A field trial was conducted to examine whether strip-tilled cover cropping followed by living mulch practice could suppress root-knot nematode (Meloidogyne incognita) and enhance beneficial nematodes and other soil mesofauna, while suppressing weeds throughout two vegetable cropping seasons. Sunn hemp (SH), Crotalaria juncea, and French marigold (MG), Tagetes patula, were grown for three months, strip-tilled, and bitter melon (Momordica charantia) seedlings were transplanted into the tilled strips; the experiment was conducted twice (Season I and II). Strip-tilled cover cropping with SH prolonged M. incognita suppression in Season I but not in Season II where suppression was counteracted with enhanced crop growth. Sunn hemp also consistently enhanced bacterivorous and fungivorous nematode population densities prior to cash crop planting, prolonged enhancement of the Enrichment Index towards the end of both cash crop cycles, and increased numbers of soil mesoarthropods. Strip-tilled cover cropping of SH followed by clipping of the living mulch as surface mulch also reduced broadleaf weed populations up to 3 to 4 weeks after cash crop planting. However, SH failed to reduce soil disturbance as indicated by the Structure Index. Marigold suppressed M. incognita efficiently when planted immediately following a M. incognita-susceptible crop, but did not enhance beneficial soil mesofauna including free-living nematodes and soil mesoarthropods. Strip-tilled cover cropping of MG reduced broadleaf weed populations prior to cash crop planting in Season II, but this weed suppression did not last beyond the initial cash crop cycle.
Crotalaria juncea; free-living nematodes; living mulch; Meloidogyne incognita; mesoarthropods; Momordica charantia; nematode community analysis; Tagetes patula
Belonolaimus longicaudatus has been reported as damaging both potato (Solanum tuberosum) and cotton (Gossypium hirsutum). These crops are not normally grown in cropping systems together in areas where the soil is infested with B. longicaudatus. During the 1990s cotton was grown in a potato production region that was a suitable habitat for B. longicaudatus. It was not known how integrating the production of these two crops by rotation or double-cropping would affect the population densities of B. longicaudatus, other plant-parasitic nematodes common in the region, or crop yields. A 3-year field study evaluated the viability of both crops in monocropping, rotation, and double-cropping systems. Viability was evaluated using effects on population densities of plant-parasitic nematodes and yields. Rotation of cotton with potato was found to decrease population densities of B. longicaudatus and Meloidogyne incognita in comparison with continuous potato. Population densities of B. longicaudatus following double-cropping were greater than following continuous cotton. Yields of both potato and cotton in rotation were equivalent to either crop in monocropping. Yields of both crops were lower following double-cropping when nematicides were not used.
Belonolaimus longicaudatus; cotton; crop rotation; cropping system; double-cropping; Gossypium hirsutum; Meloidogyne incognita; nematode; potato; root-knot nematode; Solanum tuberosum; sting nematode
Brassicas have been used frequently for biofumigation, a pest-management strategy based on the release of biocidal volatiles during decomposition of soil-incorporated tissue. However, the role of such volatiles in control of plant-parasitic nematodes is unclear. The goal of this study was to determine the direct localized and indirect volatile effects of amending soil with broccoli tissue on root-knot nematode populations. Meloidogyne incognita-infested soil in 50-cm-long tubes was amended with broccoli tissue, which was mixed throughout the tube or concentrated in a 10-cm layer. After three weeks at 28°C, M. incognita populations in the amended tubes were 57 to 80% smaller than in non-amended tubes. Mixing broccoli throughout the tubes reduced M. incognita more than concentrating broccoli in a 10-cm layer. Amending a 10-cm layer reduced M. incognita in the non-amended layers of those tubes by 31 to 71%, probably due to a nematicidal effect of released volatiles. However, the localized direct effect was much stronger than the indirect effect of volatiles. The strong direct effect may have resulted from the release of non-volatile nematicidal compounds. Therefore, when using biofumigation with broccoli to control M. incognita, the tissue should be thoroughly and evenly mixed through the soil layer(s) where the target nematodes occur. Effects on saprophytic nematodes were the reverse. Amended soil layers had much greater numbers of saprophytic nematodes than non-amended layers, and there was no indirect effect of amendments on saprophytic nematodes in adjacent non-amended layers.
