Isolation of Fungi from Heterodera glycines and in vitro Bioassays for Their Antagonism to Eggs

Twenty fungi were assayed in vitro for antagonism to eggs of Heterodera glycines. Eight of the fungi were isolated from cysts or eggs of H. glycines during the current study, one was isolated from Panagrellus redivivus, and eleven were obtained from other researchers or collections. The bioassays were conducted on eggs from nematodes that had been grown monoxenically on excised root tips. Phoma chrysanthemicola, one strain of Verticillium chlamydosporium, and one strain of V. lecanii caused a decrease (P < 0.01, P < 0.05, P < 0.05, respectively) in the number of viable eggs, although no hyphae were observed colonizing live eggs. Trichoderma polysporum infected live eggs but enhanced (P < 0.05) egg survival. Acremonium bacillisporum, Chaetomium sp., Drechmeria coniospora (two strains), Epicoccum sp., Exophiala jeanselmei, Fusarium sp., Neocosmospora vasinfecta, Scytalidium fulvum, Trichoderma harzianum (two strains), V. chlamydosporium (one strain), V. lecanii (three strains), and an unidentified fungus did not measurably affect egg viability, even though hyphae of five of these fungi were seen in live eggs. The bioassay provides a useful step in the selection of a biological control agent for this major nematode pest.     

A Bioassay to Estimate Root Penetration by Nematodes

An in vitro bioassay with a 96-well microtiter plate was used to study the effect of lectins on burrowing nematode penetration of citrus roots. In each well, one 4-mm root segment, excised from the zone of elongation of rough lemon roots, was buried in 0.88 g dry sand. Addition of a Radopholus citrophilus suspension containing ca. 300 nematodes in 50 μ1 test solution completely moistened the sand in each well. The technique assured uniform treatment concentration throughout the medium. Within 16-24 hours, burrowing nematodes penetrated citrus root pieces, primarily through the cut ends. The lectins (100 μg/ml) Concanavalin A (Con A), soybean agglutinin (SBA), wheat germ agglutinin (WGA), and Lotus tetragonolobus agglutinin (LOT) stimulated an increase in penetration of citrus root segments by Radopholus citrophilus. Concentrations as low as 12.5 μg/ml Con A, LOT, and WGA stimulated burrowing nematode penetration of citrus roots. Heat denaturation of the lectins reversed their effect on penetration; however, incubation of nematodes in lectin (25 μg/ml) with 25 mM competitive sugars did not. The reason for enhanced penetration associated with lectins is unclear.     

Growth of Potato and Control of Pratylenchus penetrans with Oxamyl-treated Seed Pieces in Greenhouse Studies

Oxamyl was applied to both uncut and cut potato tubers in aqueous solutions of 1,000 to 32,000 μg/ml. Emergence in greenhouse pots was delayed for a day or more after soaking cut tuber pieces in 32,000 μg/ml. After 10 weeks plant growth was greater, relative to the control, when Pratylenchus penetrans-infested soil was planted with cut tubers soaked for 20 minutes in 32,000 μg/ml. Soaking for 40 minutes did not increase nematode control nor affect plant growth. Oxamyl applied to tubers at 1,000 μg/ml reduced the numbers of P. penetrans in the soil by 20% and in the roots by 35%; at 32,000 μg/ml, the numbers of P. penetrans in the soil were reduced by 73-86% and in the roots by 86-97%. The numbers of P. penetrans did not increase in the roots of plants developed from cut tubers soaked in 32,000 μg/ml over a period of 10 weeks, but numbers of lesion nematodes had begun to increase in the soil.     

