Nematicide Treatments Research Articles

Improving the Efficacy against Cucumber Root-knot Nematode and Alleviating the Phytotoxicity of Fluopyram by Optimizing the Application Method

The root-knot nematode disease (RKN) caused by Meloidogyne incognita is a devastating threat to the production of crops, especially greenhouse vegetables. Fluopyram, a new nematicide, has been widely used by root drenching one-by-one plants for the management of RKN. However, as a common non-fumigation nematicide, its distribution in soil was often the key limiting factor that determined the efficacy and efficiency. To optimize the utilization of fluopyram against RKN, the control efficacy of application methods including blending-of-soil, root-irrigation, drip-irrigation, and furrow-irrigation and the correlation between nematicide distribution and efficacy were studied. The toxicities of fluopyram and abamectin to nematodes collected from different sources and backgrounds exhibited limited differences from crop and region. Compared to the control, all nematicide treatments reduced root galling by M. incognita in cucumber and increased the yield of cucumber. Blending-of-soil treatment and root-irrigation treatment were more beneficial for increasing the distribution area of nematicides in soil, then promoting the control efficacy of nematicides against RKN and improving cucumber production. This work showed that the application of fluopyram by blending-of-soil has the same efficacy as by root-irrigation in controlling RKN in cucumber production, moreover is more efficient and can be an alternative option.

Fumigation Using 1,3-Dichloropropene Manages Meloidogyne enterolobii in Sweetpotato More Effectively than Fluorinated Nematicides.

Meloidogyne enterolobii is an emerging global threat and is damaging to sweetpotato (Ipomoea batatas) production in the southeast United States. Nematicide application is one of the few management strategies currently available against this nematode, and field testing is urgently needed. The objective of this study was to assess common nematicides for management of M. enterolobii and nontarget effects on free-living nematodes in sweetpotato field production. Treatments were (i) untreated control, (ii) fumigation using 1,3-dichloropropene, or at-transplant drench of fluorinated nematicides (iii) fluazaindolizine, (iv) fluopyram, or (v, vi) fluensulfone at 2 or 4 kg a.i./ha. In 2022, a field trial was conducted under severe M. enterolobii pressure and was repeated in 2023 in the same location without treatment rerandomization. Fumigation using 1,3-dichloropropene (1,3-D) was the only consistently effective nematicide at improving marketable yield relative to control and also consistently reduced most storage root galling measurements and midseason Meloidogyne soil abundances. Fluensulfone at 4 kg a.i./ha consistently improved total yield but not marketable yield, whereas fluensulfone at 2 kg a.i./ha, fluazaindolizine, and fluopyram did not improve yield. Each fluorinated nematicide treatment reduced at least one nematode symptom or nematode soil abundances relative to control, but none provided consistent benefits across years. Even with 1,3-D fumigation, yield was poor, and none of the nematicide treatments provided a significant return on investment relative to forgoing nematicide application. There were minimal effects on free-living nematodes. In summary, 1,3-D is an effective nematicide for M. enterolobii management, but additional management will be needed under severe M. enterolobii pressure.

METHOD OF ASSESSING THE NEMATOCIDAL EFFECTIVENESS OF A BIOPREPA-RATION BASED ON PREDATORY MICROMYCETE AGAINST THE POTATO STEM NEMATODE

