Five cropping regimes involving combinations of 2 legumes, alfalfa (Medicago sativa) and yellow sweet dover (Melilotus officinalis), 2 monocots, corn (Zea mays) and sudax (Sorghum halupeuse × Sorghum sudanese), and potato (Solanum tuberosum cv. Superior) were tested for their impact on potato yields in a field infested with Pratylenchus penetrans and Verticillium dahliae. No differences in 1990 tuber yields were observed among the five cropping regimes (P < 0.05). In 1991, yields following 1 year of corn, sudax, sweet clover, or alfalfa and 2 years of potato were not different from that of 3 years of continuous potato (P < 0.05). Two years of sweet clover or alfalfa followed by potato resulted in significantly increased potato tuber yields compared with 3 years of potato (P < 0.05). The 2-year legume and 2-year grain rotations resulted in lower P. penetrans population densities at the end of the 3-year rotation compared with 3 years of continuous potato (P < 0.01). The highest preplant V. dahliae population density (34 cfu/g soil), together with a P. penetrans density of 12/100 cm³ of soil was in the sudax-sudax-potato cropping regime and resulted in the lowest potato tuber yield. The highest preplant P. penetrans population density (54/100 cm³ soil), together with a V. dahliae population density of 19.5 cfu/g soil was observed in the corn-corn-potato cropping regime and resulted in the second lowest potato tuber yield in 1991. After 3 years, potato tuber yields were negatively related to preplant densities of V. dahliae (r² = 0.237), P. penetrans (r² = 0.175), and both pathogens (r² = 0.380). A comprehensive regression model was developed to isolate pathogen effects on potato yields from cropping regime effects encompassing all 10 cropping regimes (r² = 0.915).
cropping regime; interaction; nematode; potato tuber yield; Pratylenchus penetrans; lesion nematode; Solanum tuberosum; Verticillium dahliae; verticillium wilt
The influence of Heterodera glycines (soybean cyst nematode) on the interspecific and intraspecific competition associated with Glycine max (soybean) and Chenopodium album (common lambsquarters) was studied in 1988 and 1989 in three de Wit replacement series experiments in growth chambers and microplots. Glycine max was grown alone (1 plant/experimental unit), in intraspecific competition (2 plants/experimental unit), in interspecific competition with C. album, and in presence or absence of H. glycines. No significant effects of H. glycines and C. album on G. max growth were observed 14 days after planting. By 42 days after planting, both H. glycines and C. album had a negative (P = 0.05) influence on the growth of G. max. Relative crowding coefficients for G. max were lower and deviated (P = 0.05 and P = 0.001) from 1.0 in the presence of H. glycines, compared to that of C. album and early emerged C. album in the absence of the nematode, respectively. Glycine max, therefore, became less competitive than C. album. There was a trend that the presence of H. glycines decreased the competitiveness of G. max on measures of the aggressivity and relative mixture response. Heterodera glycines decreased the aggressivity of G. max (ca. 150-350%) and increased the relative effects of intraspecific interference on G. max (ca. 10-50%) and interspecific interference (ca. 60-350%) after 42 days of plant growth, compared with plants grown in the absence of H. glycines. No H. glycines x C. album interactions were detected. Observations showed that H. glycines and early emerged C. album inhibited the growth of G. max 5-13%, as measured by plant dry weight.
aggressivity; Chenopodium album; common lambsquarters; competition; Glycine max; Heterodera glycines; interaction; interspecific competition; intraspecific competition; soybean; soybean cyst nematode
In two field trials, 10-year-old sweet and tart cherry rooted on 'Mazzard', 'Mahaleb', 'MXM 2', 'MXM 14', 'MXM 39', 'MXM 60', 'MXM 97', and 'Colt' showed 10-203 Pratylenchus penetrans per g fresh root from all tart rootstocks, and up to 46 Pratylenchus, Criconemella, and Xiphinema spp. per 100 cm³ soil. Infestation of soil containing 1-year-old Mazzard, Mahaleb, MXM 60, 'GI148-1', and 'G1148-8' with 625/100 cm³ soil of either P. penetrans or C. xenoplax resulting in final nematode population densities of 123-486 and 451-2,496/g fresh root plus 100 cm³ soil, respectively, and had little effect on plant height or dry weight after 157 days in a greenhouse. Population densities of neither nematode differed among the five rootstocks. In a second greenhouse experiment, soil containing the same rootstocks was infested with P. penetrans (1,250/100 cm³ soil), maintained for 8 months in a greenhouse, 4 months in a cold room (2-4 C), and 3 additional months in a greenhouse. The number of P. penetrans recovered at the end of 475 days was approximately 10% of those recovered in the first experiment, probably due to the cold treatment. The ability of P. penetrans and C. xenoplax to infect the cherry rootstocks may be of concern in cherry management programs.
