The possible impact of Rotylenchulus reniformis below plow depth was evaluated by measuring the vertical distribution of R. reniformis and soil texture in 20 symptomatic fields on 17 farms across six states. The mean nematode population density per field, 0 to 122 cm deep, ranged from 0.4 to 63 nematodes/g soil, and in 15 fields more than half of the R. reniformis present were below 30.5 cm, which is the greatest depth usually plowed by farmers or sampled by consultants. In 11 fields measured, root density was greatest in the top 15 cm of soil; however, roots consistently penetrated 92 to 122 cm deep by midseason, and in five fields in Texas and Louisiana the ratio of nematodes to root-length density within soil increased with depth. Repeated sampling during the year in Texas indicated that up to 20% of the nematodes in soil below 60 cm in the fall survived the winter. Differences between Baermann funnel and sugar flotation extraction methods were not important when compared with field-to-field differences in nematode populations and field-specific vertical distribution patterns. The results support the interpretation that R. reniformis below plow depth can significantly impact diagnosis and treatment of cotton fields infested with R. reniformis.
cotton; Gossypium hirsutum; management; nematode; reniform; Rotylenchulus reniformis; vertical distribution
The effects of combinations of organic amendments, phytochemicals, and plant-growth promoting rhizobacteria on tomato (Lycopersicon esculentum) germination, transplant growth, and infectivity of Meloidogyne incognita were evaluated. Two phytochemicals (citral and benzaldehyde), three organic amendments (pine bark, chitin, and hemicellulose), and three bacteria (Serratia marcescens, Brevibacterium iodinum, and Pseudomonas fluorescens) were assessed. Increasing rates of benzaldehyde and citral reduced nematode egg viability in vitro. Benzaldehyde was 100% efficacious as a nematicide against juveniles, whereas citral reduced juvenile viability to less than 20% at all rates tested. Benzaldehyde increased tomato seed germination and root weight, whereas citral decreased both. High rates of pine bark or chitin reduced plant growth but not seed germination, whereas low rates of chitin increased shoot length, shoot weight, and root weight; improved root condition; and reduced galling. The combination of chitin and benzaldehyde significantly improved tomato transplant growth and reduced galling. While each of the bacterial isolates contributed to increased plant growth in combination treatments, only Brevibacterium iodinum applied alone significantly improved plant growth.
benzaldehyde; Brevibacterium iodinum; chitin; citral; hemicellulose; Lycopersicon esculentum; phytochemicals; pine bark; Pseudomonas fluorescens; rhizobacteria; root-knot nematode; Serratia marcescens; tomato; transplants
A 3-year field rotation study was conducted to assess the potential of switchgrass (Panicum virgatum) to suppress root-knot nematodes (Meloidogyne arenaria), southern blight (Sclerotium rolfsii), and aflatoxigenic fungi (Aspergillus sp.) in peanut (Arachis hypogaea L.) and to assess shifts in microbial populations following crop rotation. Switchgrass did not support populations of root-knot nematodes but supported high populations of nonparasitic nematodes. Peanut with no nematicide applied and following 2 years of switchgrass had the same nematode populations as continuous peanut plus nematicide. Neither previous crop nor nematicide significantly reduced the incidence of pods infected with Aspergillus. However, pod invasion by A. flavus was highest in plots previously planted with peanut and not treated with nematicide. Peanut with nematicide applied at planting following 2 years of switchgrass had significantly less incidence of southern blight than either continuous peanut without nematicide application or peanut without nematicide following 2 years of cotton. Peanut yield did not differ among rotations in either sample year. Effects of crop rotation on the microbial community structure associated with peanut were examined using indices for diversity, richness, and similarity derived from culture-based analyses. Continuous peanut supported a distinctly different rhizosphere bacterial microflora compared to peanut following 1 year of switchgrass, or continuous switchgrass. Richness and diversity indices for continuous peanut rhizosphere and geocarposphere were not consistently different from peanut following switchgrass, but always differed in the specific genera present. These shifts in community structure were associated with changes in parasitic nematode populations.
