Effects of Infection by Belonolaimus longicaudatus on Rooting Dynamics among St. Augustinegrass and Bermudagrass Genotypes

Understanding rooting dynamics using the minirhizotron technique is useful for cultivar selection and to quantify nematode damage to roots. A 2-yr microplot study including five bermudagrass (‘Tifway’, Belonolaimus longicaudatus susceptible; two commercial cultivars [TifSport and Celebration] and two genotypes [‘BA132’ and ‘PI 291590’], which have been reported to be tolerant to B. longicaudatus) and two St. Augustinegrass (‘FX 313’, susceptible, and ‘Floratam’ that was reported as tolerant to B. longicaudatus) genotypes in a 5 x 2 and 2 x 2 factorial design with four replications, respectively, was initiated in 2012. Two treatments included were uninoculated and B. longicaudatus inoculated. In situ root images were captured each month using a minirhizotron camera system from April to September of 2013 and 2014. Mixed models analysis and comparison of least squares means indicated significant differences in root parameters studied across the genotypes and soil depths of both grass species. ‘Celebration’, ‘TifSport’ and ‘PI 291590’ bermudagrass, and ‘Floratam’ St. Augustinegrass had significantly different root parameters compared to the corresponding susceptible genotypes (P ≤ 0.05). Only ‘TifSport’ had no significant root loss when infested with B. longicaudatus compared to non-infested. ‘Celebration’ and ‘PI 291590’ had significant root loss but retained significantly greater root densities than ‘Tifway’ in B. longicaudatus-infested conditions (P ≤ 0.05). Root lengths were greater at the 0 to 5 cm depth followed by 5 to 10 and 10 to 15 cm of vertical soil depth for both grass species (P ≤ 0.05). ‘Celebration’, ‘TifSport’, and ‘PI 291590’ had better root vigor against B. longicaudatus compared to Tifway.     

Parasitism of Hoplolaimus galeatus on Diploid and Polyploid St. Augustine grasses

''Floratam'' and ''FX-313'' St. Augusfinegrasses (Stenotaphrum secundatum) were compared in a time-course experiment for host suitability and susceptibility to the lance nematode, Hoplolaimus galeatus. Nematode densities were determined in the soil and acid-fuchsin stained roots 42, 84, 126, 168, and 210 days after pots containing 230 cm³ of autoclaved native Margate fine sand/pot were infested with 104 ± 9 nematodes and maintained at 25 ± 2 C in the laboratory. ''FX-313'' was a more suitable host for H. galeatus. Numbers of H. galeatus reached a maximum at 210 days after inoculation, with 5,550 and 4,120 nematodes (adults plus juveniles)/pot for ''FX-313'' and ''Floratam,'' respectively. Root and shoot dry weights of both grasses were not affected by H. galeatus throughout the experiment. Three polyploid, 2n = 30 to 32 (''Floratam,'' ''FX-10,'' and ''Bitterblue'') and three diploid, 2n = 18 (''FX-313,'' ''Florida Common,'' and ''Seville'') S. secundatum genotypes were inoculated with H. galeatus (99 ± 9/pot) and compared with uninoculated controls 210 days after inoculation. St. Augustinegrass genotypes differed as hosts of H. galeatus. ''FX-313'' and ''Florida Common'' represented the high and low extremes, respectively, for nematode reproduction (9,750 and 5,490 nematodes/pot or 4,239 and 2,387 nematodes/100 cm³ of soil). However, differences in root and shoot growth were not detected 210 days after inoculation with H. galeatus.     

Influence of Belonolaimus longicaudatus on Nitrate Leaching in Turf

Experiments were conducted to quantify the effects of the sting nematode (Belonolaimus longicaudatus) on root reductions and quantity of nitrate (NO₃ ⁻) leached from ‘Tifdwarf’ bermudagrass in lysimeters. Forty lysimeters were planted with ‘Tifdwarf’ bermudagrass, of which 20 were inoculated with B. longicaudatus and 20 were noninoculated. Root length was compared between treatments at six, 12, and 18 weeks after initiation of the experiments. Turf was fertilized every three weeks, and leaching events were simulated at 21 and 42-day intervals in trial one and trial two, respectively. Leachate was collected, and the quantity of NO₃ ⁻ leached was compared between treatments. Root reductions were observed in lysimeters inoculated with B. longicaudatus at all evaluation dates. Quantity of NO₃ ⁻ leached was greater in inoculated lysimeters at the 18-week evaluation during both trials. This study indicates that nematode damage to turf roots limits root vigor and N uptake, thereby increasing nitrate leaching, adding to water quality concerns.     

