Brassicaceous seed meals are the residual materials remaining after the extraction of oil from seeds; these seed meals contain glucosinolates that potentially degrade to nematotoxic compounds upon incorporation into soil. This study compared the nematode-suppressive ability of four seed meals obtained from Brassica juncea ‘Pacific Gold’, B. napus ‘Dwarf Essex’ and ‘Sunrise’, and Sinapis alba ‘IdaGold’, against mixed stages of Pratylenchus penetrans and Meloidogyne incognita second-stage juveniles (J2). The brassicaceous seed meals were applied to soil in laboratory assays at rates ranging from 0.5 to 10.0% dry w/w with a nonamended control included. Nematode mortality was assessed after 3 days of exposure and calculated as percentage reduction compared to a nonamended control. Across seed meals, M. incognita J2 were more sensitive to the brassicaceous seed meals compared to mixed stages of P. penetrans. Brassica juncea was the most nematode-suppressive seed meal with rates as low as 0.06% resulting in > 90% suppression of both plant-parasitic nematodes. In general B. napus ‘Sunrise’ was the least nematode-suppressive seed meal. Intermediate were the seed meals of S. alba and B. napus ‘Dwarf Essex’; 90% suppression was achieved at 1.0% and 5.0% S. alba and 0.25% and 2.5% B. napus ‘Dwarf Essex’, for M. incognita and P. penetrans, respectively. For B. juncea, seed meal glucosinolate-degradation products appeared to be responsible for nematode suppression; deactivated seed meal (wetted and heated at 70 °C for 48 hr) did not result in similar P. penetrans suppression compared to active seed meal. Sinapis alba seed meal particle size also played a role in nematode suppression with ground meal resulting in 93% suppression of P. penetrans compared with 37 to 46% suppression by pelletized S. alba seed meal. This study demonstrates that all seed meals are not equally suppressive to nematodes and that care should be taken when selecting a source of brassicaceous seed meal for plant-parasitic nematode management.
amendment; isothiocyanate; glucosinolate; Pratylenchus penetrans; Meloidogyne incognita; brassica; seed meal
The efficacy of clean fallow, bermudagrass (Cynodon dactylon) as a rotational crop, and fenamiphos for control of root-knot nematode (Meloidogyne incognita race 1) and soilborne fungi in okra (Hibiscus esculentus), snapbean (Phaseolus vulgaris), and pepper (Capsicum annuum) production was evaluated in field tests from 1993 to 1995. Numbers of M. incognita in the soil and root-gall indices were greater on okra than on snapbean or pepper. Application of fenamiphos at 6.7 kg a.i./ha did not suppress numbers of nematodes on any sampling date when compared with untreated plots. The lack of efficacy could be the result of microbial degradation of the nematicide. Application of fenamiphos suppressed root-gall development on okra following fallow and 1-year sod in 1993, but not thereafter. A few galls were observed on roots of snapbean following 2- and 3-year fallow but none following 1-, 2-, and 3-year bermudagrass sod. Population densities of Pythium aphanidermatum, P. myriotylum, and Rhizoctonia solani in soil after planting vegetables were suppressed by 2- or 3-year sod compared with fallow but were not affected by fenamiphos. Yields of snapbean, pepper, and okra did not differ between fallow and 1-year sod. In the final year of the study, yields of all crops were greater following 3-year sod than following fallow. Application of fenamiphos prior to planting each crop following fallow or sod did not affect yields.
Bermudagrass; Capsicum annuum; Gynodon dactylon; Cyperus esculentus; fenamiphos; Hibiscus esculentus; management; Meloidogyne incognita; nematicide; nematode; nutsedge; okra; pepper; Phaseolus vulgaris; resistance; root-knot nematode; snapbean; sod-based rotation
Resistance of pepper species (Capsicum annuum, C. baccatum, C. chinense, C. chacoense, and C. frutescens), cultivars and accessions to the root-knot nematodes Meloidogyne incognita race 2 and M. javanica, and their graft compatibility with commercial pepper varieties as rootstocks were evaluated in growth chamber and greenhouse experiments. Most of the plants tested were highly resistant to M. javanica but susceptible to M. incognita. Capsicum annuum AR-96023 and C. frutescens accessions as rootstocks showed moderate and relatively high resistance to M. incognita, respectively. In M. incognita-infested soil in a greenhouse, AR-96023 supported approximately 6-fold less nematode eggs per gram root and produced about 2-fold greater yield compared to a nongrafted commercial variety. The commercial variety grafted on AR-96023 produced a yield as great as the non-grafted variety in the root-knot nematode-free greenhouse. Some resistant varieties and accessions used as rootstocks produced lower yields (P < 0.01) than that of the non-grafted variety in the noninfested greenhouse. Use of rootstocks with nematode-resistance and graft compatibility may be effective for control of root-knot nematodes on susceptible pepper.
