The continual detection of a slow (I1) esterase band in greenhouse cultures of Meloidogyne konaensis isolated from the field led to a hypothesis that the nematode may be polymorphic for esterase. A survey of coffee fields demonstrated at least four esterase phenotypes were present in Meloidogyne recovered. An F1 phenotype predominated (60% of the females), but an I1 phenotype was also common (30% of samples). A series of greenhouse and laboratory experiments were undertaken to understand this polymorphism. Esterase phenotype was not affected by development at 22º, 25º, or 33 ºC on tomato. Two different esterase phenotypes (I1 and F1-I1) were detected after M. konaensis was grown on tomato for several generations, even in single-egg-mass lines derived from an F1 female. Three isolates of M. konaensis differing in esterase phenotype (F1, I1, and F1-I1) did not differ morphologically but did differ in their parasitic ability. Only the F1 isolate parasitized Coffea arabica. The F1-I1 isolate had greater reproduction on Lycopersicon esculentum and Cucumis sativus than either the I1 or F1 isolate. The mechanism of the development of the polymorphism has yet to be determined. However, the F1 esterase may be useful as a marker for future research on parasitism of coffee by M. konaensis.
coffee; esterase polymorphism; genetic variation; host range; Meloidogyne konaensis; parasitism; root-knot nematode; selection
An unusual population of Meloidogyne hapla, earlier thought to be an undescribed species, was found causing large galls, without adventitious roots, and substantial damage to coffee in Maui, Hawaii. Only in Brazil had similar damage to coffee been reported by this species. Unlike M. exigua from South and Central America, this population reproduced well on coffee cv. Mokka and M. incognita-susceptible tomato but poorly on tomato with the Mi resistance gene. Characterization included SEM images, esterase isozymes, and five DNA sequences: i) the D3 segment of the large subunit (LSU-D3 or 28S) rDNA, ii) internal transcribed spacer (ITS-1) rDNA, iii) intergenic spacer (IGS) rDNA, iv) the mitochondrial interval from cytochrome oxidase (CO II) to 16S mtDNA, and v) the nuclear gene Hsp90. Sequences for ITS-1, IGS, and COII were similar to other M. hapla populations, but within species ITS-1 variability was not less than among species. One LSU-D3 haplotype was similar to a previously analyzed population with two minor haplotypes. Hsp90 exhibited some variation between Maryland and Hawaiian populations distinct from other species. Females were narrow with wide vulval slits, large interphasmidial distances, and more posterior excretory pores; 20% of perineal patterns had atypical perivulval lines. Males had a low b ratio (<12 µm). Juveniles had a short distance between stylet and dorsal gland orifice. Juvenile body length was short (<355 µm) and was different between summer and winter populations.
climate; Coffea arabica; Coffea robusta; detection; identification; India; Meloidogyne exigua; M. incognita; M. javanica; M. konaensis; molecular diagnostics; nematode; netherlands; resistance; taxonomy
Four native plant community types (in decreasing elevation: montane bog, rain forest, wet mesic forest, drier forest) on Molokai were sampled for nematodes. Six samples of 10 cores each were gathered from each community. Nematodes were extracted from 200 cm³ soil by elutriation. All extracted nematodes were counted and identified to species-level taxa. Sixty-seven species were identified among the four plant communities; only eight species occurred in all four communities. Species diversity and evenness were greater in the rain forest and mesic forest than in the bog and the drier forest, but the drier forest and mesic forest had similar species communities. The bog nematode community was not similar to the other three sites. In a presence/absence cluster analysis, all six bog sample assemblages clustered together. The rain forest samples also clustered together but were associated with the mesic forest sample closest to the rain forest edge. Of 11 nematode orders collected, Tylenchida accounted for 40% to 73% of all individuals, followed by Dorylaimida (5% to 17%). Diplogasterida were absent. No plant-parasitic nematodes of known Hawaiian agricultural importance or occurrence were collected in these native plant communities. Calculated nematode densities (76,000 to 321,300/m²) were comparable to those reported for some other Pacific tropical forests.