cherry; Criconemella xenoplax; Helicotylenchus; lesion nematode; management; Meloidogyne; nematode; Pratylenchus penetrans; Prunus avium; ring nematode; root-knot nematode; spiral nematode; rootstock; Xiphinema americanum
Plant and soil nematodes significandy impact our lives. Therefore, we must understand and manage these complex organisms so that we may continue to develop and sustain our food production systems, our natural resources, our environment, and our quality of life. This publication looks specifically at soil and plant nematology. First, the societal impact of nematodes and benefits of nematology research are briefly presented. Next, the opportunities facing nematology in the next decade are outlined, as well as the resources needed to address these priorities. The safety and sustainability of U.S. food and fiber production depends on public and administrative understanding of the importance of nematodes, the drastic effects of nematodes on many agricultural and horticultural crops, and the current research priorities of nematology.
alternative management tactics; behavior; benefit to society; beneficial nematodes; biochemistry; biological control; constraints in nematology; control; crop rotation; cultural practice; ecology; education; environment; extension; diagnostics; funding; genetics; host-parasite interaction; information transfer; molecular genetics; nematicide; nematode; nematology; nematode management; nutrient cycling; pesticide; plant parasites; research goals; research priorities; resistance; resource; science of nematology; society; spread; sustainable agriculture; systematics
During 1986 and 1988, selected farms in all of the major carrot-growing counties of Michigan were surveyed to determine the extent of infestation by Heterodera carotae and Meloidogyne hapla. Both species were found in all eight counties surveyed, but not on all farms. Heterodera carotae was recovered from 67.4% of the fields surveyed. Meloidogyne hapla was detected in 24.8% of the samples and from 69.8% of the fields. In most cases, H. carotae and M. hapla occurred in the same field.
carrot; carrot cyst nematode; Daucus carota; Heterodera carotae; Meloidogyne hapla; nematode; northern root-knot nematode
Daily irrigated, 80% pan replacement, and nonirrigated field plots of Kentucky bluegrass (Poa pratensis L.) were inoculated with a mixture of Steinernema carpocapsae (All strain) and Heterorhabditis bacteriophora (HP-88 strain) in 1988. In 1989, daily irrigated and nonirrigated plots were inoculated with HP-88 alone. The turf and associated soil contained populations of Tylenchorhynchus dubius, T. nudus, Pratylenchus penetrans, Paratylenchus projectus, and Criconemella rustica. In irrigated plots in 1988, population densities of Tylenchorhynchus spp. were lower in plots inoculated with HP-88 plus All compared with that in control plots. The same effect was absent under nonirrigated conditions. In 1989, population densities of Pratylenchus penetrans associated with inoculated turf were lower than those recovered from noninoculated turf in irrigated but not under nonirrigated conditions. Population densities of plant-parasitic nematodes were generally higher in the irrigated compared with the nonirrigated environment.
competition; Criconemella rustica; entomopathogenic nematode; Heterorhabditis bacteriophora; irrigation; nematode; Paratylenchus projectus; Poa pratensis; Pratylenchus spp.; Steinernema carpocapsae; Tylenchorhynchus spp.
