No root galling or egg mass formation was noted on betel palm (Areca catechu) 3 or 9 months after inoculation with Meloidogyne arenaria, M. hapla, M. incognita races 1 and 3, or M. javanica. Compared with uninoculated controls, a reduction (P ≤ 0.05) in fresh root weight was noted after 3 months with M. incognita race 1 but not with other species or races, No differences (P ≤ 0.05) in root weight between controls and inoculated plants were observed at 9 months, nor were any differences found in top weight at 3 or 9 months.
Areca catechu; betel palm; host range; Meloidogyne spp.; palm; pathogenicity; root-knot nematode
A nematicide, dibromochloropropane; the fungicides benomyl and maneb; an insecticide, oxydisulfoton; the herbicides trifluralin, linuron, and dinoseb; and fertilizers were applied to Heterodera glycines-infested soil. A resistant soybean cultivar alone produced the highest yield in one test, and its yield was not affected by application of pesticides or fertilizer. In two tests the cultivar that was supposed to be resistant was not. Application of nematicide alone resulted in higher yields of the susceptible cultivar, compared with the untreated check, in only one of three tests. Various combinations of pesticides also resulted in higher yields, and in all cases the nematicide was included. Pesticides and fertilizer must be used with discretion on soybean.
fertilizer; fungicide; Glycine max; herbicide; Heterodera glycines; insecticide; nematicide; soybean; soybean cyst nematode
A total of 110 species of plant nematodes were found in various habitats in Arkansas. Thirty species from 19 genera are reported here for the first time. Included in the new reports are the known plant pathogens Criconemella onoense, Hirshmanniella oryzae, Longidorus elongatus, and Pratylenchus pratensis.
Arkansas; geographic distribution; host record; survey
Root-knot nematodes suppress yields of flue-cured tobacco an estimated 0.1 to 4.8% annually in the southeastern United States, even though nematode management practices have been widely adopted. Although Meloidogyne incognita races 1 and 3 have predominated, M. arenaria, M. javanica, and M. incognita races 2 and 4 are increasingly important. Seventy-five percent of the flue-cured tobacco hectarage in North Carolina and Virginia is rotated on 2-year or 3-year intervals. Over half of the hectarage in the southeastern United States was planted with tobacco cultivars resistant to M. incognita races 1 and 3 in 1986. Resistance to other species or races of root-knot nematodes is not available in commercially available flue-cured tobacco cultivars. Most producers plow and (or) disc-out flue-cured tobacco roots and stalks after harvest. Nematicide use ranges from virtually 100% in Florida and Georgia to 60% in Virginia. Continued research is needed to develop management strategies for mixed populations of root-knot nematodes and to incorporate resistance to more root-knot nematode species and races into tobacco cultivars. Nematode advisory programs that allow producers to optimize nematicide use from an economical and ecological point of view are also needed.
chemical control; crop loss; crop rotation; cultural practice; integrated pest management; Meloidogyne spp.; nematicide; nematode advisory service; Nicotiana tabacum; resistance; root-knot nematode; tobacco
The suitability of five maturity group (MG) III and five MG IV soybean, Glycine max, cultivars as hosts for Meloidogyne incognita and M. arenaria was evaluated in a greenhouse. 'Forrest', a MG V cultivar, was used as the standard of comparison for M. incognita resistance. With M. incognita, root-gall and egg-mass indices and reproductive factors for 'Asgrow 3307', 'FFR 398', and 'Pioneer 9442' were comparable with those found on Forrest. Meloidogyne arenaria reproduction was lower (P ≤ 0.05) on 'Stevens' than on the other cultivars studied except 'TN4-86'. When grown in a field infested with M. incognita, the relative ranking of the cultivars was similar to the greenhouse results.