biodiversity; biogeography; bog; community structure; cluster analysis; hawaii; island; Molokai; nematode; rain forest; survey
Two experiments were conducted to assess nutrient partitioning in coffee (Coffea arabica cv. Typica land race Guatemala) infected with Meloidogyne konaensis. Nutrient levels were quantified from soil, roots, and leaves. In the first experiment, 500-cm3 aliquants of a Kealakekua Andisol were infested with four initial population densities of M. konaensis ranging from 0 to 1,500 freshly hatched second-stage juveniles. Coffee plants (~3 months old) were transplanted into the soil and grown for 25 weeks. Plants responded to nematode infection with decreases (P < 0.05) in concentrations of Ca, Mg, P, and B and increases (P < 0.05) in concentrations of Mn, Cu, Zn, and Ca/B in the roots. Mn and Cu uptake by roots was decreased (P < 0.05) by nematode infection even though concentrations of Mn and Cu increased (P < 0.05) in the roots. Concentrations of Ca and Mg also decreased (P < 0.05) in the leaves, whereas the concentration of Zn increased (P < 0.05). In the second experiment, the soil was amended with Zn at 0 or 5 mg/kg soil and infested with M. konaensis at 0, 100, 1,000 or 10,000 eggs/1,200 cm3 soil. Three-month-old coffee seedlings of similar height were weighed and transplanted into pots and then placed in a greenhouse and grown under 50% shade for 23 weeks. Concentrations of P, K, Ca, Mg, Mn, B, and Zn increased in roots of nematode-free plants growing in Zn-amended soil. The beneficial effects due to the Zn amendment were not apparent in nematode-infected plants. Mn, B, and Zn uptake by coffee roots and P and B concentrations in coffee leaves responded similarly. Management of M. konaensis is necessary to achieve optimal nutrient management in coffee.
aluminum; boron; calcium; Coffea arabica; coffee; copper; kona coffee root-knot nematode; macronutrient; magnesium; manganese; ?; micronutrient; nematode; phosphorus; plant nutrition; potassium; zinc
Effects of acibenzolar-s-methyl, an inducer of systemic acquired resistance in plants, on Rotylenchulus reniformis and Meloidogyne javanica in vitro and in vivo were determined. A single foliar application of acibenzolar at 50 mg/liter (5 ml of solution per plant) to 7-day-old cowpea or soybean seedlings decreased R. reniformis and M. javanica egg production by 50% 30 days after inoculation. The mechanism of acibenzolar on plant-parasitic nematodes was then investigated. Acibenzolar at 50 to 200 mg/liter did not affect movement of R. reniformis and M. javanica or penetration of second-stage juveniles (J2) of M. javanica on cowpea. However, M. javanica development was slowed and fecundity was reduced in plants treated with acibenzolar. On average, 50% of J2 that penetrated acibenzolar-treated cowpeas developed into mature females with eggs, whereas the other 50% exhibited arrested development. The number of eggs per egg mass was 450 in water-treated cowpeas, whereas the number declined to 250 in acibenzolar-treated plants. Acibenzolar may be responsible for stimulating the plants to express some resistance to the nematodes.
acibenzolar-s-methyl; cowpea; Meloidogyne javanica; reniform nematode; root-knot nematode; Rotylenchulus reniformis; soybean; systemic acquired resistance
Effect of cover crops intercropped with pineapple (Ananas comosus) on Rotylenchulus reniformis population densities and activity of nematode-trapping fungi (NTF) were evaluated in two cycles of cover crop and pineapple. Sunn hemp (Crotalaria juncea), rapeseed (Brassica napus), African marigold (Tagetes erecta), or weeds were intercropped with pineapples. Beds planted with sunn hemp or rapeseed had lower population densities of R. reniformis than African marigold, weeds, or pineapple plots during cover crop growth, and the subsequent pineapple-growing periods. Rapeseed was a good host to Meloidogyne javanica and resulted in high population densities of M. javanica in the subsequent pineapple crop. Fireweed (Erigeron canadensis) occurred commonly and was a good host to R. reniformis. Bacterivorous nematode population densities increased (P ≤ 0.05) most in sunn hemp, especially early after planting. Nematode-trapping fungi required a long period to develop measurable population densities. Population densities of NTF were higher in cover crops than weeds or pineapples during the first crop cycle (P < 0.05). Although pineapple produced heavier fruits following sunn hemp than in the other treatments (P < 0.05), commercial yields were not different among rapeseed, weed, and sunn hemp treatments.