A new species, Cactodera milleri n. sp., is described and illustrated from specimens obtained from roots of common lambsquarter, Chenopodium album L., from Mattawan, Michigan. Cactodera milleri can be differentiated from other Cactodera species by the presence of punctated egg shells and a second-stage juvenile (J2) stylet length averaging 21.8 μm as measured from freshly killed specimens in water mounts. Thirty-four plant species, including 11 weed species, 18 agronomic crop species, and 5 cactus species were tested as potential hosts of C. milleri. The new species reproduced only on Chenopodium album, C. amaranticolor Cofte. Reyn., and C. quinoa Willd. Cactodera cacti (Filipjev &Schuurmans Stekhoven, 1941) Krall &Krall, 1978, a morphologically similar species, is reexamined. A description of the female and additional morphometric and morphologic data of cysts, males, J2, and eggs are provided for several populations of C. cacti. A review of the morphometrics of all species of Cactodera and a taxonomic key to the seven species are presented.
Cactodera cacti; Cactodera milleri n. sp.; cactus cyst nematode; Chenopodium album; Chenopodium amaranticolor; Chenopodium quinoa; common lambsquarter; comparative morphology; cyst nematode; host range; new species; taxonomy
A simulation model of a single sugarbeet, Beta vulgaris L., plant infected by the sugarbeet cyst nematode, Heterodera schachtii Schmidt, was developed using published information. The model is an interactive computer simulation programmed in FORTRAN. Given initial population densities of the nematode at planting, the model simulates nematode population dynamics and the growth of plant tap and fibrous roots. The driving variable for nematode development and plant growth is temperature.
sugarbeet; sugarbeet cyst nematode; simulation modeling; Beta vulgaris; Heterodera schachtii
The impact of Glomus fasciculatum on Meloidogyne hapla associated with Allium cepa was evaluated in two experiments. Nematode density was not different in mycorrhizal and nonmycorrhizal plants 10 weeks after the joint inoculation of M. hapla and G. fasciculatum. Differences in the age structure of M. hapla populations reared on mycorrhizal and nonmycorrhizat plants were noted. G. fasciculatum enhanced leaf and bulb growth of A. cepa in the absence of M. hapla, but did not affect plant weight when nematodes were present. Survival and reproduction of M. hapla were not affected by G. fasciculatum or phosphorus (P). The estimated time required for inoculated second-stage juveniles (J2) to mature to the adult stage was 1,000 degree hours (base = 9 C) greater in mycorrhizal than in nonmycorrhizal plants supplemented with P. Although the infectivity of J2 was not measured directly, colonization of A. cepa by G. fasciculatum appeared to alter the ability of M. hapla to penetrate roots.
mycorrhizae; onion; nematode development; interaction
Nematode population trends and vertical distribution were monitored in a southwest Michigan vineyard (Vitis labrusca cv. Concord) from 1976 through 1983. Shallow (20 cm) and deep (90 cm) applications of 1,3-dichloropropene applied at 281 (shallow) plus 658 or 1,122 (deep) liters/ ha provided excellent control of Xiphinema americanum, Criconemella xenoplax, and Meloidogyne hapla. Populations of X. americanum remained below detectable levels for the entire 8-year experimental period where the fumigant was applied. X. americanum and C. xenoplax populations exhibited multiyear cycling in nonfumigated plots. M. hapla was first detected in 1978 and increased in prominence from 1980 through 1982. Criconemella spp. were commonly parasitized by an endoparasitic fungus. Parasitism was monitored and reported as an indication of nematode population quality.
Xiphinema americanum; Criconemella xenoplax; Meloidogyne hapla; spatial distribution; population quality; grapes; dagger nematode; ring nematode; northern root-knot nematode; soil fumigation; peach rosette mosaic virus
The pathogenicity of Pratylenchus penetrans (root-lesion nematode) to Phaseolus vulgaris (navy bean) was evaluated in greenhouse experiments. Shoot and root fresh weight of cv. Sanilac plants were increased 4 and 21%, respectively, by an initial population density (Pi) of 25 P. penetrans per 100 cm³ soil. Leaf area and shoot fresh and dry weights were decreased by a Pi of 50 or more P. penetrans per 100 cm³ soil. A significant positive linear relationship existed between initial soil population densities of P. penetrans and final soil and root population densities of this nematode. Three dry bean cultivars, Sanilac, Seafarer, and Tuscola, were susceptible to P. penetrans, and yields were reduced by 43-76% when plants were exposed to a Pi of 150 P. penetrans per 100 cm³ soil. P. penetrans also reproduced on bean cultivars Saginaw, Gratiot, and Kentwood, but did not decrease bean yields, suggesting that these cultivars were tolerant to this nematode.
