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.

Management of Reniform Nematode in Cotton Using Winter Crop Residue Amendments Under Greenhouse Conditions.

Rotylenchulus reniformis (reniform nematode, RN) is among the most important nematodes affecting cotton. Cultural practices, such as rotation and soil amendment, are established methods for managing RN. Management may be enhanced if crop residue has biofumigant properties against RN. The objective was to evaluate the efficacy of winter crop amendments for managing RN in the greenhouse. Reniform nematode-infested soil was amended with dry or fresh organic matter (OM, 2% w/w) from winter crops - canola, carinata, hairy vetch, oat, or no crop. Cotton was subsequently grown in this soil. Independent of the crop, dry OM amendments were more effective than no amendment at managing RN, while fresh OM amendments were not. Soil and root RN abundances and reproduction factors were generally lower in Trials 1 and 3 for dry OM than fresh OM amendments or control without OM. In Trial 2, none of the OM treatments reduced RN parameters compared with no OM control. In general, when compared to plants without RN or OM, RN did not produce significant changes in growth parameters but did affect physiology (Soil Plant Analysis Development, or SPAD, values). In conclusion, dry OM amendments can help manage RN, crop growth does not always relate to RN abundances, and SPAD values could help indicate RN presence.

Reniform Nematode Management Using Winter Crop Rotation and Residue Incorporation Methods in Greenhouse Experiments.

Rotylenchulus reniformis (reniform nematode, RN) is an important pathogen in cotton production. Cultural practices such as crop rotation and biofumigation-management of soil pathogens by biocidal compounds from crop residues-may help manage RN. The objective of this study was to evaluate the efficacy of winter crops for RN management through combinations of rotation and crop residue incorporation in a cotton greenhouse experiment. A total of 10 treatments were evaluated in soil inoculated with RN: three winter crops (carinata, oat, or hairy vetch) grown in rotation with no shoot organic matter (OM) incorporated (1-3), fresh shoot OM incorporated (4-6), or dry shoot OM incorporated (7-9), and a fallow control (10). Roots were re-incorporated in all treatments except fallow. Subsequently, cotton was grown. Oat and fallow were better rotation crops to lower soil RN abundances at winter crop termination than hairy vetch and carinata. After the OM incorporation treatments and cotton growth, oat was generally more effective at managing RN in cotton than carinata or hairy vetch. Within each crop, incorporation treatment generally did not affect RN management. Cotton growth was not consistently affected by the treatments.

Belonolaimus longicaudatus management using metam potassium and fluensulfone in potato.

Belonolaimus longicaudatus (sting nematode) is an important pest in Florida potato production and is managed primarily by fumigation using 1,3-dichloropropene (1,3-D). Other effective nematicides are needed for more flexibility in managing this pest. The objective of this study was to evaluate fluensulfone, metam potassium, and mixtures of the two products, relative to 1,3-D and untreated control, for efficacy at managing sting nematode, and for non-target effects on free-living nematodes in potato. To test this objective, a small-plot field experiment was conducted in northeast Florida in 2020 and repeated in 2021. Metam potassium fumigation (390 kg a.i./treated ha)-with or without fluensulfone-managed sting nematode soil abundances but was phytotoxic to potato. Strategies that mitigate metam potassium phytotoxicity, such as reduced application rates, are needed before efficacy of metam potassium in this system can be determined. As a preplant soil spray, fluensulfone alone (403 g a.i./treated ha) did not manage sting nematode abundances and had an inconsistent effect on yield. Fumigation with 1,3-D (88.3 kg a.i./treated ha) was the only treatment that consistently managed sting nematode and increased potato yield. Nematicides did not consistently affect free-living nematodes.

Effects of Grass-Based Crop Rotation, Nematicide, and Irrigation on the Nematode Community in Cotton.