Effects of a Mutant Strain and a Wild Type Strain of Verticillium lecanii on Heterodera glycines Populations in the Greenhouse

A wild type strain ofVerticillium lecanii and a mutant strain with increased tolerance to the fungicide benomyl were evaluated in greenhouse experiments for effects on Heterodera glycines populations. Nematodes were applied at 300 eggs and juveniles per 4,550-cm³ pot (two soybean plants in 4,990 g loamy sand per pot) and at both 300 and 10,000 eggs and juveniles per 1,720-cm³ pot (one soybean plant in 2,060 g sand per pot). With 300 nematodes added per pot, both V. lecanii strains significantly reduced nematode populations in loamy sand (fungus applied at 0.02% dry weight per dry weight loamy sand) and sand (0.006% and 0.06% fungus application rates). The mutant strain applied at 0.002% to sand also significantly reduced cyst numbers. When 10,000 nematodes were added per pot, only the mutant strain at 0.06% significantly decreased population. Various media were tested for isolation of the fungus strains from prills, loamy sand, and sand, but the fungi were recovered from few of the greenhouse pots.     

Nicotine Content of Tobacco Roots and Toxicity to Meloidogyne incognita

The motility of Meloidogyne incognita second-stage juveniles (J2) and their ability to induce root galls in tomato were progressively decreased upon exposure to nicotine at concentrations of 1-100 μg/ml. EC₅₀ values ranged from 14.5 to 22.3 μg/ml, but J2 motility and root-gall induction were not eliminated at 100 μg/ml nicotine. Nicotine in both resistant NC 89 and susceptible NC 2326 tobacco roots was increased significantly 4 days after exposure to M. incognita. The increase was greater in resistant than in susceptible tobacco. Root nicotine concentrations were estimated to be 661.1-979.1 μg/g fresh weight. More M. incognita were detected in roots of susceptible than in roots of resistant tobacco. Numbers of nematodes within resistant roots decreased as duration of exposure to M. incognita was increased from 4 to 16 days. Concentrations of nicotine were apparently sufficient to affect M. incognita in both susceptible and resistant tobacco roots. Localization of nicotine at infection sites must be determined to ascertain its association with resistance.     

Species of Root-knot Nematodes and Fungal Egg Parasites Recovered from Vegetables in Almería and Barcelona,Spain

Intensive vegetable production areas were surveyed in the provinces of Almería (35 sites) and Barcelona (22 sites), Spain, to determine the incidence and identity of Meloidogyne spp. and of fungal parasites of nematode eggs. Two species of Meloidogyne were found in Almería—M. javanica (63% of the samples) and M. incognita (31%). Three species were found in Barcelona, including M. incognita (50%), M. javanica (36%), and M. arenaria (14%). Solanaceous crops supported larger (P < 0.05) nematode numbers than cucurbit crops in Almería but not in Barcelona. Fungal parasites were found in 37% and 45% of the sites in Almería and Barcelona, respectively, but percent parasitism was never greater than 5%. Nine fungal species were isolated from single eggs of the nematode. The fungi included Verticillium chlamydosporium, V. catenulatum, Fusarium oxysporum, F. solani, Fusarium spp., Acremonium strictum, Gliocladium roseum, Cylindrocarpon spp., Engiodontium album, and Dactylella oviparasitica. Two sterile fungi and five unidentified fungi also were isolated from Meloidogyne spp. eggs.     

Meloidogyne lusitanica n. sp. (Nematoda: Meloidogynidae), a Root-knot Nematode Parasitizing Olive Tree (Olea europaea L.)

A root-knot nematode from Portugal, Meloidogyne lusitanica n. sp., is described and illustrated from specimens obtained from olive trees (Olea europaea L.). Females of the new species have a characteristic perineal pattern with medium to high trapezoidal dorsal arch with distinct punctuations in the tail terminus area. The excretory pore is located posterior to the stylet, about 1.5-2.5 stylet lengths from the anterior end. The stylet is 17.1 μm long with pear-shaped knobs. Males have a rounded, posteriorly sloping head cap and head region not annulated. The robust stylet, 24.5 μ long, has large, elongate knobs. Mean length of the second-stage juveniles is 449.5 μm, stylet length 14.2 μm, and tail length 44.1 μm. Scanning electron microscope observations provide further details of perineal patterns and head and stylet morphology of females, males, and second-stage juveniles. Meloidogyne lusitanica n. sp. did not reproduce on any of the differential hosts used to separate the four most common Meloidogyne species. The common name "olive root-knot nematode" is proposed for M. lusitanica n. sp.     

