The Role of Microbes Associated with Chicken Litter in the Suppression of Meloidogyne arenaria

The role of microbes associated with chicken litter in the suppression of Meloidogyne arenaria in amended soil was investigated. Amended soil treatments were prepared, including combinations of sterile and nonsterile chicken litter and soil. Microbial biomass in different treatments was compared by measuring carbon dioxide evolution. There was less CO₂ evolved in sterile litter than in nonsterile litter treatments. Tomato seedlings cv. Rutgers were transplanted into soil mixtures and inoculated with 2,000 M. arenaria eggs. After 10 days, fewer second-stage juveniles (J2) had penetrated the roots in soils amended with nonsterile litter than sterile litter. The effects of sterile and nonsterile litter-amended soil solutions on M. arenaria eggs and J2 were observed over a period of 6 days. A lower percentage of eggs remained apparently healthy in nonsterile than in sterile-amended soil solutions over 6 days. Microbial degradation of the egg shells was apparent. Fewer J2 survived in sterile- and nonsterile-amended-soil solutions as compared to water controls.     

Meloidogyne incognita Infested Soil Amended With Chicken Litter

The effects of chicken litter on Meloidogyne incognita in cotton, Gossypium hirsutum cv. DPL50 were determined in field microplots. Litters (manure and pine-shaving bedding) from a research facility and a commercial broiler house were used. Treatments consisted of 0.25%, 0.5%, and 1% litter by dry weight of soil for each kind of litter. Three control treatments consisted of soil not amended with litter, with and without nematodes, and one treatment to which mineral fertilizer was added at a nitrogen rate equivalent to that of the 0.5% litter rate, with nematodes. Microplots were inoculated at planting with 900 eggs/100 cm³ soil in 1993 and 1,000 eggs/100 cm³ soil in 1994. At 92 and 184 days after planting, nematode population densities decreased linearly with increasing rates of litter. Nematode numbers at midseason were larger in plots treated with mineral fertilizer than in plots treated with a rate of litter equivalent to the 0.5% rate. Fungal and bacterial population densities fluctuated throughout the growing season. Bacterial numbers had a positive linear relationship, with increasing rates of litter only in October 1993; however, significant positive relationships were observed throughout the 1994 growing season. In 1994, nematode population density at 92 days after planting decreased linearly with increasing bacterial numbers 30 days after planting. No other significant relationships between nematode densities and microbial densities were observed. Fungi and bacteria isolated from the litter and litter-amended soil were identified. Fungal genera isolated included Acremonium, Aspergillus, Eurotium, Paecilomyces, Petriella, and Scopulariopsis, whereas bacteria genera included Arthrobacter, Bacillus, and Pseudomonus.     

Differentiation of Two New York Isolates of Pratylenchus penetrans Based on Their Reaction on Potato

The behavior of two isolates of Pratylenchus penetrans on six potato clones was assessed to test the hypothesis that these nematode isolates from New York were different. Four potato cultivars (Superior, Russet Burbank, Butte, and Hudson) and two breeding lines (NY85 and L118-2) were inoculated with nematode isolates designated Cornell (CR) and Long Island (LI). Population increase and egression of nematodes from roots were used to distinguish resistance and susceptibility of the potato clones. Based on numbers of eggs, juveniles, and adults in their roots 30 days after inoculation, potato clones Butte, Hudson, and L118-2 were designated resistant to the CR isolate and susceptible to the LI isolate. More eggs were found in the roots of all plants inoculated with the LI isolate than with the CR isolate. The clones NY85 and L118-2 were inoculated with the CR and LI isolates in a 2 x 2 factorial experiment to assess differences in nematode egression. Egression was measured, beginning 3 days after inoculation, for 12 days. The rates of egression were similar for the four treatments and fit linear regression models, but differences were detected in numbers of egressed nematodes. More nematodes of the CR isolate than the LI isolate egressed from L118-2. Differences in egression of females was particularly significant and can be used as an alternative or supplement to reproduction tests to assess resistance in potato to P. penetrans and to distinguish variation in virulence.     