Glycine max; host suitability; Meloidogyne arenaria; Meloidogyne incognita; root-knot nematode; soybean
The complex nature of nematode-induced diseases of tobacco, the relationships between nematode levels and damage, the methods of determining these relationships, and the evolving nematode communities on tobacco in eastern North Carolina are described. Crop damage associated with these pathogens varies with nematode race and species, crop cultivar, microflora, and environmental conditions. Root-gall indices as well as initial and mid-season numbers of Meloidogyne spp, in soil are useful for estimating nematode-induced damage on tobacco. The increased occurrences of M. arenaria, M. javanica, and M. incognita races 2 and 4 on tobacco during the last 20 years in North Carolina are having an important economic impact on growers and pose new challenges to researchers.
chemical soil treatment; damage threshold; Meloidogyne spp.; Nicotiana tabacum; population dynamics; root-knot nematode; tobacco
Surveys from 1986 to 1988 identified 22 phytoparasitic nematode species in Arkansas cotton fields. Meloidogyne spp. was found in ca. 15% of the fields sampled. Of these samples ca. 33% were found to have a population density of 106/100 cm³ of soil or more. Rotylenchulus reniformis was found in high numbers (5,000 +/100 cm³ of soil) in 1% of the fields sampled in 1988. Heterodera glycines was found in ca. 22% of the samples, presumably because of past cropping to soybean. Other common species found were Pratylenchus alleni, P. brachyurus, P. scribneri, Tylenchorhynchus ewingi, T. goffarti, Quinisulcius acutus, Helicotylenchus dihystera, H. pseudorobustus, Hoplolaimus magnistylus, Paratrichodorus minor, and Xiphinema americanum. Paratylenchus spp. juveniles were found in ca. 10% of the samples; adults of P. projectus and P. tenuicaudatus were found in ca. 1% of the samples. Other species found only rarely were Pratylenchus zeae, Merlinius brevidens, T. martini, Helicotylenchus multicinctus, Scutellonema brachyurum, and X. chambersi.
Arkansas; cotton; crop loss estimate; Gossypium hirsutum; Helicotylenchus dihystera; Helicotylenchus pseudorobustus; Heterodera glycines; Hoplolaimus magnistylus; infestation estimate; Meloidogyne spp.; Merlinius brevidens; Paratrichodorus minor; Paratylenchus projectus; Paratylenchus tenuicaudatus; Pratylenchus alleni; Pratylenchus brachyurus; Pratylenchus scribneri; Pratylenchus zeae; Quinisulcius acutus; Scutellonema brachyurus; survey; Tylenchorhynchus ewingi; Tylenchorhynchus goffarti; Tylenchorhynchus martini; Xiphinema americanum; Xiphinema chambersi
Host suitability of commercial sunflower hybrids to Pratylenchus zeae was studied in the field and greenhouse. For comparison, one maize and one grain sorghum inbred line, both susceptible to P. zeae, were included in the greenhouse experiments. Pratylenchus zeae densities extracted from the roots of sunflower hybrids grown in naturally infested soil were low. In the first greenhouse experiment, P. zeae densities per 5 g roots and per root system were lower (P = 0.05) in four sunflower hybrids than in maize and grain sorghum. In the second greenhouse experiment, no or few P. zeae were extracted from the roots of eight sunflower hybrids grown in a sandy or sandy clay loam soil. Roots of maize and grain sorghum grown in the sandy soil supported higher (P = 0.05) P. zeae densities than those grown in the sandy clay loam soil. All sunflower hybrids tested were nonhosts or poor hosts for P. zeae.
Helianthus annuus; host suitability; Pratylenchus zeae; root-lesion nematode; South Africa; sunflower
Two lines of Aegilops squarrosa (G 3489 and G 1279) and Triticum cultivars Anza, Cocorit, Produra, Chinese Spring, Nugaines, and a synthetic hexaploid were screened for resistance to Meloidogyne chitwoodi. Reproduction of M. chitwoodi, expressed as eggs per gram root, was low (P < 0.01) on G 3489 and the synthetic hexaploid. Reproduction on all other cultivars tested was high although differences (P < 0.01) existed among them.
