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Bacillus species are among the most studied and commercially exploited biocontrol agents of plant‐parasitic nematodes. These antagonists may control nematodes by producing toxic or repellent substances, inducing systemic resistance in plants and disrupting nematode chemotaxis. Understanding the mechanism of action of antagonists increases the likelihood of success for microbiological nematicides under field conditions. Therefore, the objective of this work was to elucidate the mechanisms of action of Bacillus amyloliquefaciens strain BaNCT02 against Meloidogyne incognita. We assessed the potential of this strain for forming biofilm in roots and producing volatile and non‐volatile toxic substances. BaNCT02 did not induce systemic resistance in tomato plants against M. incognita. Scanning electron microscopy and chemotaxis analyses revealed that the bacteria form a biofilm on soybean roots and 67% of second‐stage juveniles of M. incognita are repelled by common bean roots treated with the antagonist. Additionally, BaNCT02 produces substances with toxic effects against eggs and juveniles of M. incognita, including volatile organic compounds such as 2‐undecanone and 2‐heptanone, as well as non‐volatile metabolites like proteases and chitinases. The suppressive effect of these substances on hatching and mortality of juveniles varied from approximately 70% to more than 90%. We concluded that B. amyloliquefaciens BaNCT02 forms a biofilm on root surfaces and produces volatile and non‐volatile metabolites with nematicidal and repellent effects against M. incognita. [ABSTRACT FROM AUTHOR]

Root‐knot nematodes, Meloidogyne spp., are considered one of the major biotic constraints for global rice production. Although the role of Meloidogyne graminicola in root‐knot disease progression is well investigated, negligible research has been performed to understand the damaging potential of M. incognita in rice. In this study, the comparative infection biology of M. incognita and M. graminicola was investigated in the basmati rice cultivar PB1121 growing in Pluronic gel medium and soil. Intriguingly, M. incognita laid eggs outside the galled root, whereas M. graminicola egg masses were deposited inside the galled root. This differential egg‐laying pattern can be correlated with their specific adaptations in irrigated and upland rice production systems. Although M. incognita induced a greater number of galls than M. graminicola, M. graminicola gall sizes were comparatively larger than those of M. incognita. The greater reproductive success of M. graminicola than M. incognita did not cause any difference in their yield reduction potential in PB1121. PB1121 was equally vulnerable to M. incognita and M. graminicola in terms of reduction in plant height, tiller numbers per plant and grain yield per plant. Our research suggests that M. incognita also causes economic damage to rice, and nematode management tactics must consider the damaging potential of both nematode species. [ABSTRACT FROM AUTHOR]

The attractiveness of 60 aromatic compounds, mainly carboxylic acids, alcohols, aldehydes, and phenols, to second‐stage juveniles (J2) of four Meloidogyne species (M. hapla, M. incognita, M. javanica, and M. marylandi) was evaluated based on the relative density of J2 attracted to a test compound on an agar plate in an 8.5‐cm Petri dish. Three types of nematode responses were observed in the single‐compound assays: attraction, in which J2 were attracted to test compounds; concentration‐dependent attraction, in which J2 were attracted to the zone located 1–2 cm from test compounds; and no response. None of the test compounds effectively attracted M. incognita or repelled J2 of any species. Thirty‐five compounds attracted J2 of at least one of the other three nematode species. Highly effective attractants were trans‐cinnamic acid, salicylic acid, 4′‐hydroxy‐3′‐methoxyacetophenone, o‐vanillin, carvacrol, 3‐methoxybenzyl alcohol, 2‐methoxycinnamaldehyde, trans‐p‐methoxycinnamaldehyde, 4‐methoxy‐3‐methylbenzaldehyde, 2‐methoxy‐4‐propenylphenol, and thymol. Salicylic acid dissolved in the agar reduced the attraction of M. marylandi J2 to salicylic acid and to o‐vanillin. Two‐ and three‐compound assays revealed differences in attractiveness to M. marylandi J2 between or among structural isomers of the attractants. o‐Vanillin and salicylic acid were much more attractive to M. marylandi than vanillin and the two isomers of salicylic acid, respectively. It is not clear whether nematodes utilize the attractants found in the study for locating hosts in nature, but the attractants may have potential for use in nematode control. [ABSTRACT FROM AUTHOR]