Capsicum spp.; graft compatibility; Meloidogyne incognita; Meloidogyne javanica; nematode control; pepper; resistance; root-knot nematodes; rootstock
Several cover crops with potential for use in tropical and subtropical regions were assessed for susceptibility to three common species of root-knot nematode, Meloidogyne arenaria, M. incognita, and M. javanica. Crops were selected based on potential use as organic amendments in anaerobic soil disinfestation (ASD) applications. Nematode juvenile (J2) numbers in soil and roots, egg production, and host plant root galling were evaluated on arugula (Eruca sativa, cv. Nemat), cowpea (Vigna unguiculata, cv. Iron & Clay), jack bean (Canavalia ensiformis, cv. Comum), two commercial mixtures of Indian mustard and white mustard (Brassica juncea & Sinapis alba, mixtures Caliente 61 and Caliente 99), pearl millet (Pennisetum glaucum, cv. Tifleaf III), sorghum-sudangrass hybrid (Sorghum bicolor × S. bicolor var. sudanense, cv. Sugar Grazer II), and three cultivars of sunflower (Helianthus annuus, cvs. 545A, Nusun 660CL, and Nusun 5672). Tomato (Solanum lycopersicum, cv. Rutgers) was included in all trials as a susceptible host to all three nematode species. The majority of cover crops tested were less susceptible than tomato to M. arenaria, with the exception of jack bean. Sunflower cv. Nusun 5672 had fewer M. arenaria J2 isolated from roots than the other sunflower cultivars, less galling than tomato, and fewer eggs than tomato and sunflower cv. 545A. Several cover crops did not support high populations of M. incognita in roots or exhibit significant galling, although high numbers of M. incognita J2 were isolated from the soil. Arugula, cowpea, and mustard mixture Caliente 99 did not support M. incognita in soil or roots. Jack bean and all three cultivars of sunflower were highly susceptible to M. javanica, and all sunflower cultivars had high numbers of eggs isolated from roots. Sunflower, jack bean, and both mustard mixtures exhibited significant galling in response to M. javanica. Arugula, cowpea, and sorghum-sudangrass consistently had low numbers of all three Meloidogyne species associated with roots and are good selections for use in ASD for root-knot nematode control. The remainder of crops tested had significant levels of galling, J2, and eggs associated with roots, which varied among the Meloidogyne species tested.
Anaerobic soil disinfestation; ASD; Brassica juncea & Sinapis alba; Canavalia ensiformis; cover crops; cowpea; Eruca sativa; Helianthus annuus; jack bean; management; Meloidogyne arenaria; M. incognita; M. javanica; mustard; pearl millet; Pennisetum glaucum; root-knot nematodes; sorghum-sudangrass; sunflower; Vigna unguiculata
The relationship between population densities of race 1 of Meloidogyne incognita and yield of eggplant was studied. Microplots were infested with finely chopped nematode-infected pepper roots to give population densities of 0, 0.062, 0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 32, 64, and 128 eggs and juveniles/cm³ soil. Both plant growth and yield were suppressed by the nematode. A tolerance limit of 0.054 eggs and juveniles/cm³ soil and a minimum relative yield of 0.05 at four or more eggs and juveniles/cm³ soil were derived by fitting the data with the equation y = m + (1 - m)zP⁻T. Maximum nematode reproduction rate was 12,300. Hatch of eggs from egg masses in water or from sodium hypochlorite dissolved egg masses was similar (41% and 39%), but egg viability was significantly greater from egg masses in water (58%) than from sodium hypochlorite dissolved egg masses (12%) after 4 weeks. Greater numbers of nematodes were collected from roots of tomatoes from soil infested with entire egg masses than from tomato roots from soil infested with egg masses dissolved by sodium hypochlorite.