Arachis hypogaea L; Aspergillus; microbial community; microbial diversity; nematode; Panicum virgatum; peanut; rhizosphere ecology; root-knot nematode; Sclerotium rolfsii; southern blight; switchgrass
Soybean (Glycine max) yield often is limited by the phytoparasitic nematodes Meloidogyne spp. and Heterodera glycines in the southeastern United States. We studied the effects of rotation with bahiagrass (Paspalum notatum), velvetbean (Mucuna pruiens), or continuous soybean, aldicarb, and soybean cultivar on yield and population densities in two fields infested with a mixture of Meloidogyne spp. and H. glycines. Velvetbean and bahiagrass reduced population levels of both nematode species to near zero prior to planting soybean. At harvest, both nematode populations were equal in soybean following bahiagrass and continuous soybean but were lower following velvetbean. Both bahiagrass and velvetbean as previous crops were equal in producing significantly (P < 0.003) higher yield than continuous soybean. Velvetbean increased subsequent soybean yield by 98% and bahiagrass increased subsequent soybean yield by 85% as previous crops compared to continuous soybean. The major differences between the two rotation crops were yield response of the nematode-susceptible cultivars and at-harvest nematode populations. Velvetbean tended to mask genetic differences among cultivars more so than bahiagrass. Velvetbean also produced a more long-term effect on nematode populations, with numbers of both Meloidogyne spp. and H. glycines lower in soybean following velvethean than following bahiagrass or continuous soybean.
aldicarb; bahiagrass; biodiversity; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne; Mucuna pruiens; nematode; Paspalum notatum; root-knot nematode; soybean; soybean cyst nematode; velvetbean
Host physiological events in relation to infestation by parasitic nematodes are not well documented. Soybean plant responses to Meloidogyne incognita infestation were compared to resistant (Bryan) and susceptible (Brim) cultivars at 0, 1, 3, 10, 20, and 34 days after infestation (DAI). The resistant cultivar had higher chitinase activity than the susceptible cultivar at every sample time beginning at 3 DAI. Results from isoelectric focusing gel electrophoresis analyses indicated that three acidic chitinase isozymes with isoelectric points (pIs) of 4.8, 4.4, and 4.2 accumulated to a greater extent in the resistant compared to the susceptible cultivar following challenge. SDS-PAGE analysis of root proteins revealed that two proteins with molecular weights of approximately 31 and 46 kD accumulated more rapidly and to a higher level in the resistant than in the susceptible cultivar. Additionally, three major protein bands (33, 22, and 20 kD) with chitinase activity were detected with a modified SDS-PAGE analysis in which glycolchitin was added into the gel matrix. These results indicate that higher chitinase activity and early induction of specific chitinase isozymes may be associated with resistance to root-knot nematode in soybean.
chitinase; Glycine max; isozymes; Meloidogyne incognita; nematode; pathogenesis-related protein; resistance; soybean
The recent loss of many effective nematicides has led to renewed interest in alternative methods of nematode management. Greenhouse experiments were conducted to determine the effects of rapeseed and velvetbean green manures, and supplemental urea, on the root-knot nematodes Meloidogyne arenaria and M. incognita. Green manures were incorporated with M. arenaria-infested soil using rates totaling 200,300, and 400 mg N/kg soil. Squash plants grown in this soil were evaluated using a gall index and plant dry weight. A second experiment tested ratios of rapeseed green manure to urea resulting in rates of 50, 100, and 150 mg N/kg soil on viability ofM. incognita eggs and degree of galling on squash test plants. A third experiment examined combinations of velvetbean green manure and urea resulting in rates of 100, 200, and 300 mg N/kg soil on viability of M. incognita eggs. When applied at rates of 200, 300, and 400 mg N/kg soil, rapeseed green manure was more effective than velvetbean green manure at reducing galling of squash roots caused by M. arenaria. Decreased viability of M. incognita eggs was observed from treatments that received rates ≥ 1200 mg N/kg soil with higher percentages of N from urea.