Aim – Studing of methods for determining the effectiveness of Nematophagin BT against potato stem nematode in the laboratory. Materials and methods. For the experiment, potato tubers with signs of damage by the stem nematode Ditylenchus destructor Thorne, 1945 were selected. The method of treatment of cut potato tubers with the preparation was used. It was compared with the method of treatment of whole tubers in the laboratory. The effect of the microbiological nematicidal preparation (Nematofagin BT) developed by ITI Biotechnology of NAAS was determined. The effectiveness of the microbiological preparation of nematicidal action (Nematofagin BT), developed by ITI Biotechnology of NAAS, was determined. The active ingredient of the drug is a microscopic fungus-predator Arthrobotrys oligospora strain 12, the initial culture of which is deposited in the collection of microorganism cultures of the D.K. Zabolotny Institute of Microbiology and Virology of the National Academy of Sciences of Ukraine F100047. Results. The methods of laboratory evaluation of the nematicidal effect of the biological product against potato stem nematode are described. In laboratory conditions, to determine the effectiveness of the drug, it is more informative to use cut tubers that have been infected with stem nematode. This method requires much more time to set up, but the bioagent has bigger accessibility to the pest. The use of whole tubers is less labor-intensive, but there is a possibility of using uninfected material in the experiment. The expediency of using these methods in laboratory conditions for the selection of active strains and determination of their effectiveness is shown. Conclusion. The method of nematicidal treatment of cut tubers with established infection of stem nematode is more informative than the use of whole tubers. It is advisable to analyze for damage to potatoes by nematodes when using pieces of affected potatoes from 3 to 7 days after treatment with a 3% solution of the biological product with an exposure of 5 hours. In laboratory conditions, both methods of treatment of cut and whole tubers with the preparation can be used to test the effect of Nematophagin BT on potato stem nematode. Nematophagin BT showed nematicidal activity against potato stem nematode in laboratory conditions.

Performance of biological and chemical nematicides in different soils to control Meloidogyne incognita in tomato plants

AbstractThree 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.

Evaluation of fluopyram for disease and root knot nematode control along with yield response on peanut

Efficacy of in-furrow application of fluopyram + imidacloprid alone or followed by fluopyram + prothioconazole at-pegging and aldicarb for managing peanut root-knot nematode populations, root and pod galling due to nematodes, and yield, along with non-target effects on leaf spot diseases and stem rot were compared on the root-knot susceptible cultivar Georgia-06G over seven years on an irrigated site with an established population of Meloidogyne arenaria race 1. In all years, fungicides were applied to all plots following a Peanut Rx application schedule. Root-knot nematode populations, nematode damage, and yield along with leaf spot severity and stem rot incidence significantly differed among years; except for nematode populations, these measured variables also differed by nematicide treatment. Averaged over years, galling and root damage was significantly reduced with aldicarb compared to the no-nematicide control but not with either of the fluopyram treatments. While similar late-season root-knot nematode populations were noted for all nematicide programs and the non-treated control, pooled over years, significant yield gains were obtained with aldicarb and fluopyram programs with the two-treatment program providing greater yields than the aldicarb treatment. Leaf spot severity, averaged over years, was similar in aldicarb and control treatments; however, both fluopyram treatments had significantly lower leaf spot severity than the aldicarb treatment. Stem rot incidence did not differ among nematicide treatments. In addition, pooled over years, there was a negative relationship between juvenile populations and yield, but this was relatively weak. Weather, particularly extreme rain conditions, impacted yield directly as well as indirectly by affecting leaf spot severity and nematode activity.

Use of Visible Spectral Index and Soybean Plant Variables to Study Hidden Nematicide Phytotoxicity

Significant crop losses are due to plant-parasitic nematodes. Nematicides are expensive and potentially toxic to men, the environment, and plants. This study evaluated the hidden phytotoxicity effects of nematicides in soybeans. Two soybean cultivars (8473RSF and M7198IPRO) were evaluated with five nematicide treatments (biological, cadusaphos, abamectin, fluensulfone, and an untreated control) for changes in chlorophylls, biometrics, and spectral (TGI visible spectral index captured with a smartphone camera) variables to determine and anticipate the identification of plant stresses. Evaluations occurred 33, 47, and 66 days after sowing (DAS). The a/b chlorophyll proportion was greatest for M7198IPRO and cadusaphos. The chlorophyll variables did not present significant interactions or differences at 47 DAS, indicating that possible nematicide effects were transient and should be evaluated earlier than 33 DAS. Leaf area, leaf mass, and shoot mass were smaller for 8473RSF and outstanding for abamectin and fluensulfone. The response of the spectral index did not present significant interaction among the factors; however, at 33 and 47 DAS, the index was low for 8473RSF and lowest for cadusaphos only at 33 DAS. The correlations between the spectral index and other variables were significant and moderate for soybean total leaf area. Although no apparent phytotoxicity symptoms caused by nematicides were observed, the visible vegetation index generated using a smartphone camera can still improve crop management solutions.

Plant growth promoting Bacillus species elicit defense against Meloidogyne incognita infecting tomato in polyhouse.