Plant-parasitic and free-living nematodes - bacterivores, fungivores, omnivores, predators - comprise the nematode community. Nematicide application and crop rotation are important tools to manage plant-parasitic nematodes, but effects on free-living nematodes and nematode ecological indices need further study. The nematicide fluopyram was recently introduced in cotton (Gossypium hirsutum) production and its effects on the nematode community need assessment. This research was conducted in 2017 and 2018 at a long-term field site in Quincy, FL where perennial grass/sod-based (bahiagrass, Paspalum notatum) and conventional cotton rotations were established in 2000. The objective of this research was to evaluate the effects of fluopyram nematicide, crop rotation phase, and irrigation on free-living nematodes and nematode ecological indices based on three soil sampling dates each season. We did not observe consistent effects of crop rotation phase on free-living nematodes or nematode ecological indices. Only omnivores were consistently negatively impacted by fluopyram. Nematode ecological indices reflected this negative effect by exhibiting a degraded/ stressed environmental condition relative to untreated plots. Free-living nematodes were not negatively impacted by nematicide when sod-based rotation was used.

Belonolaimus Longicaudatus Host Status and Pathogenicity on Sweetpotato.

Sting nematode is acutely damaging to a wide range of crops and is relatively common in sandy soils in the southeastern United States. Sweetpotato is an important crop in this region, and its production may be expanding to localities where sting nematode is an important pest. Despite this, the relationship between sweetpotato and sting nematode is not well-defined. Therefore, the objectives of this study were to assess (1) the relative host status of sweetpotato for sting nematode and (2) damage potential of sting nematode on sweetpotato in repeated greenhouse experiments. A known sting nematode host (field corn), a known poor host (sunn hemp), and sweetpotato cultivars susceptible ('Beauregard') and resistant ('Covington') to southern root-knot nematode were challenged with sting nematode. In both trials, field corn supported greater final soil sting nematode abundances than sunn hemp or either sweetpotato cultivar. Based on the average reproductive factor, field corn was confirmed as a susceptible host, whereas sunn hemp and sweetpotato were poor hosts. Sting nematode did not impair the growth of any crop, suggesting greenhouse conditions were not conducive to damage since field corn sustains damage in field conditions. These results suggest that sunn hemp and sweetpotato could be useful rotation crops for managing sting nematode, but future work is needed to assess sting nematode pathogenicity on these crops under field conditions.

Meta-Analysis of the Field Efficacy of Seed- and Soil-Applied Nematicides on Meloidogyne incognita and Rotylenchulus reniformis Across the U.S. Cotton Belt.

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.

Organic or conventional production system and nutrient rate affect the nematode community in carrot production.

Organic and conventional production are common in horticulture crops and each system may exert a different influence on the soil ecosystem, particularly the nematode community. Crop nutrient rate is an important choice in both production systems. The objectives of this study were to assess the impacts of (i) organic and conventional production systems and (ii) nutrient rate in both systems on the nematode community in carrot production. To investigate these objectives, field studies in organic and conventional production - which included fumigation with 1,3-dichloropropene - were conducted in North-Central Florida. In both production systems, nutrient rate treatments were 168, 224, 280, 336, and 392 kg N/ha. Poultry litter was the nitrogen source in organic production whereas synthetic, inorganic fertilizer was used in conventional production. All nematode trophic groups were consistently more abundant in organic than conventional production. The nematode community was more diverse and had greater trophic structure in organic production. Greater rates of organic nutrients increased enrichment opportunists (bacterivores and fungivores), but inconsistently across years. Conventional production had similar results except that only moderate nutrient rates increased fungivore abundances. Extreme enrichment opportunists (Rhabditis spp.) drove bacterivore trends in organic production whereas moderate enrichment opportunists (Cephalobus spp.) drove trends in conventional production. Nutrient rates did not affect omnivore-predators, herbivores, nematode community diversity, or structure in either system. In summary, type of production system, organic or conventional, exerts a strong influence on the nematode community, but nutrient rate has less consistent effects in horticulture production.

Meloidogyne incognita management by nematicides in tomato production.