Effects of Formulation and Host Nematode Density on the Ability of In Vitro-Produced Pasteuria Endospores to Control its Host Belonolaimus longicaudatus

The effect of nematode population density at the time of application and formulations of in vitro-produced Pasteuria spp. endospores on the final population density of Belonolaimus longicaudatus was studied in an 84-d-long pot bioassay. The experiment utilized a factorial design consisting of 30 or 300 B. longicaudatus /100 cm(3) of sandy soil and three formulations of in vitro-produced Pasteuria spp. endospores (nontreated, granular, or liquid). No differences were observed in percent endospore attachment between nematode inoculum levels during either trial. Granular and liquid formulations of in vitro-produced endospores suppressed nematode population densities by 22% and 59% in the first trial and 20% and 63% in the second, respectively compared with the nontreated control. The liquid formulation increased percent endospore attachment by 147% and 158%, respectively, compared with the granular formulation. The greatest root retention by the host plant was observed at the lower B. longicaudatus inoculation level following application of the liquid formulation. While both the granular and liquid formulations reduced B. longicaudatus population densities in the soil, the liquid spore suspension was most effective.     

Effects of a Commercial Formulation of Paecilomyces lilacinus Strain 251 on Overseeded Bermudagrass Infested with Belonolaimus longicaudatus

Belonolaimus longicaudatus is an important parasite of both warm-season bermudagrass and winter overseed grasses used on golf courses in the southeastern United States. Field trials were conducted to study the effects of a commercial formulation of Paecilomyces lilacinus strain 251 applied to overseed grasses during the winter and early spring on population density of B. longicaudatus and bermudagrass health in late spring after bermudagrass broke dormancy. These studies found that P. lilacinus reduced numbers of B. longicaudatus in most cases, but not below damaging levels. Multiple applications of 1 × 10¹⁰ spores/m² were generally more effective than 2 × 10¹⁰ spores/m² in reducing nematode numbers and improving turf roots. These results indicate that application of this formulation of P. lilacinus strain 251 to overseeded turf in the spring may be a useful integrated pest management tool for B. longicaudatus on bermudagrass, but is not sufficient as a stand-alone nematode management tactic.     

In Vitro Culture and Feeding Behavior of Belonolaimus longicaudatus on Excised Zea mays Roots

A greenhouse population of the sting nematode, Belonolaimus longicaudatus, obtained from an infested golf course in California''s Coachella Valley, was surface-decontaminated and cuhured on excised roots of Zea mays supported by Gamborg''s B5 medium. At 26-27 °C the females laid eggs, and newly emerged juveniles of the second generation completed three molts within 29 days after egg deposition. Sixty days after inoculation with 60 females and 40 males, an average of 529 nematodes and 83 eggs were recovered from the culture. The feeding process consisted of probing, stylet penetration, ingestion, and stylet retraction. Feeding seemed to be necessary before egg deposition or molting occurred. The sting nematode was observed feeding exclusively as an ectoparasite and preferably at the region of cell division and elongation. Vigorous feeding by many nematodes usually caused discoloration of root tips and termination of growth.     

Extraction Efficiency of Belonolaimus longicaudatus from Sandy Soil

Numbers of Belonolaimus longicaudatus extracted from sandy soils (91-92% sand) by sieving and centrifugation were only 40-55% of those extracted by sieving and incubation on a Baermann tray. Residues normally discarded at each step of the sieving plus Baermann tray extraction procedure were examined for nematodes to obtain estimates of extraction efficiencies. For third-stage and fourth-stage juveniles, males, and females, estimates of extraction efficiency ranged from 60 to 65% in one experiment and 73 to 82% in another. Estimated extraction efficiencies for second-stage juveniles were lower (33% in one experiment, 67% in another) due to losses during sieving. When sterilized soil was seeded with known numbers of B. longicaudatus, 60% of second-stage juveniles and 68-76% of other stages were recovered. Most stages of B. longicaudatus could be extracted from these soils by sieving plus Baermann incubation with an efficiency of 60-70%.     