Ananas comosus; Brassica napus; Crotalaria juncea; marigold; Meloidogyne javanica; nematode; nematode-trapping fungi; rapeseed; root-knot; reniform; sunn hemp; Tagetes erecta; weeds
Heterodera glycines, the soybean cyst nematode, is a major yield-limiting pathogen in most soybean production areas worldwide. Field populations of H. glycines exhibit diversity in their ability to develop on resistant soybean cultivars. Since 1970, this diversity has been characterized by a bioassay used to assign a race classification to a population. The value of the race scheme is reflected in the number and quality of resistant soybean cultivars that have been developed and released by soybean breeders and nematologists working in concert. However, the race scheme also has been misapplied as a means of studying H. glycines genotypes, in part due to the use of the term "race." For fungal and bacterial pathogen species, "race" can theoretically be applied to individuals of a population, thus allowing inference of individual genotypes. Application of a race designation to an individual egg or second-stage juvenile (J2) of H. glycines is not possible because a single J2 cannot be tested on multiple hosts. For other nematode species, "race" is defined by host ranges involving different plant species, whereas the H. glycines race test involves a set of lines of the same plant species. Nonetheless, because H. glycines populations vary in genetic diversity, and this variation has implications for management strategies, a mechanism is needed for documenting and discussing population differences. The HG Type scheme described herein avoids the implication of genetic uniformity or predictability in contrast to the way the race scheme has been used.
Heterodera glycines; HG type; nematode; races; soybean cyst nematode
The effects of intercycle cover crops on Rotylenchulus reniformis population densities in pineapple were evaluated in one greenhouse and two field experiments. In the greenhouse, Crotalaria juncea, Brassica napus, and Tagetes erecta were planted for 3 months and then incorporated. These treatments were compared to weedy fallow with or without 1,3-dichloropropene (1,3-D) in three soils (Makawao fallow, Wahiawa fallow, and Wahiawa pineapple) naturally infested with R. reniformis. All cover crop incorporation suppressed R. reniformis numbers in cowpea more than did the weedy treatment in the Makawao (P < 0.05) but not in the Wahiawa soils. Crotalaria juncea treatment increased bacterivorous nematodes and nematode-trapping fungal population densities more than the other treatments in Makawao fallow and Wahiawa pineapple-planted soils. The field trials included the same plants as well as Sinapis alba. Treatments with Crotalaria juncea and 1,3-D maintained lower R. reniformis population densities on pineapple longer than other cover crops or weedy fallow treatments. Crotalaria juncea could have suppressed R. reniformis because it is a poor host and because it enhances nematode-trapping fungi when incorporated into soil. Treatment with 1,3-D reduced microbial activities but produced the greatest pineapple yield.
Brassica napus; cover crop; Crotalaria juncea; management; marigold; nematode; pineapple; rapeseed; Rotylenchulus reniformis; Sinapis alba; soil; sunn hemp Tagetes erecta; yellow mustard
Nematode occurrence at specific locations throughout a water catchment-irrigation system was determined. Soil samples were collected from five water source locations on the slopes of Olomana Mountain and Maunawili Valley and from about 40 plant species on 18 farms (56 ha of 480 ha irrigated by the reservoir). Water was sampled from the catchment reservoir at 0.3 m, 9 m, and 18 m (bottom). A farm irrigated with potable water was sampled and compared to areas of the same farm irrigated from the reservoir. Nematodes present in soil from the mountain and farms were root-knot (Meloidogyne spp.), lesion (Pratylenchus spp.), reniform (Rotylenchulus reniformis), stunt (Tylenchorhynchus sp.), ring (Criconema spp.), dagger (Xiphinema sp.), spiral (Helicotylenchus sp.), Tylenchus sp., Aphelenchus sp., and pin (Paratylenchus sp.) nematodes. The economically important genera Rotylenchulus, Meloidogyne, and Pratylenchus occurred in very low numbers (10, 41, and 10/250 cm³ soil, respectively) and in low frequency (10%, 25%, and 8% of the samples, respectively) in the mountain samples compared with high numbers (170-895/250 cm³ soil) from farms. Frequency of occurrence over all farms was near 40% for Meloidogyne and 80% for Rotylenchulus. No nematodes were detected in water from the reservoir. One sample from the outlets contained two specimens of plant-parasitic nematodes. The population densities of nematodes were not different between the soil samples collected from crops irrigated by potable or reservoir water.