Meloidogyne incognita (southern root-knot nematode, SRKN) is a major pest in tomato (Solanum lycopersicum) production in the Southeastern United States. Management has relied on fumigant and carbamate non-fumigant nematicides. New non-fumigant nematicides, such as fluopyram, are available and field evaluation of new nematicides is needed. The objectives of this research were to assess the efficacy of new (fluopyram) and established (oxamyl) non-fumigant nematicides as well as fumigation (1,3-dichloropropene) for (1) SRKN management, and (2) impacts on total soil abundances of non-target, free-living nematodes in field tests in Florida. Fumigation with 1,3-D consistently managed SRKN and, in two of three trials, increased yield relative to untreated. Oxamyl and fluopyram also had efficacy in managing SRKN, but were inconsistent from year to year. Oxamyl provided better root galling control than fluopyram in one of two trials, but otherwise those nematicides provided similar SRKN management and yield response. Supplementing 1,3-D fumigation with fluopyram did not improve SRKN management or yield relative to fumigation alone. Fumigation consistently reduced free-living nematode abundances relative to untreated. Oxamyl and fluopyram were more inconsistent, but always reduced total free-living nematode abundances when effective against SRKN. In summary, while non-fumigant nematicides provided some management of SRKN, fumigation continued to be the most consistent option. All nematicides had deleterious effects on free-living nematodes.

Nematicide influence on cotton yield and plant-parasitic nematodes in conventional and sod-based crop rotation.

Plant-parasitic nematodes (Rotylenchulus reniformis (reniform, RN), Helicotylenchus dihystera (spiral), and Mesocriconema ornatum (ring)) and yield were investigated in cotton phases of conventional (peanut-cotton-cotton) and sod-based (bahiagrass-bahiagrass-peanut-cotton) rotations with or without irrigation and fluopyram nematicide at a long-term research site, established in 2000, in Quincy, Florida, USA. Objectives were to determine impacts of nematicide application on cotton yield and evaluate effects of nematicide on plant-parasitic nematodes in these rotations in 2017 and 2018. Reniform nematode population densities were greater in conventional cotton than sod-based cotton. Ring and spiral nematode population densities were greater in sod-based cotton than conventional cotton. Plots receiving nematicide had increased RN population densities in preplant 2018 soil samples and spiral nematode population densities in preplant 2017, harvest 2017, preplant 2018, and harvest 2018 soil samples compared to untreated plots. Cotton seed yield in conventional rotation was increased by 18% following nematicide application in 2017 but decreased by 10% in sod-based rotation in 2018, relative to the untreated control. Sod-based rotation had greater cotton yield than conventional rotation in 2017 and 2018. Nematicide application did not improve cotton yield in sod-based rotation and was inconsistent in conventional rotation.Plant-parasitic nematodes (Rotylenchulus reniformis (reniform, RN), Helicotylenchus dihystera (spiral), and Mesocriconema ornatum (ring)) and yield were investigated in cotton phases of conventional (peanut­cotton­cotton) and sod-based (bahiagrass­bahiagrass­peanut­cotton) rotations with or without irrigation and fluopyram nematicide at a long-term research site, established in 2000, in Quincy, Florida, USA. Objectives were to determine impacts of nematicide application on cotton yield and evaluate effects of nematicide on plant-parasitic nematodes in these rotations in 2017 and 2018. Reniform nematode population densities were greater in conventional cotton than sod-based cotton. Ring and spiral nematode population densities were greater in sod-based cotton than conventional cotton. Plots receiving nematicide had increased RN population densities in preplant 2018 soil samples and spiral nematode population densities in preplant 2017, harvest 2017, preplant 2018, and harvest 2018 soil samples compared to untreated plots. Cotton seed yield in conventional rotation was increased by 18% following nematicide application in 2017 but decreased by 10% in sod-based rotation in 2018, relative to the untreated control. Sod-based rotation had greater cotton yield than conventional rotation in 2017 and 2018. Nematicide application did not improve cotton yield in sod-based rotation and was inconsistent in conventional rotation.