Parasitism of Nematodes by the Fungus Hirsutella rhossiliensis as Affected by Certain Organic Amendments

Experiments were conducted to determine whether the addition of organic matter to soil increased numbers of bacterivorous nematodes and parasitic activity of the nematophagous fungus Hirsutella rhossiliensis. In a peach orchard on loamy sand, parasitism of the plant-parasitic nematode Criconemella xenoplax by H. rhossiliensis was slightly suppressed and numbers of C. xenoplax were not affected by addition of 73 metric tons of composted chicken manure/ha. In the laboratory, numbers of bacterivorous nematodes (especially Acrobeloides spp.) and fungivorous nematodes increased but parasitism of nematodes by H. rhossiliensis usually decreased with addition of wheat straw or composted cow manure to a loamy sand naturally infested with H. rhossiliensis. These results do not support the hypothesis that organic amendments will enhance parasitism of nematodes by H. rhossiliensis.     

Effects of Resistance in Phaseolus vulgaris on Development of Meloidogyne Species

Use of resistant Phaseolus vulgaris germplasm has a potential role in limiting damaging effects of Meloidogyne spp. on bean production. Effects of two genetic resistance systems in common bean germptasm on penetration and development of Meloidogyne spp. were studied under growth room conditions at 22°C to 25°C. Nemasnap (gene system 1) and G1805 (gene system 2) were inoculated with second-stage juveniles (J2) of M. incognita race 2 and M. arenaria race 1, respectively; Black Valentine was used as the susceptible control. Up to 7 days after inoculation, there were no differences in numbers of M. incognita J2 penetrating roots of Black Valentine and Nemasnap; subsequently, more nematodes were present in Black Valentine roots (P < 0.05). More nematodes reached advanced stages of development in Black Valentine than in Nemasnap roots (P < 0.05). Total numbers of M. arenaria were greater in Black Valentine than in G 1805 roots from 14 days after inoculation (P < 0.05). Advanced stages of development occurred earlier and in greater numbers in Black Valentine plants than in G1805 plants. In these studies, resistance to M. incognita race 2 and M. arenaria race 1 in bean germplasm, which contain gene system 1 and gene system 2, respectively, was expressed by delayed nematode development rather than by differential penetration compared with susceptible plants.     

Response of Plant Parasitic and Free Living Soil Nematodes to Composted Animal Manure Soil Amendments

In an outside pot experiment, dry pig manure processed on pine sawdust litter and fermented for seven days by house fly larvae (fermented manure), and pine sawdust applied alone, and in combination with a spring application of inorganic nitrogen fertilizer were used to determine their effects on plant parasitic and free-living soil nematodes on sugar beets (cv. Antek). Non amended soil was used as a control. All treatments with fermented pig manure and sawdust with nitrogen fertilizer decreased number of plant parasitic nematodes and also root-fungal feeding nematodes compared to the untreated control. Sawdust applied alone had no effect on plant parasitic and root-fungal feeding nematode suppression. Free-living nematodes which were mainly bacteriovores and fungivores were significantly more abundant in soil amended with fermented pig manure, while the sawdust had no effect on these nematodes. The effect of all tested treatments on omnivores-predators was rather random, and in general, the number of these nematodes decreased after soil amendment applications compared to the untreated control.     

Comparative Studies on Root Invasion,Root Galling,and Fecundity of Three Meloidogyne spp. on a Susceptible Tobacco Cultivar

Root invasion, root galling, and fecundity of Meloidogyne javanica, M. arenaria, and M. incognita on tobacco was compared in greenhouse and controlled environment experiments. Significantly more M. javanica than M. arenaria or M. incognita larvae were found in tobacco roots at 2, 4, and 6 d after inoculation. Eight days after inoculation there were significantly more M. arenaria and M. javanica than M. incognita larvae. Ten days after inoculation no significant differences were found among the three Meloidogyne species inside the roots. Galls induced by a single larva or several larvae of M. javanica were significantly larger than galls induced by M. incognita: M. arenaria galls were intermediate in size. Only slight differences in numbers of egg masses or numbers of eggs produced by the three Meloidogyne species were observed up to 35 d after inoculation.     