Aegilops squarrosa; Columbia root-knot nematode; Meloidogyne chitwoodi; resistance; Triticum aestivum; wheat
In 1984-85 metham-sodium and the combination of 1,3-dichloropropene plus aldicarb decreased (P = 0.05) soil population densities of Pratylenchus penetrans at planting, midseason, and at harvest relative to the untreated control. These treatments increased (P = 0.05) marketable potato tuber yield from 27% to 46% in 1984 and from 23% to 37% in 1985, as compared with the control. In 1984 oxamyl (10% granular and 24% liquid) applied immediately after planting increased (P = 0.05) only the total yield; oxamyl applied 2 weeks after planting failed to control P. penetrans and to increase total or marketable yields. Oxamyl (10 G) applied 2 weeks after planting decreased (P = 0.05) Pf. In 1985 oxamyl (10 G) reduced (P = 0.05) P. penetrans population densities at midseason and harvest, whereas oxamyl (24 L) reduced only harvest population densities. In 1985 neither formulation of oxamyl increased tuber yield.
aldicarb; fumigation; nematicide; oxamyl; potato; Pratylenchus penetrans; root-lesion nematode; Solanum tuberosum; 1,3-dichloropropene
To determine the efficacy of selected nematicides under different soil pH regimes in a sandy soil, soil pH ranges were achieved by adding lime or sulfur. Nematicides increased soybean yields, and their efficacy was generally not influenced by soil pH. Belonolaimus longicaudatus was negatively correlated (r = -0.58, P = 0.01) with yield in 1977.
Belonolaimus longicaudatus; chemical control; Criconemella ornata; DBCP; ethoprop; fenamiphos; fensulfothion; Glycine max; Heterodera glycines; ring nematode; soybean; soybean cyst nematode; sting nematode
The population dynamics and damage potential of an undescribed species of Belonolaimus were investigated for 2 years in a naturally infested commercial corn field in southwestern Kansas and for a third year in a field microplot study. Population trends and vertical distribution of nematode life-stages were monitored and relationships between corn yields and initial or midseason nematode population densities were described using regression analyses. Nematode populations in field plots and in the top 30 cm of microplots increased following seedling emergence, then declined steadily. Numbers of adult nematodes remained relatively stable in all studies, but shifts were observed in the vertical distribution of females in microplots. Females and juveniles in microplots were concentrated in the upper 30 cm of soil 3 weeks after planting but were below normal sample depths by mid-July. Corn yields decreased linearly with increasing initial and midseason nematode population densities.
Belonolaimus sp.; corn; crop loss; damage potential; population dynamics; sting nematode; vertical distribution; Zea mays
In a 1987 field study juveniles of Meloidogyne arenaria assayed at the time of peanut harvest were almost undetectable in plots planted with American jointvetch (Aeschynomene americana), castor bean (Ricinus communis), partridge pea (Cassia fasiculata), sesame (Sesamum indicum), and cotton (Gossypium hirsutum), whereas plots with peanut (Arachis hypogaea) averaged 120 juveniles/100 cm³ soil. Application of aldicarb in peanut resulted in an average of 27 juveniles/100 cm³ soil. In 1988 all plots were planted to peanut and the aldicarb treatment was repeated in plots that had the nematicide in 1987. In 1988 peanut yields from plots that had no peanut in 1987 were 51-69% higher than the yield from those with continuous peanut and no nematicide. Aldicarb resulted in a 57% increase in yield, which is comparable to 1-year rotation to a nonhost crop. In 1988 harvest-time M. arenaria juvenile population densities in soil were the lowest in plots that had castor bean in 1987; however, the partridge pea-peanut and the sesame-peanut rotations also reduced numbers of juveniles when compared with continuous peanut with no nematicide. The aldicarb treatment resulted in juvenile population densities equivalent to those found with either the partridge pea or the sesame rotations. Rotations with American joint vetch or cotton did not result in lower juvenile population densities in peanut in 1988.