root-knot nematode; tolerance limit; eggplant; inoculum; Solanum melongena; Meloidogyne incognita
Four pepper genotypes classified as resistant and four pepper genotypes classified as susceptible to several avirulent populations of M. incognita were compared for their reactions against a population of Meloidogyne incognita (Chitwood) Kofoid and White which had been shown to be virulent to resistant bell pepper (Capsicum annuum) in preliminary tests. The virulent population of M. incognita originated from a commercial bell pepper field in California. The resistant pepper genotypes used in all experiments were the Capsicum annuum cultivars Charleston Belle, Carolina Wonder, and Carolina Cayenne, and the C. chinense cultigen PA-426. The susceptible pepper genotypes used in the experiments were the C. annuum cultivars Keystone Resistant Giant, Yolo Wonder B, California Wonder, and the C. chinense cultigen PA-350. Root gall indices (GI) were ≥ 3.0 for all genotypes in both tests except for PA-426 (GI=2.57) in test 1 and ‘Carolina Cayenne’ (GI=2.83) in test 2. Numbers of eggs per gram fresh root weight ranged from 20,635 to 141,319 and reproductive indices ranged from 1.20 to 27.2 for the pepper genotypes in both tests, indicating that all eight pepper genotypes tested were susceptible to the M. incognita population used in these tests. The M. incognita population used in these studies overcame resistance conferred by the N gene in all resistant genotypes of both C. annuum and C. chinense.
Capsicum annuum var. annuum; Capsicum chinense; Meloidogyne incognita; methyl bromide alternatives; nematode resistance
Meloidogyne incognita-infected and noninfected tubers of yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus) were treated with 56 L/ha 1,3-dichloropropene (1,3-D) in microplots and subsequently examined for tuber and nematode viability in the greenhouse using a chile pepper (Capsicum annuum) bioassay system. The study was conducted three times. Nutsedge tuber viability and M. incognita harbored in both yellow and purple nutsedge tubers were unaffected by 1,3-D treatment. Nematode reproduction on nutsedges and associated chile pepper plants varied among years, possibly due to differing levels of tuber infection or soil temperature, but was not affected by fumigation. The presence of M. incognita resulted in greater yellow nutsedge tuber germination and reproduction. The efficacy of 1,3-D for management of M. incognita in chile pepper production is likely to be reduced when nutsedges are present in high numbers, reinforcing the importance of managing these weeds and nematodes simultaneously.
Capsicum annuum; chile pepper; Cyperus esculentus; Cyperus rotundus; 1,3-dichloropropene; fumigant; management; Meloidogyne incognita; nematicide; perennial weed; purple nutsedge; root-knot nematode; tuber; yellow nutsedge
Field trials were conducted during 1986, 1988, 1989, and 1991 to compare the effects of 1,3-dichloropropene, fenamiphos, and carbofuran on yield and quality of chile peppers (Capsicum annuum) in soil infested with Meloidogyne incognita. When compared with untreated plots, numbers of M. incognita juveniles recovered from soil 60 and(or) 90 days after chile pepper emergence were reduced (P = 0.05) following 1,3-D treatment every year except 1986. Nematode numbers were also reduced (P = 0.05) by fenamiphos in 1989. Chile pepper yields were significantly higher than those in untreated control plots (P = 0.05) all 4 years in plots treated with 1,3-D and in 1989 in plots treated with fenamiphos. Use of carbofuran did not significantly reduce nematode numbers or enhance yields in these experiments. Green chile pepper fruit quality was enhanced (P = 0.05) following 1,3-D treatments in 1988 and 1989 but was unaffected by fenamiphos or carbofuran application. Increasing placement depth of 1,3-D from 28 to 48 cm increased (P = 0.05) red chile pepper yield compared with that obtained with conventional placement in 1988 only, and did not affect green chile pepper yield.
