the major pest on banana, and caused yield loss &gt;75% on banana.

Relationship between soil organic matter and nematodes in sugarcane fields

Sugarcane plays an important socio-economic role in northeastern Brazil. However, the low yield in this region is associated with several factors (e.g. frequent occurrence of plant-parasitic nematodes). In order to observe the influence of soil organic matter on the nematodes, this study aimed to characterize the spatial nematode distribution in a sugarcane field. The study was carried out in Goiana - Pernambuco State (Brazil), fifty days after sugarcane cutting (10 days after vinasse application). The sampling scheme consisted of a regular 60 × 50-m grid, 10 m spaced, through 0 to 0.2 m depth. Spatial distribution was evaluated by semivariograms fit and performed by ordinary kriging interpolation for mapping. Exponential and spherical models promoted the best fit to semivariograms, resulting in ranges from 16 to 19 m. There was a strong negative correlation between soil organic matter and plant-parasitic nematode population density. Free-living nematodes had a similar distribution pattern as soil organic matter content. These results indicated that soil organic matter had important effects on spatial distribution of both plant-parasitic and free-living nematodes.

Effect of Previous Rotation on Plant Parasitic Nematode Population in Peanut and Crop Yield

Core Ideas A diverse crop rotation reduces soil parasitic nematode population. Impact of previous rotation can persist for multiple years. Wheat yield was greater after continuous peanut than yield of rotations including corn and cotton. Crop rotation is an important part of peanut (Arachis hypogaea L.) production systems to maintain yield through avoidance of plant parasitic nematodes and diseases. Research was conducted at two locations in North Carolina to determine changes in plant parasitic nematode populations and peanut yield in 2013 following a rotation sequence that included two cycles of corn (Zea mays L.) followed by wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] (2007–2010), corn (2011), and cotton (Gossypium hirsutum L.) (2012). Prior to rotations from 2007 to 2013, both short and long rotations of corn, cotton, peanut, and soybean were planted in these plots from 2001 to 2005. Decreases in populations of root knot nematode (Meloidogyne spp.) and stunt nematode (Tylenchorhynchus spp.) from 2006 to 2013 were the greatest when peanut was grown continuously from 2001 to 2006. Yields of corn, cotton, soybean, and wheat (2007–2012) were not affected by rotation from 2001 to 2006 at one location. However, at a second location wheat yield during 2008 and 2010 was greater following continuous peanut from 2001 to 2006 than yield following other rotations. Corn yield in one year following continuous peanut was greater than yield following several other rotations with fewer years of peanut or soybean. While peanut yield in 2006 was affected by rotation sequence in previous years (2001–2005), after 6 years of rotation from 2007 to 2012 peanut in 2013 did not differ in yield regardless of rotation from 2001 to 2006. These data indicate that developing adequate diversity of rotation can decrease plant parasitic nematode populations to levels that allow high peanut yield regardless of rotation history.

Confirmation of bioactivities of active ingredients of nemarioc-AL and nemafric-BL phytonematicides

ABSTRACTNemarioc-AL and Nemafric-BL phytonematicides consistently reduced populations of plant-parasitic nematodes. The contribution of juvenile hatch inhibition to the overall reduction of the nematode numbers by the two phytonematicides, with cucurbitacin A and B as active ingredients, respectively, remains undocumented. The objectives of this study were to examine (i) the response of Meloidogyne incognita second-stage juveniles (J2) hatch to increasing concentration of cucurbitacins A and B, (ii) the potential saturation of J2 hatch when exposed to cucurbitacins for extended incubation periods, (iii) the minimum inhibition concentration for J2 hatch and (iv) the reversibility of J2 hatch inhibition.. Eggs of M. incognita were exposed to a series of purified cucurbitacin A and B concentrations over five incubation periods of 24, 48, 72 h and extended incubation periods of 7 and 10 days. Methanol-dissolved cucurbitacin A and B were each diluted and pipetted into well-plates making 11 concentrations, ranging from 0.0 to 2.5 µg.ml−1 water solvent. Juvenile counts were made after 24, 48 and 72 h, with those for saturation assessed at 7 and 10 days. Thereafter, treatments were diluted five times, incubated again for 5 days and counted to establish reversibility of J2 hatch inhibition. In all incubation periods, treatment effects were highly significant (P ≤ 0.01), with J2 hatch and cucurbitacin concentrations exhibiting quadratic relations. Minimum inhibition concentrations of the two cucurbitacins were between 1.13 and 1.40 µg.ml−1. Treatment effects for reversibility to J2 hatch inhibition were not significant (P > 0.05). In conclusion, J2 hatch inhibition could be one of the waysthrough which the two phytonematicides reduced population densities of Meloidogyne species.