amendment; biofumigation; broccoli; Brassica oleracea; management; Meloidogyne incognita; root-knot nematode; soil
Broccoli (Brassica oleracea), carrot (Daucus carota), marigold (Tagetes patula), nematode-resistant tomato (Solanum lycopersicum), and strawberry (Fragaria ananassa) were grown for three years during the winter in a root-knot nematode (Meloidogyne incognita) infested field in Southern California. Each year in the spring, the tops of all crops were shredded and incorporated in the soil. Amendment with poultry litter was included as a sub-treatment. The soil was then covered with clear plastic for six weeks and M. incognita-susceptible tomato was grown during the summer season. Plastic tarping raised the average soil temperature at 13 cm depth by 7°C.The different winter-grown crops or the poultry litter did not affect M. incognita soil population levels. However, root galling on summer tomato was reduced by 36%, and tomato yields increased by 19% after incorporating broccoli compared to the fallow control. This crop also produced the highest amount of biomass of the five winter-grown crops. Over the three-year trial period, poultry litter increased tomato yields, but did not affect root galling caused by M. incognita. We conclude that cultivation followed by soil incorporation of broccoli reduced M. incognita damage to tomato. This effect is possibly due to delaying or preventing a portion of the nematodes to reach the host roots. We also observed that M. incognita populations did not increase under a host crop during the cool season when soil temperatures remained low (< 18°C).
biofumigation; crop rotation; management; Meloidogyne incognita; Solanum lycopersicum
Densities of plant-parasitic nematodes were compared on six crops grown for forage during the summer of 1991 at seven sites in north central Florida. The cropping treatments were 'Howard' soybean (Glycine max), 'Deltapine 105' soybean, velvetbean (Mucuna deeringiana), 'California Blackeye #5' cowpea (Vigna unguiculata), 'Pioneer 3098' tropical corn (Zea mays), and 'Asgrow Chaparral' sorghum (Sorghum bicolor). Highest final densities (Pf) of Meloidogyne incognita and Criconemella spp. were obtained following corn or sorghum at most sites. The lowest Pf of M. incognita occurred after velvetbean at all seven sites, but Pf after cowpea were equivalent to Pf after velvetbean at four of seven sites. Cultivar choice is critical in planning rotations to suppress M. incognita because results obtained here and elsewhere have shown great differences among sorghum and cowpea cultivars. The Pf of Pratylenchus spp. were lowest following velvetbean at four of seven sites. There were no differences in densities of Paratrichodorus minor among crops, but populations increased at a greater rate if initial density (Pi) was low. Multiplication rates (Pf/Pi) of most nematode species on most crops varied inversely with Pi. An accurate impression of nematode multiplication and host status could not be obtained unless a range of Pi was examined.
corn; cover crop; cowpea; Criconemella ornata; Criconemella sphaerocephala; crop rotation; cropping system; Glycine max; nematode; Meloidogyne incognita; Mucuna deeringiana; Paratrichodorus minor; Pratylenchus brachyurus; Pratylenchus scribneri; sorghum; Sorghum bicolor; soybean; velvetbean; Vigna unguiculata; Zea mays
Organic matter and its replenishment has become a major component of soil health management programs. Many of the soil's physical, chemical, and biological properties are a function of organic matter content and quality. Adding organic matter to soil influences diverse and important biological activities. The diversity and number of free-living and plant-parasitic nematodes are altered by rotational crops, cover crops, green manures, and other sources of organic matter. Soil management programs should include the use of the proper organic materials to improve soil chemical, physical, and biological parameters and to suppress plant-parasitic nematodes and soilborne pathogens. It is critical to monitor the effects of organic matter additions on activities of major and minor plant-parasitic nematodes in the production system. This paper presents a general review of information in the literature on the effects of crop rotation, cover crops, and green manures on nematodes and their damage to economic crops.
cover crops; crop rotation; green manure; nematode control
Twenty-two cover crops were evaluated for their ability to reduce damage by root-knot nematode, Meloidogyne javanica, to taro, Colocastia esculenta, in a tropical cropping system. Cover crops were grown and incorporated into the soil before taro was planted. Barley, greenpanic, glycine, marigold, sesame, sunn hemp, and sorghum x sudangrass DeKalb ST6E were poor or nonhosts to the nematode as measured by low population changes of nematodes in soil between cover crop planting and taro planting. Alfalfa, buckwheat, cowpea, lablab, Lana vetch, mustard, oat, okra, rhodes grass, ryegrain, ryegrass, siratro, sweet corn, and wheat allowed nematode populations to increase dramatically. Taro yields were greatest in the marigold plots and lowest in the ryegrain plots. Taro corm weight decreased with increasing initial nematode population (Pi) (r = 0.22, P = 0.056). Siratro, ryegrass, and Blizzard wheat plots had higher taro yield than plots with similar Pi's but planted to other cover crops. These cover crops may have antagonism to other soil microorganisms or their decomposition products may be toxic or adversely affect the nematodes. Cover crops can be an effective and valuable nematode management tactic for use in minor tropical cropping systems such as taro.
