Host Status of Selected Crops to Meloidogyne chitwoodi.

Various crops were tested in greenhouse and field trials for their potential utility in the rotation sequence in the potato cropping system in Meloidogyne chitwoodi-infested soils of the Klamath Basin in northeastern California and southern Oregon. Two Solarium accessions from the International Potato Center in Peru were potential sources of resistance to M. chitwoodi. Cultivars of barley, oat, rye, wheat, and white lupine were maintenance hosts, supporting the nematode population at its current level without substantial increase or decline. Poor to nonhosts to race 1 of the nematode included cultivars of alfalfa, amaranth, oilseed radish, oilseed rape, and safflower. These crops have potential for inclusion in the cropping system but are subject to various constraints, including frost sensitivity and availability of markets. Sugarbeet, a new crop in the area, is a maintenance or better host of M. chitwoodi. Potato, tomato, and sunflower are excellent hosts.

On the methodology of nematode extraction from field samples: baermann funnel modifications.

Routine quantitative nematode extraction for pest management purposes remains a problem. There is need for more knowledge of the parameters limiting efficiency of the various available methods. Sedimentation rates for several species of nematodes have been confirmed as slow and highly variable and therefore not suitable for quantitative separation of nematodes. Funnel losses with clean and unpitted glassware, whether closed or open stemmed, with or without misting, are negligible so long as misting periods are neither inadequate nor excessive; i.e., approximately a 1.5-min water spray period in a 10-min cycle. Tissue paper used to retain soil, sievings, or other substrate in the funnel extraction can greatly inhibit the passage of nematodes depending upon the tissue properties and the nematode species.

On the methodology of nematode extraction from field samples: density flotation techniques.

Density flotation has been frequently used for the extraction of nematodes from field samples. Density flotation curves for four nematode species and five solutes have been prepared. The curves confirm that flotation was governed by several factors: solute density, solute osmotic activity, and physiological properties of the nematode species. Nematode viability and function can be adversely affected by improper selection of solute for density extraction of nematodes; nevertheless, some nematode species can be enriched from mixtures by density and solute selection.

On the methodology of nematode extraction from field samples: comparison of methods for soil extraction.

The commonly used nematode extraction methods were compared using three soil types and four nematode species. The comparison was repeated in three trials by the same operator to estimate operator reproducibility. Extraction efficiency was dependent upon method, soil type, and nematode species, and reproducibility was not particularly satisfactory for routine analyses. Extraction by any method tested was less than 50% efficient. Quantitative nematode extraction methodology needs serious attention.

On the transport of nematodes by the wind.

The possible effectiveness of atmospheric transport of nematode forms (dry larvae or eggs) as a means for introducing new species to a given environment is examined. Given the measured sedimentation velocities for a range of forms (0.1 >/= Ws >/= 0.6 mps), the necessary conditions on the wind speed required for natural erosion are defined. With these results scenarios for lofting, transport, and diffusion of these forms are examined using relevant gaussian plume models. Results indicate that on rare occasions individuals can be deposited up to 40 km from their original location. Redepositions up to 5 km per erosion event should be fairly common occurances when dry loose soil conditions or dry tillage operations combine with optimal atmospheric conditions and the presence of significant numbers of nematodes at the surface.

Behavioral Effects of Carbofuran and Phenamiphos on Pratylenchus vulnus. I. Motility and Dispersion.

The motility and dispersion of Pratylenchus vulnus was affected by lower concentrations of phenanliphos (an organophosphate) than of carbofuran (a carbamate). At the higher concentrations in the active ranges, somatic musculature activity was inhibited while the activity of internal-organ muscnlature persisted. Treated nematodes recovered when placed in aerated distilled water, but recovery decreased as treatment concentrations increased. Second-stage larvae dispersed more slowly than later stages or adults. Dispersion from a point source followed a natural log pattern under ideal conditions, similar to a diffusion pattern.

Behavioral Effects of Carbofuran and Phenamiphos on Pratylenchus vulnus. II. Attraction to Bean Roots.

Pratylenchus vulnus (L, L, adults) are attracted to the roots of growing bean seedlings. The attraction is inhibited by treating the nematodes with solutions of carbofuran or phenamiphos at concentrations below those necessary to inhibit motility and dispersion. Nematicide treatments of plants without treatment of nematodes are ineffectual because nematodes are attracted equally well to treated and untreated seedlings.