The effects of four nematicidal rhizobacterial isolates; Bacillus subtilis, Bacillus pumilus, Bacillus megaterium, and Bacillus cereus on infection and multiplication of root-knot nematode, Meloidogyne incognita on tomato were compared with the application of a chemical nematicide, fluopyram 34.48% SC (Velum Prime). The bio-efficacy trial conducted in pots preinoculated with the above isolates followed by M. incognita inoculation resulted in a significant reduction in percent root galling viz. 91.95 in B. subtilis, 84.21 in B. pumilus, 83.70 in B. megaterium, and 81.8 in B. cereus, at 75 days after inoculation (DAI). The reproduction factor of the nematode was the lowest (15.83) in B. subtilis, followed by B. pumilus (21.00), compared with 48.16 in control, with enhanced photosynthetic and transpiration rates. The mechanism of induced resistance was assessed usingquantitative reverse-transcription polymerase chain reaction(qRT-PCR) for quantification of three key defense genes (PR-1b, JERF3, and CAT) at 0,2,4,8 and16 days DAI. The defence genes, PR-1b, JERF3, and CAT were expressed at 2.5-7.5-folds in rhizobacterialtreated plants, but not in nematicide treatment. The defense enzymes viz., super oxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (PO), and phenylalanine ammonia lyase (PAL) when quantified (μmol/mg protein) showed an increase from 1.5 to 17.5 for SOD, 2.1 to 7.8 in PPO, 1.8 to 10.2 in PO, and 1.8 to 8.7 in PAL during 0 to 16 DAI, in rhizobacteria-treated plants.

Efficacy of five nematicides against root-knot nematode when applied via single and double drip tapes in a Florida sandy soil.

The efficacy of drip-applied nematicides depends on adequate product distribution, which can be difficult in sandy soils. Three new non-fumigant nematicides (fluazaindolizine, fluensulfone, fluopyram), together with two old nematicides, oxamyl and metam potassium, were evaluated when applied via single and double drip tapes to control root-knot nematode in cucumber and squash in Florida between February 2020 and December 2022. Nematicide applications via double drip tapes resulted in lower root gall infection (and tend to have higher yield) as compared to a single tape for fluopyram, but no difference was noted between single and double tapes for oxamyl and fluazaindolizine. Fluensulfone response was somewhere in between and metam potassium had higher squash yield when applied with double tapes. Root-knot infection was higher in cucumber than in squash, and metam potassium had the highest yields and lowest nematode infection compared to other nematicide treatments. The benefit of double versus single drip tapes depended on the type of nematicide that was applied and was evident for nematicides that have poor water solubility like fluopyram. Some benefit was noted for metam potassium, but no or limited benefit was noted for oxamyl, fluazaindolizine and fluensulfone. © 2023 Society of Chemical Industry.

Combined effects of Ascophyllum nodosum seaweed extract and biological control agents on Meloidogyne javanica in soybean

This study aimed to investigate the efficacy of Ascophyllum nodosum extract, in combination or not with biocontrol agents, in the management of Meloidogyne javanica in soybean, assess treatment effects on soil biological activity, and determine the total phenolic content of the extract. The experiment was conducted according to a 5 × 2 factorial design, with three biocontrol agents (Bacillus methylotrophicus, Pochonia chlamydosporia, and Trichoderma harzianum), a chemical nematicide (abamectin, positive control), and an untreated (negative) control, each in the presence and absence of A. nodosum extract. Treatments included six replications. Nematode inoculation (2000 eggs + juveniles of M. javanica per plant) was performed at the time of sowing. Sixty days later, plants were evaluated for height, shoot weights, numbers of M. javanica eggs and J2 extracted from roots, and soil biological activity. Biological and chemical nematicide treatments were effective in reducing M. javanica multiplication. There was a synergic effect of A. nodosum extract on M. javanica multiplication for the treatments with A. nodosum + T. harzianum, A. nodosum + abamectin (Trial 1) and A. nodosum + P. chlamydosporia (Trial 2). B. methylotrophicus and T. harzianum treatments enhanced plant development and soil microbial biomass carbon. Higher values of soil basal respiration and metabolic quotient (qCO2) were observed in the A. nodosum + abamectin treatment. A. nodosum extracts at 75 g L−1 had a total phenolic content of 13 255 and 11 608 mg GAE 100−1 g in Trials 1 and 2, respectively.