barley; Colocagia esculenta; control; cover crop; Crotalafia juncea; glycine; greenpanic; Hordeum vulgare; management; marigold; cover crop; Crotalaria juncea; glycine; greenpanic; Hordeum vulgate; management; marigold; Meloidogyne javanica; nematode; Neonotonia wightii; Panicum maximum; root-knot nematode; sesame; Sesamum indicum; sorghum x sudangrass DeKalb ST6E; sunn hemp; sustainable agriculture; Tagetes erecta; taro; tropical cover crops
Changes in population levels of Meloidogyne hapla, M. incognita, Pratylenchus coffeae, and P. penetrans were studied in 12 strawberry fields in the Dahu region of Taiwan. Ten potential rotation crops and two cultural practices were evaluated for their effect on nematode populations and influence on strawberry yield. Rotation with rice or taro and the cultural practice of flooding and bare fallowing for four months were found to reduce nematode soil populations to two or fewer nematodes per 100 ml soil. Average strawberry yields increased between 2.4% to 6.3% following taro compared to the bare fallow treatment. Corn suppressed M. incognita and M. hapla populations and resulted in an increased in strawberry yield compared to bare fallow. Other phytopathogens also present in these fields limited taro as the rotation choice for nematode management. Results of this research and economic analysis of the input requirements for various rotation crops, corn and bare fallow were recommended as the most appropriate rotation strategies for nematode management in strawberry in this region.
bitter gourd; Capsicum annuum; Colocasia esculena; corn; fallow; Glycine max; Hibiscus esculentus; India sesbania; lana vetch; Lycopersicon esculentum; Meloidogyne hapla; Meloidogyne incognita; Momordica charantia; Okra; Oryza sativa; pepper; Pratylenchus coffeae; Pratylenchus penetrans; rice; rotation; Sesbania sesban; soybean; strawberry yield; taro; Vicia sativa; Zea mays
As an entrée to characterizing plant parasitic nematode genomes, 5,700 expressed sequence tags (ESTs) from the infective second-stage larvae (L2) of the root-knot nematode Meloidogyne incognita have been analyzed. In addition to identifying putative nematode-specific and Tylenchida-specific genes, sequencing revealed previously uncharacterized horizontal gene transfer candidates in Meloidogyne with high identity to rhizobacterial genes.
Plant parasitic nematodes are major pathogens of most crops. Molecular characterization of these species as well as the development of new techniques for control can benefit from genomic approaches. As an entrée to characterizing plant parasitic nematode genomes, we analyzed 5,700 expressed sequence tags (ESTs) from second-stage larvae (L2) of the root-knot nematode Meloidogyne incognita.
From these, 1,625 EST clusters were formed and classified by function using the Gene Ontology (GO) hierarchy and the Kyoto KEGG database. L2 larvae, which represent the infective stage of the life cycle before plant invasion, express a diverse array of ligand-binding proteins and abundant cytoskeletal proteins. L2 are structurally similar to Caenorhabditis elegans dauer larva and the presence of transcripts encoding glyoxylate pathway enzymes in the M. incognita clusters suggests that root-knot nematode larvae metabolize lipid stores while in search of a host. Homology to other species was observed in 79% of translated cluster sequences, with the C. elegans genome providing more information than any other source. In addition to identifying putative nematode-specific and Tylenchida-specific genes, sequencing revealed previously uncharacterized horizontal gene transfer candidates in Meloidogyne with high identity to rhizobacterial genes including homologs of nodL acetyltransferase and novel cellulases.
With sequencing from plant parasitic nematodes accelerating, the approaches to transcript characterization described here can be applied to more extensive datasets and also provide a foundation for more complex genome analyses.
Soil populations of plant-parasitic nematodes were monitored bimonthly for 18 months in irrigated and nonirrigated corn plantings using four production systems: conventional and minimum tillage with crop residue returned and minimum tillage with 60% or 90% of previous corn crop residue removed. Populations of Meloidogyne incognita, Scutellonema brachyurum, Pratylenchus scribneri, and Paratrichodorus christiei varied among the tillage, nematicide, and irrigation treatments. Meloidogyne incognita and P. christiei populations were not significantly affected by tillage method, but S. brachyurum populations were highest during April 1981 and 1982 in minimum tillage treatments where crop debris was not removed. In contrast, S. brachyurum populations were lowest during the same period in minimum tillage plots where 90% of previous crop debris had been removed or where residues were incorporated with conventional tillage. Populations of P. scribneri were lowest in minimum tillage during August 1981 and April 1982. Regardless of tillage system, corn yields in all nonirrigated plots were increased during 1982 by application of carbofuran (2.24 kg a.i./ha). No yield increases were observed following nematicide application in 1981.