Aeschynomene americana; American jointvetch; Arachis hypogaea; Cassia fasiculata; castor bean; cotton; cropping system; cultural practice; Gossypium hirsutum; Meloidogyne arenaria; peanut; pest management; Ricinus communis; root-knot nematode; rotation; sesame; Sesamum indicum
A field infested with Meloidogyne arenaria and with a history of peanut yield losses was divided into two equal parts. One-half of the field (bahia site) was planted to bahiagrass in 1986 and maintained through 1987. The other half (peanut site) was planted to soybean in 1986 and peanut in 1987 with hairy vetch planted each fall as a cover crop. In 1988 identical nematicide treatments including 1,3-dichloropropene (1,3-D), aldicarb, and ethoprop were applied to the two sites, and the sites were planted with the peanut cultivar Florunner. At mid-season, population levels of M. arenaria second-stage juveniles in the bahia site were relatively low, compared with those in the peanut site. At harvest, however, population levels were high in both sites. No nematicide treatment increased yields over the untreated control in either site (P ≤ 0.05). Bahiagrass alone and the combination of bahiagrass and 1,3-D applied broadcast resulted in 6.6-fold and 9.7-fold increases in yield, respectively, over the untreated control in the peanut site. All treatments in the bahia site resulted in increased vegetative growth and yields, compared with the duplicate treatments in the peanut site.
aldicarb; Arachis hypogaea; bahiagrass; crop rotation; 1,3-dichloropropene; ethoprop; Meloidogyne arenaria; nematicide; Paspalum notatum; peanut
Studies were conducted on the host suitability of four citrus rootstocks--rough lemon (Citrus limon), sour orange (C. aurantium), trifoliate orange (Poncirus trifoliata cv. Argentina), and Swingle citrumelo (C. paradisi x P. trifoliata)--to Tylenchulus graminis which was previously considered a "grass" race of T. semipenetrans. In an uncultivated field, sour orange seedlings grown with T. graminis-infected broomsedge (Andropogon virginicus) were not infected with this nematode after 18-month's exposure to T. graminis population densities ranging from < 0.01 to 0.4 second-stage juveniles (J2)/cm³ soil. In a greenhouse test, two T. graminis populations from two Florida locations did not infect sour orange seedlings grown for 2 years in soil naturally infested with 0.3 and 1.3 J2/cm³. Rough lemon, trifoliate orange, and Swingle citrumelo seedlings suppressed T. graminis initial population densities of 7 to final values of < 0.1 J2/cm³ soil. Final values of > 70.0 J2/cm³ occurred in soil with broomsedge. These findings provide conclusive evidence that T. graminis is a specific parasite of grasses and does not infect citrus.
Andropogon virginieus; broomsedge; Citrus aurantium; Citrus limon; citrus nematode; Citrus paradisi x Poncirus trifoliata; host preference; Poncirus trifoliata; rough lemon; sour orange; survival; Swingle citrumelo; trifoliate orange; Tylenchulus graminis; Tylenchulus semipenetrans
Field and greenhouse evaluations of 116 wild Arachis spp. genotypes demonstrated the presence of resistance to reproduction of the root-knot nematode Meloidogyne arenaria race 1. Resistance in greenhouse tests was based on test lines having ≤ 2.5% of the number of eggs per gram of roots as did the susceptible A. hypogaea cv. Tamnut 74. In field tests, resistant genotypes were identified on the basis of having lower (P = 0.05) final nematode population densities than did Tamnut 74. Resistance was identified in genotypes from 11 of 15 wild species tested and in 10 of 20 genotypes belonging to undescribed species. Results of field and greenhouse experiments were similar; 26 of 31 genotypes common to both tests gave similar responses in both tests. Resistance to M. arenaria was identified in the complex hybrid TP-135, which was derived from A. hypogaea cv. Florunner x (A. batizocoi K 9484 x [A. cardenasii GKP 10017 x A. chacoensis GKP 10602])⁴x. In a single greenhouse test, three of six genotypes resistant to M. arenaria were also resistant to M. hapla. These data indicate that the Arachis spp. germplasm contains several sources of resistance to M. arenaria and possibly M. hapla. Some of this resistance is in germplasm that is genetically compatible with A. hypogaea. The complex hybrid TP-135 incorporates resistance from wild species into the genetic background of A. hypogaea. On the basis of these data, we believe it may be possible to develop peanut cultivars with high levels of resistance to M. arenaria and M. hapla.
