Three Ektaphelenchus species with unusual spicules are redescribed. Ektaphelenchus obtusus and E. riograndensis are redescribed from newly discovered material in the collection of the USDA Forest Service RMRS. Lectotype slides are designated for both species. Ektaphelenchus obtusus is characterized by a set-off head, lips of unequal size, double rows of oocytes and spermatocytes, and a hooked spicule terminus. Ektaphelenchus riograndensis is distinguished by a rounded head with six equal lips, and spicules with a large, rounded apex, and recurved terminus. A bursa and gubernaculum are absent in both species. Ektaphelenchus scolyti is redescribed from type material deposited in the collection of Rothamsted Experimental Station. It is characterized by a well set-off head, double rows of oocytes and spermatocytes, and spicules with a hooked terminus. A bursa and gubernaculum are absent.
Aphelenchina; Cryptaphelenchoides scolyti; Ektaphelenchus macrostylus; Ektaphelenchus obtusus; Ektaphelenchus riograndensis; Ektaphelenchus scolyti; lectotype; nematode; taxonomy
A total of 33 corn hybrids were evaluated in a series of greenhouse and field trials to determine if they differed in resistance to either Meloidogyne incognita race 3 or M. arenaria race 1. Reproduction of M. incognita race 3 and M. arenaria race 1 on the hybrids was also compared. Reproduction of M. arenaria differed among corn hybrids after 58 to 65 days in greenhouse experiments; however, reproduction was similar among hybrids in the field experiment. No hybrids were consistently resistant to M. incognita. Two isolates of M. arenaria and two of M. incognita were evaluated in the greenhouse trials, and no evidence of isolate-dependent resistance was observed. Meloidogyne incognita reproduced better than M. arenaria on the hybrids in this study. A survey of 102 corn fields from 11 counties throughout southern Georgia was conducted to determine the relative frequency of M. incognita and M. arenaria. Meloidogyne species were found in 34 of the fields surveyed, and 93.9% of these were identified as M. incognita. The frequency of occurrence of M. incognita was 99.6% if the previous crop was cotton and 84.6% if the previous crop was peanut. Pratylenchus spp. were extracted from all intact corn root systems examined.
corn; host suitability; Meloidogyne arenaria race 1; M. incognita race 3; peanut root-knot nematode; resistance; southern root-knot nematode; survey; Zea mays
The efficacy of rye (Secale cereale) and wheat (Triticum aestivum) winter cover crops and cotton stalk and root destruction (i.e., pulling them up) were evaluated in field tests during two growing seasons for Hoplolaimus columbus management in cotton. The effect of removing debris from the field following root destruction also was evaluated. Wheat and rye produced similar amounts of biomass, and both crops produced more biomass (P ≤ 0.05) following cotton root destruction. Cover crops did not suppress H. columbus population levels or increase subsequent cotton yields. Cotton root destruction did not affect cotton stand or plant height the following year. Cotton root destruction lowered (P ≤ 0.05) H. columbus population levels at planting in 1996 but not in 1997, but cotton yield was not increased by root destruction in either year. Removing debris following root destruction did not lower H. columbus levels compared to leaving debris on the soil surface. This study suggests that a rye or wheat cover crop or cotton root destruction following harvest is ineffective for H. columbus management in cotton.
Columbia lance nematode; cotton; cover crop; Gossypium hirsutum; Hoplolaimus columbus; nematode management; root destruction; rye; Secale cereale; Triticum aestivum; wheat
The efficacy of foliar applications of oxamyl were evaluated for the management of Rotylenchulus reniformis on cotton in Mississippi. Two tests were established in Tallahatchie County on a fine sandy loam soil (56.8% sand, 37.8% silt, 5.3% clay, pH 5.4, and 0.3% OM) naturally infested with R. reniformis. Oxamyl was applied as a foliar spray at 0.14, 0.27, or 0.53 kg a.i./ha to cotton plants that had reached the sixth true leaf growth stage. A second oxamyl application was applied 14 days after the first treatment at the same rates. All oxamyl treatments also received aldicarb at 0.59 kg a.i./ha at planting. Controls consisted of aldicarb alone, disulfoton (which is not a nematicide), and an untreated control. Oxamyl reduced R. reniformis numbers at 79 and 107 days after planting in Test 1 and at 62 and 82 days after planting in Test 2 compared to aldicarb at 0.59 kg a.i./ha alone and the controls that received neither material. Average reniform population densities in oxamyl-treated plots were 24.5% and 30% lower than with aldicarb alone and the controls. Cotton plant height was greater in plots that received oxamyl at all rates than in the controls. Cotton in oxamyl plus aldicarb and aldicarb alone treatments produced more bolls per plant and had a greater total boll weight than disulfoton and the untreated control. Seed cotton yields were greater in oxamyl-treated plots than for disulfoton-treated and the untreated control.