alginate; ammonia; Brassica napus; Cucurbita pepo; green manure; Meloidoyne arenaria; Meloidogyne incognita; Mucuna deeringiana; nitrogen; organic amendment; rapeseed; root-knot nematode; squash; velvetbean
The effects of cropping systems (fallow, rotation with sorghum-sudangrass hybrid [Sorghum bicolor × S. sudanense], and continuous soybean [Glycine max]), nematicide (aldicarb) treatment, and soybean cultivar on yield and nematode population densities were studied in a field infested with a mixture of Meloidogyne spp. and Heterodera glycines. Soybean following sorghum-sudangrass yielded 111 kg/ha more than soybean following fallow and 600 kg/ha more than continuous soybean. Aldicarb treatment increased yield by 428 kg/ha, regardless of previous crop. Cultivars interacted significantly with nematicide treatment and previous crop with respect to yield. Sorghum-sudangrass reduced numbers of Meloidogyne spp. compared with fallow and continuous soybean, but cropping system did not affect H. glycines numbers. The cultivar × previous crop and cultivar × nematicide interactions were significant for numbers of Meloidogyne spp. and H. glycines. We concluded that sorghum-sudangrass hybrid and fallow are effective in reducing yield losses caused by mixed populations of Meloidogyne and H. glycines. Highest yields were obtained using crop rotation and cultivars with the highest levels of resistance to both nematodes.
aldicarb; biodiversity; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne; nematode; root-knot nematode; sorghum-sudangrass; Sorghum bicolor; Sorghum sudanense; soybean cyst nematode; soybean
The efficacy of mixtures of dry olive (Olea europea) pomace with biuret, guanidine, and melamine for control of root-knot nematodes (Meloidogyne spp.) on tomato (Lycopersicon esculentum) was studied in greenhouse experiments. Olive pomace (OP) applied pre-plant at 10 g/kg soil was phytotoxic. Mixtures of OP (10 g/kg soil) with biuret or guanidine at 200-300 mg/kg soil reduced or eliminated the phytotoxic effect, controlled root-knot nematodes, and increased soil esterase activity indicative of microbial activity. The addition of biuret or guanidine without OP to soil at rates <300 mg/kg soil did not control root-knot nematodes. Melamine applied at 100-400 mg/kg soil was phytotoxic as were mixtures of melamine with OP. Treatment of OP with anhydrous ammonia increased N content of the material. In another greenhouse experiment, NH₃-treated OP added to soil was not phytotoxic to tomato, suppressed root-knot nematodes, and increased soil esterase activity. Greenhouse and microplot experiments with OP plus chicken litter demonstrated the efficacy of these combination amendments to control root-knot nematodes and increase tomato yields in Meloidogyne-infested soil.
amendments; anhydrous ammonia; biuret; chicken litter; control; guanidine; melamine; Meloidogyne spp.; nematode; Olea europaea; olive pomace; tomato; root-knot nematode
The efficacy of coastal bermudagrass (Cynodon dactylon) as a rotation crop for controt of root-knot nematode (Meloidogyne arenaria) in 'Florunner' peanut (Arachis hypogoea) was evaluated in a 3-year field trial. Coastal bermudagrass-peanut rotation (CBP) was compared with peanut monoculture without nematicide (P - ) and peanut monoculture with aldicarb (P + ). The performance of CBP was also compared with 'Pensacola' bahiagrass (Paspalum notatum)-peanut (BP), and 'Deltapine 90' cotton (Gossypium hirsutum)-peanut (CP) rotations. Each rotation crop was grown for 2 years (1991, 1992) and peanut was planted without nematicide the third year (1993). In contrast with peanut, the alternate crops of bahiagrass, bermudagrass, and cotton did not support M. arenaria populations. In 1993, the lowest numbers of M. arenaria second-stage juveniles (J2) in soil were in plots with CP and BP; these rotations resulted in the highest peanut yields. CBP failed to increase peanut yield and resulted in the highest population densities of M. arenaria J2. In 1993, aldicarb reduced J2 densities in the soil but did not increase peanut yields. Rotations of BP and CP reduced incidence of southern blight (Sclerotium rolfsii) in peanut, but neither CBP nor aldicarb affected the disease.
aldicarb; Arachis hypogaea; bahiagrass; bermudagrass; cotton; crop rotation; cultural practice; Cynodon dactylon; forage; Gossypium hirsutum; grasses; Meloidogyne arenaria; nematode; nematode control; Paspalum notatum; peanut; Sclerotium rolfsii; root-knot; southern blight; sustainable agriculture
The effect of previous crops - soybean (Glycine max) or velvetbean (Mucuna deeringiana) - and aldicarb on yield and nematode numbers for selected soybean cultivars was studied in a field infested with a mixture of Meloidogyne arenaria and Heterodera glycines. Soybean following velvetbean yielded 959 kg/ha more than soybean following soybean. Nematicide treatment resulted in increased yield, and there was no interaction between nematicide treatment and previous crop. Cultivars interacted significantly with nematicide treatment but not with previous crop for yield. Velvetbean reduced numbers of H. glycines but not M. arenaria. Cultivars interacted with previous crop, and the previous crop × nematicide x cultivar interaction was significant for both M. arenaria and H. glycines. We concluded that velvetbean is effective in reducing yield losses caused by mixed populations of M. arenaria and H. glycines, regardless of genetic resistance of soybean cultivar.