Meloidogyne incognita; Scutellonema brachyurum; Pratylenchus scribneri; Paratrichodorus christiei; carbofuran; Zea mays
The efficacy of a double-cross corn (Zea mays) hybrid (Old Raccoon selection X T216) X (Tebeau selection X Mp 307) resistant to Meloidogyne incognita as a rotational crop, and fenamiphos treatment for management of root-knot nematode (M. incognita race 1) in squash (Cucurbita pepo var. melopepo) was evaluated in field tests during 1996 and 1997. Numbers of M. incognita in the soil and root-gall indices were lower on the resistant hybrid than on a commercial cultivar DeKalb DK-683. Treatment means across both corn entries had lower root-gall indices following fenamiphos treatment. In soil collected 2 September 1997, there were more colony-forming units (cfu) per gram of oven-dried soil of Pythium spp. from plots planted to DK-683 treated with fenamiphos than in untreated plots (88 vs. 59 cfu). Some corn plots had individual plants with 10% to 15% of the crown and brace roots decayed, but no differences due to fenamiphos treatment. Lodging of stalks was 40% to 50% more in the double-cross hybrid than in DK-683. Yield was greater from DK-683 than the double-cross hybrid. Based on cultivar means across fenamiphos treatments and fenamiphos treatment means across cultivars, root-gall indices and yield of squash were significantly lower following the double cross hybrid than DK-683 and in fenamiphos-treated plots than in untreated plots of squash. Yield of squash was not affected by at-planting treatment with fenamiphos on the preceding crops of corn. Nematode resistance must be transferred into the elite materials of commercial seed companies to reach its full potential as a nematode management strategy.
corn; crop rotation; Cucurbita pepo; fenamiphos; maize; management; Meloidogyne incognita; nematicide; nematode; Pythium; resistance; Rhizoctonia solani; root-knot nematode; squash; stalk rot; Zea mays
The effects of a soil hardpan and Meloidogyne incognita on cotton root architecture and plant growth were evaluated in microplots in 2010 and 2011. Soil was infested with M. incognita at four different levels with or without a hardpan. The presence of a hardpan resulted in increased plant height, number of main stem nodes, and root fresh weight for cotton seedlings both years. Meloidogyne incognita decreased height and number of nodes for seedlings in 2010. Nematode infestation increased seedling root length and enhanced root magnitude, altitude, and exterior path length in 2010. This was also the case for root length and magnitude in 2011 at lower infestation levels suggesting compensatory growth. A hardpan had no consistent effect on these root parameters but increased root volume in both years. A hardpan hastened crop maturity and increased the number of fruiting branches that were produced, while M. incognita infection delayed crop development and reduced plant height and number of bolls. Both M. incognita infection and a hardpan reduced taproot length and root dry weight below the hardpan in both years. Root topological indices under all the treatments ranged from 1.71 to 1.83 both years indicating that root branching followed a herringbone pattern. The techniques for characterizing root architecture that were used in this study provide a greater understanding of changes that result from disease and soil abiotic parameters affecting root function and crop productivity.
ecology; host-parasite relationship; root-knot nematode; root topology; soil hardpan
Pearl millet (Pennisetum glaucum) has potential as a grain crop for dryland crop production in the southeastern United States. Whether or not pearl millet will be compatible in rotation with cotton (Gossypium hirsutum), corn (Zea mays), and peanut (Arachis hypogaea) will depend, in part, on its host status for important plant-parasitic nematodes of these crops. The pearl millet hybrid 'TifGrain 102' is resistant to both Meloidogyne incognita race 3 and M. arenaria race 1; however, its host status for other plant-parasitic nematodes was unknown. In this study, the reproduction of Belonolaimus longicaudatus, Paratrichodorus minor, Pratylenchus brachyurus, and Meloidogyne javanica race 3 on pearl millet ('HGM-100' and TifGrain 102) was compared relative to cotton, corn, and peanut. Separate greenhouse experiments were conducted for each nematode species. Reproduction of B. longicaudatus was lower on peanut and the two millet hybrids than on cotton and corn. Reproduction of P. minor was lower on peanut and TifGrain 102 than on cotton, corn, and HGM-100. Reproduction of P. brachyurus was lower on both millet hybrids than on cotton, corn, and peanut. Reproduction of M. javanica race 3 was greater on peanut than on the two millet hybrids and corn. Cotton was a nonhost. TifGrain 102 was more resistant than HGM-100 to reproduction of B. longicaudatus, P. minor, and M. javanica. Our results demonstrated that TifGrain 102 was a poor host for B. longicaudatus and P. brachyurus (Rf < 1) and, relative to other crops tested, was less likely to increase densities of P. minor and M. javanica.