application technique; Capsicum annuum; carbofuran; chile pepper; crop quality; depth of placement; fenamiphos; fumigation; Meloidogyne incognita; nematode; 1,3-dichloropropene; root-knot nematode; yield
Extracts of Chinese herbal medicines from plants representing 13 families were tested for their ability to suppress plant-parasitic nematodes. Effective concentration (EC50 and EC90) levels for 18 of the extracts were determined in laboratory assays with Meloidogyne javanica juveniles and all stages of Pratylenchus vulnus. Efficacy of 17 extracts was tested against M. javanica in soil. Generally, EC50 and EC90 values determined in the laboratory were useful indicators for application rates in the soil. Extracts tested from plants in the Liliaceae reduced galling of tomato by M. javanica and were not phytotoxic. Similarly, isothiocyanate-yielding plants in the Brassicaceae suppressed root galling without phytotoxicity. Other plant extracts, including those from Azadirachta indica, Nerium oleander, and Hedera helix, suppressed root galling but were phytotoxic at the higher concentrations tested. Many of these plant sources have been tested elsewhere. Inconsistency in results across studies points to the need for identification of active components and for determination of concentration levels of these components when plant residues or extracts are applied to soil.
botanicals; herbal remedies; Meloidogyne javanica; natural products; plant extracts; plant-parasitic nematodes; Pratylenchus vulnus; suppression; toxic effects; phytotoxicity
Two microplot experiments in 1981 and 1983 provided information on the effect of different population densities of Meloidogyne incognita race 1 and yield of sweet pepper. Microplots were square concrete pipes (30 × 30 cm and 50 cm long) filled with 40 liters of soil infested with 0, 0.062, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256, and 512 eggs and juveniles/cm³ soil. Tolerance limits of 2.2 and 0.165 eggs and juveniles/cm³ soil and minimum yields of 58% and 20% of the controls were obtained in 1981 and 1983, respectively. Maximum reproduction rates of the nematode were 274 and 1,498 at the lowest initial population density. The population of the nematode declined rapidly after harvest, and only 13% and 6.5% of eggs and juveniles were detected in the soil after 1 and 6 months, respectively.
root-knot nematode; tolerance limit; population decline; sweet pepper
Stability of resistance to Meloidogyne incognita (Kofoid &White) Chitwood was determined in pepper (Capsicum chinense Jacq. and C. annuum L.) at 24, 28, and 32 °C. Reactions of the C. annuum cultivars Charleston Belle and Keystone Resistant Giant and the C. chinense cultigens PA-426 and PA-350 to M. incognita were compared. Charleston Belle is homozygous for the N gene that confers resistance to M. incognita in C. annuum, and Keystone Resistant Giant is the susceptible recurrent parent of Charleston Belle. PA-426 is homozygous for a single dominant resistance gene that is allelic to the N gene, and PA-350 is susceptible. Root galling, egg-mass production, numbers of eggs per g fresh root, and reproductive factor of M. incognita increased for all pepper genotypes as temperature increased. Severity of root galling and nematode reproduction were less for PA-426 and Charleston Belle compared to PA-350 and Keystone Resistant Giant at all temperatures. However, both PA-426 and Charleston Belle exhibited a partial loss of resistance at the higher temperatures. For example, at 32 °C, the numbers of M. incognita eggs per g fresh root and the reproductive index for PA-426 and Charleston Belle were in the susceptible range. Nevertheless, the gall index for both cultivars was still within the resistant range. Both PA-350 and Keystone Resistant Giant exhibited highly susceptible reactions at 28 and 32 °C. Although the resistances of PA-426 and Charleston Belle were somewhat compromised at high temperatures, cultivars possessing these resistances will still be useful for managing M. incognita under high soil temperatures.
Capsicum annuum L.; C. chinense Jacq.; habanero; heat stability; Meloidogyne incognita; resistance; root-knot nematode; Scotch Bonnet pepper; soilborne pathogen; soil temperature; vegetable breeding
The aim of the present study was the estimation of changes in the phytotoxicity of soils amended with sewage sludge with relation to Lepidium sativum, Sinapis alba and Sorghum saccharatum. The study was realised in the system of a plot experiment for a period of 29 months. Samples for analyses were taken at the beginning of the experiment, and then after 5, 17 and 29 months. Two kinds of sewage sludge, with varying properties, were added to a sandy soil (soil S) or a loamy soil (soil L) at the dose of 90 t/ha. The addition of sewage sludge to the soils at the start of the experiment caused a significant reduction of both seed germination capacity and root length of the test plants, the toxic effect being distinctly related to the test plant species. With the passage of time the negative effect of sewage sludge weakened, the extent of its reduction depending both of the kind of sewage sludge applied and on the type of soil. Phytotoxicity of the soils amended with the sewage sludges was significantly lower at the end of the experiment than at the beginning. The species of the plants grown on the soils also had a significant effect on their phytotoxicity. The greatest reduction of toxicity was observed in the soil on which no plants were grown (sandy soil) and in the soil under a culture of willow (loamy soil). Solid phase of sewage sludge-amended soils was characterised by higher toxicity than their extracts.