Nematicide efficacy at managing Meloidogyne arenaria and non-target effects on free-living nematodes in peanut production.

Meloidogyne arenaria (peanut root-knot nematode (PRKN)) is a major pest of peanut. Nematicide application is an important tool for the management of PRKN. Nematicides with minimal effects on free-living nematodes are desired. Fluopyram nematicide is recently introduced in peanut production and needs to be assessed. The objective of this research is to evaluate fluopyram and the established nematicides 1,3-Dichloropropene (1,3-D) and aldicarb for efficacy at managing PRKN and impacts on free-living nematodes. Nematicides were evaluated in field studies in 2017 and 2018 conducted in commercial peanut fields. All nematicides increased peanut yield in 2017 compared with untreated control, but did not affect soil PRKN abundances or root galling. In 2018, PRKN infestation was too low to accurately assess PRKN management by nematicides. Aldicarb and fluopyram did not affect any free-living nematode trophic group or individual genera. In contrast, 1,3-D decreased total fungivore and fungivore genera Filenchus and Aphelenchus soil abundances, but did not affect bacterivores, omnivore-predators, total herbivores, or any other nematode genera. In summary, 1,3-D, but not aldicarb or fluopyram, had non-target effects on free-living nematodes, particularly fungivores.Meloidogyne arenaria (peanut root-knot nematode (PRKN)) is a major pest of peanut. Nematicide application is an important tool for the management of PRKN. Nematicides with minimal effects on free-living nematodes are desired. Fluopyram nematicide is recently introduced in peanut production and needs to be assessed. The objective of this research is to evaluate fluopyram and the established nematicides 1,3-Dichloropropene (1,3-D) and aldicarb for efficacy at managing PRKN and impacts on free-living nematodes. Nematicides were evaluated in field studies in 2017 and 2018 conducted in commercial peanut fields. All nematicides increased peanut yield in 2017 compared with untreated control, but did not affect soil PRKN abundances or root galling. In 2018, PRKN infestation was too low to accurately assess PRKN management by nematicides. Aldicarb and fluopyram did not affect any free-living nematode trophic group or individual genera. In contrast, 1,3-D decreased total fungivore and fungivore genera Filenchus and Aphelenchus soil abundances, but did not affect bacterivores, omnivore-predators, total herbivores, or any other nematode genera. In summary, 1,3-D, but not aldicarb or fluopyram, had non-target effects on free-living nematodes, particularly fungivores.

Fluensulfone and 1,3-dichloroprene for plant-parasitic nematode management in potato production.