root-lesion nematode; bean yields; cultivars; population densities
The influence of Meloidogyne hapla and Glomus fasciculatum on Allium cepa (onion) grown in organic soil was evaluated under greenhouse conditions. In the absence of G. fasciculatum, M. hapla significantly retarded the growth of A. cepa cv. Krummery Special and MSU 8155 × 826, but had no detrimental influence on Downing Yellow Globe, Spartan Banner, or Spartan Sleeper. All five cultivars maintained populations of M. hapla, Final root population densities of M. hapla associated with Spartan Banner, Krummery Special, MSU 8155 × 826, and Spartan Sleeper were significantly greater than those recovered from Downing Yellow Globe. Final root population densities of M. hapla were directly proportional to the initial population densities. Root colonization of onion by G. fasciculatum significantly enhanced the growth and development of Downing Yellow Globe. The rate of increase of A. cepa growth and the final spore density were directly proportional to the initial spore density of G. fasciculatum. Final population densities of M. hapla in the presence of G. fasciculatum were generally greater than in the absence of the fungus. After 15 weeks, A. cepa plants grown in the presence of both M. hapla and G. fasciculatum were significantly larger than those grown in the presence of only M. hapla.
vesicular-arbuscular mycorrhizae; northern root-knot nematode; onion
The joint action of a plant parasitic nematode, Pratylenchus penetrans (root-lesion nematode), and an insect defoliator, Leptinotarsa decemlineata (Colorado potato beetle), on growth, development, and yield of Solanum tuberosum cv. Superior was studied in the field. Three population densities of P. penetrans were superimposed on each of three population levels of L. decemlineata. The major impact of P. penetrans on final yield was through a reduction in the number of tubers formed during tuber initiation. Defoliation by L. decemlineata increased with time as larvae advanced through successive instars and densities increased. This resulted in a significant reduction in tuber weight and numbers. Total yield of S. tuberosum was decreased by 66% with increasing population densities of L. decemlineata and 27 % with increasing densities of P. penetrans. L. decemlineata feeding did not affect soil population densities of P. penetrans. Root population densities of P. penetrans, however, were significantly (P = 0.05) higher in plants maintained beetle free than in plants grown in the presence of the beetles.
yield; crop loss; interaction; root-lesion nematode; Colorado potato beetle; potato
Integrated pest management (IPM) is an interdisciplinary science dealing with the development, evaluation, and implementation of pest control strategies that result in favorable economic, ecologic, and sociologic consequences. IPM has received considerable attention during the past few years, and this has led to recommendations directly related to the growth of the science of hematology. This report describes the current state of IPM in relation to the role of hematology, with special emphasis on scientific personnel requirements. All current indications are that IPM will continue to grow, very likely at an increased rate. This will place additional research, extension, and teaching demands on current hematology programs and should result in an expended resource base for nematology.
Field population densities of Ditylenchus dipsaci associated with shoot tissue of Phlox subulata were monitored during two consecutive growing seasons and intervening periods of overwintering and plant storage. The population density increased significantly through four peaks during the first growing season, and decreased significantly during storage at 5-7 C or overwintering in the field. During the second growing season, there was only a single increase to a moderate population density, followed by a severe population decline associated with the poor physiological condition of the host. A simple model is proposed to explain the population dynamics of D. dipsaci during the first growing season.
ground phlox; moss pink; Michigan
The ontogeny of carrots (Daucus carota cv. 'Spartan Premium') grown under greenhouse conditions in pots of organic soil infected with Meloidogyne hapla was influenced detrimentally as early as 4 days after seeding, as determined through analysis of plant surface area, dry weight, fresh weight, net assimilation rate, relative growth rate, and leaf-area ratio. Only 58% of the diseased carrots were suitable for fresh market, compared with 97% of those grown in nematode-free soil. Growth and development of the shoot system (height, surface area, dry weight, and fresh weight) were retarded by M. hapla as early as 12 days after seeding. During the first 12 days after seeding, root dry weight was greater for diseased plants than for controls. Root growth and development (surface area, dry weight, and fresh weight) associated with this nematode, however, were retarded as early as 16 days after seeding. M. hapla caused a delay in the occurrence of 2nd-, 4th-, and 5th-order roots, and an increase in the occurrence of 6th-order roots in infected plants. Parasitized plants had 44% fewer roots (primary through 6th-order) and 50% less total root length.