Population Dynamics of Belonolaimus longicaudatusin a Cotton Production System

Belonolaimus longicaudatus is a recognized pathogen of cotton (Gossypium hirsutum), but insufficient information is available on the population dynamics and economic thresholds of B. longicaudatus in cotton production. In this study, data collected from a field in Florida were used to develop models predicting population increases of B. longicaudatus on cotton and population declines under clean fallow. Population densities of B. longicaudatus increased on cotton, reaching a carrying capacity of 139 nematodes/130 cm³ of soil, but decreased exponentially during periods of bare fallow. The model indicated that population densities should decrease each year of monocropped cotton, if an alternate host is not present between sequential cotton crops. Economic thresholds derived from published damage functions and current prices for cotton and nematicides varied from 2 to 5 B. longicaudatus/130 cm³ of soil, depending on the nematicide used.     

Damage Function and Economic Threshold for Belonolaimus longicaudatus on Potato

Belonolaimus longicaudatus has long been recognized as a pathogen of potato (Solanum tuberosum). However, a damage function relating expected yield of potato to population densities of B. longicaudatus at planting has not been derived, and the economic threshold for nematicide application is unknown. The objectives of this study were to derive the damage function of B. longicaudatus on potato and to calculate the economic threshold population density. The damage function data for B. longicaudatus on potato were obtained from an ongoing field study to evaluate cropping systems and nematode management practices. Soil samples were collected from experimental field plots, and nematodes were extracted from a 130-cm³ subsample with a centrifugal-flotation method. A damage function was derived by linear regression of potato yield on nematode population density at planting. Based on this derived damage function and published potato prices, the economic threshold for nematicide application was calculated at 2 to 3 B. longicaudatus/130 cm³ of soil, which was near the detection threshold based on methodology used in this study.     

Slit Injection of 1,3-Dichloropropene for Management of Belonolaimus longicaudatus on Established Bermudagrass

Belonolaimus longicaudatus is a serious problem on bermudagrass, a common warm-season turfgrass, in Florida. The cancellation of organophosphate nematicides necessitates that new management tools be identified for use on sports turf. Postplant application of 1,3-dichloropropene (1,3-D) on bermudagrass was evaluated for management of B. longicaudatus on golf course fairways and driving ranges. A series of 10 experiments were conducted to evaluate the effectiveness of 1,3-D in reducing population densities of B. longicaudatus and enhancing bermudagrass recovery from nematode damage. In 5 of 10 experiments, 1,3-D injected at 46.8 liters/ha was effective in reducing population densities of B. longicaudatus (P < 0.05) compared to untreated plots 2 to 4 weeks after treatment. One month after treatment, population densities of B. longicaudatus ranged from 59% to 97% of those in untreated plots. Nematode suppression generally lasted 2 months or less. Turf visual performance was improved following injection with 1,3-D (P < 0.05) over untreated plots when other factors were not limiting. Turf root development also was enhanced following injection with 1,3-D. Postplant injection of 1,3-D could be a useful nematode management tool for certain sports turf applications.     

Effects of a Commercial Formulation of Bacillus firmus I-1582 on Golf Course Bermudagrass Infested with Belonolaimus longicaudatus

One of the primary pests of bermudagrass (Cynodon spp.) on golf courses in the southeastern United States is Belonolaimus longicaudatus (sting nematode). In 2011, a commercial formulation of Bacillus firmus I-1582, Nortica 5WG, was launched in the United States for management of plant-parasitic nematodes on turfgrasses. To test the efficacy of late winter/early spring application of this biopesticide on B. longicaudatus, two field trials in 2009 compared B. firmus with fenamiphos and untreated control treatments. In 2011, two additional field trials compared treatment with B. firmus with untreated control only. These trials measured treatment effects on the population density of B. longicaudatus, turf root length, and turf percent green cover. In all four trials, treatment with B. firmus improved root length and decreased numbers of B. longicaudatus in contrast to the untreated. These results indicate that late winter/early spring application of B. firmus is an effective biopesticide treatment for management of B. longicaudatus on golf course bermudagrass.     

Saline Irrigation Affects Belonolaimus longicaudatus and Hoplolaimus galeatus on Seashore Paspalum

Seashore paspalum (Paspalum vaginatum) has great potential for use in salt-affected turfgrass sites. Use of this grass on golf courses, athletic fields, and lawns in subtropical coastal areas may aid in conservation of freshwater resources. Belonolaimus longicaudatus and Hoplolaimus galeatus are considered among the most damaging root pathogens of turfgrasses in Florida. Glasshouse experiments were performed in 2002 and 2003 to examine the effects of increasing levels of irrigation salinity on B. longicaudatus and H. galeatus. Irrigation treatments were formulated by concentrating deionized water to six salinity levels (0, 5, 10, 15, 20, and 25 dS/m). Final population densities of H. galeatus followed a negative linear regression (r² = 0.92 and 0.83; P <= 0.01) with increasing salinity levels. Final population densities of B. longicaudatus were quadratically (r² = 0.72 and 0.78; P <= 0.01) related to increasing salinity levels from 0 to 25 dS/m. An increase in population densities of B. longicaudatus was observed at moderate salinity levels (10 and 15 dS/m) compared to 0 dS/m. Root-length comparisons revealed that B. longicaudatus caused root stunting at low salinity levels, 0 to 10 dS/m, but roots were not affected at 15 to 25 dS/m. These results indicate that the ability of B. longicaudatus to feed and stunt root growth was negatively affected at salinity levels of 15 dS/m and above.     