Arachis hypogaea; Belonolaimus longicaudatus; corn; cotton; Gossypium hirsutum; lesion nematode; Meloidogyne javanica; Paratrichodorus minor; peanut; pearl millet; Pennisetum glaucum; Pratylenchus brachyurus; reproduction; resistance; root-knot nematode; sting nematode; stubby-root nematode; Zea mays
The effects of a root-knot nematode-resistant tomato cultivar and application of the nematicide ethoprop on root-knot nematode injury to cucumber were compared in a tomato-cucumber double-cropping system. A root-knot nematode-resistant tomato cultivar, Celebrity, and a susceptible cultivar, Heatwave, were grown in rotation with cucumber in 1995 and 1996. Celebrity suppressed populations of Meloidogyne incognita in the soil and resulted in a low root-gall rating on the subsequent cucumber crop. Nematode population densities were significantly lower at the termination of the cucumber crop in plots following Celebrity than in plots following Heatwave. Premium and marketable yields of cucumbers were higher in plots following Celebrity than in plots following Heatwave. Application of ethoprop through drip irrigation at 4.6 kg a.i./ha reduced root galling on the cucumber crop but had no effect on the nematode population density in the soil at crop termination. Ethoprop did not affect cucumber yield. These results indicate that planting a resistant tomato cultivar in a tomato-cucumber double-cropping system is more effective than applying ethoprop for managing M. incognita.
cucumber; cultural control; double crop; Meloidogyne incognita; nematode; root-knot nematode; tomato; trellising
Ten cultivars of watermelon were evaluated for their response to a Puerto Rican population of Meloidogyne incognita under greenhouse conditions in a 2-year study (1989 and 1990). Ten-day-old seedlings were planted in steam-sterilized soil in 15-cm-d plastic pots. The nematode inoculum consisted of 10,000 eggs and (or) second-stage juveniles (J2)/plant. The cultivars were Sugar Baby, Charleston Gray, Seedless, Prince Charles, Charleston 76, Jubilee, Florida Giant, Royal Charleston, Royal Sweet, and Royal Jubilee, with tomato cv. Rutgers included as a susceptible check. A completely randomized design with 10 replications was used. Fifty-five days after soil infestation, root-gall indices, numbers of nematode eggs per root system, and J2 per 250 cm³ of soil were recorded. All cultivars were susceptible. Sugar Baby had the lowest root-gall index, egg and J2 numbers, and a reproductive factor (Rf) of 2.89. Rf differed (P ≤ 0.05) among cultivars and ranged up to 7.36. Sugar Baby, Seedless, and Florida Giant showed the lowest susceptibility to M. incognita, whereas Charleston 76 and Charleston Gray were the most susceptible.
Citrullus lanatus; fruits; host status; Meloidogyne incognita; nematode; Puerto Rico; root-knot nematode; susceptibility; vegetables; watermelon
The antibiotic 2,4-diacetylphloroglucinol (DAPG), produced by some strains of Pseudomonas spp., is involved in suppression of several fungal root pathogens as well as plant-parasitic nematodes. The primary objective of this study was to determine whether Wood1R, a D-genotype strain of DAPG-producing P. fluorescens, suppresses numbers of both sedentary and migratory plant-parasitic nematodes. An experiment was conducted in steam-heated soil and included two seed treatments (with Wood1R and a control without the bacterium) and six plant-nematode combinations which were Meloidogyne incognita on cotton, corn, and soybean; M. arenaria on peanut; Heterodera glycines on soybean; and Paratrichodorus minor on corn. Wood 1R had no effect on final numbers of M. arenaria, P. minor, or H. glycines; however, final numbers of M. incognita were lower when seeds were treated with Wood1R than left untreated, and this reduction was consistent among host plants. Population densities of Wood1R were greater on the roots of corn than on the other crops, and the bacterium was most effective in suppressing M. incognita on corn, with an average reduction of 41%. Despite high population densities of Wood1R on corn, the bacterium was not able to suppress numbers of P. minor. When comparing the suppression of M. incognita on corn in natural and steam-heated soil, egg production by the nematode was suppressed in natural compared to steamed soil, but the presence of Wood1R did not result in additional suppression of the nematodes in the natural soil. These data indicate that P. fluorescens strain Wood1R has the capacity to inhibit some populations of plant-parasitic nematodes. However, consistent suppression of nematodes in natural soils seems unlikely.
