This study compares nematode prevalence in upland rice fields, which differed in cropping intensity, in three agroecological zones of Ivory Coast. Eighty nematode species from 35 genera were found associated with rice. Population densities of Helicotylenchus spp. were significantly lower in long fallows in the forest zone, but the mean population densities of all other nematode genera and species did not differ significantly between fallow regimes in any of the three agroecologies. Mean nematode population densities exhibited a trend, decreasing, under longer fallows in the forest and savannah zones. Nematode diversity was greatest in the forest-savannah, decreased in the savannah and was least in the humid forest. The population density and prevalence of some nematode genera differed between agroecologies. Of the known pests of rice, Meloidogyne spp. were most prevalent in the forest, whilst Pratylenchus spp. were more prevalent in the forest-savannah and savannah. Heterodera spp. occurred in the forest and forest-savannah, but its prevalence was low. (C) Orstom/Elsevier, Paris.
La sensibilite du pou de tete, Pediculus humanus capitis, aux nematodes entomoparasites Steinernema rara, S. feltiae, Heterorhabditis bacteriophora (souches Oliva et Rio Negro) a ete evaluee. Tous ces nematodes (a l'exception de S. feltiae) tuent les adultes et les nymphes, mais non les oeufs. La souche Rio Negro de H. bacteriophora et S. rara se montrent bien plus agressives envers les adultes et les nymphes que les autres nematodes. H. bacteriophora souche Oliva est plus agressif envers les adultes. La penetration des larves infestantes a lieu apparemment par les spiracles et le diametre du corps des larves infestantes constituerait un facteur limitant. Le parasitisme du pou de tete par des nematodes entomoparasites est relate pour la premiere fois.
The effects of methyl bromide, itaconate dimethyl (ID), cadusaphos, and Pasteuria penetrans on Meloidogyne javanica reproduction and gall index and yield of three successive vegetable crops were evaluated. Only methyl bromide treatments achieved a drastic reduction of nematode populations, resulting in low galling indices and significantly increased yield. Soil recolonization by nematodes during the second year was important and caused yield reduction. LD had no nematicidal effect but caused a slight yield increase. Cadusaphos had a delayed effect on nematode build-up and significantly increased yields. During the first crop, Pasteuria penetrans had no direct effect on nematode populations, gall indices, and yield, but it multiplied actively in the soil. This effectively suppressed nematode populations and reduced gall indices on successive crops, which increased yield. (C) Elsevier - ORSTOM.
The parasitic feeding behaviour of Mesocriconema xenoplax on roots of walnut (Juglans regia L.) was investigated with Scanning Electron Microscopy. Roots of cv. Bleggiana seedlings showed lesions produced by the nematode penetration through the first epidermis layers and the cortex, with associated cell disruption. In the lesions were seen epidermis and cortex fragments that had been removed or detached by nematodes during their migrations between the two root layers. Specimens of M. xenoplax were frequently observed deeply inserted inside roots and an extensive area of epidermis erosion was also visible surrounding the lesions. Eggs were observed in the roots, where they were deposited beneath the epidermis. Root penetration by nematodes and their migrations under the epidermis were considered to be the primary cause of root damage. The feeding of M. xenoplax was found to be a more complex process than regular ectoparasitism and was characterized as an ecto-endoparasitic behaviour. The implications of this behaviour for nematode dispersal and host selection for resistance are discussed.
Les especes pakistanaises P. faisalabadensis et P. psidii decrites par Nasira et Maqbool (1994) sont proposees comme synonymes mineurs de P. mirzai (Siddiqi, 1960) Siddiqi, 1974 a la suite d'une etude de specimens types. La presence d'une deuxieme paire de papilles post-cloacales chez P. mirzai est mise en question.
Pasteuria penetrans dans le sol (en pots ou en champ) apres trois cycles culturaux a ete observee apres re-incorporation de racines de concombre ou de tomate infestees par Meloidogyne spp. eux-memes parasites par P. penetrans. Lors d'une experience en pOtS, la re-inoculation de racines de tomates infestees par Meloidogyne spp. parasitees par P. pene/rans augmente le nombre de spores a lU1 niveau tel que l'invasion par le nematode en est empechee. Lors d'une experience en champ, les juveniles de deuxieme stade extraits du sol apres trois cycles de culture de concombre ne presentent que huit spores fL'(ees en moyenne. Ni la fixation ni le developpement du parasite ne sont affectes si les spores de P. penetrans sont exposees a ces quatre fongicides courants. © OrstomlElsevier, Paris
Soils from various habitats in Guadeloupe (Grande Terre, Passe Terre) and neighbouring islands (Marie-Galante, La Desirade, Petite Terre, Les Saintes, Saint-Barthelemy, Saint-Martin) were assessed for entomopathogenic nematodes using the Galleria baiting technique. Entomopathogenic nematodes were found in 35 of the 538 sites (6%). The genera observed were Heterorhabditis in 34 of these 35 sites (97%) and Steinernema in one site (3%). Two species of Heterorhabditis were found: H. indica (88%) and H. bacteriophora (12%). The one Steinernema was probably a new species, which is being studied. Nematodes occurred in coastal (91.4%), tropical low lands (5.7%), and tropical middle altitude (2.9%) areas. No entomopathogenic nematodes were found in mountain areas. (C) Orstom/Elsevier, Paris.