Florida produces 35% of the spring potato (Solanum tuberosum) crop in the USA, but plant-parasitic nematodes suppress yield in the region. The stubby-root nematodes, Paratrichodorus (Nanidorus) spp. and Trichodorus spp., vectors for corky ringspot disease, and sting nematode (Belonolaimus longicaudatus) are among the most damaging nematodes in Florida potato production. Nematicide application is an important component of nematode management in this system, but relatively few nematicides are currently available. Therefore, pre-plant applications of fluensulfone nematicide at various rates (3, 4, 6, and 8 l/ha) and the commercial standard fumigant 1,3-dichloropropene (1,3-D) were tested for management of plant-parasitic nematodes in three field trials from 2016 to 2018. Both fluensulfone, at all rates, and 1,3-D consistently decreased sting nematode abundance relative to the untreated control at harvest. Neither fluensulfone nor 1,3-D affected stubby-root nematode abundances at harvest. Efficacy of fluensulfone and 1,3-D for lesion nematode (Pratylenchus sp.) management varied by year. In 2016 and 2018, fluensulfone at most rates and 1,3-D increased marketable potato yield relative to the untreated control with increases by 49 to 66% and 33 to 55% in 2016 and 2018, respectively. In 2017, fluensulfone at lower rates (3, 4, and 6 l/ha) increased marketable potato yield relative to the untreated control by 41 to 61%, but fluensulfone at 8 l/ha and 1,3-D had similar yields to the untreated control. Results suggest that nematicidal activity of fluensulfone and 1,3-D varies by target nematode with both products effective against sting nematode, ineffective against stubby-root nematodes, and inconsistent against lesion nematode. In conclusion, fluensulfone and 1,3-D are effective options for sting nematode management in Florida potato production.Florida produces 35% of the spring potato (Solanum tuberosum) crop in the USA, but plant-parasitic nematodes suppress yield in the region. The stubby-root nematodes, Paratrichodorus (Nanidorus) spp. and Trichodorus spp., vectors for corky ringspot disease, and sting nematode (Belonolaimus longicaudatus) are among the most damaging nematodes in Florida potato production. Nematicide application is an important component of nematode management in this system, but relatively few nematicides are currently available. Therefore, pre-plant applications of fluensulfone nematicide at various rates (3, 4, 6, and 8 l/ha) and the commercial standard fumigant 1,3-dichloropropene (1,3-D) were tested for management of plant-parasitic nematodes in three field trials from 2016 to 2018. Both fluensulfone, at all rates, and 1,3-D consistently decreased sting nematode abundance relative to the untreated control at harvest. Neither fluensulfone nor 1,3-D affected stubby-root nematode abundances at harvest. Efficacy of fluensulfone and 1,3-D for lesion nematode (Pratylenchus sp.) management varied by year. In 2016 and 2018, fluensulfone at most rates and 1,3-D increased marketable potato yield relative to the untreated control with increases by 49 to 66% and 33 to 55% in 2016 and 2018, respectively. In 2017, fluensulfone at lower rates (3, 4, and 6 l/ha) increased marketable potato yield relative to the untreated control by 41 to 61%, but fluensulfone at 8 l/ha and 1,3-D had similar yields to the untreated control. Results suggest that nematicidal activity of fluensulfone and 1,3-D varies by target nematode with both products effective against sting nematode, ineffective against stubby-root nematodes, and inconsistent against lesion nematode. In conclusion, fluensulfone and 1,3-D are effective options for sting nematode management in Florida potato production.

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.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.

Swine manure application enriches the soil food web in corn and soybean production.

Strategies for managing plant-parasitic nematodes while promoting soil quality are needed in corn (Zea mays) and soybean (Glycine max) cropping systems. Therefore, a series of two-year experiments were conducted in Minnesota to determine the simple and interactive effects of manure or conventional fertilizer and short-term crop rotation on the nematode community, a sensitive indicator of soil ecology. The two-year crop sequences were Sus-Sus, Res-Sus, and Corn-Sus, where Sus and Res are soybean susceptible and resistant to Heterodera glycines (soybean cyst nematode: SCN), respectively. The fertilizer treatments were liquid swine manure, conventional phosphorus (P)-potassium (K) fertilizer, and no fertilizer. Crop sequence and fertilizer choice had individual main effects, but did not have an interactive effect on the nematode community. Swine manure affected the nematode community in ways that conventional PK fertilizer or no fertilizer did not, substantially enhancing populations of bacterivores in colonizer-persister group 1, which are extreme enrichment opportunists. Manure application did not affect other groups of free-living nematodes and decreased nematode community diversity. Conventional PK fertilizer did not influence the nematode community compared with untreated control. The effects of short-term crop sequences were much less pronounced and consistent than manure application, but corn altered the environment to favor fungivores while soybean increased bacterivore abundances.Strategies for managing plant-parasitic nematodes while promoting soil quality are needed in corn (Zea mays) and soybean (Glycine max) cropping systems. Therefore, a series of two-year experiments were conducted in Minnesota to determine the simple and interactive effects of manure or conventional fertilizer and short-term crop rotation on the nematode community, a sensitive indicator of soil ecology. The two-year crop sequences were Sus-Sus, Res-Sus, and Corn-Sus, where Sus and Res are soybean susceptible and resistant to Heterodera glycines (soybean cyst nematode: SCN), respectively. The fertilizer treatments were liquid swine manure, conventional phosphorus (P)-potassium (K) fertilizer, and no fertilizer. Crop sequence and fertilizer choice had individual main effects, but did not have an interactive effect on the nematode community. Swine manure affected the nematode community in ways that conventional PK fertilizer or no fertilizer did not, substantially enhancing populations of bacterivores in colonizer-persister group 1, which are extreme enrichment opportunists. Manure application did not affect other groups of free-living nematodes and decreased nematode community diversity. Conventional PK fertilizer did not influence the nematode community compared with untreated control. The effects of short-term crop sequences were much less pronounced and consistent than manure application, but corn altered the environment to favor fungivores while soybean increased bacterivore abundances.