Criconema; dagger nematode; Hawaii; Helicotylenchus; irrigation; lesion nematode; Meloidogyne; nematode; Paratylenchus; pin nematode; Pratylenchus; reniform nematode; ring nematode; root-knot nematode; Rotylenchulus; spiral nematode; watershed; Xiphinema
Field experiments were conducted to determine peanut growth and yield responses to selected fumigant and nonfumigant nemaficide treatments in 1988 and 1989. All treatments with the fumigant 1, 3-D significantly suppressed nematode reproduction (Meloidogyne arenaria, M. hapla, and Mesocriconema ornatum) and enhanced peanut yields over the other treatments in four tests in 1988. Yield increases with the fumigant ranged from about 20% to 100% over the untreated control. Test sites in 1989 had lower nematode levels than those for 1988, and fewer positive plant and nematode responses were detected. Treatments with 1,3-D improved peanut quality but not yield in one experiment with low levels of M. hapla and M. ornatum in 1988. The 1,3-D + chloropicrin treatments at another site gave higher peanut yields than 1,3-D alone.
Arachis hypogaea; chemical control; management; Meloidogyne arenaria; Meloidogyne hapla; Mesocriconeraa ornatum; nematicides; nematode; peanut
Effects of gamma-irradiation on the root-knot nematode Meloidogyne javanica were investigated. A dose of 7.5 kGy killed all second-stage juveniles (J2) within 1 day after treatment. Egg hatch was completely inhibited at 6.25 kGy. A bioassay on tomato measuring galling and egg production was used to determine the infectivity of irradiated J2 and J2 hatched from irradiated eggs. The J2 and eggs irradiated with a dose of 4.25 kGy did not induce galls or reproduce on tomato plants. When nematodes were exposed to combined irradiation and heat treatment, no synergistic effect on J2 or eggs was measured. Heat treatment at 49° C for 10 minutes or 20 minutes without irradiation immobilized J2 and prevented egg development. Irradiation rates needed to kill or incapacitate M. javanica were high and may be impractical as a quarantine measure.
Cobalt-60; control; dose; gamma-irradiation; heat treatment; kGy; Meloidogyne javanica; quarantine; root-knot nematode
The use of plant-covers oat (Arena sativa L.), rhodesgrass (Chloris gayana Kunth), soybean (Glycine max [L.] Merr.), and marigold (Tagetes patula L.) during pineapple inter-cycle planting periods was investigated at two sites (Kunia and Whitmore, Oahu, HI) as a potential means to reduce population densities of Rotylenchulus reniformis, Helicotylenchus dihystera, and Paratylenchus spp. Clean fallow and fallow covered with pineapple-plant residues (mulch) were the controls without plant-cover. Regardless of treatments, population densities of R. reniformis declined with time at both sites to low residue levels by the end of the 6-month period. Treatment means of R. reniformis population densities in the plant-cover treatments were lower than the controls' (P = 0.05). The plant-cover treatments also effected higher rates of R. reniformis population decline at both sites during the period, being 2.0 to 2.2 times that of the mulch control and 1.2 to 1.4 times that of the fallow control. Plant-covers' effect on H. dihystera during the same period at both sites was variable, resulting in decreased, unchanged, or increased population densities. The change was especially obvious in the oat-cover treatment, where H. dihystera population densities increased 9 to 15-fold at both sites. Population of Paratylenchus spp. was absent or present at low levels at the sites throughout the period. Biological activities antagonistic to R. reniformis at Kunia were estimated at the end of 6 months by comparing the extent of nematode's reproduction (on cowpea seedlings) in the treatment soils that had been subjected to autoclaving or freezing temperature. Although higher indices of antagonistic activities were observed in soils with prior plant-cover treatments than in soils from the controls, none of the treatments resulted in conferring soils the increased ability to suppress re-introduced R. reniformis populations or enhance subsequent pineapple-plant growth.