Carrots; northern root-knot nematode
A 16.4-ha arca at the Michigan State University Water Quality Research Site was surveyed to obtain information on the habitats and prominence of taxa of the Criconematinae. Fifteen species representing six genera (Macroposthonia, Lobocriconema, Criconema, Crossonema, Nothocriconema, and Xenocriconemella) of this subfamily were recovered from the experimental site. Species occurrence and population densities were evaluated by using prominence and importance values. The Criconematinae was one of the most prominent and important nematode subfamilies recovered from this area. The species successfully inhabited a broad range of woodlot and field vegetations, and soil management groups. Taxa of the Criconematinae were generally more prominent in woodlot than in field vegetations, although with several important exceptions, especially within the genus Macroposthonia. The second-most prominent and important species recovered was an tandescribed species of Lobocriconerna. It is described as Lobocriconema thornei n. sp., including scanning electron micrographs of females, and descriptions of several of the juvenile stages.
Ecology; Macroposthonia; Lobocriconema; Criconema; Crossonema; Nothocriconema; Xenocriconemella
From the fall of 1968 through the summer of 1973, a Georgia cotton field with a lengthy history of the Cotton Stunt Disease Complex was sampled for the presence of plant parasitic nematodes. Although Meloidogyne incognita was recovered on all sampling dates, concomitant populations of Hoplolaimus columbus were not recovered until the spring of 1970. During the succeeding four growing seasons, the population density and horizontal distribution of H. columbus increased, and H. columbus replaced M. incognita as the predominant phytopathogenie species. A second Georgia cotton field containing concomitant populations of H. columbus and M. incognita was observed from the fall of 1971 through the summer of 1973. In this case the horizontal distribution of both species remained relatively constant and the population density of H. columbus increased steadily. In both locations, the presence of either H. columbus or M. incognita significantly inhibited the presence of the concomitant species. In general, however, the initial spring or final fall population densities of H. columbus or M. incognita had no significant influence on the population density of the concomitant species, The data are also discussed in relation to the biological significance of H. columbus in the southeastern coastal plain.
cotton; soybean; Gossypium hirsutum; Glycine max; evolutionary biology
Populations of Pratylenchus brachyurus on cotton were increased significantly in the presence of either Meloidogyne incognita or M. arenaria.This occurred with either simultaneous inoculation or prior invasion by M. incognita. P. brachyurus penetrated cotton roots previously invaded by, or simultaneously inoculated with, M. incognita, as well as, or better than, in the absence of M. incognita. Prior invasion by M. incognita, however, suppressed P. brachyurus populations on tomato, while it had no effect on alfalfa and tobacco. Populations of M. incognita on cotton were generally inhibited by the presence of P. brachyurus. Simultaneous inoculation with, or previous invasion by, P. brachyurus also inhibited root penetration by M. incognita. These findings emphasize the importance of host susceptibility in the study of concomitant nematode populations.
cotton, Gossypium hirsutum; tomato, Lycopersicon esculentum; alfalfa, Medicago sativa; tobacco, Nicotiana tabacum; Meloidogyne incognita; Meloidogyne arenaria; coinhabitants.
Foliar applications of oxamyl (methyl N', N'-dimethyl-N-[(methylcarbamoyl)oxy]-l-thiooxamimidate) were applied 24 hr before transplanting seedlings to soil infested with Rotylenchulus reniformis. With a single application of oxamyl, tomato seedlings required 600 ppm to significantly inhibit R. reniformis penetration. Cotton seedlings, however, required a single application of 2400 ppm for significant inhibition of penetration, but only 600 ppm when two or more applications were used.