aldicarb; cotton; Gossypium hirsutum; management; nematicide; nematode; oxamyl; reniform nematode; Rotylenchulus reniformis
Population densities of the Mediterranean biotype of Tylenchulus semipenetrans were monitored in soil and citrus roots at 3-month intervals for 3 consecutive years in four citrus orchards in the provinces of Tarragona (Amposta and Xalamera) and Valencia (Moncada and Ca´rcer). Nematode population densities in soil peaked once a year in April or July depending on the orchard and year. Numbers of females per gram of root increased once or twice each year. The maximum density of eggs per gram of root was recorded in April at Xalamera and Ca´rcer orchards, but there was no recognizable peak in the other two orchards. Numbers of nematodes in soil, females or eggs per gram of root, or eggs per female were correlated with either temperature or rainfall in the sampling month, 1 month before sampling, or in the second preceding month, depending on the orchard. Members of the Pasteuria group were present in the four citrus orchards, and a positive relationship occurred between nematodes in soil and bacterial parasitism (r² = 0.75) in the orchard at Amposta.
citrus nematode; Pasteuria spp.; population dynamics; Tylenchulus semipenetrans
The effect of 93 field crop and pasture cultivars on the end-of-season population densities of Pratylenchus thornei in soil was determined in the field in southeastern Australia. Wheat and barley cultivars had different effects on the population densities of P. thornei. Most commercial wheat cultivars that are grown in southeastern Australia were susceptible, while the barley cultivars were resistant or moderately resistant. Lentil, field pea, fenugreek, linseed, and medic were found to be resistant to P. thornei, while faba bean and canola were moderately resistant and narbon bean, subterranean clover, and vetch were susceptible. This study will enable growers to select rotational crops to reduce the population densities of these nematodes and therefore minimize the yield loss they cause.
barley; canola; crop rotation; faba bean; fallow; field crop; field pea; lentil; management; Pratylenchus thornei; resistance; root lesion nematode; vetch; wheat
During 1993-94, several fumigant and nonfumigant nematicides were tested alone and in combination at various rates for control of Columbia root-knot nematode (Meloidogyne chitwoodi) in potato. Ethoprop, oxamyl, or metam sodium alone did not adequately reduce tuber infection. Metam sodium plus ethoprop reduced culled tubers to 3%, and metam sodium plus 2 or 3 foliar applications of oxamyl reduced culls to ≤10% in all but one instance. Fosthiazate provided excellent control of tuber infection with or without metam sodium. Rates of 1,3-dichloropropene (1,3-D) below 234 liters/ha did not always adequately control tuber damage, but 140 liters/ha of 1,3-D plus ethoprop reduced the percentage of culled tubers to zero. 1,3-Dichloropropene plus chloropicrin did not provide better control than 1,3-D alone. Combinations of 1,3-D at 94 liters/ha or greater plus metam sodium at 374 liters/ha or greater consistently provided excellent control of tuber damage by M. chitwoodi and would be the treatment of choice where soilborne fungal pathogens are also present.