Ananas comosus; antagonistic plant; fallow; freezing soil; Helicotylenchus dihystera; marigold; nematode management; oat; Paratylenchus; plant-cover; rhodesgrass; Rotylenchulus reniformis; soybean
A non-chemical technique for surface sterilizing plant-parasitic nematodes for aseptic cultures is described. The method is most applicable to nematodes with active migratory infective stages and requires only a few starting specimens. Rate of achieving a primary aseptic culture with the technique ranged from 60%-100% depending on the conditions of the specimens collected for culturing. Aseptic cultures of species of Meloidogyne, Rotylenchuluz, Pratylenchus, and Radopholus initiated with the method remained contamination-free after 12 months of maintenance in tomato root explant or alfalfa callus cultures. Further studies of Pluronic F127, a polyol gel medium employed in the technique to confine the spread of contaminating bacteria or fungi associated with the nematodes, showed that the polyol gel was a suitable support medium for culturing corn root explant, alfalfa callus tissues, and consequently Pratylenchus species including P. agilis, P. brachyurus, P. scribneri, and P. penetrans. During the course of 10 months, P. penetrans reared in polyol-base medium followed a standard biological growth curve, multiplied to a higher population density, maintained a similar female-to-male ratio, and possessed a similar tendency to reside inside or outside host tissues as did P. penetrans reared in agar-base medium. The percentages of P. penetrans juveniles in the sub-populations residing outside or inside the host tissues reared in polyol-base medium also were similar to and fluctuated temporally in like manner as those reared in agar-base medium. Members of these sub-populations from the polyol- or agar-base were equally infective and reproductive after 9 months of culturing.
aseptic culture; axenizing technique; Meloidogyne; nematode; Pluronic F127; Pratylenchus agilis; Pratylenchus brachyurus; Pratylenchus penetrans; Pratylenchus scribneri; population dynamics; Radopholus; Rotylenchulus; sterilization
Ethoprop and disodium tetrathiocarbonate (TTC) were evaluated as replacements of fenamiphos and 1,3-dichloropropene (1,3-D) for control of Rotylenchulus reniformis on pineapple in Hawaii. Treatments were established in a field on the Del Monte Fresh Fruit (Hawaii) plantation in spring 1991. Preplant soil treatments consisted of fumigation with 1,3-D at 226 kg a.i./ha and TTC at 135 kg or 270 kg a.i./ha. Postplant nematicides for the 1,3-D treated plots were fenamiphos (3.4 kg a.i./ha trimonthly) and ethoprop (3.4 or 6.7 kg a.i./ha monthly). Tetrathiocarbonate was applied postplant to the TTC-treated plots every 2 months at 67 kg a.i./ha. Nematode population densities were monitored in all plots at 3-month intervals. Tetrathiocarbonate was not effective in reducing the preplant soil population densities of R. reniformis or limiting subsequent nematode damage to the plants. Ethoprop and fenamiphos reduced nematode damage, resulting in greater yield in the first and second crop harvests (P < 0.05). Ethoprop was an effective alternative to fenamiphos for control of R. reniformis in pineapple.
Ananas comosus; chemical control; ethoprop; fenamiphos; nematicide; nematode; pineapple; reniform nematode; Rotylenchulus reniformis; tetrathiocarbonate
Soils from 320 sites representing diverse undisturbed habitats from five Hawaiian Islands were assessed for occurrence of Pasteuria-like organisms. Mean annual rainfall at sites ranged from 125-350 cm, elevation from 69-2,286 m, and annual mean temperature from 12-24 C. Seven different natural communities were represented: wet lowland, mesic lowland, wet montane, mesk montane, dry montane, mesic subalpine, and dry alpine. Pasteuria spp. in a soil sample was detected by baiting with infective stages of Helicotylenchus dihystera, Meloidogyne javanica, Pratylenchus brachyurus, and Rotylenchulus reniformis, followed by cultivation of the nematodes on pineapple plants for 10-11 months. All nematode baits except R. reniformis were readily recovered from the soil samples. A sample was considered Pasteuria-positive if at least 5 % of the nematode specimens showed endospore attachment. Thirteen percent of all samples were positive for Pasteuria-like organisms. The frequencies of association between Pasteuria spp. and Meloidogyne, Helicotylenchus, or Pratylenchus species were 52%, 24%, and 24%, respectively. Positive samples were more prevalent on the older islands of Kauai and Oahu (75%), in lowland communities (61%), and in areas with introduced vegetation (60%). More than 27% of the positive samples were associated with plant species in a few selected families that included Meliaceae and Myrtaceae. Occurrence of Pasteuria spp. seemed to be positively associated with mean annual rainfall or temperature, but negatively associated with elevation.
bacterium; biological control; Hawaiian Islands; Helicotylenchus; Meloidogyne; microbial ecology; native vegetation; natural community; Pasteuria; pineapple; plant-parasitic nematode; Pratylenchus; Rotylenchulus; tropics
The effects of temperature on embryogenesis and postinfection development in Meloidogyne konaensis were examined. Embryogenesis was evaluated at 5, 8, 10, 13, 16, 20, 22, 24, 26, 28, 30, 35, and 40 C. No embryonic development occurred at 5 C. Some development, although incomplete, occurred at 8 and 10 C. The rate of embryogenesis was linear from 13 to 30 C, but decreased at 35 C. The lowest egg mortality occurred at 24 C, whereas all eggs died within 24 hours at 40 C. Postinfection development was determined on coffee and tomato in a greenhouse at an average temperature of 30 C and in a growth chamber with a constant temperature of 26 C. Development of M. konaensis J2 to mature female required 38 and 48 days on coffee at 30 and 26 C, respectively. This process took 20 and 26 days, respectively, on tomato.