Effect of Different Rates, Application Timing, and Combination of Nonfumigant Nematicides in Control of Meloidogyne incognita in Watermelon

The use of plasticulture systems, which consist of raised beds, plastic mulch, and drip irrigation, for watermelon production has increased in the Southern United States in recent decades. The root-knot nematode (RKN), Meloidogyne incognita, is a significant pathogen of watermelon production in plasticulture systems and can cause varying levels of yield loss depending on the nematode population density if not properly controlled. A few new nonfumigant nematicides (fluensulfone, fluazaindolizine, and fluopyram) have emerged in the last decade to help manage RKNs. A 2-year field study was conducted to examine the impact of different rates, application timing (i.e., days before transplanting, at transplanting, and days after transplanting), and combinations of these new nematicides and an older one (oxamyl) in control of RKN in watermelon cultivar Fascination. The nematicide treatments, except for a single-time application of oxamyl in 2019 and 2020, significantly reduced root galling compared with the untreated check. Similarly, all treatments, except a single application of oxamyl in 2020, resulted in a lower soil population level of M. incognita than the untreated check. All nematicide treatments, except a single application of fluensulfone and a two-time application of fluopyram at a half-recommended rate, increased fruit yields when compared with the untreated check. Overall, the drip application of new chemistries, known as 3-F nematicides, has been shown to be a useful option for RKN management in watermelon. At-planting application of fluazaindolizine or fluopyram and two-time applications of oxamyl based on the manufacturer's recommended rate show potential to prevent crop loss.

Sustainable management of the potato cyst nematode, Globodera rostochiensis, with two microbial fermentation products.

Potato cyst nematodes (PCN) cause an overall 9% yield loss of total potato production worldwide. Research on sustainable management of PCN is still under progress. Two microbial fermentation products (MFPs) from Alltech, a proprietary blend formulated with a bacterial fermentation media and a Cu component (MFP5075), and a microbial based product (MFP3048), were evaluated against the PCN Globodera rostochiensis. In laboratory tests, effectiveness of the MFPs was recorded in terms of PCN juveniles (J2) hatching from cysts, J2 mortality and their attraction toward potato roots using pluronic gel. Greenhouse trials were conducted to study the effect of the products on PCN infestation in potato plants and a pilot scale experiment was conducted to study the impact of these MFPs on nematode biodiversity in garden soil. All treatments were performed within a concentration range of 0, 0.5, 1, and 2% (v/v) MFP5075 and 2, 6, 10, and 20 g/10 ml (w/v) MFP3048. The attraction assay, juvenile hatching and the PCN infestation in plants results were compared with those in an untreated control and a commercial nematicide (Nemguard™) treatment. After 24 h of treatment with 0.5 and 1% MFP5075, a 13-fold and 43-fold reduction, respectively, relative to J2 survival was recorded compared to that of untreated control. However, no J2 survived at 2% and above concentration of the MFP5075 treatment. Treatment with MFP3048 was effective in causing mortality of J2 only after 48-h. In the attraction assay, a 20-fold and 8-fold reduction in number of J2 attracted toward potato roots was observed, when treated with MFP5075, compared to the untreated and the Nemguard™ treatment, respectively. Subsequently, 30–35 PCN cysts were treated with both products dissolved in potato root diffusate and the results were recorded in terms of number of J2 hatched in each treatment after 10 days. No J2 hatched in the MFP5075 treatment, whereas mean numbers (±SE) of 243 ± 11.5, 30 ± 2.5, and 1.3 ± 0.6 J2 were noted in the untreated control, MFP3048, and the Nemguard™ treatment, respectively. The treatment with the MFPs compromised the integrity of the unhatched J2, which looked granular, whereas the internal organs of the unhatched J2 could be clearly identified in the untreated control. In plant infestation studies, treatment with MFP3048 and MFP5075 caused 90.6 and 84.9 percent reduction in PCN infestation, respectively, in terms of cysts developed on roots compared to untreated control. Overall, results indicate that the MFPs could potentially provide a promising alternative for sustainable PCN management.