Gossypium hirsutum; L ycopersicon esculentum; Vydate®
The rate of recovery of Pratylenchus brachyurus from cotton roots was enhanced when the tissue was incubated in solutions containing 10 ppm ethoxyethyl mercuric chloride, 50 ppm dihydrostreptomycin sulfate, 50, 100, or 1,000 ppm diisobutylphenoxethyl dimethyl benzyl ammonium chloride, or mixtures of these compounds. Incubation in 10 or 100 ppm zinc sulfate, zinc chloride, or magnesium chloride also enhanced the rate of recovery. Incubation solutions containing 1 or 1,000 ppm zinc chloride or magnesium chloride had no influence on this phenomenon, whereas, 10,000 ppm zinc sulfate, zinc chloride, or magnesium chloride retarded the rate of recovery. A t all incubation intervals during the first 21 days after the roots were removed from soil, the P. brachyurus population consisted of approximately 25% second-stage juveniles, 44% third and fourth-stage juveniles, and 31% females. At least 88% of the second-stage juveniles and 51% of the third and fourth-stage juveniles passed through a single 325-mesh sieve, whereas, 84% of the females collected were retained on a sieve of this mesh.
Gossypium hirsutum; Extraction; Incubation
The nematodes, Pratylenchus brachyurus, Trichodorus christiei, and T. porosus and the soil-borne fungi, Rhizoctonia solani, Pythium debaryanum, P. irregulare, P. ultimum, and Fusarium spp. were the pathogens most frequently found in the roots and rhizosphere of field-grown cotton (Gossypium hirsutum) showing "stunt" symptoms. Field-plot application of the nematicide D-D (l,2-dichloropropane, 1,3-dichloropropene) at 373.4 liter/ha (40 gal/A) significantly increased plant growth and yield. A fungicidal mixture of Dexon (p-dimethylaminobenzenediazo sodium sulfonate at 23.5 kg/ha (2l lb/A) and Terraclor (pentachloronitrobenzene at 25.2 kg/ha (22.5 lb/A) was phytotoxic, but combined nematicide/fungicide treatments were not. Greenhouse temperature-tank experiments in soils from two locations showed significantly improved root and shoot growth following methyl bromide fumigation at both 25 C and 18 C and more severe "stunt" at the lower temperature.
Pratylenchus brachyurus; Trichodorus christiei; Trichodorus porosus; Soil-borne fungi; Fusarium spp.; Pythium spp.; Rhizoctonia spp.; Cotton; Gossypium hirsutum; Fumigation; Methyl bromide; 1,2-dichloropropane; 1,3-dichloropropene; Soil fungicide; p-dimethylaminobenzenediazo sodium sulfonate; Pentachloronitrobenzene
The onchiostyle of Trichodorus porosus has an anterior outer portion, a fine inner spear and a posterior onchiostyle extension. The extension has a ventral lumen and is fused to the pharynx wall. The inner spear enters the dorsal wall of the outer onchiostyle posterior to the guide ring and extends anteriorly inside the anterior portion of the onchiostyle. Muscle cells are absent in the basal position of the esophagus. The glandular portion of the basal part of the esophagus consists mainly of endoplasmic reticulum lined with ribosomes. A sinus empties into the lumen through the dorsal esophageal gland orifice. The configuration of the intesinal lumen is highly variable. The rectum is attached to the dorsal and ventral walls of the body cavity by striated rectal muscle cells.
Trichodorus porosus; Digestive system; Ultrastructure; Rough endoplasmic reticulum, ; Onchiostyle; Esophagus; Intestine
The somatic musculature of Trichodorus porosus is transversely striated, and that of Criconemoides similis is obliquely striated. The species also differ in configuration of the myofibrils, arrangement of the filaments within the myofibrils, and abundance of sarcoplasmic reticulum. Both species are platymyarian and meromyarian. The muscle cells are composed of myofibrils, sarcoplasm, sarcoplasmic reticulum, and various organelles. The myofibrils of both species contain actin and myosin filaments.
Trichodorus porosus; Criconemoides similis; Somatic musculature; Ultrastructure