Effect of Soybean Tip Removal on Penetration and Development of Heterodera glycines

On a few occasions, soybeans with broken root tips were included in tests to evaluate resistance to Heterodera glycines. Although females developed on these plants, the numbers tended to be lower than on similarly treated intact roots. To test the possibility that removal of the root meristem affected nematode development, a culture system using pruned soybeans was devised that permitted access to the roots without disturbing the plants. Treatments included removal of 2 mm of root tip at various times ranging from 24 hours before to 10 days after inoculation, or roots left intact. In each experiment, all roots were inoculated at the same time with equal numbers of freshly hatched second-stage juveniles of Heterodera glycines. No differences in nematode development were detected in plants with root tips removed after inoculation compared to the control. When tips were removed at or before inoculation, fewer juveniles entered roots and relatively fewer nematodes developed. Penetration levels and development correlated with root tip removal such that progressively fewer nematodes entered roots and relatively greater numbers of nematodes remained undeveloped as the time interval between root tip removal and inoculation was increased.     

Penetration and Post-infectional Development and Reproduction of Meloidogyne arenaria Races 1 and 2 on Susceptible and Resistant Soybean Genotypes

Penetration, post-infectional development, reproduction, and fecundity of Meloidogyne arenaria races 1 and 2 were studied on susceptible (CNS), partially resistant (Jackson), and highly resistant (PI 200538 and PI 230977) soybean genotypes in the greenhouse. The ability to locate and invade roots was similar between races, but more juveniles penetrated roots of susceptible CNS than the resistant genotypes. At 10 days after inoculation, 56% and 99% to 100% of race 1 second-stage juveniles were vermiform or sexually undifferentiated in CNS and the resistant genotypes, respectively. In contrast, only 2%, 42%, 44%, and 62% of race 2 juveniles had not initiated development in CNS, Jackson, PI 200538, and PI 230977, respectively. By 20 days after inoculation, 88% to 100% of race 2 nematodes in roots of all genotypes were females, whereas only 25% and 1% of race 1 were females in CNS and the resistant genotypes, respectively. For all four genotypes, race 1 produce 85% to 96% fewer eggs per root system 45 days after inoculation than race 2. At 45 days after inoculation race 2 produced more eggs on CNS than the other genotypes.     

Effect of Compost and Manure Soil Amendments on Nematodes and on Yields of Potato and Barley: A 7-Year Study

A 7-year study located in Prince Edward Island, Canada, examined the influence of compost and manure on crop yield and nematode populations. The compost used in this study consisted of cull waste potatoes, sawdust, and beef manure in a 3:3:1 ratio, respectively. No plant-parasitic nematodes were detected in samples collected from windrow compost piles at 5- and 30-cm depths prior to application on field plots. Low population densities of bacterial-feeding nematodes were recovered from compost windrows at the 5-cm depth. Field plots of potato (Solanum tuberosum cv. Kennebec) received compost applied at 16 metric tonnes per hectare, or beef manure applied at 12 metric tonnes per hectare. An adjacent trial with barley (Hordeum vulgare cv. Mic Mac) received only the compost treatment. In both trials the experimental design was a complete randomized block with four replicates. Data averaged over seven growing seasons indicated that population levels of root-lesion nematodes (primarily Pratylenchus penetrans) were higher in root-zone soil in potato plots treated with either compost or manure compared to the untreated control plots. The soil amendments did not affect root-knot nematode (Meloidogyne hapla) population densities in the potato plots, but clover-cyst nematodes (Heterodera trifolii) were more numerous in the root-zone soils of barley treated with compost compared to the untreated plots. Numbers of bacterial-feeding nematodes (primarily Diplogaster lheritieri) were greater in soil in potato plots treated with manure and in soil around barley roots than in untreated plots. Total yields of potato tubers averaged over seven growing seasons increased by 27% in the plots treated with either compost or manure. Grain yields of barley also were increased by 12% when compost was applied. These results indicated that organic amendments increased crop yields, but the impacts on different nematode species varied and usually increased soil population levels.     