Alabama; aldicarb; biodiversity; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; Mucuna deeringiana; nematode; root-knot nematode; soybean cyst nematode; soybean; vetvetbean
Results from a greenhouse experiment at Cabrils, Spain, with two velvetbean (Mucuna deeringiana) accessions (Florida and Mozambique) growing in sterilized sandy loam and inoculated with Meloidogyne arenaria race 2, M. incognita race 1, and M. javanica revealed that the legume was not a host for these nematodes. In contrast, roots of 'Clemson Spineless' okra (Hibiscus esculentum), 'Summer Crookneck' squash (Cucurbita pepo), and 'Davis' soybean (Glycine max) were galled by all three root-knot nematodes. Greenhouse experiments at Auburn, Alabama, using soils infested with Heterodera glycines (race 14) + M. incognita or with H. glycines + M. arenaria (race 2) showed that, in contrast to Davis soybean, a Mexican and the Florida velvetbean accessions were not hosts for the nematodes. An experiment with 'Florunner' peanut (Arachis hypogaea) and the Florida velvetbean in a field infested with M. arenaria (race 1), near Headland, Alabama, showed that significant juvenile populations of the nematode at peanut harvest time were present only in plots with peanut. A microplot rotation experiment demonstrated that 'Black Beauty' eggplant (Solanum melongena) following the Florida velvetbean had heavier shoots and lower numbers of M. arenaria juveniles in the roots and in the soil than eggplant after Summer Crookneck squash or Davis soybean.
cropping system; Heterodera glycines; Meloidogyne arenaria; Meloidogyne incognita; Meloidogyne javanica; Mucuna deeringiana; nematode; nematode control; pest management; root-knot nematode; rotation; soybean cyst nematode; velvetbean
The value of cotton (Gossypium hirsutum cv. Deltapine 90) in rotation with peanut (Arachis hypogaea cv. Florunner) for the management of root-knot nematode (Meloidogyne arenaria) and southern blight (Sclerotium rolfsii) was studied for 6 years in a field at the Wiregrass Substation in southeast Alabama. Peanut yields following either 1 or 2 years of cotton (C-P and C-C-P, respectively) were higher than those of peanut monoculture without nematicide [P(-)]. At-plant application of aldicarb to continuous peanut [P(+)] averaged 22.1% higher yields than those for P(-) over the 6 years of the study. The use of aldicarb in cotton and peanut in the C-C-P rotations increased yields of both crops over the same rotations without the nematicide. When the nematicide was applied to both crops in the C-P rotation, peanut yields were increased in only two of the possible three years when peanut was planted. Application of aldicarb to cotton only in the C-P rotation did not improve peanut yields over those obtained with the rotation without nematicide. Juvenile populations of M. arenaria determined at peanut-harvest time were lowest in plots with cotton. Plots with C-P or C-C-P had lower populations of the nematode than those with either P(-) or P(+). The incidence of southern blight (Sclerotium rolfsii) in peanut was lower in plots with the rotations than in those with peanut monoculture. Aldicarb application had no effect on the occurrence of southern blight.