1,3-dichloropropene; aldicarb; ethoprop; fosthiazate; fumigants; Meloidogyne; metam sodium; nematicides; oxamyl; potato; root-knot nematode
Rhizobacteria were isolated from the rhizoplane and rhizosphere of soybean plants from fields in Arkansas and tested for their effect on numbers of soybean cyst nematode (Heterodera glycines). In initial greenhouse tests in heat-treated silt loam soil, 138 of the 201 bacterial isolates tested had no influence on numbers of cysts and eggs + second-stage juveniles (J2) of H. glycines, 36 reduced (suppressive isolates) and 27 increased (enhancing isolates) numbers of cysts and (or) eggs + J2 when compared to the controls (P ≤ 0.05). When 20 suppressive and five enhancing isolates were retested in the same soil, the results were highly variable and inconclusive. The 25 isolates were then evaluated in vitro for their effects on eggs and J2 of H. glycines. No clear relationship was detected between the inhibition of egg hatch or immobilization of J2 in vitro and antagonistic activity toward nematodes in vivo. Amendment of the soil with 0.1% (w/w) peptone or casein hydrolysate did not improve the effects of suppressive isolates on numbers of H. glycines. Nineteen of the 25 isolates were identified based on analysis of fatty acid methyl esters, and they are in 11 different genera.
biological control; Glycine max; Heterodera glycines; rhizobacteria; soybean; soybean cyst nematode
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
Corky ringspot disease (CRS) of potato, caused by tobacco rattle virus that is vectored by stubby-root nematodes (Paratrichodorus spp.), is often controlled by aldicarb. When use of aldicarb on potato was suspended in 1989, an increase in crops rejected due to CRS in the Columbia Basin of the U.S. Pacific Northwest occurred. During 1992-94, several fumigant and nonfumigant nematicides were tested alone and in combination for control of P. allius and CRS. Aldicarb alone significantly reduced CRS but not to acceptable levels. Metam sodium or ethoprop alone did not control CRS, but metam sodium plus ethoprop provided adequate control under light disease pressure. Two or three postemergence applications of oxamyl, either with or without metham sodium, appeared to control CRS at low pressure. Fosthiazate reduced CRS incidence when used alone but not in combination with metam sodium. At low P. allius population densities, 1,3 dichloropropene (1,3-D) controlled CRS at 94 liters/ha, and rates of 140 liters/ha or greater were adequate at higher population densities. Treatment with 1,3-D plus chloropicrin was no better than 1,3-D alone and did not always control CRS. Combinations of 1,3-D at 94 liters/ha or greater plus metam sodium at 374 liters/ha or greater controlled CRS. Paratrichodorus allius numbers were higher and severity of CRS greater after wheat than after field corn, but P. allius declined rapidly after potato was planted and remained at low levels until harvest.
1,3-dichloropropene; aldicarb; chloropicrin; corky ringspot; ethoprop; fosthiazate; fumigants; metam sodium; nematicides; oxamyl; Paratrichodorus; potato; stubby-root nematode; tobacco rattle virus
Thirteen indigenous and exotic Acacia species grown in Saudi Arabia were evaluated for their host status for Meloidogyne javanica in pot tests both in the growth chamber and under outdoor conditions. In both experiments, 21-day-old seedlings were transplanted individually into 15-cm-diam. plastic pots containing a steam-sterilized mixture of equal parts loam and sandy loam. Seedlings were inoculated with 5,000 M. javanica eggs/plant 30 days later. After 120 days, fresh root weight, disease index (1-9 scale), the number of eggs/pot (Pf), eggs/g fresh root, and a reproductive factor (Rf) were determined. Results of both the growth chamber and the outdoor tests were similar. Species were grouped into host suitability categories according to Rf, and they were also grouped into resistance categories based on the sum of gall index, gall size, and percentage of the root system that was galled. Only A. salicina was a poor host and was resistant to M. javanica. Acacia farnisiana, A. gerrardii subsp. negevensis var. najdensis, and A. saligna were excellent hosts and highly susceptible. Both A. nilotica and A. stenophylla were classified as good hosts and highly susceptible, while A. ampliceps, A. ehrenbergiana, A. gerrardii subsp. negevensis var negevensis, A. sclerosperma, A. seyal, A. tortilis, and A. tortilis subsp. spirocarpa were also good hosts but were classified as susceptible rather than highly susceptible. This is the first report on the susceptibility of Acacia species to M. javanica in Saudi Arabia, including some new hosts worldwide.