Variability among Populations of Meloidogyne arenaria

Variability in reproduction and pathogenicity of 12 populations of Meloidogyne arenaria race 1 was evaluated on Florunner peanut, Centennial soybean, Rutgers tomato, G70, K326, and Mc944 tobacco, and Carolina Cayenne, Mississippi Nemaheart, and Santanka pepper. Differences among M. arenaria populations in rates of egg production 45 days after inoculation were observed for all cultivars except Santanka pepper. Differences among populations in dry top weights or fresh root weights were recorded on all cultivars. Numbers of nematode eggs produced on Florunner peanut varied from 3,419 to 11,593/g fresh root weight. On resistant tobacco cultivars (G70 and K326), one nematode population produced high numbers of eggs (12,042 and 6,499/g fresh root weight on G70 and K326, respectively), whereas the other populations produced low numbers of eggs (less than 500 eggs/g fresh root weight on both cultivars). Two variant M. arenaria race 1 populations were identified by factor analysis of reproductive rates on all nine cultivars. Differences m reproduction and pathogenicity observed among populations would affect the design of sustainable management systems for M. arenaria.     

Effects of midas® on nematodes in commercial floriculture production in Florida

Cut flower producers currently have limited options for nematode control. Four field trials were conducted in 2006 and 2007 to evaluate Midas® (iodomethane:chloropicrin 50:50) for control of root-knot nematodes (Meloidogyne arenaria) on Celosia argentea var. cristata in a commercial floriculture production field in southeastern Florida. Midas (224 kg/ha) was compared to methyl bromide:chloropicrin (98:2, 224 kg/ha), and an untreated control. Treatments were evaluated for effects on Meloidogyne arenaria J2 and free-living nematodes in soil through each season, and roots at the end of each season. Plant growth and root disease were also assessed. Population levels of nematodes isolated from soil were highly variable in all trials early in the season, and generally rebounded by harvest, sometimes to higher levels in fumigant treatments than in the untreated control. Although population levels of nematodes in soil were not significantly reduced during the growing season, nematodes in roots and galling at the end of the season were consistently reduced with both methyl bromide and Midas compared to the untreated control. Symptoms of phytotoxicity were observed in Midas treatments during the first year and were attributed to Fe toxicity. Fertilization was adjusted during the second year to investigate potential fumigant/fertilizer interactions. Interactions occurred at the end of the fourth trial between methyl bromide and fertilizers with respect to root-knot nematode J2 isolated from roots and galling. Fewer J2 were isolated from roots treated with a higher level of Fe (3.05%) in the form of Fe sucrate, and galling was reduced in methyl bromide treated plots treated with this fertilizer compared to Fe EDTA. Reduced galling was also seen with Midas in Fe sucrate fertilized plots compared to Fe EDTA. This research demonstrates the difficulty of reducing high root-knot nematode population levels in soil in subtropical conditions in production fields that have been repeatedly fumigated. Although soil population density may remain stable, root population density and disease can be reduced.     

Penetration of Susceptible and Resistant Tobacco Cultivars by Meloidogyne Juveniles

Rates of penetration of Meloidogyne incognita, M. arenaria, and M. javanica into tobacco cultivars NC2326 (susceptible to all three species) and K399 (resistant to M. incognita) and a breeding line that had been selected for resistance to M. incognita were compared. Meloidogyne incognita penetrated NC2326 rapidly during the first 24 hours after inoculation. Numbers of M. incognita continued to increase gradually through the 14-day experiment. Higher numbers of M. incognita were observed in the roots of K399 during the first 24 hours than were observed in NC2326. The number of M. incognita in K399 peaked 4 days after inoculation, then declined rapidly as the nematodes that were unable to establish a feeding site left the root or died. Numbers of M. incognita in the breeding line followed the same pattern as with K399, but in lower numbers. Numbers of M. arenaria showed little difference between cultivars until 7 days after inoculation, then numbers increased in NC2326. Numbers of M. javanica fluctuated in all cultivars, resulting in patterns of root population different from those observed for M. incognita or M. arenaria. Resistance to M. incognita appears to be expressed primarily as an inability to establish a feeding site rather than as a barrier to penetration. Some resistance to M. arenaria may also be present in K399 and the breeding line.     