The recent ban of the most efficient chemical nematicides has left growers without methods for controlling the carrot cyst nematode Heterodera carotae. This phytoparasitic nematode species has a very narrow host range and causes severe crop losses in the main carrot‐growing regions worldwide. The development of alternative means of management of H. carotae is thus essential, and knowledge is required about the adaptive abilities of H. carotae, which mainly depend on gene flow among populations. The goal of this study was to describe the genetic structure of H. carotae populations at the spatial scale of the main infested French carrot‐producing region, i.e. Lower Normandy, and to disentangle the causes of the heterozygote deficit in this polyvoltine species. Microsatellite genotyping of populations collected at both the plant and field scales showed that: (i) the heterozygote deficit is mainly due to substructure; and (ii) there is strong gene flow among populations, leading to low FST and to no clear genetic structure at the spatial scale explored here. Soil transport through both agricultural machinery and the transport of leek seedlings is probably responsible for the very strong H. carotae migration among fields and production areas. Measures should be considered to limit the passive spread of H. carotae. [ABSTRACT FROM AUTHOR]

The impact of increasing temperatures on the population dynamics of the soil‐dwelling nematode Globodera pallida, a persistent and economically important pest of potatoes, was investigated. The reproductive factor (final population⁄initial population) and length of life cycle were found to be temperature sensitive. Pot experiments performed over 4 months allowed comparison of the effect on development of G. pallida of two temperature regimes: an average temperature comparable to current field conditions (14.3 °C) and an average temperature above current field conditions (17.3 °C). A larger second generation of juveniles was observed at 17.3 °C compared to 14.3 °C. Multiplication of G. pallida at field sites in Shropshire and East Lothian (average soil temperatures of 15.5 and 14.1 °C, respectively, during potato cropping) was also examined. A quantitative PCR assay and visual examination of roots were used to monitor the dynamics of the G. pallida populations in both field sites at 4‐weekly intervals. Four cultivars, Desirée, Cara, Maris Piper and Estima, were grown with and without nematicide treatments. Nematicide treatments suppressed population increases at both sites. Females were observed on the roots of cvs Cara and Desirée at the end of the growing season in Shropshire, but not at East Lothian, and are likely to represent a second generation. [ABSTRACT FROM AUTHOR]

Ochradenus baccatus is a widely distributed shrub in desert regions of the Middle East and North Africa. This plant's nematicidal activity against the root-knot nematode Meloidogyne javanica was evaluated because it has been found to contain exceptionally high levels of glucosinolates. In in vitro assays with aqueous extracts of the plant, 100% of second-stage juveniles were immobilized after exposure to 4% root-core extract for 48 h; 8% root-core extract suppressed their hatching by 87%, whereas stem, flower and root bark showed lower activity. Incorporation of root core or bark into the soil, as fresh or dry powder at 1 and 0·5% (w/w), respectively, reduced the number of nematodes recovered from the soil by 95-100%, whereas the flower and stem were much less effective. Results from further pot experiments indicated that only the root bark consistently contains nematicidal compounds which are effective in soil, whereas the nematicidal activity of the root core in soil was inconsistent. The presence of non-volatile lipophilic and lipophobic nematicidal compounds in the root bark was suggested by extraction with different polar solvents, but these compounds do not seem to be isothiocyanates - glucosinolate-hydrolysed compounds with nematicidal activity. Very poor host status of Ochradenus baccatus to M. javanica, M. incognita and M. hapla, but with root-penetration rates of juveniles similar to those in tomato roots, suggest that this plant may be used as a cover plant or trap plant to reduce nematode populations in the soil. [ABSTRACT FROM AUTHOR]

Nematicidal activity of the leaf powder, leaf extracts and formulated leaf extracts of Myrtus communis, an evergreen shrub that is widely distributed in Israel and other Mediterranean countries, was evaluated using the root-knot nematode Meloidogyne javanica in in vitro and pot experiments. Leaf powder added to sand at 0·1% (w/w) reduced the number of juveniles recovered from the sand by more than 50%. Reduction in galling index and number of nematode eggs on tomato roots was also observed by incorporating the leaf powder at 0·1-0·4% (w/w) in the soil in pot experiments. Leaf powder extracts with methanol or ethanol showed the highest nematicidal activity among all extracts tested. Emulsifiable concentrates of leaf-paste extract at a concentration as low as 0·005% (a.i., w/w) reduced the number of juveniles recovered from treated sand and the gall index of cucumber seedlings. The extract paste at 26 g m−2 was also effective in reducing the gall index of tomato plants in field-plot experiments. The leaf powder at 0·2% and the formulated leaf-paste extract at 0·02% were also nematicidal to Tylenchulus semipenetrans and Ditylenchus dipsaci, but not to Pratylenchus penetrans or Steinernema feltiae. At least three nematicidal compounds were found in the leaf extract upon fractionation by thin-layer chromatography. The results suggest that the leaf powder and paste extract of M. communis are potential nematicides against root-knot nematodes. [ABSTRACT FROM AUTHOR]