chemical control; crop rotation; Meloidogyne arenaria; nematicide; nematode; pest management; root-knot nematode; Sclerotium rolfsii; southern blight
The relative efficacy of rotations of soybean with sorghum and tropical corn for nematode management was studied for 2 years in a field infested with root-knot (Meloidogyne arenaria) and soybean cyst (Heterodera glycines, race 14) nematodes. Corn, sorghum, and soybean cv. Kirby were planted in 1989, and in 1990 the same areas were planted with seven soybean cultivars with and without at-plant application ofaldicarb. Corn and sorghum did not support H. glycines, but significant juvenile populations of the nematode in soil were associated with Kirby soybean. Numbers of H. glycines and M. arenaria juveniles in 1990 depended on cultivar and cropping system but were little affected by nematicide treatment. Lowest numbers of H. glycines juveniles were associated with Leflore soybean and the corn-soybean rotation. Numbers of M. arenaria juveniles were highest with Leflore and lowest with Braxton and Brim soybean. The sorghum-soybean rotation resulted in slightly higher numbers of M. arenaria juvenile populations than soybean monoculture or the corn-soybean rotation. Aldicarb increased yields of some cultivars, but its use was not justified economically. Yields of all cultivars were from 19-287% higher in rotation systems than in monoculture.
aldicarb; control; corn; cropping system; cultural practice; Glycine max; Heterodera glycines; Meloidogyne arenaria; nematicide; nematode; pest management; root-knot nematode; rotation; sorghum; Sorghum bicolor; soybean; soybean cyst nematode; Zea mays
The relative value of 'Hale' castorbean (Ricinus communis) and 'Pensacola' bahiagrass (Paspalum notatum) as rotational crops for the management of Meloidogyne arenaria and southern blight (Sclerotium rolfsii) in 'Florunner' peanut (Arachis hypogaea) production was studied for 3 years in a field experiment in southeast Alabama. Peanut following 2 years of castorbean (C-C-P) yielded 43% higher than monocultured peanut without nematicide. At-plant application of aldicarb (30.5 g a.i./100 m row in a 20-cm-wide band) to monocultured peanut resulted in an average 38.9% increase in yield over the 3 years of the experiment. Peanut yield following 2 years of bahiagrass (B-B-P) was 36% higher than monocultured peanut without nematicide. Aldicarb application had no effect on southern blight, but both C-C-P and B-B-P rotations reduced the incidence of the disease in peanut. Juvenile populations of M. arenaria in soil at peanut harvest time were lower in plots with C-C-P than in those with the B-B-P rotation, and both rotations resulted in lower numbers of juveniles in soil than in the untreated monocultured peanut.
aldicarb; antagonistic plants; Arachis hypogaea; bahiagrass; castorbean; control; crop rotation; cropping systems; management; Meloidogyne arenaria; nematode; Paspalum notatum; peanut; Ricinus communis; root-knot nematode
In a 1987 field study juveniles of Meloidogyne arenaria assayed at the time of peanut harvest were almost undetectable in plots planted with American jointvetch (Aeschynomene americana), castor bean (Ricinus communis), partridge pea (Cassia fasiculata), sesame (Sesamum indicum), and cotton (Gossypium hirsutum), whereas plots with peanut (Arachis hypogaea) averaged 120 juveniles/100 cm³ soil. Application of aldicarb in peanut resulted in an average of 27 juveniles/100 cm³ soil. In 1988 all plots were planted to peanut and the aldicarb treatment was repeated in plots that had the nematicide in 1987. In 1988 peanut yields from plots that had no peanut in 1987 were 51-69% higher than the yield from those with continuous peanut and no nematicide. Aldicarb resulted in a 57% increase in yield, which is comparable to 1-year rotation to a nonhost crop. In 1988 harvest-time M. arenaria juvenile population densities in soil were the lowest in plots that had castor bean in 1987; however, the partridge pea-peanut and the sesame-peanut rotations also reduced numbers of juveniles when compared with continuous peanut with no nematicide. The aldicarb treatment resulted in juvenile population densities equivalent to those found with either the partridge pea or the sesame rotations. Rotations with American joint vetch or cotton did not result in lower juvenile population densities in peanut in 1988.
Aeschynomene americana; American jointvetch; Arachis hypogaea; Cassia fasiculata; castor bean; cotton; cropping system; cultural practice; Gossypium hirsutum; Meloidogyne arenaria; peanut; pest management; Ricinus communis; root-knot nematode; rotation; sesame; Sesamum indicum
Previous cropping sequence (corn-soybean vs. soybean-soybean) and aldicarb effects on soybean yield and nematode numbers at harvest for soybean cultivars with various combinations of nematode resistance were determined in 1988 in a sandy loam soil infested with Meloidogyne arenaria race 2 and Heterodera glycines races 3 and 4 at Elberta, Alabama. Yield and nematode numbers differed among cultivars with 'Leflore' having the highest yield. Aldicarb treatment resulted in increased soybean yield but did not affect nematode numbers. Previous cropping sequence did not affect soybean yield or numbers of H. glycines, but soybean following corn-soybean had higher numbers of M. arenaria than soybean following soybean-soybean. The only significant statistical interaction was aldicarb x cultivar for numbers of H. glycines.