Development of Meloidogyne arenaria on Peanut and Soybean under Two Temperature Cycles

Florunner peanut and three soybean cultivars, Centennial, Gasoy 17, and Wright, were inoculated with 48-hour age cohorts of Meloidogyne arenari race 1 second-stage juveniles and placed in a growth chamber set to simulate early season (low temperature) and midseason (high temperature) conditions. Percentages of the initial inoculum penetrating roots 4 and 8 days after inoculation were 2-3 times higher in soybean cultivars than in peanut; 25% on susceptible soybean and 9% on peanut. Penetration and early development of M. arenaria were greater in the higher temperature environment. Penetration percentages were expressed as a function of cumulative degree-days by regression models. Development of M. arenaria 10, 20, and 30 days after inoculation was more rapid on peanut than on soybean. The resistant soybean cultivar Wright had slower development rates than did the other two soybean cultivars. Nematode growth and development were dependent on temperature. In greenhouse experiments, production of eggs by M. arenaria was more than 10 times greater on peanut than on susceptible soybean. The reproductive factor for Wright soybean was less than one, but plant growth parameters indicated that this cultivar was intolerant of M. arenavia.     

Host-Parasite Relationships of Meloidogyne arenaria and M. incognita on Susceptible Soybean

Pathogenicity and reproduction of single and combined populations of Meloidogyne arenaria and M. incognita on a susceptible soybean (Glycine max cv. Davis) were investigated. Significant galling and egg mass production were observed on roots of greenhouse-grown soybean inoculated with M. arenaria and M. incognita, in combination and individually. M. arenaria produced more galls and egg masses than M. incognita, whereas in combined inoculation with both nematode species, gall and egg production was intermediate. In growth chamber tests, inoculations with M. arenaria and M. incognita, singly or in combination, produced more galls and egg masses at 30 C than at 25 C. At 25 C, M. arenaria alone produced significantly more galls and egg masses than the combined M. arenaria plus M. incognita, while M. incognita produced the fewest. At 30 C, numbers of egg masses produced by M. arenaria did not differ significantly from combined M. arenaria and M. incognita. In temperature tank tests, M. incognita produced more galls and egg masses at 28 C than at 24 C soil temperature. In contrast, numbers of galls, egg masses, and eggs of M. arenaria were slightly higher at 24 C than at 28 C. Combined inoculum of both nematode species produced greater numbers of galls at 24 C than at 28 C.     

Population Dynamics of Heterodera glycines Life Stages on Soybean

Population fluctuations of Heterodera glycines differ in fields with high and low initial population densities. In a field with low initial numbers of nematodes, the numbers of cysts and eggs in soil remained low through 100 days from planting then increased during the remainder of the growing season. In a field with high initial nematode populations, numbers increased at 30 days, decreased to low numbers at 100 days, and then resurged to maximum populations at harvest. Numbers of juveniles were greatest at 100 days in the low initial population density field and at planting in the high initial population density field. The initial numbers of eggs in the soil gave the best correlation to soil and root nematode populations 15 and 30 days later. Juveniles in the soil at planting gave the largest correlation coefficients with nematode populations in the roots at 15 days in the field with the low initial population density. Eggs and juveniles in the soil at harvest were poorly related to numbers that overwintered.     

Distribution of Field Corn Roots and Parasitic Nematodes in Subsoiled and Nonsubsoiled Soil

A field trial was conducted for 2 years in an Arredondo fine sand containing a tillage pan at 15-20 cm deep to determine the influence of subsoiling on the distribution of corn roots and plant-parasitic nematodes. Soil samples were taken at various depths and row positions at 30, 60, and 90 days after planting in field corn subsoiled under the row with two chisels and in non-subsoiled corn. At 30 and 60 days, in-row nematode population densities to 60 cm deep were not affected by subsoiling compared with population densities in nonsubsoiled plots. After 90 days, subsoiling had not affected total root length or root weight at the 20 depth-row position sampling combinations, but population densities of Meloidogyne incognita and Criconemella spp. had increased in subsoiled corn. Numbers of Pratylenchus zeae were not affected. Subsoiling generally resulted in a change in distribution of corn roots and nematodes in the soil profile but caused little total increase in either roots or numbers of nematodes. Corn yield was increased by subsoiling.     