Acacia species; forest trees; host suitability; Meloidogyne javanica; reproduction; resistance; root-knot nematode; screening; susceptibility
The soil fumigant 1,3-dichloropropene (1,3-D) formulated with chloropicrin is viewed as a likely alternative for replacing methyl bromide in Florida when the latter is phased out in 2005. Therefore, it behooves us to learn more about using 1,3-D in deep, sand soils. Two trials were conducted on spring squash to determine the most effective rate of 1,3-D for the control of Meloidogyne spp. Rates tested included 0, 56, 84, 112, and 168 liters/ha of 1,3-D applied broadcast with conventional chisels 30 cm deep. The chisel traces were sealed by disking immediately after fumigant application. Cucurbita pepo cv. Sunex 9602 was sown 7 days after fumigation. The population density of plant-parasitic nematodes in soil and root-knot nematode galling severity was determined at 34 and 65 days after planting (DAP), and the number of marketable fruit and yield were determined. The number of fruit and yield were higher in all plots that received 1,3-D than in untreated controls. The number of Meloidogyne spp. second-stage juveniles was lower in all fumigated plots in trial 1 at both 34 and 65 DAP, and in trial 2 at 65 DAP, than in the untreated control. The severity of root galling was decreased with all treatments in both trials, with broadcast rates of 84, 112, and 168 liters/ha providing the best control of root-knot nematodes in spring squash grown in sandy soil. Satisfactory management of root knot on squash grown in early spring months in north Florida can be achieved with low rates of 1,3-D.
Cucurbita pepo; 1,3-dichloropropene; efficacy; fumigation; management; Meloidogyne arenaria; Meloidogyne incognita; nematode; rate; root-knot nematode; squash
A survey of 100 cotton fields selected randomly in 1995 and 1996 was conducted in the High Plains of Texas to determine the incidence and potential severity of Meloidogyne incognita and Thielaviopsis basicola. Information was obtained from producers for each field on their nematicide application rates and fungicide seed treatments. The percent of squares and bolls set was evaluated for 20 plants in each field during late July 1995 and early August 1996. Thielaviopsis basicola was identified in 55% of the fields in 1995 and 73% of the irrigated fields in 1996. Meloidogyne incognita was found in 39% and 43% of the fields in 1995 and 1996, respectively. Both M. incognita and T. basicola were found together in approximately 30% of the fields. The average rate of aldicarb used in 1995 and 1996 was higher when fields were infested with both T. basicola and M. incognita than for fields infested with none or only one of the pathogens. However, there was no relationship between the use of fungicide treatments active against T. basicola and the potential for root necrosis, or presence of either or both pathogens (T. basicola and M. incognita). Aldicarb rates and usage of fungicide seed treatments were chosen by producers before fields were surveyed (i.e., the survey did not influence grower practices). In 1995, but not in 1996, the association of M. incognita and potential root necrosis (based on a bioassay from soil samples) was negatively correlated with the number of squares, percentage of squares set, and percentage of bolls set. The association between M. incognita and T. basicola, or potential severity of root necrosis, could not be correlated with fruit attributes in 1996 under warm spring conditions but was negatively correlated with fruit attributes in 1995 under cool spring conditions.
cotton; disease survey; management practices; Meloidogyne incognita; Thielaviopsis basicola
A survey conducted from May 1995 through August 1998 revealed diverse nematode communities in Louisiana sugarcane fields. High populations of Mesocriconema, Paratrichodorus, Pratylenchus, and Tylenchorhynchus were widespread in nine sugarcane production parishes. Comparisons of plant cane and ratoon sugarcane crops indicated that nematode community levels increase significantly in successive ratoon crops. Nematicide trials evaluated the efficacy of aldicarb, ethoprop, and phorate against indigenous nematode populations. Aldicarb consistently increased the number of millable stalks, cane tonnage, and yield of sucrose in soils with a high sand content. Yield increases were concomitant with reductions in the density of the nematode community shortly after planting and at harvest. In soils with a higher clay content, the chemicals were less effective in controlling nematode populations and, as a result, yield increases were minimal.
aldicarb; chemical control; distribution; ethoprop; frequency; Helicotylenchus spp.; lesion nematode; Mesocriconema spp.; nematode; nematode management; Paratrichodorus spp.; Pratylenchus spp.; ring nematode; Saccharum officinarum; spiral nematode; stubby-root nematode; stunt nematode; sugarcane; Tylenchorhynchus spp.