aldicarb; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; root-knot nematode; soybean; soybean cyst nematode
Bahiagrass (Paspalum notatum) cultivars Argentine, Pensacola, and Tifton-9 were non-hosts for Meloidogyne arenaria, M. incognita, and Heterodera glycines in a greenhouse experiment using field soil infested with these nematodes. The effect of Pensacola bahiagrass in rotation with peanut (Arachis hypogaea) on M. arenaria was studied in 1986 and 1987 in a field at the Wiregrass substation near Headland, Alabama. Each year soil densities of second-stage juveniles of M. arenaria, determined near peanut harvest, were 96-98% lower under bahiagrass than under peanut. In 1987 peanut yields in plots following bahiagrass were 27% higher than in plots under peanut monoculture. Juvenile population densities in bahiagrass-peanut plots were 41% lower than in plots with continuous peanut. Using bahiagrass for reducing population densities of M. arenaria and increasing peanut yield was as effective as using aldicarb at the recommended rates for peanut.
aldicarb; Arachis hypogaea; bahiagrass; control; cropping system; Heterodera glycines; management; Meloidogyne arenaria; Meloidogyne incognita; peanut; Pratylenchus brachyurus; root-knot nematode; rotation
Rotating soybean (Glycine max cv. Kirby) with peanut (Arachis hypogaea cv. Florunner) for managing Meloidogyne arenaria race 1 was studied for 3 years (1985-87) in a field near Headland, Alabama. Each year soybean plots had lower soil numbers of M. arenaria second-stage juveniles (J2) at peanut harvest than did plots in peanut monocnlture. Peanut following either 1 or 2 years of soybean resulted in approximately 50% reduction in J2 soil population densities and a 14% (1-year soybean) or 20% (2-year soybean) increase in yields compared with continuous peanut. The soybean-peanut rotation increased peanut yield equal to or higher than the yield obtained with continuous peanut treated with aldicarb at 0.34 g a.i./mL.
Arachis hypogaea; cultural practice; Glycine max; integrated pest management; Meloidogyne arenaria; nematode control; peanut; plant breeding; population dynamics; root-knot nematode; soybean
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
Vigna unguiculata, Cassia fasiculata, and Sesamum indicum did not support Meloidogyne arenaria, M. incognita, or Heterodera glycines race 4 in greenhouse studies with soils from peanut and soybean fields. Fagopyron eseulentum, Cyamopsis tetragonoloba, and Cucurbita pepo were hosts to the two Meloidogyne spp. but were nonhosts to H. glycines. Meloidogyne arenaria and M. incognita galled but reproduced poorly in the roots of three types of Amaranthus cruentus, and low densities of these two Meloidogyne spp. (< 10 second-stage juveniles/100 cm³ soil) occurred in soil cultivated with this crop. In a field study no juveniles of M. arenaria determined at peanut harvest were recovered from plots with Ricinus communis, Gossypium hirsutum, Aeschynomene americana, C. fasiculata, or S. indicum. Peanut plots averaged 120 juveniles/100 cm³ soil. Application of aldicarb (12 kg a.i./ha broadcast) in peanut resulted in an average of 27 juveniles/100 cm³ soil. Several crops were as effective as aldicarb treatment for reducing soil juvenile population densities of M. arenaria.