Optimizing anaerobic soil disinfestation for fresh market tomato production: Nematode and weed control, yield, and fruit quality

Anaerobic soil disinfestation (ASD) has potential as an alternative to chemical-fumigation for controlling soilborne pathogens and pests. Previously, control of nutsedge was sub-optimal and the quantity of inputs for commercial production was an impediment to adoption. Field studies were conducted in Citra and Immokalee, Florida to assess the effects of ASD with reduced amendments and inclusion of a pre-emergent herbicide on weed and nematode populations, tomato yield, and fruit quality. Pre-plant soil treatments included ASD with 6.9m3ha−1 of molasses and 11Mgha−1 of composted poultry litter (CPL) (ASD0.5), ASD with 13.9m3ha−1 of molasses and 22Mgha−1 of CPL (ASD1.0), and chemical soil fumigation using Pic-Clor 60 (CSF). Subplot treatments were halosulfuron-methyl (Sandea®) herbicide and no herbicide application. ASD0.5 reached high and equivalent accumulation of anaerobic conditions as ASD1.0 during the three-week soil treatment in both locations. Root galling and plant-parasitic nematode population at harvest in ASD treatments were similar in nematode suppression to CSF in both locations, while ASD1.0 resulted in higher non-parasitic nematode populations in soil compared to CSF in Citra. In Citra, ASD treatments did not differ from CSF in total marketable fruit yield; however, ASD0.5 resulted in higher total yield of extra-large fruit than CSF and ASD1.0. In Immokalee, no difference was observed in total marketable yield between ASD0.5 and CSF, whereas ASD1.0 produced 26.3% and 20.4% higher total marketable yield than that of CSF and ASD0.5, respectively. ASD treatments had no impact on fruit quality attributes including color, firmness, pH, total soluble solids, and dry matter content. Herbicide application improved nutsedge control and had no negative impact on the development of anaerobicity in ASD-treated plots, while total marketable yield and fruit quality were not impacted by herbicide treatment in either location. Despite some variations between the two locations, reduced application rates of CPL and molasses produced results similar to the full rates of amendment as well as the fumigation treatment. Overall, combining ASD with an herbicide had no negative impacts on crop production and resulted in improved weed control.

The Mesostigmatid Mite Protogamasellus mica, an Effective Predator of Free-Living and Plant-Parasitic Nematodes

Protogamasellus mica was extracted from a sugarcane field in Australia and cultured on bacterial-feeding nematodes. Studies with various nematodes in laboratory arenas showed that one mite and its progeny reduced nematode numbers by between 26 and 50 nematodes/day. A bacterivore (Mesorhabditis sp.), a fungivore (Aphelenchus avenae), and two plant parasites (root-knot nematode, Meloidogyne javanica and root-lesion nematode, Pratylenchus zeae) were all reduced at much the same rate despite the fact that the nematodes are quite different in size and motility and belong to different trophic groups. When sugarcane was grown in the greenhouse for 8 wk, stunt nematode (Tylenchorhynchus annulatus), a plant parasite that feeds ectoparasitically on roots, was almost eliminated from pots inoculated with the mite, and numbers of microbivores and root-lesion nematode were markedly reduced. Huge reductions in nematode populations were also observed when mites were added to microcosms containing small quantities of defaunated soil. These results show that P. mica multiplies rapidly when nematodes are available as a food source and has the capacity to play a role in regulating populations of both plant-parasitic and free-living nematodes. Future research should focus on understanding the crop and soil management practices required to enable this mite and other predatory species to thrive.

Cover Crop Management in Vineyards of the Lower Orange River Region, South Africa: 2. Effect on Plant Parasitic Nematodes

This study was conducted as part of a larger investigation into the effect of management practices on selected sown cover crops and the effects thereof on grapevine performance. The aim of this study was to determine the effect of these cover crops on plant parasitic nematode populations under natural field conditions. The trial site was in an own-rooted Sultanina vineyard situated in the Lower Orange River of the Northern Cape Province. Three management practices were applied selectively to ten cover crop species, with two control treatments consisting of weeds. Nematodes were monitored for a period of four years. ‘Saia’ oats were indicated as being poor hosts to both root-knot and root-lesion nematodes, while ‘Overberg’ oats showed poor host status against ring nematodes. ‘Midmar’ ryegrass and ‘Paraggio’ medic were also poor hosts for root-knot nematodes, while grazing vetch appeared to be a good host for root-knot nematodes. The most notable result from this study was the relatively high numbers of all three nematodes on the vine row, as opposed to the inter-row where cover crops were established. This indicates that vines were much better hosts for these nematodes than the cover crops. It is recommended that if more definite trends are to be observed, Brassica species, which have direct toxic/repellant effects on nematodes, should be tested.