The tobacco cyst nematode (Globodera tabacum solanacearum) continues to pose a serious threat to flue-cured tobacco production in Virginia and nearby states. Soils were sampled from five uninfested and two infested flue-cured tobacco-producing locations. Twenty-three edaphic factors were characterized to determine if any were correlated with G. t. solanacearum reproduction. Comparisons were also made between pasteurized and natural soils to determine if biological suppression of G. t. solanacearum reproduction might be occurring in currently uninfested areas. Differences in G. t. solanacearum reproduction were noted among the soils, but results were inconsistent across the three trials conducted in this study. Only soil pH correlated significantly with nematode reproduction, and then only in one of three trials. Globodera tabacum solanacearum reproduced with similar efficiency in natural and pasteurized soils.
cyst nematode; flue-cured tobacco; Globodera tabacum solanacearum; nematode; Nicotiana tabacum; soil edaphic factors; suppressive soil; tobacco cyst nematode
Eighty-one cultivars from 12 field crop species were assessed for suitability as hosts to the root lesion nematode, Pratylenchus neglectus, in two field trials. Host status was assessed on the basis of either final P. neglectus densities in soil or multiplication rate under different crops. Both techniques gave consistent results for crop and cultivar ranking, and it was therefore concluded that, in these trials, final population density could be used for screening cultivars for resistance to P. neglectus. Differences were observed among crops and cultivars for host suitability to P. neglectus. Chickpea, wheat, and canola were good hosts, while barley, oat, durum wheat, medic, and vetch were moderate hosts. Field pea, faba bean, and triticale were poor hosts. A range in host suitability was observed for wheat, barley, and oat cultivars.
barley; canola; chickpea; control; faba bean; field pea; host suitability; medic; multiplication; oat; resistance; root lesion nematode; rotation; susceptibility; triticale; vetch; wheat
Two hundred twenty-six soybean cultivars were tested in greenhouse pot experiments during summer 1999 to determine their suitability as hosts for the reniform nematode, Rotylenchulus reniformis. The cultivars included new entries into the Arkansas and Mississippi soybean variety testing programs and entries submitted by extension nematologists from Auburn University and Louisiana State University. Also included in the R. reniformis tests were the resistant cultivars Forrest and Hartwig, the susceptible control Braxton, and fallow infested soil that served as controls. Total number of eggs + nematodes extracted from the soil and roots per pot, reproductive indices (Pf/Pi) based on the number of nematodes extracted from the soil and roots/initial inoculum level, calculated for each cultivar, and the ratio of the Pf/Pi of each cultivar to the Pf/Pi of Forrest are reported. Cultivars with reproduction not significantly different from Forrest were not suitable hosts, whereas those with greater reproductive indices were considered suitable hosts. One of the 12 cultivars of the relative maturity group (RMG) <=4.4 was not a suitable host. For the 4.5 to 4.9 RMG, 24 of 72 cultivars were not suitable hosts, whereas 9 of 41 cultivars in RMG 5.0 to 5.4 were not suitable hosts. In the 5.5 to 5.9 RMG cultivars, 11 of 66 were not suitable hosts; for the 6.0 or greater RMG, 11 of 35 were not suitable hosts. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode.