antibiotic; biological control; corn; DAPG; Heterodera glycines; Meloidogyne arenaria; Meloidogyne incognita; Paratrichodorus minor; Pseudomonas fluorescens; root-knot nematode; stubby-root nematode; Zea mays
Two experiments were conducted in north-central Florida to examine the effects of various winter cover crops on plant-parasitic nematode populations through time. In the first experiment, six winter cover crops were rotated with summer corn (Zea mays), arranged in a randomized complete block design. The cover crops evaluated were wheat (Triticum aestivum), rye (Secale cereale), oat (Avena sativa), lupine (Lupinus angustifolius), hairy vetch (Vicia villosa), and crimson clover (Trifolium incarnatum). At the end of the corn crop in year 1, population densities of Meloidogyne incognita were lowest on corn following rye or oat (P ≤ 0.05), but no treatment differences were observed in year 2. Wheat was a good host to Paratrichodorus minor, whereas vetch was a poor host, but numbers of P. minor were not lower in vetch-planted plots after corn was grown. The second experiment used a split-plot design in which rye or lupine was planted into field plots with histories of five tropical cover crops: soybean (Glycine max), cowpea (Vigna unguiculata), sorghum-sudangrass (Sorghum bicolor × S. sudanense), sunn hemp (Crotalaria juncea), and corn. Population densities of M. incognita and Helicotylenchus dihystera were affected by previous tropical cover crops (P ≤ 0.05) but not by the winter cover crops present at the time of sampling. Plots planted to sunn hemp in the fall maintained the lowest M. incognita and H. dihystera numbers. Results suggest that winter cover crops tested did not suppress plant-parasitic nematodes effectively. Planting tropical cover crops such as sunn hemp after corn in a triple-cropping system with winter cover crops may provide more versatile nematode management strategies in northern Florida.
crop rotation; cropping systems; Helicotylenchus dihystera; Meloidogyne incognita; Mesocriconema ornata; M. sphaerocephala; nematode management; Paratrichodorus minor; Pratylenchulus brachyurus; P. scribneri; root-knot nematode; sustainable agriculture; weeds
The effect of previous crops--soybean (Glycine max) or corn (Zea mays)--and aldicarb (2.2 kg a.i./ha) on yield and nematode numbers at harvest for soybean cultivars with various combinations of nematode resistance was determined in a sandy loam soil infested with Meloidogyne arenaria race 2 and Heterodera glycines races 3 and 4 at Elberta, Alabama, in 1987. Cultivars had an effect on yield and nematode numbers (P = 0.01), as did the interaction of previous crop and cultivar. The nematicide treatment x cultivar interaction was significant for yield, and the three-way interaction was significant for numbers of M. arenaria. A previous crop of corn had no effect on M. arenaria numbers, but it reduced numbers of H. glycines from 93 to 25 J2/100 cm³ of soil and increased soybean yield from 1,963 to 2,560 kg/ha. Aldicarb reduced M. arenaria numbers from 230 to 186 J2/100 cm³ soil and increased yield from 2,062 to 2,460 kg/ha but it had no effect on H. glycines numbers. Rotation with corn was an effective control measure for H. glycines and enhanced the yields of H. glycines-susceptible cultivars.
Alabama; aldicarb; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; root-knot nematode; soybean cyst nematode; soybean
Terminated small grain cover crops are valuable in light textured soils to reduce wind and rain erosion and for protection of young cotton seedlings. A three-year study was conducted to determine the impact of terminated small grain winter cover crops, which are hosts for Meloidogyne incognita, on cotton yield, root galling and nematode midseason population density. The small plot test consisted of the cover treatment as the main plots (winter fallow, oats, rye and wheat) and rate of aldicarb applied in-furrow at-plant (0, 0.59 and 0.84 kg a.i./ha) as subplots in a split-plot design with eight replications, arranged in a randomized complete block design. Roots of 10 cotton plants per plot were examined at approximately 35 days after planting. Root galling was affected by aldicarb rate (9.1, 3.8 and 3.4 galls/root system for 0, 0.59 and 0.84 kg aldicarb/ha), but not by cover crop. Soil samples were collected in mid-July and assayed for nematodes. The winter fallow plots had a lower density of M. incognita second-stage juveniles (J2) (transformed to Log10 (J2 + 1)/500 cm3 soil) than any of the cover crops (0.88, 1.58, 1.67 and 1.75 Log10(J2 + 1)/500 cm3 soil for winter fallow, oats, rye and wheat, respectively). There were also fewer M. incognita eggs at midseason in the winter fallow (3,512, 7,953, 8,262 and 11,392 eggs/500 cm3 soil for winter fallow, oats, rye and wheat, respectively). Yield (kg lint per ha) was increased by application of aldicarb (1,544, 1,710 and 1,697 for 0, 0.59 and 0.84 kg aldicarb/ha), but not by any cover crop treatments. These results were consistent over three years. The soil temperature at 15 cm depth, from when soils reached 18°C to termination of the grass cover crop, averaged 9,588, 7,274 and 1,639 centigrade hours (with a minimum threshold of 10°C), in 2005, 2006 and 2007, respectively. Under these conditions, potential reproduction of M. incognita on the cover crop did not result in a yield penalty.