The essential oil of Chrysanthemum coronarium flowerheads showed strong nematicidal activity in vitro and in growth-chamber experiments. Essential oil concentrations of 2, 4, 8 and 16 µ L mL-1 , significantly reduced hatch, J 2 survival (determined by final value and area under curves of cumulative percentage hatch or mortality) and reproduction rate of Meloidogyne artiellia in vitro , with the lowest values occurring at 16 µ L mL-1 . In pot trials with chickpea cv. PV 61, essential oil concentrations of 10–40 µ L per 500 cm3 soil, applied on sterile cotton pellets, also significantly reduced the nematode's reproduction rate. The biological processes of mortality and hatching/reproduction were adequately described by the monomolecular and expanded negative exponential models, respectively. Effectiveness of soil amendment with either flowers, leaves, roots or seeds of C. coronarium , and flowers from several species of Asteraceae (Chrysanthemum segetum , Calendula maritima , Calendula officinalis and Calendula suffruticosa ) at 5 g per 500 cm3 soil was tested for suppression of M. artiellia and growth of chickpea cv. PV 61 under growth-chamber conditions. In these tests, flowers of all five Asteraceae species and various parts of C. coronarium significantly reduced reproduction rates of M. artiellia , by 83·0–95·9%, with the minimum rates occurring in infected chickpea plants amended with flowers of C. officinalis and C. suffruticosa . The in vitro and in planta results suggest that the essential oil of C. coronarium and organic amendments from Asteraceae species may serve as nematicides. [ABSTRACT FROM AUTHOR]

A 3-year field study examined the effects of 1,3-dichloropropene or oxamyl on tuber yields in four early- and five late-maturing potato cultivars. The nematicide treatments increased total tuber yield by ≈ 12% for early-maturing cultivars, but by less than 2% for the late-maturing cultivars. The treatments reduced the numbers of root lesion nematodes (primarily Pratylenchus penetrans), which were the dominant plant parasitic nematodes at the site. Covariance analysis indicated that treatment effects on total tuber yield were no longer significant after adjusting for root lesion nematodes in soil at harvest, confirming that these nematodes had a direct effect on the host. As expected, there were significant inverse relationships (P = 0·05) between total tuber yields and numbers of root lesion nematodes in soil and in roots. However, the application of nematicides in late-maturing cultivars was found to be of no practical value. Crop production systems designed to reduce or optimize pesticide applications can form one criterion in the development of more environmentally sensitive management strategies. The merit of utilizing chemicals for root lesion nematode control are considered with regard to cultivar maturity. [ABSTRACT FROM AUTHOR]

A 2-year study investigated the relationship between the nematicides aldicarb and fosthiazate and populations of plant growth-promoting (PGP) and plant-growth-inhibiting (PGI) bacteria, and root-lesion nematodes and bacteria-feeding nematodes in the root-zone soils of potatoes. Fewer (P < 0.05) bacterial genera and species were recovered from aldicarb-treated soils than from the fosthiazate and untreated soils but bacterial population densities were greatest in the aldicarb-treated soils. In potato plantlet bioassays using root-zone bacteria from the three soil sources, bacteria from the aldicarb-treated soils reduced (P < 0.01) the mean wet and dry weight of shoots and roots compared with those from the fosthiazate and untreated soils. In the field, fosthiazate (but not aldicarb) significantly increased tuber yields and reduced nematode population densities of Pratylenchus penetrans in roots and soil. Population densities of bacteria-feeding nematodes (primarily Diplogaster lheritieri) were not affected by either nematicide. Aldicarb appeared to suppress the populations of plant-growth-promoting bacteria that contribute to enhanced growth in potatoes. This is attributed to the long-term use of aldicarb at the trial site, which may have encouraged the selection, or adaptation, of soil microorganisms that degrade carbamate pesticides but do not enhance potato growth. [ABSTRACT FROM AUTHOR]