Effects of Belonolaimus longicaudatus Management and Nitrogen Fertility on Turf Quality of Golf Course Fairways

Field experiments evaluated the effects of nematicide and fertility on performance of ‘Tifway 419’ bermudagrass parasitized by the sting nematode (Belonolaimus longicaudatus). Plot treatments were nontreated or nematicide (1,3-dichloropropene) treated combined with different nitrogen (N) fertilizer levels. Effects of treatments on numbers of B. longicaudatus and turf performance were compared. Nematicide consistently reduced numbers of B. longicaudatus, but fertilizer level had no effect on B. longicaudatus. Turf performance of nematicide-treated plots was improved compared with nontreated plots during both experiments. Increasing N fertilizer level improved turf performance in nematicide-treated plots in some cases, but had no effect on turf performance in nontreated plots in either experiment. Results suggest that increasing N fertilizer levels may not improve turf performance at sites infested with B. longicaudatus unless nematode management tactics are effective in reducing nematode densities.     

Host Status of 'SeaIsle 1' Seashore Paspalum (Paspalum vaginatum) to Belonolaimus longicaudatus and Hoplolaimus galeatus

Belonolaimus longicaudatus and Hoplolaimus galeatus are considered among the most damaging pathogens of turfgrasses in Florida. However, the host status of seashore paspalum (Paspalum vaginatum) is unknown. Glasshouse experiments were performed in 2002 and 2003 to determine the tolerance of ''SeaIsle 1'' seashore paspalum to a population of B. longicaudatus and a population of H. galeatus, and to compare to ''Tifdwarf'' bermudagrass for differences. Both nematode species reproduced well on either grass, but only B. longicaudatus consistently reduced root growth as measured by root length. Belonolaimus longicaudatus reduced root growth (P ≤ 0.05) by 35% to 45% at 120 days after inoculation on both grasses. In 2003, higher inoculum levels of H. galeatus reduced root growth (P ≤ 0.05) by 19.4% in seashore paspalum and by 14% in bermudagrass after 60 and 120 days of exposure, respectively. Percentage reductions in root length caused by H. galeatus and B. longicaudatus indicated no differences between grass species, although Tifdwarf bermudagrass supported higher soil population densities of both nematodes than SeaIsle 1 seashore paspalum.     

Yield Reduction and Root Damage to Cotton Induced by Belonolaimus longicaudatus

Sting nematode (Belonolaimus longicaudatus) is recognized as a pathogen of cotton (Gossypium hirsutum), but the expected damage from a given population density of this nematode has not been determined. The objective of this study was to quantify the effects of increasing initial population densities (Pi) of B. longicaudatus on cotton yield and root mass. In a field plot study, nematicide application and cropping history were used to obtain a wide range of Pi values. Cotton yields were regressed on Pi density of B. longicaudatus to quantify yield losses in the field. In controlled environmental chambers, cotton was grown in soil infested with increasing Pi''s of B. longicaudatus. After 40 days, root systems were collected, scanned on a desktop scanner, and root lengths were measured. Root lengths were regressed on inoculation density of B. longicaudatus to quantify reductions in the root systems. In the field, high Pi''s (>100 nematodes/130 cm³ of soil) reduced yields to near zero. In controlled environmental chamber studies, as few as 10 B. longicaudatus/130 cm³ of soil caused a 39% reduction in fine cotton roots, and 60 B. longicaudatus/130 cm³ of soil caused a 70% reduction. These results suggest that B. longicaudatus can cause significant damage to cotton at low population densities, whereas at higher densities crop failure can result.     