Population Changes of Tylenchulus semipenetrans Under Localized Versus Uniform Drought in the Citrus Root Zone

Population development of Tylenchulus semipenetrans in dry soil was investigated in a greenhouse study. Citrus seedlings were grown in sandy soil in vertical tubes with upper and lower sections. Nematode population densities in the upper tubes were measured at 16, 23, and 37 days, post-treatment. Three treatments consisted of i) irrigating both tubes when soil water potential reached -1 5 kPa (non-drought), ii) irrigating only the bottom tube (local drought), and iii) no irrigation (uniform drought). Soil water potential in the upper tubes did not differ under local and uniform drought during the first 16 days post-treatment, when it approached - 125 kPa. Thereafter, the water potential of soil under uniform drought continued to decrease, while that under local drought stabilized at approximately -150 kPa. Treatments had no consistent effects on female T. semipenetrans counts from soil or roots. However, after 37 days, numbers of eggs, juvenile, and male nematodes per gram of root under local drought were more than 2.4-fold greater than those under non-drought or uniform drought. Numbers of juvenile and male nematodes in soil were 6.5 times higher under local drought than under non-drought after 37 days. Nematodes did not survive in soil under uniform drought. Most of the eggs recovered on each date, from roots under local and non-drought, hatched within 35 days. Sixteen days of uniform drought reduced cumulative egg hatch to 51%, and almost no eggs hatched after 23 and 37 days of uniform drought. Thus, the response of T. semipenetrans to dry soil is fundamentally different, depending on whether all or part of the rhizosphere experiences drought. These data and field observations suggest that hydraulic lift via the root xylem may prolong the activity of some nematodes and possibly other rhizosphere-inhabiting organisms in dry soil.     

Effect of Broccoli (Brassica oleracea) Tissue, Incorporated at Different Depths in a Soil Column, on Meloidogyne incognita

Brassicas have been used frequently for biofumigation, a pest-management strategy based on the release of biocidal volatiles during decomposition of soil-incorporated tissue. However, the role of such volatiles in control of plant-parasitic nematodes is unclear. The goal of this study was to determine the direct localized and indirect volatile effects of amending soil with broccoli tissue on root-knot nematode populations. Meloidogyne incognita-infested soil in 50-cm-long tubes was amended with broccoli tissue, which was mixed throughout the tube or concentrated in a 10-cm layer. After three weeks at 28°C, M. incognita populations in the amended tubes were 57 to 80% smaller than in non-amended tubes. Mixing broccoli throughout the tubes reduced M. incognita more than concentrating broccoli in a 10-cm layer. Amending a 10-cm layer reduced M. incognita in the non-amended layers of those tubes by 31 to 71%, probably due to a nematicidal effect of released volatiles. However, the localized direct effect was much stronger than the indirect effect of volatiles. The strong direct effect may have resulted from the release of non-volatile nematicidal compounds. Therefore, when using biofumigation with broccoli to control M. incognita, the tissue should be thoroughly and evenly mixed through the soil layer(s) where the target nematodes occur. Effects on saprophytic nematodes were the reverse. Amended soil layers had much greater numbers of saprophytic nematodes than non-amended layers, and there was no indirect effect of amendments on saprophytic nematodes in adjacent non-amended layers.     

Changes in populations of soil microorganisms,nematodes, and enzyme activity associated with application of powdered pine bark

Evaluation of enzyme activities in combination with taxonomic analyses may help define the mechanisms involved in microbial decomposition of orgaic amendments and biological control of soilborne pathogens. In this study, powdered pine bark was added to nematode-infested soil at rates of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 g kg^–1. Total fungal populations did not differ among treatments immediately after application of pine bark. After 7 days, fungal populations were positively correlated with increasing levels of pine bark. This increase was sustained through 14 and 21 days.Penicillium chrysogenum andPaecilomves variotii were the predominant fungal species isolated from soil amended with pine bark. Total bacterial populations did not change with addition of pine bark at 0, 7, and 14 days after treatment. At 21 and 63 days, total bacterial populations declined in soil receiving the highest rates of pine bark. Addition of pine bark powder to soil caused a shift in predominant bacterial genera fromBacillus spp. in nonamended soil, toPseudomonas spp. in amended soil. Soil enzyme activities were positively correlated with pine bark rate at all sampling times. Trehalase activity was positively correlated with total fungal populations and with predominant fungal species, but was not related to bacterial populations. The number of non-parasitic (non-stylet bearing) nematodes andMeloidogyne arenaria in soil and roots were not correlated with pine bark rate. However,Heterodera glycines juveniles in roots, and the number of cysts g^–1 root, declined with increasing levels of pine bark.Journal Series Series No. 18-933598 Alabama Agricultural Experiment Station