Surveys made during 1972–75 of 113 potato crops (cvs. Pentland Dell and Pentland Crown) growing in sandy soils, mainly in north Yorkshire, showed that .the incidence of spraing caused by tobacco rattle virus tended to decline with an Increase in the number of barley crops .grown in the three years prior to potatoes. In five potato crops the incidence of spraing was not affected by varying weed control in the preening barley crop. Field trials during 1973–75 tested the effects of aldicarb, oxamyl, fenamiphos, carbofuran and phorate on the incidence of spraing in cvs. Pentland Dell, Pentland Crown and Pentland Hawk. All these chemicals except phorate decreased spraing, but aldicarb and oxamyl were the most effective. Broadcast applications followed by rotavation seemed more effective than in-furrow treatments. [ABSTRACT FROM AUTHOR]

Either of two fumigant nematicides, dazomet or dichloropropanedichloropropene, applied prior to planting at 336 kg a.i./ha, gave good control of Longidorus elongatus (de Man) Thorne & Swanger and transmission of raspberry ringspot virus in a raspberry plantation. Either of two oxime-carbamate nematicides, aldicarb or oxamyl, at 7-84 kg a.i./ha gave only moderate control of nematode numbers and only limited control of virus transmission. Quintozene (89-6 kg a.i./ha) decreased L. elongatus numbers slowly and controlled virus transmission in the field. Pratylenchus crenatus Loof numbers were controlled only by dazomet, dichloropropane-dichloropropene or aldicarb. In a supplementary field experiment the acquisition and transmission of tomato black ring virus by L. elongatus in strawberries was inhibited by oxamyl for less than 19 wk. Little difference in the duration of the inhibitory effect was found between the three rates of oxamyl tested (5-56, 11-2 and 22-4 kg a.i./ha). [ABSTRACT FROM AUTHOR]

Field trials in Scotland in 1972 and 1973 tested the effects of three systemic nematicides (aldicarb, fenamiphos and oxamyl) and the fumigant dichloropropane-dichloropropene mixture (D-D) on the incidence of spraing in potato tubers (cv. Pentland Dell) and on total numbers of trichodorid nematodes, the vectors of tobacco rattle virus. Spraing incidence was least in plots treated with aldicarb or oxamyl. D-D and fenamiphos were effective in decreasing spraing incidence in one year but not in the other. Whereas D-D killed the trichodorid vectors, aldicarb and oxamyl did not kill them but apparently affected their behaviour. None of the chemicals was phytotoxic or decreased tuber yield. [ABSTRACT FROM AUTHOR]

The vigour and yield of sugar beet grown on Heterodera schachtii-infested soils, with organic matter contents of 14 to 68 per cent, were increased by aldicarb granules applied in the seed furrow in field trials in eastern England in 1968 to 1970. Sugar yields were smallest on the most heavily infested sites; yield increases on plots treated with aldicarb were greatest at doses ranging from II to 31 oz active ingredient/acre (770-2,170 g/ha), but increases were not enough to ensure a satisfactory crop. Post-crop numbers of cyst eelworm were not decreased by treatment. Other candidate nematicides — chlorfenvinphos, diazinon, fensulfothion, methomyl, 'Neosar', oxamyl, pirimiphos-methyl, 'Prophos', thionazin, RD 18502, C14421 and R17210 — had no beneficial effect and several, especially at higher doses, were phytotoxic. [ABSTRACT FROM AUTHOR]

Tobacco rattle virus occurs in about 10 per cent, and tomato blackring virus in about 5 per cent, of fields in England affected with Docking disorder. Leaf symptoms caused by TRV, TBRV or by both viruses together may be indistinguishable in sugar beet. Sugar-beet plants showing TRV in June were symptomless in October and were then only half the weight of symptomless neighbouring plants. Sugar beet infected through the seed with TBRV were symptomless and not stunted under glasshouse conditions. Treatment with either ‘D-D’ soil fumigant or the systemic nematicide methomyl decreased the proportion of plants showing TRV in the field. Although widely distributed in England, neither TRV nor TBRV seems likely to cause a serious disease of sugar-beet crops. [ABSTRACT FROM AUTHOR]