Parasitism of Xiphinema rivesi and X. americanum by Zoosporic Fungi

Living Xiphinema americanum (Xa) and X. rivesi (Xr) extracted from soil samples and stored for 1-5 days at 4 or 20 C contained aseptate fungal hyphae. The fungi directly penetrated the nematode''s cuticle from spores encysted near the head. Penetration through the stoma, vulva, or anus was rare. Catenaria anguillulae (Cat), Lagenidium caudatura (Lag), Aphanomyces sp. (Aph), and Leptolegnia sp. (Lep) were isolated into pure culture from infected nematodes. The pathogenicity of these zoosporic fungi was determined by incubating mixed freshly extracted Xa and Xr in 2% soil extract (pH = 6.7, conductivity = 48 μmhos, 20 ± 2 C) containing zoospores obtained from single-spore isolates. After 4 days, Cat, Lag, Aph, and Lep had infected 78, 18, 13, and 22%, respectively, of the nematodes. Both Xa and Xr were infected by every fungus; however, the relative susceptibility of Xa and Xr to these fungi was not determined. All noninoculated control nematodes remained uninfected and alive. In a second experiment, parasitism of Xa and Xr by Aph and Lep was increased when nematodes were incubated in 2% soil extract for 4 days before exposure to zoospores. In a third experiment, parasitism of Xa and Xr by Cat was greater in diluted saturation soil extract (conductivity = 100-400 μmhos) than in undiluted saturation extract (conductivity = 780 μmhos). Cat produced small zoospores (4-μm-d), bulbous infection hyphae, and assimilative hyphae of varying diameters in nematodes, whereas Lag, Aph, and Lep produced large zoospores (8-μm-d) and tubular, uniform infection and assimilative hyphae in nematodes.     

Effects of Eight Herbicides on In Vitro Hatching of Heterodera glycines

Laboratory studies were conducted to evaluate effects of selected herbicides on hatching of free eggs of the soybean cyst nematode, Heterodera glycines. The herbicides used were Atrazine (atrazine), Basagran (bentazon), Bladex (cyanazine), Blazer (acifluorfen), Command (clomazone), Lasso (alachlor), Sonalan (ethalfluralin), and Treflan (trifluralin). Treatments comprised two concentrations of commercial herbicide formulations and deionized water and 3.14 mM zinc sulfate as negative and positive controls, respectively. Eggs were extracted from females and cysts, surface disinfested, and incubated in herbicide or control solutions at 25 ± 2 C in darkness. Hatched second-stage juveniles were counted every other day for 24 days. Hatching of H. glycines eggs in 50 and 500 μg/ml Blazer was 42 to 67% less than that in deionized water and 6l to 78% less than that in zinc sulfate solution. Zinc sulfate significantly increased hatching activity in 50 μg/ml but not 500 μg/ml Blazer. The other herbicides tested at various concentrations had no significant effect on egg hatching. The specific component of Blazer inhibiting egg hatching is unknown. Suppression of hatching by Blazer indicates that this postemergence soybean herbicide may have a potential role in managing H. glycines.     

Microbial Degradation of a Macrotetrolide Miticide in Soil

Macrotetrolide, a miticide consisting of tetranactin, trinactin, and dinactin, was readily biodegradable and hence did not accumulate in soil. [U-¹⁴C]macrotetrolide was rapidly degraded via its constituent hydroxycarboxylic acids to carbon dioxide and water. In culture media, however, the mixture was hydrolyzed to homononactic and nonactic acids by three strains of Bacillus sp. and two of Micrococcus sp. The latter strains were able to hydrolyze 500 μg of the antibiotic per ml within a few days and to grow in the presence of 4,000 μg of the antibiotic per ml. However, they were unable to assimilate the constituent acids which accumulated in the culture medium.     