Glycine max; nematode; reniform nematode; reproductive index; rotation; Rotylenchulus reniformis; soybean
A survey was conducted in northeastern Louisiana to determine the frequency and abundance of plant-parasitic nematodes associated with cotton. In fall 1997 and 1998, more than 600 soil samples were collected from cotton fields representing 6,200 ha, which is 5.3% of the cotton production hectarage in this region. Composite soil samples were collected from 10 ha in each field. Nematodes were extracted by gravity screening and sucrose centrifugation, identified to genus, and quantified. Nine genera of plant-parasitic nematodes were identified. Rotylenchulus reniformis was found in 67% of the fields sampled, with an average population of 12,959 juveniles and vermiform adult stages per 500 cm³ of soil. Meloidogyne incognita was identified in 25% of the fields sampled, with an average population of 998 juveniles per 500 cm³ of soil. Hoplolaimus spp. were identified in 3%, or 155 ha, with an average population of 282 juveniles and adult stages per 500 cm[sup3] of soil. Rotylenchulus reniformis and M. incognita occurred at population levels above reported economic thresholds in 49% and 21% of the fields, respectively.
cotton; Gossypium hirsutum; Meloidogyne incognita; nematode; Rotylenchulus reniformis; survey
The effects of soybean maturity and determinacy on the host-parasite relationships of Heterodera glycines were investigated in a field microplot study over 2 years. Determinate and indeterminate isolines of the maturity group (MG) III cultivar Williams 82 and the MG V cultivar Essex were grown in microplots artificially infested with a race 3 isolate of H. glycines at three initial population (Pi) densities (0, 300, and 3,000 eggs/100 cm³ soil). Soybean seed yields, nematode final population (Pf) densities and reproductive index (Pf/Pi), and root colonization by Macrophomina phaseolina, the causal agent of charcoal rot, were monitored in each year. Seed yields were reduced (P ≤ 0.05) in the presence of H. glycines in both years, but losses were greater in 1996 in the absence of drought stress. Yield loss was lower (P ≤ 0.06) for the determinate isoline of Essex than for the other cultivar-isoline treatments across years. Nematode reproduction was density-dependent in the more conducive environment of 1996 but was unaffected by soybean maturity or determinacy traits. Root colonization by M. phaseolina increased (P ≤ 0.05) in the presence of high H. glycines densities on determinate, but not indeterminate, isolines. Differences in H. glycines-induced yield loss among cultivar-isoline treatments were not related to nematode reproduction, M. phaseolina colonization, or environmental stresses. These results indicate that the effects of soybean maturity and determinacy on H. glycines-soybean interactions are not independent and that their combined effects must be considered in geographic regions where both traits vary.
Glycine max; Heterodera glycines; soybean cyst nematode; soybean determinacy; soybean maturity group
The potential of different bacterial-feeding Rhabditida to consume isolates of Burkholderia cepacia with known agricultural biocontrol ability was examined. Caenorhabditis elegans, Diploscapter sp., Oscheius myriophila, Pelodera strongyloides, Pristionchus pacificus, Zeldia punctata, Panagrellus redivivus, and Distolabrellus veechi were tested for growth on and preference for Escherichia coli OP50 or B. cepacia maize soil isolates J82, BcF, M36, Bc2, and PHQM100. Considerable growth and preference variations occurred between nematode taxa on individual bacterial isolates, and between different bacterial isolates on a given nematode. Populations of Diploscapter sp. and P. redivivus were most strongly suppressed. Only Z. punctata and P. pacificus grew well on all isolates, though Z. punctata preferentially accumulated on all isolates and P. pacificus had no preference. Oscheius myriophila preferentially accumulated on growth-supportive Bc2 and M36, and avoided less supportive J82 and PHQM100. Isolates with plant-parasitic nematicidal properties and poor fungicidal properties supported the best growth of three members of the Rhabditidae, C. elegans, O. myriophila, and P. strongyloides. Distolabrellus veechi avoided commercial nematicide M36 more strongly than fungicide J82.
accumulation; attraction Caenorhabditis elegans; Diploscapter sp.; Distolabrellus veechi; ecology; Escherichia coli OP50; nutrition; Oscheius myriophila; Panagrellus redivivus; Pelodera strongyloides; phylogeny; Pristionchus pacificus; repellence; Rhabditida; toxicity; Zeldia punctata
A new apparatus to release eggs from cysts of soybean cyst nematode (Heterodera glycines) is described and its efficiency evaluated. A rubber stopper was mounted on a bolt, and cysts were ground against a 60-mesh screen. Eggs and second-stage juveniles were washed into a series of screens nested underneath the apparatus. This method was fast and efficient, and had no ill effect on prepared inoculum.