Aldicarb; conservation tillage; cotton; Gossypium hirsutum; Meloidogyne incognita; root-knot nematode
Management of Meloidogyne incognita on soybean as affected by winter small grain crops or fallow, two tillage systems, and nematicides was studied. Numbers of M. incognita did not differ in plots planted to wheat and rye. Yields of soybean planted after these crops also did not differ. Numbers of M. incognita were greater in fallow than in rye plots, but soybean yield was not affected by the two treatments. Soybean yields were greater in subsoil-plant than in moldboard plowed plots. Ethylene dibromide reduced nematode population densities more consistently than aldicarb and phenamiphos. Also, ethylene dibromide increased yields the most and phenamiphos the least. There was a positive correlation (P = 0.001) of seed size (weight of 100 seeds) with yield (r = 0.79), indicating that factors affecting yield also affected seed size.
aldicarb; conservation tillage; ethylene dibromide; Glycine max; Meloidogyne incognita; moldboard plow; phenamiphos; root-knot nematode; rye; Secale cereale; soybean; subsoil-plant; tillage; Triticum aestivum; wheat
In the southeastern United States, a cotton-peanut rotation is attractive because of the high value and extensive planting of both crops in the region. The objective of this experiment was to determine the effects of cotton-peanut rotations, rye, and soil chemical treatments on management of plant-parasitic nematodes, thrips, and soilborne fungal diseases and on crop yield. Peanut-cotton-rye rotations were conducted from 1988 to 1994 on Tifton loamy sand (Plinthic Kandiudult) infested primarily with Meloidogyne incognita race 3, Belonolaimus longicaudatus, Sclerotium rolfsii, Rhizoctonia solani, and Fusarium oxysporum. Continuous peanut, continuous cotton, cotton-peanut rotation, or peanut-cotton rotation were used as main plots; winter rye or fallow as sub-plots; and cotton with and without aldicarb (3.36 kg a.i./ha), or peanut with and without aldicarb (3.36 kg a.i./ha) plus flutolanil (1.12 kg a.i./ha), as sub-sub-plots. Population densities of M. incognita and B. longicaudatus declined rapidly after the first crop in continuous peanut and remained low thereafter. Neither rye nor soil chemical treatment affected M. incognita or B. longicaudatus population density on peanut or cotton. Cotton and peanut yields from the cotton-peanut rotation were 26% and 10% greater, respectively, than those from monoculmre over the 7-year study. Cotton and peanut yields were improved 9% and 4%, respectively, following rye vs. fallow. Soil chemical treatments increased yields of cotton 23% and peanut 32% over those of untreated plots. Our data demonstrate the sustainable benefits of using cotton-peanut rotations, winter rye, and soil chemical treatments to manage plant-parasitic nematodes and other pests and pathogens and improve yield of both cotton and peanut.
Arachis hypogaea; Belonolaimus longicaudatus; cotton; Criconemella ornata; crop rotation; fallow; Frankliniella spp., Gossypium hirsutum; management; Meloidogyne incognita; monocrop; nematicide; nematode; peanut; population dynamics; ring nematode; root-knot nematode; rye; Secale cereale; sting nematode; thrips
Nematicides are used to control a wide variety of nematodes on many crops; unfortunately, oftentimes the control they provide is erratic. This erratic behavior is not always predictable and has been associated with chemical, physical, and biological degradation of nematicides. Their accelerated degradation is an agricultural problem that has been observed in crop monocultures and in other crop production systems where a biodegradable compound is repeatedly applied to the same soil. The problem can occur in field soil and golf course greens; it is not unique to any single nematicide or class of nematicides, but rather to many classes of pesticides. As indicated by the population density of root-knot nematodes (Meloidogyne incognita) in the soil in a 6-year sweet corn-sweet potato-vetch rotation, the efficacy of the nematicide fenamiphos diminished during the third year. Therefore, use of the nematicide applied immediately before planting sweet corn, sweet potato, and vetch should not exceed 3 years. After 3 years, the crop rotation and(or) the nematicide should be changed.