Electronic supplementary material
The online version of this article (doi:10.1007/s11270-012-1248-8) contains supplementary material, which is available to authorized users.
Phytotoxicity; Sewage sludge; Field experiment; Solid phase; Extracts
The effects of Meloidogyne incognita on the Big Jim, Jalapeno, and New Mexico No. 6 chile (Capsicum annuum) cultivars were investigated in microplots for two growing seasons. All three cultivars were susceptible to M. incognita and reacted similarly to different initial populations of this nematode. Severe stunting and yield suppressions occurred at all initial M. incognita densities tested ranging from 385 to 4,230 eggs and larvae/500 cm³ soil. Regression analysis of the microplot data from a sandy loam soil showed yield losses of 31% for the 1978 season and 25% for the 1979 season for the three cultivars for each 10-fold increase in the initial population of M. incognita.
Capsicum annuum; Meloidogyne incognita; root-knot nematode; pepper
Meloidogyne incognita (Mi) reproduction and host plant responses in chile pepper (Capsicum annuum) and yellow nutsedge (Cyperus esculentus = YNS) to three sources of inoculum obtained by rearing a single Mi population on chile, YNS, and tomato were evaluated in two factorial greenhouse experiments. The interactive effects of Mi inoculum source and crop-weed competition were determined. In the absence of YNS competition, chile growth was reduced less by Mi inoculum from chile than by inoculum from YNS or tomato. When YNS was present, chile root weight was not affected and shoot weight increased with Mi initial inoculation, regardless of inoculum source. Chile plants inoculated with Mi from tomato exhibited double the nematode reproduction observed with inoculum from chile or YNS. With chile present, Mi reproduction on YNS was nearly three times greater with inoculum from tomato, but reproduction was similar among inoculum sources when chile was absent. Reductions in YNS root mass due to competition from chile failed to reduce the total number of Mi eggs produced on YNS plants. Differences in total Mi reproduction among inoculum sources were not attributable to differences in root growth or plant competition. This study illustrates the influence of Mi-YNS interactions and previous hosts on severity of Mi infection.
Capsicum annuum; chile pepper; Cyperus esculentus; host-parasite relationship; inoculum source; interaction; Meloidogyne incognita; root-knot nematode; weed; yellow nutsedge
The effects of soil type and initial inoculum density (Pi) on the reproductive and damage potentials of Meloidogyne incognita and Rotylenchulus reniformis on cotton were evaluated in microplot experiments from 1991 to 1993. The equilibrium nematode population density for R. reniformis on cotton was much greater than that of M. incognita, indicating that cotton is a better host for R. reniformis than M. incognita. Reproduction of M. incognita was greater in coarse-textured soils than in fine-textured soils, whereas R. reniformis reproduction was greatest in a Portsmouth loamy sand with intermediate percentages of clay plus silt. Population densities of M. incognita were inversely related to the percentage of silt and clay, but R. reniformis was favored by moderate levels of clay plus silt (ca. 28%). Both M. incognita races 3 and 4 and R. reniformis effected suppression of seed-cotton yield in all soil types evaluated. Cotton-yield suppression was greatest in response to R. reniformis at high Pi. Cotton maturity, measured as percentage of open bolls at different dates, was affected by the presence of nematodes in all 3 years.