apparatus; chemical; eggs; extraction; Heterodera glycines; inoculation; mechanical; method; nematode; soybean; soybean cyst nematode
Yield of the soybean (Glycine max) cultivar Hartwig with resistance to all races of Heterodera glycines was compared to that of the susceptible cultivar, Deltapine 105, in a field infested with race 2 of this pathogen. The field had previously been in a cropping sequence experiment that provided a range of H. glycines population densities affording the opportunity to evaluate yield potential of resistant and susceptible cultivars in the presence of different levels of soybean cyst nematode in 1992. Plots were planted again in 1993 with the two cultivars in sequences that included Hartwig following Hartwig or Deltapine 105, and Deltapine 105 following Hartwig or Deltapine 105. The yield of Hartwig was inferior to Deltapine 105 at low population densities of H. glycines, but Hartwig yielded more than Deltapine 105 at high population densities. Hartwig was effective in suppressing H. glycines population density compared to susceptible Deltapine 105. The seed yield of Hartwig following Deltapine 105 or Hartwig, and Deltapine 105 following Hartwig yielded more than Deltapine 105 grown for 2 years.
crop loss; damage function; Glycine max; Heterodera glycines; host plant resistance; nematode; plant disease loss; soybean; soybean cyst nematode
Aphelenchoides microstylus n. sp. and Seinura onondagensis n. sp., a nematode predator, are described from dead Scots pine (Pinus sylvestris L.) in Onondaga County, New York. Females of A. microstylus are 370 to 485 µm long. The body is slender and tapers posteriorly to an amucronate, pointed terminus. The head is continuous with the body, and lips bear a stylet guide. Diagnostic characters of females are three incisures in the lateral field, a short stylet (6-7.5 µm) with small basal knobs, a single row of oocytes, and a long postuterine sac (25-50 µm). Males are characterized by small spicules (10-11µm); two pairs of post-anal, subventral papillae; and a single row of spermatocytes. A bursa and gubernaculum are absent. Seinura onondagensis females are characterized by a body of moderate length (475-595 µm), finely annulated cuticle, and a slightly set-off head. Diagnostic characters are four incisures in the lateral field, long stylet without basal knobs (17-22 µm), single row of oocytes, and presence of a postuterine sac (14-38 µm). Males are unknown. The monospecific genus Indaphelenchus is proposed as a synonym of Seinura, and S. siddiqii n. comb. is proposed for the only species, I. siddiqii.
Aphelenchina; Aphelenchoides microstylus; bark beetle; Indaphelenchus siddiqii; nematode; new combination; new species; New York; Pinus sylvestris; predator; scots pine; Seinura onondagensis; synonym; taxonomy
Root-lesion nematodes (primarily Pratylenchus penetrans) were monitored in two marigold cultivars (Tagetes tenuifolia cv. Nemakill and cv. Nemanon), annual ryegrass (Lolium multiflorum cv. Lemtal), red clover (Trifolium pratense cv. Florex), and soybean (Glycine max cv. Proteus), and in the following potato (Solanum tuberosum cv. Superior) crop during three growth sequences. Meadow fescue (Festuca elatior cv. Miner) and bee plant (Phacelia tanacetifolia cv. Gipha) were added to the trial in the second year. Black-eyed Susan (Rudbeckia hirta, unidentified cv.) and two additional marigold cultivars (T. patula ssp. nana, unidentified cv., and T. erecta cv. Crackerjack) were included in the final sequence. Population levels of root-lesion nematodes were consistently lower under marigolds compared to the other cover crops tested. Correspondingly, average potato tuber yields were significantly higher (8-14%) when potato followed marigolds. The highest levels of root-lesion nematodes occurred under red clover and soybean, and the average potato tuber yields were lowest following these crops.
crop sequence; lesion nematode; marigold; potato; Pratylenchus penetrans; Tagetes spp.