Arachis hypogaea; Arachis spp.; Meloidogyne arenaria; M. hapla; peanut; resistance
Twenty-six susceptible and resistant soybean, Glycine max, cultivars in Maturity Groups V, VI, VII, and VIII were compared with Coker 156, Wright, and PI97100 for tolerance to Heterodera glycines races 3 and 14. Seed yields were compared in nematicide-treated (EDB, fenamiphos) and untreated plots at two H. glycines-infested locations over 3 years. Coker 488, DP 417, and NK S72-60 had the highest average tolerance indices ([yield in untreated plot + yield in nematicide-treated plot] x 100) of the race 3-susceptible cultivars to races 3 and 14. Plant height and seed weight of untreated soybean plants were suppressed in race 3-infested soil, but only plant height was suppressed at the race 14-infested location. Several race 3-resistant and race 14-susceptible cultivars were moderately tolerant to race 14.
Heterodera glycines; soybean cyst nematode; Glycine max; susceptibility; resistance; tolerance; yield; soybean
In 1986, metam-sodium broadcast at 152, 76, 38, 19, and 9.5 kg a.i./ha suppressed the population density of 19,600 Pratylenchus penetrans/kg soil at planting by 100, 90, 63, 23, and 14%, respectively, and in 1987, with 1,370 P. penetrans/kg soil, by 99, 88, 57, 11, and 1%. At harvest, soil population densities increased 2.2-fold in 1986 and 13.9-fold in 1987. Rate of population increase was similar at all rates of nematicide except it was slower at 152 kg a.i./ha in 1987. In both years, shoot and root weights did not differ (P = 0.05). In 1986 the number of tubers in plots treated with 76 and 152 kg metam-sodium a.i./ha and the marketable tuber weight at the three highest rates did not differ significantly from the untreated control. However, 76 and 152 kg a.i./ha resulted in larger numbers of tubers relative to the three lowest rates of metam-sodium and in higher tuber weight relative to the two lowest rates. Yield differences were not statistically significant in 1987, probably because of low infestation levels.
chemigation; irrigation; metam-sodium; nematicide; potato; Pratylenchus penetrans; root-lesion nematode; Solanum tuberosum
Taylor's Power Law was fit to Tylenchulus semipenetrans population data obtained from individual trees in a survey of 50 Florida citrus orchards (geographic survey) and to data from individual trees within a single orchard collected at regular intervals for 2 years (temporal survey). No significant differences were detected between slope or intercept values when log variance was regressed against log mean for the geographic and temporal data sets. The geographic survey was divided into two subsets of data according to the perceived size of patches of T. semipenetrans. Subsets consisted of orchards which appeared to have numerous small patches of trees infected by the nematode (small patch) and orchards in which most of the trees were infected (large patch). The slope value for the orchards with smaller patches of nematodes was different (P ≤ 0.05) from that from large-patch orchards. Assuming mean nematode levels of 1,000 juveniles and males/100cm³ soil, sample sizes (predicted standard error to mean ratio = 0.20) estimated from the relationships of variances to means were 12 trees in the geographic survey and 11 trees in the temporal. Omission of the small-patch data from the geographic survey resulted in a 17% reduction in optimum sample size. Sample size in sporadically infested orchards was estimated to be 69 trees. A data transformation of x0.23 was calculated from parameters of Taylor's Power Law fit to the survey data.
citrus; citrus nematode; population distribution; sampling; Taylor's Power Law; Tylenchulus semipenetrans
In Arkansas wheat is commonly grown either in rotation or double cropped with soybean. Surveys from 1986 to 1988 identified 18 phytoparasitic nematode species in Arkansas wheat fields. The frequency of occurrence, as a percentage of the total number of samples (199), for the following nematodes was Heterodera glycines 43%, Quinisulcius acutus 40%, Pratylenchus scribneri 37%, Helicotylenchus pseudorobustus 15 %, Xiphinema americanum 14%, Paratylenchus tenuicaudatus 13 %, Pratylenchus alleni 10%, Merlinius brevidens 8%, Tylenchorhynchus ewingi 7%, Paratrichodorus minor 5%, T. martini 4%, and Hoplolaimus magnistyIus, Paratylenchus projectus, and juveniles of Meloidogyne spp. 2%. Helicotylenchus dihystera, Paratylenchus elachistus, and Tylenchorhynchus claytoni were each found in one wheat field.