cotton; ecology; edaphic factor; Gossypium hirsutum; Meloidogyne incognita; nematode; plant-disease loss; reniform nematode; root-knot nematode; Rotylenchulus reniformis; soil texture; yield
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
An experiment was conducted at the farm of Zonal Adaptive Research Station, Uttar Banga Krishi Viswavidhyalaya, Pundibari, Cooch Behar, West Bengal to evaluate the effect of pendimethalin on the yield, weed density and phytotoxicity in different varieties of rai (Brassica juncea) and yellow sarson (B. campestris var. yellow sarson) under higher soil moisture regime in Terai region of West Bengal. Pre-emergence application of pendimethalin at higher dose i.e. 1.0 kg/ha recorded higher plant mortality (30.92%) due to the presence of higher concentration of pendimethalin residue (0.292 µg/g) till the tenth day of crop age and consequently had the reduced yield (12.59 q/ha) than the dose of 0.7 kg/ha (13.33 q/ha) where plant mortality was only 12.62% due to comparatively lower level of pendimethalin residue (0.192 µg/g). Although the application of pendimethalin at the rate of 1.0 kg/ha was able to control weed more efficiently (18.96/m2) than the dose of 0.7 kg/ha (30.41/m2) and subsequent lower doses. The herbicide leached down to the root zone resulting in phytotoxicity towards crop. Yellow sarson group (Brassica campestris) showed more susceptibility than rai (Brassica juncea) group against pendimethalin application at higher doses.
rape seed; mustard; pendimethalin; dinitroaniline; phytotoxicity; leaching
The efficacy of abamectin as a seed treatment for control of Meloidogyne incognita on cotton was evaluated in greenhouse, microplot, and field trials in 2002 and 2003. Treatments ranging from 0 to 100 g abamectin/100 kg seed were evaluated. In greenhouse tests 35 d after planting (DAP), plants from seed treated with abamectin were taller than plants from nontreated seed, and root galling severity and nematode reproduction were lower where treated seed were used. The number of second stage juveniles that had entered the roots of plants from seed treated with 100 g abamectin/kg seed was lower during the first 14 DAP than with nontreated seed. In microplots tests, seed treatment with abamectin and soil application of aldicarb at 840 g/kg of soil reduced the number of juveniles penetrating seedling roots during the first 14 DAP compared to the nontreated seedlings. In field plots, population densities of M. incognita were lower 14 DAP in plots that received seed treated with abamectin at 100 g/kg seed than where aldicarb (5.6 kg/ha) was applied at planting. Population densities were comparable for all treatments, including the nontreated controls, at both 21 DAP and harvest. Root galling severity did not differ among treatments at harvest.
abamectin; Avermectin; Gossypium hirsutum; Meloidogyne incognita; nematicide
Seeds of 'Coker 68-15' wheat and 'Maton' rye were immersed for 5 min in acetone solutions of oxamyl, carbofuran, or phenamiphos containing 0, 0.25, 0.5, 1.25, 2.5, or 5.0% (w/v) nematicide; after drying, seeds were planted in pots containing 500 gm of sandy loam naturally infested with Hoplolaimus galeatus and Tylenchorhynchus claytoni. In sterilized soil, only the 5% concentrations of all nematicides were toxic to rye, whereas both the 2.5 and 5% concentrations were damaging to wheat. Phenamiphos was generally the most phytotoxic compound. Numbers of T. claytoni in soil declined sharply in response to seed treatment with all nematicides. In soil planted with wheat, numbers were reduced 80% by the 1.25% treatment; little additional control was shown with higher concentrations. Soil with rye showed a 40-60% reduction in numbers of T. claytoni with the 1.25% solutions and little change at higher concentrations. Hoplolaimus galeatus developed only in pots with rye; root populations were suppressed (30-50%) by treatment with 1.25% or higher concentrations of all nematicides.
control; oxamyl; carbofuran; phenamiphos; Secale; cereale; Triticum aestivum; Hoplolaimus galeatus; Tylenchorhynchus claytoni
Cultivars of oilseed radish (Raphanus sativus var. oleifera cv. Adagio, Nemex, Pegletta, Renova, Siletina, Siletta Nova, and Ultimo), white mustard (Sinapis alba cv. Albatross, Emergo, Maxi, Martigena, Metex, and Serval), buckwheat (Fagopyrum esculentum cv. Prego, Tardo), and phacelia (Phacelia tanacetifolia cv. Angelia) were tested for susceptibility to Meloidogyne incognita race 3 and Meloidogyne javanica. Experiments were conducted in growth chambers at 25 C and 16 hours light for 42 days after inoculation with second-stage juveniles (J2). All cultivars were susceptible to M. incognita and M. javanica. The oilseed radish (cv. Nemex, Pegletta, and Renova) and white mustard (cv. Emergo) were also examined to determine the influence of Heterodera schachtii on susceptibility to Plasmodiophora brassicae as measured by incidence and severity of root galling. All cultivars were susceptible, and neither the severity nor incidence of clubroot galling was affected by H. schachtii.