Hirsutella rhossiliensisand Verticillium chlamydosporium as Biocontrol Agents of the Root-knot Nematode Meloidogyne hapla on Lettuce

Hirsutella rhossiliensis and Verticillium chlamydosporium infected second-stage juveniles (J2) and eggs of Meloidogyne hapla, respectively, in petri dishes and in organic soil in pots planted to lettuce in the greenhouse. In vitro, H. rhossiliensis produced 78 to 124 spores/infected J2 of M. hapla. The number of J2 in roots of lettuce seedlings decreased exponentially with increasing numbers of vegetative colonies of H. rhossiliensis in the soil. At an infestation of 8 M. hapla eggs/cm³ soil, 1.9 colonies of H. rhossiliensis/cm³ soil were needed for a 50% decrease in J2 penetration of lettuce roots. Egg-mass colonization with V. chlamydosporium varied from 16% to 43% when soil was infested with 8 M. hapla eggs and treated with 5,000 or 10,000 chlamydospores of V. chlamydosporium/cm³ soil. This treatment resulted in fewer J2 entering roots of bioassay lettuce seedlings planted in the infested soils after harvesting the first lettuce plants 7 weeks after infestation with M. hapla. Hirsutella rhossiliensis (0 to 4.3 colonies/cm3 soil), V. chlamydosporium (500 to 10,000 chlamydospores/cm3 soil), or their combination, added to organic soils with 8 M. hapla eggs/cm³ soil, generally did not affect lettuce weight, root galling, or egg production of M. hapla. However, when lettuce was replanted in a mix of infested and uninfested soil (1:3 and 1:7, v:v), egg production was lower in soils with V. chlamydosporium than in soils without the fungus. Both fungi have potential to reduce the M. hapla population, but at densities below 8 eggs/cm³ soil.     

Extraction of saponins and toxicological profile of Teucrium stocksianum boiss extracts collected from District Swat,Pakistan

Background

The current era is facing challenges in the management of neoplasia and weeds control. The currently available anti-cancer and herbicidal drugs are associated with some serious side effects. Therefore numerous researchers are trying to discover and develop plant based alternative particularly for the rational management of cancer and weed control. Teucrium stocksianum possess antioxidant and analgesic activities. The current study was designed to evaluate crude saponins (CS), methanolic extract and sub-fractions of T. stocksianum for cytotoxic and phytotoxic potentials. CS, methanolic extract and sub-fractions were extracted from powdered plant material using different solvents. Cytotoxic potential of the extracts at a dose of 10, 100 and 1000 μg/ml were evaluated against Brine shrimp’s nauplii. Phytotoxic assay also performed at the same concentration against Lemna minor. Etoposide and Paraquat were used as positive controls in cytotoxic and phytotoxic assays respectively.

Results

The percent yield of crude saponins was (5%). CS demonstrated tremendous brine shrimp lethality showing < 10 μg/ml LC₅₀. The n-hexane (HF) and chloroform fractions (CF) demonstrated excellent cytotoxicity with 80 and 55 μg/ml LC₅₀ respectively. Whereas the methanolic extract (TSME), ethyl acetate (EAF) and aqueous fractions (AF) revealed moderate cytotoxicity showing 620, 860 and 1000 μg/ml LC₅₀ values respectively. In phytotoxic assay profound inhibition was displayed by HF (96.67%) and TSME (95.56%, 30 μg/ml LC₅₀) against the growth of Lemna minor at 1000 μg/ml respectively. Both CF and EAF demonstrated profound phytoxicity (93.33%) respectively at highest concentration (1000 μg/ml), while AF and CS demonstrated weak phytotoxicity with 1350 and 710 μg/ml LC₅₀ values respectively.