Surnrnary - We present a method for estimating entomopathogenic nematode densities in soil samples based on repeated sampling with wax moth, Galleria me//onella larvae as bait hosts. This method has a very high extraction efficiency and is less time consuming than other methods. Ten bait insects are added per sampIe and are replaced every 3 days with fresh insects until nematode infections cease. The estimation of nematode density is based on a strong linear relationship berween the loglo of the number of nematode-infected bait insects and the loglo of the number of nematodes found in these bait insects. This relationship was tested for two nematode species in field samples of natural populations and for three nematode species and three soil types in the laboratory. The sJope of the linear regression line varied only slightly among trial, species, and soil type. Resume - Estimation de populations de nematodes entomopathogenespar correlation entre densite des nema todes et mortalite des insectes appâts - Il est decrit une methode d'estimation des larves infestantes de nematodes ento mopathogenes presentes dans des echantillons de sol, methode basee sur des echantillonnages repetes des larves de Galleria mellonelLa jouant le role d'appât. L'efficacite d'extraction de cette methode est tres elevee et elle apparait beaucoup plus rapide que les autres methodes en usage. Dix larves sont placees dans chaque echantillon et sont regulierement remplacees par de nouveaux insectes jusqu'a ce que l'infestation par les nematodes cesse. L'estimation de la densite des nematodes est basee sur une relation lineaire forte entre Je Jog 1o du nombre de larves infestees par les nematodes et le loglo du nombre de nematodes retrouves dans ces larves. Cette relation a ete calculee pour deux especes de nematodes dans des echantillons provenant du champ (populations naturelles) et en laboratoire pour trois especes de nematodes et trois types de sol. La pente de la courbe de regression lineaire ne presente qu'une faible variation entre essais, especes et types de sol.
Some bacteria associated with Arthrobotrys oligospora ORS 18692 S7 isolated from a vegetable-producing area in Senegal were tested for their potential effects on fungus development (saprophytic growth and trapping activity), multiplication of Meloidogyne mayaguensis on tomato plants, and growth of the host-plant. Three bacterial strains enhanced in vitro fungal activity against the nematode, which resulted in better control of the nematode and improved plant growth. These bacteria were called Nematophagous fungus Helper Bacteria (NHB). No criteria could be found for predicting the helper effect of these bacteria. The potentialities of NHB for nematode biocontrol are discussed. (C) Elsevier - ORSTOM.
Protodorylaimus dalmassoi (Loof, 1985) Andrassy, 1988 is described and illustrated from material collected in two localities of peninsular Spain. Its relationships with species of the genera Prodorylaimus Andrassy, 1959 and Oxydiroides Altherr, 1972 is briefly discussed and its inclusion in Protodorylaimus Andrassy, 1988 is supported. (C) Orstom/Elsevier, Paris.
A detailed SEM study on morphological modifications of lateral fields in infective juveniles of dumpy Sfdpy-1 (pn7, pn11, pn29, and pn31), segmented Sfseg-1(pn12), and double dumpy segmented Sfdpy-1(pn7)Sfseg-1(pn12) mutants of Steinernema feltiae is presented. Lateral fields of all mutants examined differed significantly from those of wild-type individuals. A wide spectrum of changes in morphology, arrangement, and number of individual ridges were observed. Combined action of mutations of both Sfdpy-1 and Sfseg-1 genes examined in double mutants further widened the range of observed variation. This produced much greater irregularity in morphology and arrangement of individual ridges than any of the parental mutations separately. The range of variation in mutant nematode lateral fields appeared to be gene specific but not allele specific: morphological modifications in infective juveniles carrying mutations of the Sfdpy-1 gene were significantly different from the modifications in juveniles with mutations of the Sfseg-1 gene, whereas individuals with different mutant alleles of the Sfdpy-1 gene had rather similar modifications, Since distinctive lateral fields are dauer-specific in S. feltiae, this suggests that both genes may play a significant role in the process of cuticle formation in dauers of this nematode.
Ditremamermis montana n. sp., a parasite of larvae of Simulium rubiginosum (Diptera: Simuliidae) from Buenos Aires Province, is described and illustrated. This new species is characterized by having large amphids, vagina transversally oriented, barrel-shaped, located near the middle of the body, male with L-shaped spicules without sculpturing, and Ventral row of genital papillae with eight preanal and seven postanal papillae. Hexamermis australis n. sp., a parasite of Scarites anthracinus Fabricius (Coleoptera: Carabidae) is described and illustrated. It is characterized by medium-sized, pocket-shaped amphids, J-shaped vagina, spicules paired without sculpturing, and genital papillae in six rows including ten preanal and seventeen postanal papillae.
Trois populations de Xiphinema dentatum provenant de regions montagneuses de Yougoslavie sont decrites. Les caracteristiques morphologiques et biometriques sont etudiees et comparees avec celles des autres populations de X. dentatum precedemment decrites pour reevaluer la variabilite et les limites de cette espece. Des epines ont ete observees pour la premiere fois dans l'uterus de specimens de la annulation type de X. turcicum.