Arkansas; crop loss estimate; Helicotylenchus pseudorobustus; Heterodera glycines; Hoplolaimus magnistylus; Meloidogyne spp.; Merlinius brevidens; infestation estimate; Paratrichodorus minor; Paratylenchus projectus; P. tenuicaudatus; Pratylenchus alleni; P. scribneri; P. zeae; Quinisulcius acutus; survey; Triticum aestivum; Tylenchorhynchus ewingi; T. martini; wheat; Xiphinema americanum
Grapefruit trees on sour orange rootstock on the east coast of Florida were treated with 22.3 kg a.i./ha fenamiphos (broadcast equivalent) in 1.52-m bands extending from the dripline to beneath the canopy, in 1.52-m bands extending from the dripline toward the row middle, or left as untreated controls. During the course of the experiment, mean density of feeder roots and Tylenchulus semipenetrans in control plots was 3.8 and 5.8 times greater, respectively, in samples from beneath tree canopies than from 90 cm beyond the dripline on the top of beds. Population densities of T. semipenetrans in each zone (under canopy vs. row middle) were smallest when treatment occurred in that zone. Nematode levels beneath the canopy were 11% of control levels 19 weeks following treatment when fenamiphos was applied beneath the canopy and 52% of controls when treated at the dripline. The number of female T. semipenetrans per gram root weight was also reduced under the canopy by the under-canopy treatment. Fruit yield 5 months following nematicide application was not affected by treatment. Percentage change in yield between that harvest and a harvest 16 months after treatment was + 17% in the under-canopy treatment, - 1% in the dripline treatment, and - 17% in the untreated controls.
chemical control; citrus; citrus nematode; fenamiphos; Tylenchulus semipenetrans
A survey of 552 soybean fields in 20 counties in Nebraska in 1986-88 revealed 35 fields infested with the soybean cyst nematode (SCN), Heterodera glycines. Identification was confirmed with a greenhouse bioassay, using 'Lee 74' soybean, and by the application of a DNA hybridization probe derived from SCN mitochondrial DNA. Most of the SCN-infested fields were located on the Missouri River floodplain and in the southeastern corner of the state.
Glycines max; Heterodera glycines; Nebraska; soybean; soybean cyst nematode; survey
Previous cropping sequence (corn-soybean vs. soybean-soybean) and aldicarb effects on soybean yield and nematode numbers at harvest for soybean cultivars with various combinations of nematode resistance were determined in 1988 in a sandy loam soil infested with Meloidogyne arenaria race 2 and Heterodera glycines races 3 and 4 at Elberta, Alabama. Yield and nematode numbers differed among cultivars with 'Leflore' having the highest yield. Aldicarb treatment resulted in increased soybean yield but did not affect nematode numbers. Previous cropping sequence did not affect soybean yield or numbers of H. glycines, but soybean following corn-soybean had higher numbers of M. arenaria than soybean following soybean-soybean. The only significant statistical interaction was aldicarb x cultivar for numbers of H. glycines.
aldicarb; crop rotation; Glycine max; Heterodera glycines; host-plant resistance; Meloidogyne arenaria; root-knot nematode; soybean; soybean cyst nematode
A survey was conducted in four major flue-cured tobacco producing countries to determine use of nematicides for control of plant-parasitic nematodes on flue-cured tobacco. Included in the survey were scientists from Brazil, Canada, the United States, and Zimbabwe. Nematicides were used on 60-95% of the flue-cured tobacco crop in these regions. The choice of fumigant and nonfumigant nematicides, however, varied greatly as influenced by the edaphic factors, nematode species, and other pests present. The major nematicides, application methods, and efficacy evaluation systems used in these countries were addressed.
chemical control; Globodera tabacum; Meloidogyne spp.; nematicide; Nicotiana tabacum; Pratylenchus spp.; survey; tobacco