Conclusion

Cytotoxicity and phytotoxicity assays indicated that the crude saponins, n-hexane and chloroform fractions of T. stocksianum could play a vital role in the treatment of neoplasia and as potential natural herbicides. Therefore these sub-fractions are recommended for further investigation with the aim to isolate novel anti-cancer and herbicidal compounds.     

Effects of Aldicarb on the Behavior of Heterodera schachtii and Meloidogyne javanica

The toxic effects of sublethal concentrations ofaldicarb were studied on eggs and second-stage larvae and males of Heterodera schachtii and second-stage larvae only of Meloidogyne javanica in a quartz sand substrate. Aldicarb was more toxic to eggs of H. schachtii than to those of M. javanica. Complete suppression of hatching occurred between 0.48 and 4.8 μg/ml aldicarb for H. schachtii whereas 100% inhibition of hatch of M. javanica occurred between 4.8 and 48.0 μg/ml. M. javanica hatch was stimulated at 0.48 μg/ml aldicarb. Migration of second-stage larvae of H. schachtii and M. javanica in sand columns was inhibited under continuous exposure to 1 μg/ml aldicarb. Infection of sugarbeet and tomato seedlings by larvae was inhibited at 1 μg/ml. H. schachtii males failed to migrate toward nubile females at 0.01 μg/ml aldicarb. This was partially confirmed in a field study in which adding aldicarb to soil resulted in fewer females being fertilized.     

Association of Verticillium chlamydosporium and Paecilomyces lilacinus with Root-knot Nematode Infested Soil

Population densities of Meloidogyne incognita and the nematophagous fungi, Paecilomyces lilacinus and Verticillium chlamydosporium, were determined in 20 northern California tomato fields over two growing seasons. Paecilomyces lilacinus was isolated from three fields, V. chlamydosporium was isolated from one field, and both fungi were isolated from 12 fields. Verticillium chlamydosporium numbers were positively correlated with numbers of M. incognita and P. lilacinus. Paecilomyces lilacinus numbers were positively correlated with V. chlamydosporium numbers, but they did not correlate with M. incognita numbers. The correlation coefficients were low (R < 0.5) but significant (P < 0.05). All P. lilacinus and V. chlamydosporium field isolates parasitized M. incognita eggs in vitro. In a greenhouse study, numbers of V. chlamydosporium and P. lilacinus increased more in soils with M. incognita-infected tomato plants than in soil with uninfected tomato plants. After 10 weeks, the Pf/ Pi of second-stage juveniles in soils infested with P. lilacinus, V. chlamydosporium, and M. incognita was 47.1 to 295.6. The results suggest V. chlamydosporium and P. lilacinus are not effectively suppressing populations of M. incognita in California tomato fields.     

Description of Hemicycliophora biosphaera n. sp. from Arizona (Nemata: Criconematidae)

Hemicycliophora biosphaera n. sp. (Nemata: Criconematidae) was found in soil from a fallow field plot within the Biosphere 2 Center, Oracle, Arizona. The nematode species is characterized by continuous and irregular breaks in transverse striae in the lateral field, smooth annules, a rounded-truncate lip region with rounded anterior margins, three lip annules, first labial annule elevated and widened laterally, dome-shaped and elevated labial disc, stylet length (76-97 (μm), VA%T value (30-59), 234-273 body annules, and tail with a terminus offset, cylindrical to slightly conoid digit. Hemicycliophora biosphaera n. sp. most closely resembles H. armandae but differs from it in body width (30-39 vs. 38-54 μm), stylet length (76-97 vs. 95-119 μm), greater number of annules between the excretory pore and esophagus base (4-16 vs. 2), length of the tail terminal spike (16-28 vs. 32 μm), lower Rvan value (9-15 vs. 16), and indistinct spetanatheca vs. distinct spermatheca.     