control; degradation; enhanced degradation; fenamiphos; management; Meloidogyne incognita; nematicide; nematode; root-knot nematode; rotation
Observations in three Australian sugarcane fields suggested that the soil just under the trash blanket (the covering of crop residue that remains on the soil surface after crops are harvested) was suppressive to plant-parasitic nematodes. Roots were concentrated in this upper layer of soil but plant-parasitic nematode populations were relatively low and roots showed few signs of nematode damage. Root biomass was much lower 15 cm further down the soil profile, where root health was poor and populations of plant-parasitic nematodes were 3-5 times higher than near the soil surface. A bioassay in which Radopholus similis (a nematode that does not occur in sugarcane soils) was inoculated into heat-sterilized and untreated soils, confirmed that biological factors were limiting nematode populations in some of the soils, with soil from 0-2 cm much more suppressive than soil from 15-17 cm. Surface soil from one site was highly suppressive, as only 16% of R. similis recoverable from heated soil were retrieved from this soil after 8 days. Numerous soil chemical, biochemical, and biological properties were measured, and non-linear regression analysis identified two major groups of factors that were significantly associated with suppressiveness. One group reflected the amount of organic matter in soil (total C, total N, and labile C) and the other was associated with the size of the free-living nematode community (total numbers of free-living nematodes, and numbers of plant associates, bacterial feeders, fungal feeders, and carnivores). These results suggested that suppressiveness was biologically mediated and was sustained by C inputs from crop residues and roots. Since nematode-trapping fungi in the test soils could not be quantified using traditional dilution plating methods, their possible role as suppressive agents was assessed by generating TRFLP profiles with Orbiliales-specific primers, and by sequencing cloned PCR products. Although the molecular data were obtained from a limited number of samples, the level of suppression was significantly correlated to the number of Orbiliales clone groups and was also related to the number of Orbiliales species and TRFs, suggesting that this group of fungi may have been one of the suppressive factors operating in the test soils.
biological control; clone library; mulch; nematode community analysis; nematode-trapping fungi; Orbiliales; predatory nematodes; organic matter-mediated suppression; TRFLP; sugarcane; suppressive soil
Field plots of Tifton loamy sand were treated with methyl bromide, DD-MENCS, or ethoprop for control of root-knot nematodes, Meloidogyne incognita, in a multiple cropping system of turnips, field corn, and southern peas. Annual applications of methyl bromide and DD-MENCS in November or December suppressed nematode numbers to very low levels through September, but numbers increased in the following October, November, and/or December. No benefit was found from ethoprop applied to DD-MENCS-treated plots before the planting of each crop. Nematode numbers were not significantly suppressed by ethoprop alone. Concentrations of ethoprop in the 0-15-cm soil layer were near 6 μg/g at application but were < 1μg/g of soil 5 days later on corn and southern peas and 30 days later on turnips. Ethoprop concentrations of 4.6 to 5.6 μg/g of soil are too low for adequate control of root-knot nematodes on field corn and southern peas in multiple cropping systems. Stepwise regression analyses indicated that 81% and 36% of the variations in concentration of ethoprop in the soil were attributable to the amount of water that the plots received when the maximum soil temperature ranged from 10 C to 19 C and from 31 C to 41 C, respectively, and that 11% was attributable to the maximum soil temperature within the temperature range of 17 C to 33 C.
Nematode control; dissipation of ethoprop; multiple-cropping; Meloidogyne incognita
Greenhouse experiments with two susceptible hosts of Meloidogyne incognita, a dwarf tomato and wheat, led to the identification of a soil in which the root-knot nematode population was reduced 5- to 16-fold compared to identical but pasteurized soil two months after infestation with 280 M. incognita J2/100 cm3 soil. This suppressive soil was subjected to various temperature, fumigation and dilution treatments, planted with tomato, and infested with 1,000 eggs of M. incognita/100 cm3 soil. Eight weeks after nematode infestation, distinct differences in nematode population densities were observed among the soil treatments, suggesting the suppressiveness had a biological nature. A fungal rRNA gene analysis (OFRG) performed on M. incognita egg masses collected at the end of the greenhouse experiments identified 11 fungal phylotypes, several of which exhibited associations with one or more of the nematode population density measurements (egg masses, eggs or J2). The phylotype containing rRNA genes with high sequence identity to Pochonia chlamydosporia exhibited the strongest negative associations. The negative correlation between the densities of the P. chlamydosporia genes and the nematodes was corroborated by an analysis using a P. chlamydosporia-selective qPCR assay.
biological control; dwarf tomato; Meloidogyne incognita; Pochonia chlamydosporia; root-knot nematode; Solanum lycopersicon; suppressive soil; Triticum aestivum; wheat