Bio-Management of Root-Knot Nematodes on Cucumber Using Biocidal Effects of Some Brassicaceae Crops

Biofumigant and crop sequencing are effective and safe control system activators that maintain soil fertility and reduce pest populations. The study goals were to find new pesticide-free therapies for root-knot nematode management on cucumbers to maintain high yields and protect the environment and human health. In 2018 and 2019, the research employed a fully randomized block design under field conditions with five treatments and control: two bio- fumigants, cultivation of cucumber after broccoli plantlets incorporation (BPI) and radish plantlets incorporation (RPI), two crop sequence treatments (cultivation after broccoli (BCS) and radish (RCS), and nematicide treatment). Cucumber cultivation after BPI treatment exhibited the best horticultural traits, which reflected positively on early and total productivity. The increased yield was gained by suppressing all nematode parameters, the number of nematode larvae, galls, and egg masses, as well as egg hatching reduction. The most effective biocides, total phenols, myrosinase activity, total glucosinolates (GSLs), and isothiocyanates (ITCs) in brassica crops were estimated for their pesticide properties. The highest amount was released with BPI treatment, compared to adult plants and radish in its two stages. The bio-managed treatments revealed superior effectiveness compared to nematicide application and control to suppress the nematode population while enhancing cucumber growth and production.

Meta-Analysis of the Field Efficacy of Seed- and Soil-Applied Nematicides onMeloidogyne incognita and Rotylenchulus reniformis Across the U.S. CottonBelt.

Meta-analysis was used to compare yield protection and nematode suppression provided by two seed-applied and two soil-applied nematicides against Meloidogyne incognita and Rotylenchulus reniformis on cotton across 3 years and several trial locations in the U.S. Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in furrow, and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response ([Formula: see text]), with an average increase of 176 and 197 kg/ha relative to the nontreated control in M. incognita and R. reniformis infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables (cultivar resistance [M. incognita only], nematode infestation level, nematicide treatment, application method, trial location, and growing season) were used depending on nematode species. In M. incognita-infested fields, greater yield protection was observed with nematicides applied in furrow and with seed-applied + in-furrow than with solo seed-applied nematicide applications. Most notable of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared with thiodicarb. In R. reniformis-infested fields, moderator variables provided no further explanation of the variation in yield response produced by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in M. incognita- and R. reniformis-infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in M. incognita- and R. reniformis-infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U.S. Cotton Belt.

The impact of fluazaindolizine on free-living nematodes and the nematode community structure in a root-knot nematode infested vegetable production system.

Fluazaindolizine is a novel sulfonamide nematicide that is currently under commercialization in various countries. Four trials (two in tomato, two in zucchini) were carried out over two growing seasons in a root-knot nematode (RKN; Meloidogyne incognita)-infested plastic house to test the effects of a single application of fluazaindolizine at 1000 and 2000 g ha-1 , on RKN, the resident nematode community and to estimate any side effects on the soil food web and soil ecological functions. The composition of the nematode community was evaluated at three sampling times, pre-treatment (before soil preparation), at planting (after nematicide application) and at harvest. Nematode abundance and nematode-based ecological indices, such as maturity indices, soil food web indices (Structure, Basal, Enrichment index) and metabolic footprints were calculated and compared between the untreated and nematicide treatments at various sampling times. In both crops the test rates of fluazaindolizine significantly reduced both the soil numbers of RKN as well as the observed root galling at harvest. Fluazaindolizine treatments showed a low impact on the numbers of other plant-parasitic nematodes, and at harvest the numbers of some ectoparasites as Telotylenchus even showed higher values within the nematicide-treated plots than in the untreated control. Overall, fluazaindolizine treatments neither decreased the bacterivorous, fungivorous or omnivorous nematode densities, nor reduced the maturity and soil food web indices. However, we observed some slight reductions in the structure index as well as increases in the basal index that might indicate some adverse impact on soil functions resulting from the nematicide application. Still those impacts were considered small compared to the impact of the soil preparation. Overall, fluazaindolizine showed a good level of selectivity towards RKN and therefore could become a useful tool within integrated nematode management approaches that also complements soil health and maintaining diversity in soil.