Effects of Cover Crops on Pratylenchus penetrans and the Nematode Community in Carrot Production.

Cover cropping is a common practice in U.S. Midwest carrot production for soil conservation, and may affect soil ecology and plant-parasitic nematodes-to which carrots are very susceptible. This study assessed the impact of cover crops-oats (Avena sativa), radish (Raphanus sativus) cv. Defender, rape (Brassica napus) cv. Dwarf Essex, and a mixture of oats and radish-on plant-parasitic nematodes and soil ecology based on the nematode community in Michigan carrot production systems. Research was conducted at two field sites where cover crops were grown in Fall 2014 preceding Summer 2015 carrot production. At Site 1, root-lesion (Pratylenchus penetrans) and stunt (Tylenchorhynchus sp.) nematodes were present at low population densities (less than 25 nematodes/100 cm3 soil), but were not significantly affected (P > 0.05) by cover crops. At Site 2, P. penetrans population densities were increased (P ≤ 0.05) by 'Defender' radish compared to other cover crops or fallow control during cover crop growth and midseason carrot production. At both sites, there were few short-term impacts of cover cropping on soil ecology based on the nematode community. At Site 1, only at carrot harvest, radish-oats mixture and 'Dwarf Essex' rape alone enriched the soil food web based on the enrichment index (P ≤ 0.05) while rape and radish increased structure index values. At Site 2, bacterivore abundance was increased by oats or radish cover crops compared to control, but only during carrot production. In general, cover crops did not affect the nematode community until nearly a year after cover crop growth suggesting that changes in the soil community following cover cropping may be gradual.

Efficacy of Organic Soil Amendments for Management of Heterodera glycines in Greenhouse Experiments.

In a repeated greenhouse experiment, organic soil amendments were screened for effects on population density of soybean cyst nematode (SCN), Heterodera glycines, and soybean growth. Ten amendments at various rates were tested: fresh plant material of field pennycress, marigold, spring camelina, and Cuphea; condensed distiller's solubles (CDS), ash of combusted CDS, ash of combusted turkey manure (TMA), marigold powder, canola meal, and pennycress seed powder. Soybeans were grown for 70 d in field soil with amendments and SCN eggs incorporated at planting. At 40 d after planting (DAP), many amendments reduced SCN egg population density, but some also reduced plant height. Cuphea plant at application rate of 2.9% (amendment:soil, w:w, same below), marigold plant at 2.9%, pennycress seed powder at 0.5%, canola meal at 1%, and CDS at 4.3% were effective against SCN with population reductions of 35.2%, 46.6%, 46.7%, 73.2%, and 73.3% compared with control, respectively. For Experiment 1 at 70 DAP, canola meal at 1% and pennycress seed powder at 0.5% reduced SCN population density 70% and 54%, respectively. CDS at 4.3%, ash of CDS at 0.2%, and TMA at 1% increased dry plant mass whereas CDS at 4.3% and pennycress seed powder at 0.1% reduced plant height. For Experiment 2 at 70 DAP, amendments did not affect SCN population nor plant growth. In summary, some amendments were effective for SCN management, but phytoxicity was a concern.