Coffee arabica; coffee; degree-days; embryogenesis; kona coffee root-knot nematode; life-history; life-cycle; Lycopersicon esculentum; M. konaensis; nematode; postinfection development; root-knot; tomato
Population densities ofMeloidogyne konaensis were determined in March and July of 1991 and 1992 on coffee cultivars Guatemalan and 502, and on four rootstocks (Purpuree, Congensis, Deweveri, and Kaffe) with Guatemalan or 502 as a scion. Three-dimensional spatial patterns were characterized on roots of Guatemalan and Deweveri. Population densities differed among rootstocks (P < 0.05) and times (P < 0.01). The greatest number of second-stage juveniles (J2) occurred on Guatemalan and fewest J2 on Purpuree and Deweveri rootstocks. More nematodes were found in March than in July of both years. The spatial distribution varied by positions and depths on Guatemalan. The highest nematode population density occurred at 60 cm from the base of the tree and 15-45 cm deep. Numbers of nematodes were relatively low at all positions and all depths on the Guatemalan-Deweveri combination.
coffee arabica; coffee; ecology; Kona coffee; root-knot nematode; Meloidogyne konaensis; nematode; population distribution
A host suitability study of 32 plant species to Meloidogyne konaensis included 54 vegetable cultivars, 12 field crop cultivars, one Gardenia sp., and two weed species. Host suitability was classified according to a M. konaensis reproductive factor: final population density (Pf) (eggs + J2) / initial population density (Pi) (eggs). The number of eggs per gram dry root, and a galling index was also included. Reproductive factor ranges and percentages of plants in the ranges were as follows: Pf/Pi > 5.0, 56.5%; 5.0 ≥ Pf/Pi > 1.0, 24.6%; 1.0 ≥ Pf/Pi > 0, 15.9%; and Pf/Pi = 0, 3%. Peanut and 'Decicco' broccoli were nonhosts. Few or no galls were observed on pepper, corn, ginger, waterchestnut, 'Michihili' chinese and 'Marion' market cabbage, although the reproductive factor of M. konaensis was above 5 on these plants.
field crops; gardenia; Meloidogyne konaensis; nematode; nonhosts; root-knot nematode; vegetable; weed
Meloidogyne konaensis n. sp. is described from coffee from Kona on the island of Hawaii. The perineal pattern of the female is variable in morphology, the medial lips of the female are divided into distinct lip pairs, and the excretory pore is 2-3 stylet lengths from the base of the stylet. Mean stylet length is 16.0 μm, and the knobs gradually merge with the shaft. The knobs are indented anteriorly and rounded posteriorly and the dorsal esophageal gland orifice (DEGO) is long, 3.5-7 μm. The morphology of the stylet of the male is the most useful diagnostic character, with 6-12 large projections protruding from the shaft. One medial lip may be divided into distinct lip pairs. A large intestinal caecum often extends nearly to the level of the DEGO. Mean juvenile length is 502 μm, mean stylet length is 13.4 μm, and mean tail length is 58 μm. The tail may be distinctly curved ventrally and the phasmids are located in the ventral incisure about one anal body width posterior to the anus.
host range; Meloidogyne species; morphology; nematode; scanning electron microscopy; taxonomy
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
The efficacy of 1,3-dichloropropene (1,3-D) applied with one or two chisels was determined for control of Rotylenchulus reniformis on pineapple. The soil was fumigated with 1,3-D at 157 liters/ha with either a single chisel 46 cm deep or two chisels 41 cm deep in replicated experiments conducted in four commercial fields. Soil samples were collected before fumigation and 45 days afterward from three depths and three positions. The three depths were 0-15, 16-30, and 31-45 cm; and the three positions were the center of the bed, plant line, and interbed area. The single-chisel injection was comparable to the two chisels in percentage control of R. reniformis. Satisfactory control was achieved in three fields (percentage reduction from untreated = 79, 81, and 83) but not in the fourth field. The highest level of control was at the lowest soil depth (31-45 cm) nearest the points of injection. Among the sampling positions, control in the interbed area was generally the lowest. A single-chisel injection may be recommended because of the slightly enhanced control.