Biocontrol of Meloidogyne sp. on Tomato Plants by Selected Bacillus spp

Meloidogyne spp., are recognize as the most economically important worldwide. It is difficult to control Meloidogyne spp., because they have wide range of hosts. Due to the high toxicity of chemical nematicides, it is necessary to develop new control strategies. Our previous research showed that some Bacillus spp. effective as biocontrol agents of plant pests and diseases. They have multifunction, such as plant growth promoter, phosphate dissolving bacteria, etc. The aim of this research was to obtain the selected Bacillus spp. to control Meloidogyne spp., to enhance growth and yield of tomato. The treatments were 8 strains of Bacillus spp., Carbofuran, Meloidogyne spp. inoculated tomato and control. The Bacillus spp. have inoculated as seed treatment and seedling treatment before transplanting. The Meloidogyne spp. have inoculated on 4 weeks tomato plants. The parameters were disease development, multiplication of Meloidogyne spp., growth and yield of tomato. The results showed that Bacillus spp. reduced the number of galls, egg masses, eggs per egg mass and nematode per 300 g soil compared to the inoculated control, but the nematicide treatments was more effective to control Meloidogyne spp. Conversely, three strains of Bacillus spp. showed to enhance the growth and yield of tomato than Carbofuran.

Assessing the efficacy of alternative chemical and organic products against Meloidogyne spp. in sweetpotato

Root-knot nematodes (Meloidogyne spp.) are considered as the most serious nematode pest in the world and have been reported to cause up to 57–67 % crop yield losses in untreated conditions in Australia. Chemical control has been the most popular method to manage root-knot nematodes due to its high efficacy. However, ‘fenamiphos’ the most widely used active ingredient in nematicides, has recently been reviewed by the Australian Pesticides and Veterinary Medicines Authority and subsequently has been recommended for removal from the commercial market in Australia due to concerns about its potential to contribute to adverse environmental and human health impacts. Due to this pressure of nematicide restrictions, alternative chemical and organic formulations were assessed against root-knot nematodes in a sweetpotato field trial comparing with untreated control and chemical control ‘oxamyl’ (currently registered chemical for sweetpotato). Fluensulfone significantly reduced soil root-knot nematode numbers compared to other treatments, giving the highest marketable yield in this trial. Abamectin did not give significant root-knot nematode control or damage reduction. Organic nematicide treatments (garlic formulation and nutrient and microbial formulation) did not show a significant reduction of soil root-knot nematode numbers and root damage. No significant effect of nematicides was found on non-target organisms (soil bacteria and nematodes) at 24 weeks after planting.

Response to nematicide by cotton genotypes varying in reniform nematode resistance

AbstractReniform nematode (RN, Rotylenchulus reniformis Linford & Oliveria) is a parasite that reduces and limits cotton (Gossypium hirsutum L.) yields. At present, nematicides and crop rotations are the most effective management tool for producers. Our study investigated the use of six composite breeding lines that have quantitative trait loci (QTLs) for RN resistance and the interaction effect of a nematicide under high RN pressure. The study compared these genotypes in both a non‐RN field and a RN‐infected field under a Velum Total (active ingredients fluopyram and imidacloprid) treatment at Tennessee Valley Research and Extension Center near Belle Mina, AL. In both years, the breeding lines outyielded commercial controls and the parental lines in RN infested field with and without Velum Total. Five out of the six breeding lines contained both chromosome 21 (Renbarb1 and Renbarb2) resistant QTLs, which reduced RN egg numbers (P < .05) and produced higher yields than the commercial checks. These lines can be considered moderately resistant to RN. The remaining line contained one QTL Renbarb1, produced good yield, and is considered tolerant, despite the fact that it had high RN egg numbers. However, adding a nematicide treatment did increase yields in all material tested. Therefore, further work at increasing resistance from other genetic sources is needed to completely eliminate nematicide use.

African Rhino plantain clone (Musa AAB) behavior when using chicken manure as soil amendment and nematicides.