Ultrastructural Changes Caused by Fusarium oxysporum f. sp. lycopersici in Meloidogyne javanica Induced Giant Cells in Fusarium Resistant and Susceptible Tomato Cultivars

Tomato (Lycopersicon esculentum Mill.) seedlings, susceptible (cv. Pearson A-I Improved) and resistant (cv. Pearson Improved) to race 1 Fusarium oxysporum f. sp. lycopersici (Sacc.) Snyd &Hans., were inoculated with Meloidogyne javanica (Trueb) Chitwood second-stage juveniles and 3 weeks later with race 1 F. oxysporum f. sp. lycopersici spores. One week after fungal inoculation, no fungus was visible in root tissue of the tomato cultivars and the giant cells were normal. Two weeks after fungal inoculation, abundant hyphae were visible in xylem tissues of Fusarium-susceptible but not of Fusarium-resistant plants. In susceptible plants, giant cell degeneration occurred, characterized by membrane and organelle disruption. In addition, where hyphae were in direct contact with the giant cell, dissolution of the giant cell wall occurred. Three weeks after fungal inoculation, fungal hyphae and spores were visible inside xylem tissues and giant cells in Fusarium-susceptible plants and in xylem tissue of the resistant plants. In susceptible and resistant plants, giant cell degeneration was apparent. Giant cell walls were completely broken down in Fusarium-susceptible tomato plants. In both cultivars infected by Fusarium, giant cell nuclei became spherical and dark inclusions occurred within the chromatin material which condensed adjacent to the fragmented nuclear membrane. No such ultrastructural changes were seen in the giant cells of control plants inoculated with nematode alone. Giant cell deterioration in both cultivars is probably caused by toxic fungal metabolites.     

Fungal Parasitism of Heterodera glycines Eggs as Influenced by Egg Age and Pre-colonization of Cysts by Other Fungi

The objective of this study was to determine the effect of egg age and pre-colonization of cysts by a saprophytic or parasitic fungus on parasitism of Heterodera glycines eggs by other parasitic fungi. In agar and in soil tests, fungi generally parasitized more eggs in early developmental stages than eggs containing a juvenile. The effect of pre-colonization of cysts by a fungus on parasitism of eggs by other fungi depended on the fungi involved. In most cases, pre-colonization of cysts by an unidentified, saprophytic fungal isolate (A-1-24) did not affect parasitism of eggs in the cysts subsequently treated with other fungi. However, pre-colonization of cysts by A-1-24 reduced fungal parasitism of eggs in cysts subsequently treated with Cylindrocarpon destructans isolate 3. In agar tests, pre-colonization of cysts by Chaetomium cochliodes, a saprophytic or weakly parasitic fungus, reduced parasitism of eggs in cysts subsequently treated with Verticillium chlamydosporium Florida isolate, Fusarium oxysporum, Fusarium solani, ARF18, and another sterile fungus. However, in soil tests, pre-colonization of cysts by C. cochliodes had no effect on parasitism of eggs by subsequent fungal parasites. In another test, parasitism of eggs by V. chlamydosporium in cysts was not affected by pre-colonizing fungi C. destructans, F. oxysporum, and F. solani but was reduced by Mortierella sp., Pyrenochaeta terrestris, and C. cochliodes. Parasitism of eggs in cysts by ARF18 was reduced by pre-colonizing fungi C. destructans, F. oxysporum, F. solani, P. terrestris, and C. cochliodes but not Mortierella sp.     