Soil injection in March 1961 with D-D (400 lb/acre), chloropicrin P4 gal/acre) or metham-sodium (110 gal/acre) did not kill enough of its eelworm vectors (Xiphinema diversicaudatum) adequately to control arabis mosaic virus in strawberries planted in May, on a site where a crop grubbed in 1960 had shown severe and widespread infection. After further clearance of this site in August 1962, retreatment the same month and replanting in October, the D-D and chloropicrin treatments kept vector numbers very low for nearly three years, greatly decreased virus spread, and increased both plant vigour and yield. Chloropicrin gave consistently more vigour than D-D, as well as more and better fruit, probably not due to superior vector or virus control, but to more pronounced side effects. Dazomet granules at 200 lb/acre had little effect. [ABSTRACT FROM AUTHOR]

The article presents the results of the experiments done in vitro and in the glasshouse, regarding the efficacy and mode of action of the new non-volatile compound 2,4-dichlorophenyl methanesulphonate as a nematicide. In vitro, dichlorophenyl methanesulphonate acts on contact with Turbatrix aceti, Panagrellus redivivus and Ditylenchus dipsaci, while in the glasshouse it is effective against root-knot nematodes on tomato for eight to twelve days. It is found ineffective against Heterodera rostochiensis.

This article discusses the chemical control of potato root eelworm in glasshouse soils using dazomet. The effectiveness of dazomet dust applied to the soil surface and then rotavated in to a depth of approximately 9 inches was compared with similar surface application followed by mixing into the soil by double forking and with similar surface treatment followed by single forking, in replicated randomized plots, for the control of potato root eelworm in glasshouse soils at three centers. With the three treatments the post-treatment cyst densities remained approximately the same as the initial cyst densities but the number of hatched larvae was markedly reduced, a kill of at least 95 per cent being obtained.

This article cites a series of experiments regarding the use of metham-sodium and D-D against potato root eelworm in commercial glasshouses in England. The sites chosen had experienced tomato crop losses of varying severity, towards which eelworm was at least contributory. All trials were randomized blocks replicated two-seven times. The soils were deeply cultivated to a fine tilth immediately before the application of the nematicides. The findings showed that the degree of eelworm kill was inconsistent both with chemicals. Over the trials as a whole metham-sodium was superior to D-D and more efficient when used as a drench than when injected. Moreover, in spite of the variable kill, crop responses occurred in all cases.

This article describes a technique for testing the effects of metham sodium and other chemicals on potato root eelworm using glass cylinders of standard size set in sanded clay pots. Methods of assessing nematicidal effects are compared and some of the difficulties discussed. Standard hatching tests tended to over-estimate the kill, larval viability assessments, based on the kinking method, slightly under-estimated the kill, but gave a closer comparison with root larval invasion counts.

This article presents a study on hatching tests and counts of primary galls in the assessment of nematicides against meloidogyne species. The efficacy of potential nematicides is also often assessed by dosing soil infested with meloidogyne species and counting number of primary galls produced on suitable hosts such as tomato or lettuce. Egg masses were collected from galled tomato roots and sorted into batches of approximately equal size. Soil water and potato root diffusate gave lower hatches than distilled water. There was no evidence of a hatching effect from potato root diffusate although potato is a host and closely related to tomato on which the egg masses had developed.

This article presents a study on the effect of ammoniacal gas liquor on Potato Root eelworm, Heterodera rostochiensis. In view of the shortage of sulphur, sulphuric acid and ammonium sulphate, the direct use of ammoniacal liquor as a nitrogenous fertilizer had been envisaged. A technique for the testing of nematicides under the controlled conditions of a pot test had been developed in 1952, and it was decided to apply this method for the testing of the gas liquor. A feature of the technique is the simultaneous testing of several materials using one batch of mixed infested soil in cylindrical glazed pots each holding 20 pounds.

This article discusses the control of eelworm among Narcissus plants in the Isles of Scilly, England. Stem and bulb eelworm sometimes causes serious loss of early daffodils on the Isles of Scilly. Bulbs are generally hotwater treated before planting, but it may be necessary to replant into eelworm infested soil. The crop usually remains in the ground for three years. Trials were carried out with soil fumigants and nematicidal surface seals in an attempt to disinfect soil and prevent contamination of clean bulbs. In the first year of flowering no eelworm infested plants were found by visual inspection of the treated plots, and laboratory examination of suspected specimens also gave negative results. Adjacent untreated beds showed attacked plants. When eelworm patches occur in beds of Narcissus left in the ground for more than a year it is desirable to check their spread. It is necessary to treat an area larger than the visibly infested patch.