buckwheat; clubroot of crucifers; Fagopyrum esculentum; Meloidogyne incognita; Meloidogyne javanica; nematode; oilseed radish; Phacelia tanacetifolia; Plasmodiophora brassicae; Raphanus sativus; root-knot nematode; Sinapis alba; trap crop; white mustard
Two greenhouse experiments were conducted to examine the effect of Crotalaria juncea amendment on Meloidogyne incognita population levels and growth of yellow squash (Cucurbita pepo). In the first experiment, four soils with a long history of receiving yard waste compost (YWC+), no-yard-waste compost (YWC-), conventional tillage, or no-tillage treatments were used; in the second experiment, only one recently cultivated soil was used. Half of the amount of each soil received air-dried residues of C. juncea as amendment before planting squash, whereas the other half did not. Crotalaria juncea amendment increased squash shoot and root weights in all soils tested, except in YWC+ soil where the organic matter content was high without the amendment. The amendment suppressed the numbers of M. incognita if the inoculum level was low, and when the soil contained relatively abundant nematode-antagonistic fungi. Microwaved soil resulted in greater numbers of M. incognita and free-living nematodes than frozen or untreated soil, indicating nematode-antagonistic microorganisms played a role in nematode suppression. The effects of C. juncea amendment on nutrient cycling were complex. Amendment with C. juncea increased the abundance of free-living nematodes and Harposporium anguillulae, a fungus antagonistic to them in the second experiment but not in the first experiment. Soil histories, especially long-term yard waste compost treatments that increased soil organic matter, can affect the performance of C. juncea amendment.
free-living nematode; nematode-trapping fungi; organic amendments; root-knot nematode; soil ecosystem; soil nutrient; sunn hemp; tillage
Tannins, which are water-soluble polyphenols, are toxic to numerous fungi, bacteria, and yeasts. Our objectives were to study the efficacy of tannic acid in control of Meloidogyne arenaria on tomato and its effects on the behavior of M. arenaria, M. incognita, Heterodera glycines, and Radopholus similis. Three concentrations of tannic acid, 0.1, 1.0, and 10 g/500 cm³ of soil, were applied preplant (powder) and at-plant (powder and drench) into soil infested with M. arenaria. Tannic acid at the 1.0-g rate reduced galling compared with the untreated control, regardless of methods of application. The 0.1-g rate resulted in no reduction in galling when applied preplant but reduced galling when applied as a drench and in one of two experiments when applied at-plant. The 10-g rate was phytotoxic to tomato seedlings except when applied 7 days preplant. In the latter case, root galling was suppressed to very low numbers. In behavior studies on water agar, Meloidogyne second-stage juveniles were attracted to areas with an increasing tannic acid gradient. Radopholus similis was repelled from the tannic acid gradient in one of two experiments. There was no effect on H. glycines. The response of M. arenaria second-stage juveniles to different concentrations of tannic acid dissolved in alginate was tested. Movement behavior of the second-stage juveniles were observed at 1,000 and 10,000 μg/ml of tannic acid, but not at 10 and 100 μg/ml.
alginate; attractant; burrowing nematode; Heterodera glycines; Meloidogyne arenaria; Meloidogyne incognita; nematode; polyphenol; Radopholus similis; repellent; root-knot nematode; soybean cyst nematode; tannic acid
To evaluate the antioxidant and antiglycation potential of polyphenols from three spices; alligator pepper, ginger and nutmeg.
Polyphenol extracts of these spices were subjected to brine-shrimp lethality assay, phytotoxicity test, DPPH and superoxide anion radical scavenging as well as BSA-glucose antiglycation assay.