Factors affecting efficient in vitro micropropagation of Muscari muscarimi Medikus using twin bulb scale

Endemic Muscari muscarimi Medikus is the most fragrant plant among Muscari species and has a high ornamental potential. The natural populations of M. muscarimi, are severely affected by increased environmental pollution and urbanization. There is a need to develop a micropropagation method that should serve effectively for commercial propagation and conservation. Therefore, the study targeted to set up a strategy for efficient in vitro bulblet regeneration system of M. muscarimi using twin scale bulb explants on 1.0 × MS medium containing 4.44, 8.88, 17.76 μM BAP (6-Benzylaminopurine) plus 2.685, 5.37, 10.74 μM NAA (α-Naphthalene acetic acid). Maximum number of 19 daughter axillary bulblets and 16 daughter adventitious bulblets per twin bulb scale explant was regenerated on 1.0 × MS medium containing 17.76 μM BAP plus 10.74 μM NAA and 17.76 μM BAP plus 2.685 μM NAA respectively. The daughter bulblets regenerated on twin bulb scales on 8 out of 9 regeneration treatment could be easily rooted on 1.0 × MS medium containing 4.9 μM IBA (Indole-3-butyric acid). The daughter bulblets regenerated on 9th treatment (1.0 × MS medium containing 17.76 μM BAP plus 10.74 μM NAA) were transferred to 1.0 × MS medium containing 30 g/l sucrose to break negative carry over effect of this dose of BAP–NAA, where they grew 2–3 roots of variable length. Daughter bulblet diameter was increased by culturing them on 1.0 × MS medium containing 4.44 μM BAP plus 5.37 μM NAA. The results verified that both age and the source of explants had significant effect on regeneration. In another set of experiments, twin scales were obtained from in vitro regenerated daughter bulblets, although they induced bulblets, yet their bulblet regeneration percentage, mean number of bulblets per explant and their diameter were significantly reduced. In vitro regenerated bulblets were acclimatized in growth chamber under ambient conditions of temperature and humidity on peat moss, where they flowered. The study provides important information about selection of suitable micropropagation medium, strategies to improve bulblet diameter and rooting of M. muscarimi which offers a scope for commercial propagation.Abbreviations: MS medium, Murashige Skoog medium; BAP, 6-Benzylaminopurine; NAA, α-Naphthalene acetic acid; IBA, Indole-3-butyric acid     

Effects of Selected Nematicides on Hatching of Heterodera schachtii

Aldicarb, carbofuran, fensulfothion, and phenamiphos were tested in concentrations of 1-100 μg/ml for their effects on hatching of Heterodera schachtii. Exposure of cysts to 1 μg aldicarb or carbofuran/ml stimulated hatch whereas phenamiphos and, to a lesser degree, fensulfothion inhibited hatch. Addition of aldicarb to sugarbeet root diffusate or 4 mM zinc chloride suppressed activities of these hatching agents. Transfer of cysts previously treated with aldicarb or carbofuran to zinc chloride or water rapidly initiated hatch which finally exceeded the hatch from cysts not treated with the nematicides.     

Nematostatic Activity of Oxamyl and N,N-Dimethyl-1-cyanoformamide (DMCF) on Meloidogyne incognita Juveniles

The nematostatic activity of oxamyl, methyl-N'',N''-dimethy]-N-hydroxy-l-thiooxamimidate (oxamyl-oxime) and N,N-dimethyl-l-cyanoformamide (DMCF) was studied by immersing 10 Meloidogyne incognita second-stage juveniles into aqueous solutions of various concentrations of each chemical. At concentrations of 500 to 8,000 μg/ml, oxamyl quickly immobilized immersed juveniles. In all other concentrations studied (down to 4 μg/ml), oxamyl stopped or reduced movement of juveniles within 24 hours. DMCF also quickly immobilized juveniles at concentrations of 4,000 and 8,000 μg/ml and reduced movement at 2,000 μg/ml. Lower concentrations had no observed effect on movement. In solutions of the oxime from 2,000 to 8,000 μg/ml, some reduction of movement was observed, but most juveniles maintained some motion over a period of 24 hours. Juveniles were transferred to water from 4,000 μg/ml solutions of oxamyl and DMCF after various intervals of time in order to determine the effect of duration of exposure to the chemicals on the ability of the immobilized juveniles to recover normal motion. Some recovery was observed even after 24 hours of exposure to DMCF, but none after exposure to oxamyl for longer than 40 minutes.