Damage Potential and Reproduction of Belonolaimus longicaudatus and Hoplolaimus galeatus on Alyceclover

Alyceclover (Alysicarpus spp.) is an annual, high-quality leguminous forage, suitable for production under tropical and subtropical climates where the husbandry of conventional leguminous forages, Trifolium spp., is uneconomical. The damage potential and reproduction of Belonolairaus longicaudatus and Hoplolaimus galeatus on alyceclover were studied under greenhouse conditions, using sand and sandy clay loam soil materials, respectively. Both nematode species reproduced on alyceclover, but only B. longicaudatus was pathogenic. Symptoms of B. longicaudatus damage were suppression of shoot yield, limited root system, stunting, incipient wilting, and occasional seedling mortality. In one experiment, the threshold-damage density was three nematodes/100 cm³ sand, whereas in the other experiment it was zero nematodes.     

Life Cycle and Mating Behavior of Belonolaimus longicaudatus in Gnotobiotic Culture

The life cycle of Belonolaimus longicaudatus was observed in vitro on excised roots of Zea mays. Roots were cultured on Gamborg''s B5 medium in petri dishes with 1.5% agar adjusted to pH 5.8 and incubated at 28 °C in darkness. Second-stage juveniles (J2) fed on the roots and started the second molt (M2) to the third-stage juveniles 2 days after inoculation (DAI). The third molt (M3) to the fourth-stage juveniles occurred 7 DAI, followed by the fourth molt (M4) to males 13 DAI or to females 14 DAI. Nematode gender differences were observed by the end of the fourth molt. The first male appeared 15 DAI and the first female 17 DAI, after which mating occurred. Males were attracted to females, and mating was observed. Mating was required for reproduction. Fertilized females began to lay eggs 19 DAI and continued egg laying without the further presence of males during a 90-day observation. All of the eggs hatched. Unfertilized females rarely laid eggs, and none of the eggs were able to hatch. Feeding took place between each molt and before egg deposition occurred. The first-stage juveniles molted in the eggs 4 days after deposition, and J2 hatched from eggs 5 days after egg deposition. The life cycle from J2 to J2 was completed in 24 days.     

Niche Distribution of Paratrichodorus minor and Belonolaimus longicaudatus Following Fumigation on Potato and Cabbage

An experiment was conducted to determine population changes and niche variation in the soil at two depths (0 to 20 cm and 20 to 40 cm) of Paratrichodorus minor and Belonolaimus longicaudatus populations following fumigation. Eight plots each of potato (Solanum tuberosum) and cabbage (Brassica oleracea var. capitata), fumigated with 1, 3-dichloropropene or nonfumigated, were established. Eight plots of sorghum-sudangrass hybrid (Sorghum bicolor × S. arundinaceum var. sudanense) were also used to monitor depth distribution (0 to 20 cm and 20 to 40 cm) of B. longicaudatus and P. minor following each cabbage/potato season. Soil samples were taken 0 to 20 cm and 20 to 40 cm deep during the potato/cabbage, and sorghum-sudangrass growing seasons. During the 1993-94 and 1994-95 potato/cabbage seasons, P. minor was found at highest numbers at 20 to 40 cm, whereas numbers of B. longicaudatus were highest at 0 to 20 cm. During the 1994 and 1995 sorghum-sudangrass growing seasons, B. longicaudatus numbers were highest at 0 to 20 cm. Paratrichodorus minor numbers were highest at 0 to 20 cm and at 20 to 40 cm deep in the 1994 and 1995 sorghum-sudangrass growing seasons, respectively. Reduction by soil fumigation of B. longicaudatus at 0 to 20 cm deep did not affect depth distribution or cause P. minor populations to increase in potato or cabbage plots. Paratrichodorus minor numbers increased at 20 to 40 cm deep in the 1994-95 cabbage season after soil fumigation.     

Ultrastructure and Development of Pasteuria sp. (S-1 strain), an Obligate Endoparasite of Belonolaimus longicaudatus (Nemata: Tylenchida)

Pasteuria sp., strain S-1, is a gram-positive, obligate endoparasitic bacterium that uses the phytoparasitic sting nematode, Belonolaimus longicaudatus, as its host in Florida. The host attachment of S-1 appears to be specific to the genus Belonolaimus with development occurring only in juveniles and adults of B. longicaudatus. This bacterium is characterized from other described species of Pasteuria using ultrastructure of the mature endospore. Penetration, development, and sporogenesis were elucidated with TEM, LTSEM, and SEM and are similar to other nematode-specific Pasteuria. Recent analysis of 16S rDNA sequence homology confirms its congeneric ranking with other Pasteuria species and strains from nematodes and cladocerans, and corroborates ultrastructural, morphological, morphometric, and host-range evidence suggesting separate species status.