Results obtained showed that polyphenol extract of ginger has the highest antioxidant potential with IC50 0.075 and 0.070 mg/mL for DPPH and superoxide anion radical scavenging assay while alligator pepper displayed highest antiglycation activity with IC50 0.125 mg/mL. However, nutmeg extract exhibited weakest cytotoxic and phytotoxic potential with LD50 4359.70 and 1490 µg/mL respectively.
It can be concluded that the polyphenol extracts of alligator pepper, ginger and nutmeg displayed good antioxidant as well as antiglycation potential and are safe for consumption.
Glycation; Hyperglycemia; Polyphenols; Spices; Free radicals; Antioxidants
Pre-plant soil fumigation with methyl bromide and host resistance were compared for managing the southern root-knot nematode (Meloidogyne incognita) in pepper. Three pepper cultivars (Carolina Cayenne, Keystone Resistant Giant, and California Wonder) that differed in resistance to M. incognita were grown in field plots that had been fumigated with methyl bromide (98% CH₃Br : 2% CCl₃NO₂ [w/w]) before planting or left untreated. Carolina Cayenne is a well-adapted cayenne-type pepper that is highly resistant to M. incognita. The bell-type peppers Keystone Resistant Giant and California Wonder are intermediate to susceptible and susceptible, respectively. None of the cultivars exhibited root galling in the methyl bromide fumigated plots and nematode reproduction was minimal (<250 eggs/g fresh root), indicating that the fumigation treatment was highly effective in controlling M. incognita. Root galling of Carolina Cayenne and nematode reproduction were minimal, and fruit yields were not reduced in the untreated plots. The root-galling reaction for Keystone Resistant Giant was intermediate (gall index = 2.9, on a scale of 1 to 5), and nematode reproduction was moderately high. However, yields of Keystone Resistant Giant were not reduced in untreated plots. Root galling was severe (gall index = 4.3) on susceptible California Wonder, nematode reproduction was high, and fruit yields were reduced (P ≤ 0.05) in untreated plots. The resistance exhibited by Carolina Cayenne and Keystone Resistant Giant provides an alternative to methyl bromide for reducing yield losses by southern root-knot nematodes in pepper. The high level of resistance of Carolina Cayenne also suppresses population densities of M. incognita.
Capsicum annuum; Meloidogyne incognita; methyl bromide alternatives; nematode management; nematode resistance; pepper; root-knot nematodes
Background and Aims
Karrikinolide (KAR1) is a smoke-derived chemical that can trigger seeds to germinate. A potential application for KAR1 is for synchronizing the germination of weed seeds, thereby enhancing the efficiency of weed control efforts. Yet not all species germinate readily with KAR1, and it is not known whether seemingly non-responsive species can be induced to respond. Here a major agronomic weed family, the Brassicaceae, is used to test the hypothesis that a stimulatory response to KAR1 may be present in physiologically dormant seeds but may not be expressed under all circumstances.
Seeds of eight Brassicaceae weed species (Brassica tournefortii, Raphanus raphanistrum, Sisymbrium orientale, S. erysimoides, Rapistrum rugosum, Lepidium africanum, Heliophila pusilla and Carrichtera annua) were tested for their response to 1 µm KAR1 when freshly collected and following simulated and natural dormancy alleviation, which included wet–dry cycling, dry after-ripening, cold and warm stratification and a 2 year seed burial trial.
Seven of the eight Brassicaceae species tested were stimulated to germinate with KAR1 when the seeds were fresh, and the remaining species became responsive to KAR1 following wet–dry cycling and dry after-ripening. Light influenced the germination response of seeds to KAR1, with the majority of species germinating better in darkness. Germination with and without KAR1 fluctuated seasonally throughout the seed burial trial.
KAR1 responses are more complex than simply stating whether a species is responsive or non-responsive; light and temperature conditions, dormancy state and seed lot all influence the sensitivity of seeds to KAR1, and a response to KAR1 can be induced. Three response types for generalizing KAR1 responses are proposed, namely inherent, inducible and undetected. Given that responses to KAR1 were either inherent or inducible in all 15 seed lots included in this study, the Brassicaceae may be an ideal target for future application of KAR1 in weed management.
Brassicaceae; butenolide; germination; karrikinolide; karrikins; KAR1; physiological dormancy; seed dormancy; weeds