The effects of chicken manure as a soil amendment and the application of nematicides on plant characteristics, yield and foliar nutrient content of the African Rhino plantain clone were evaluated. Chemical properties of the soil were monitored after chicken manure application. Chicken manure, at a rate of 25 t/ha, was incorporated during soil preparation. The nematicide treatment Included the use of etoprop at planting, followed by oxamyl at six and 12 months after planting. The application of chicken manure significantly increased the height and diameter of the pseudostem, reduced the number of days from planting to shooting, and increased bunch weight, and yield per hectare. With the use of chicken manure a yield of 34,242 kg/ha was obtained. This yield represents a 33% increase over that of the treatment without chicken manure. The use of nematicides significantly diminished the number of collapsed plants and Increased plantain yield. The use of chicken manure Increased the foliar content of N and Ca whereas the use of nematicide had no effect on any of the nutrient foliar content. The chemical properties of the soil (pH; organic matter; electric conductivity; N, P, K, Ca and Mg content) were not affected by the use of chicken manure.

Nematicide Effects on Arthropods in Bermudagrass

In turfgrass systems, nematicides are a valuable tool for managing plant-parasitic nematode populations, but few studies have examined non-target nematicide effects on arthropods. Our study evaluated effects of turfgrass nematicide formulations of abamectin (Divanem SC), fluopyram (Indemnify), furfural (MultiGuard Protect EC), and fluensulfone (Nimitz Pro G) on arthropod populations in bermudagrass (Cynodon spp.; Poaceae). A randomized block design was used with 5 replications of the 4 nematicide treatments and an untreated control. Plots were 6 m2 with 0.6 m untreated borders between adjacent plots. Data were collected from 1.5 m2 subplots located in the center of the treatment plots. Nematicides were applied at labeled rates every 4 wk as a summer treatment program from 7 Jun to 30 Aug 2016 and from 24 Apr to 18 Jul 2017 at the University of Florida Plant Science Research and Education Unit in Citra, Florida, USA. Samples were collected before treatment and at 2 d, 14 d, 56 d, and 238 d after the final treatment. Data from each nematicide treatment were compared to the untreated data at each sample date using analysis of covariance with initial population counts serving as the covariate. Abamectin treatments significantly increased fungivore mite abundance relative to the untreated control at 2 sampling dates in 2016 and 3 sampling dates in 2017. Abamectin also decreased collembolan abundance significantly at 2 sampling dates in 2017. Fluopyram increased predatory mite abundance significantly at 3 sampling dates in 2016; decreased collembolan abundance significantly at 4 sampling dates in 2017; and significantly increased phytophagous insect abundance at 2 dates in 2017. Furfural and fluensulfone had low impacts on arthropod abundance. The results of this study suggest nematicides can impact arthropods in bermudagrass, which could affect organic matter decomposition and nutrient cycling processes.

Effect of fungal, oomycete and nematode interactions on apple root development in replant soil

BackgroundApple replant disease (ARD) is a phenomenon associated with poor tree establishment at sites where the same, or a closely-related species, has grown for at least 1–2 years. No single organism has been identified as the universal causal agent, but there is increasing evidence that multiple soil-borne plant pathogenic fungi and oomycetes form an ARD disease complex. Root damage caused by root lesion nematodes has also been implicated in facilitating the entry of pathogens into root tissues resulting in the development of severe ARD.MethodsWe used a reductionist approach to determine effects of one or more members of the ARD complex on ARD in a number of selected rootstock genotypes with contrasting characteristics. Through a 15-month pot-based experiment in which semi-selective biocides were applied to soil from a replant orchard, we investigated (1) the nature of the interactions (i.e. antagonistic, additive or synergistic) between different groups of soil biota and ARD severity, and (2) whether rootstock characteristics modify ARD severity.ResultsThere might be competitive interactions between oomycetes and fungal pathogens in infecting apple roots and hence subsequent ARD development. Controlling all three ARD components (oomycetes, fungi, and nematodes) led to the best root development. However, these effects on root development were not manifested in the above-ground tree development 15 months after treatment. Specific soil biocide treatments against fungi and oomycetes led to large changes in soil microbial communities whereas the nematicide treatment led to least changes. In spite of the observed ARD, comparing rhizosphere microbial sequences among treatments failed to reveal candidate pathogens for ARD.ConclusionsCandidate ARD oomycetes and fungal pathogens are likely to engage in competitive interactions among themselves in infecting apple roots. Although soil amendments affected soil microbiota, such effects appear to be very unpredictable.