Amaranthus cruentus; Arachis hypogaea; Cassia fasiculata; cropping system; Cucurbita pepo; cultural practice; Cyamopsis tetragonoloba; Fagopyron esculentum; Glycine max; Heterodera glycines; Meloidogyne arenaria; Meloidogyne incognita; peanut; pest management; population dynamics; root-knot nematode; rotation; Sesamum indicum; soybean cyst nematode; Vigna unguiculata
Results of mycological surveys of root-knot and cyst nematodes from tropical regions indicate that most fungal species associated with females or cysts of species of Globodera, Heterodera, and Meloidogyne are those found with nematodes from temperate areas. Some fungal species, however, were found in higher frequency in tropical regions than in temperate countries; e.g., Cylindrocarpon destructans and Ulocladium atrum were the most common species associated with G. pallida and G. rostochiensis cysts in Peru. These fungi are not so frequent in nematodes from temperate areas. Fungi associated with diseased nematodes in the tropics vary greatly in nutritional requirements and include thermophilic species as well as cold-tolerant fungi. Multi-cropping systems possible in most tropical regions may be designed to increase the frequency of occurrence of microbial species antagonistic to phytonematodes.
amendment; biological control; cyst nematode; microbial ecology; pest management; root-knot nematode
One susceptible and six nematode-resistant soybean cultivars were evaluated in the field for their effects on seed yield, nematode populations, and response to the fumigant nematicide, ethylene dibromide. The soil was a loamy sand infested with Meloidogyne arenaria and Heterodera glycines. Cultivars significantly affected yield and numbers of H. glycines but did not affect M. arenaria numbers. Fumigation increased yield and reduced M. arenaria numbers but did not affect numbers of H. glycines. The interaction between cultivars and fumigation was significant for yield but not for nematode numbers.
Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; root-knot nematode; soybean; soybean cyst nematode
A field study was conducted to evaluate one susceptible and six nematode-resistant soybean cultivars for their effects on seed yield, nematode populations, and response to a fumigant nematicide, ethylene dibromide. The soil was a sandy loam, and the field was infested with a mixture of Meloidogyne incognita, M. arenaria, and Heterodera glycines. Soybean cultivars significantly affected yield and juvenile numbers of Meloidogyne spp. but did not affect the H. glycinesjuvenile population. Fumigation increased yield and numbers of H. glycines juveniles, whereas the numbers of Meloidogyne spp. juveniles were decreased. The interaction between cultivars and fumigation treatment was significant for yield but not for nematode numbers.
Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; Meloidogyne incognita; root-knot nematode; soybean; soybean cyst nematode
The effects of aldicarb on soybean cyst (Heterodera glycines) and root-knot (Meloidogyne incognita and M. arenaria) nematode populations, early season insect pests and soybean (Glycine max) yield were evaluated in five field experiments in northern and southern Alabama. Aldicarb significantly (P = 0.05) reduced nematode populations in only two cases: M. arenaria in Centennial soybean in the Wiregrass site and M. incognita in Bedford soybean in a Tennessee Valley site. No significant difference (P = 0.05) in mean percentage main stem or petiole girdling by threecornered alfalfa hopper (Spissistilus festinus) or in mean number of plants damaged by lesser cornstalk borer (Elasmopalpus lignosellus) occurred among treatments in any experiment. Soybean yields were significantly (P = 0.05) increased in only two cases: in the nematode susceptible Essex and Cobb cultivars planted in the Tennessee Valley and Gulf Coast sites, respectively. Unusually dry 1986 weather conditions may have reduced the activity of aldicarb.
Meloidogyne arenaria; Meloidogyne incognita; Heterodera glycines; Spissistilus festinus; Elasmopalpus lignosellus; aldicarb; soybean; Glycine max
The efficacy of methyl bromide for control ofMeloidogyne arenaria and to increase yields of 'Florunner' peanut (Arachis hypogaea) was studied in a field at the Wiregrass Substation near Headland, Alabama. Methyl bromide was applied in the row at a depth of 35 cm using a subsoiler-bedder 2 weeks before planting at rates of 0, 34, 50, 67, 101, and 118 kg a.i./ha. Methyl bromide treatments of 67 kg a.i./ha or higher resulted in significant (P = 0.05) yield increases similar to those obtained in the same experiment with at-plant applications of aldicarb (2.2 kg a.i./ha), EDB (1.55 ml a.i./m row), or 1,3-D (5.10 ml a.i./m row). The relation between yield (Y) and methyl bromide rate (x) was described (R² = 0.97**) by the exponential function: Y = 2,302.963eb, where b = (- 1.901 - ln x)²/169.482. M. arenaria juvenile populations in soil in mid-August were too low to permit establishment of a relation between application rate of methyl bromide and size of the population.
aldicarb; Arachis hypogaea; chemical control; ethylene dibromide; methyl bromide; peanut; pest management