Ananas comosus; 1,3-dichloropropene; fumigation; nematicide; nematode; pineapple; reniform nematode; Rotylenchulus reniformis
Differential sensitivity of Meloidogyne arenaria, M. hapla, M. incognita, M. javanica, and Heterodera glycines races 1 and 5 to the nonfumigant nematicides aldicarb, ethoprop, and fenamiphos was evaluated using a 48-hour root-penetration bioassay. Generally, H. glycines was more tolerant of the nematicides, especially ethoprop, than were the Meloidogyne species. Among Meloidogyne species, M. incognita was most sensitive to aldicarb and fenamiphos, but its reaction to ethoprop was similar to the other three Meloidogyne species.
aldicarb; differential sensitivity; ethoprop; fenamiphos; Glycine max; Heterodera glycines; juvenile; Meloidogyne arenaria; Meloidogyne hapla; Meloidogyne incognita; Meloidogyne javanica; nematicide; nematode penetration; root-knot nematode; soybean; soybean cyst nematode
The rates of soybean root penetration by freshly hatched second-stage juveniles (J2) of Meloidogyne arenaria, M. hapla, M. incognita, M. javanica, and Heterodera glycines races 1 and 5 were examined over a period of 1 to 240 hours. Heterodera glycines entered roots more quickly than Meloidogyne spp. Penetration by most nematodes was accomplished within 48 hours. The increases in penetration after 48 hours were insufficient to warrant further assessments. Penetration of J2 into roots of soybean seedfings in a styrofoam container was as good or better than in a clay pot. Thus, rapid and accurate root-penetration assessments can be made at 48 hours after inoculation.
Glycine max; Heterodera glycines; infection; Meloidogyne arenaria; M. hapla; M. incognita; M. javanica; nematode; penetration; root; soybean
Population changes of Heterodera glycines eggs on soybean in small field plots were influenced by the lepidopterous insect pest, Helicoverpa zea; however, few effects on eggs due to the presence of annual weeds were detected. Soybeans defoliated 15-35% by H. zea during August remained green and continued to produce new flowers and pods later into the season than soybeans without H. zea, resulting in higher numbers of H. glycines eggs at harvest on insect-defoliated soybeans. Final H. glycines populations also were influenced by soil population density (Pi) of the nematode at planting. Fecundity of H. glycines was generally greater at the undetected and low Pi than at high Pi levels. Soybean yields were suppressed 12, 22, and 30% by low, moderate, and high H. glycines Pi, respectively. When weed competition and H. zea feeding damage effects were added, yields were suppressed 34, 40, and 57% by the three respective nematode Pi levels. Effects among the three pests on soybean yield were primarily additive.
Annual weed; Glycine max; Helicoverpa zea; Heterodera glycines; nematode; pest complex; population dynamics; soybean; weed; yield
Three field experiments were established in a loamy sand soil in the Coastal Plain of North Carolina to determine downward movement of aldicarb and fenamiphos with a nematode bioassay. Penetration of bioassay plant roots by Meloidogyne incognita was measured at 1, 3, 7, 14, 21, and 28 days after treatment in the greenhouse as a means of determining nematicide effectiveness. Chemical movement was similar in planted and fallow soil. Nematicidal activity was greater in soil collected from the 0 to 10 cm depth than from the 10 to 20 cm depth. Fenamiphos suppressed host penetration by the nematode more than aldicarb under the high rainfall (19 cm) and low soil temperatures that occurred soon after application in the spring. During the summer, which had 13 cm precipitation and warmer soil temperatures, both chemicals performed equally well at the 0 to 10 cm depth. At the lower soil level (10 to 20 cm), aldicarb limited nematode penetration of host roots more quickly than fenamiphos. Both of these chemicals moved readily in the sandy soil in concentrations sufficient to control M. incognita. Although some variability was encountered in similar experiments, nematodes such as M. incognita have considerable potential as biomonitors of nematicide movement in soil.
aldicarb; chemical movement; fenamiphos; Glycine max; Meloidogyne incognita; nematicide; nematode; root-knot nematode; soybean