Behavioral Effects of Carbofuran and Phenamiphos on Pratylenchus vulnus. III. Penetration and Development.

Penetration of bean roots by Pratylenchus vulnus was inhibited by continuous exposure of the nematode to carbofuran and phenamiphos and by drenches of higher concentrations of these chemicals. The inhibition was explicable by inhibition of motility, dispersion, and attraction. If incubated in aerated distilled water, nematodes treated with carbofuran and phenamiphos recovered and reproduced as well as untreated nematodes. Foliar treatments were ineffective. Apparently, no basipetal transport of carbofuran and phenamiphos occurs in beans. Both nematicides arrested nematode development by interfering with egg production and transitions between life stages.

Response of Pinus ponderosa Seedlings to Stylet-Bearing Nematodes.

Of 12 stylet-bearing nematodes used for inoculations, Pratylenchus penetrans, P. brachyurus, P. vulnus, Ditylenchus destructor, Meloidogyne incognita, M. javanica, and M. hapla reproduced on Pinus ponderosa, while Xiphinema index, Aphelenchus avenae, Paratylenehus neoamblycephalus, Tylenchulus semipenetrans, and Macroposthonia xenoplax did not. P. vulnus, P. brachyurus, P. penetrans, A. avenae, D. destructor, T. semipenetrans, and P. neoamblycephalus significantly suppressed both the shoot and root wet weights of ponderosa pine seedlings obtained from stands in five different locations. X. index significantly suppressed root wet weights, M. xenoplax siguificantly suppressed shoot wet weight, and M. incognita, M. javanica, and M. hapla suppressed neither at the inoculation levels used. Injurious nematodes tended to suppress root growth more than shoot growth. Seedlings from two locations produced greater shoot growth wet weight than did seedlings from the other three locations. The more injurious nematodes tended to cause an increase in the water content of shoots. Frequency analyses of seedling population shoot-root ratios indicated that ponderosa pine seedlings could be selected for better shoot-root ratios as well as for resistance to several pathogenic nematodes.

Resistant Host Responses to Ten California Populations of Meloidogyne incognita.

Resistant and susceptible cultivars of tomato, lima beans, cotton, and alfalfa were tested with 10 populations of Meloidogyne incognita from different California locations. Nine of the populations differed in aggressiveness on the nine cultivars tested. Two populations were especially aggressive toward resistant tomato cultivars.

Ultrastructure of the anterior body region of marine nematode Deontostoma californicum.

The ultrastructure of the anterior body region of the free-living marine nematode Deontostoma calilornicum was studied by electron microscopy. The body wall consists of a nine-layered cuticle, a cellular hypodermis containing eight nerve bundles, and a well-developed coelomyarian somatic musculature. Nerves in the dorsal, lateral, ventral, and submedian hypodermal chords anterior to the nerve ring were observed with regularity. Structure of subventral somatic setae suggests a mechanoreceptive function. The esophagus is cellular and consists of three marginal cells alternating with an equal number of radial muscle cells, three esophageal glands, and three enteric nerves. The membranes of adjacent esophageal cells are sinuous. Apices of the triradiate lumen are connected with the outer wall of each marginal cell by bands of electron-dense nonmyofibrils, whereas two types of myofilaments run radially between the apophyses of the lumen and the outer walls of radial cells. Each myofibril, which forms hemidesmosomes at both ends, is interpreted to be the morphological equivalent of one sarcomere. Synaptic junctions between the processes of muscles, gland cells, and axons of the enteric nerves are described in detail.

Nematicidal injection: targeted control of plant-parasitic nematodes of trees and vines.

Pressurized injection of nematicidal solutions was effective for control of nematodes within trees and vines. Significant (P = 0.01) control of Pratylenchus vulnus on grape was attained with four nonfumigants (carbofuran, oxamyl, phenamiphos, and sulfocarb) and one fumigant nematicide (DBCP). Pratylenchus penetrans was controlled (P = 0.05 and 0.1) in apples and walnuts with sulfocarh and oxamyl. This species also was controlled in apples with carbofuran and phenamiphos. The advantages of pressure injection over traditional methods of nematicide applications are discussed.

Ultrastructure of the Lamellated Cytoplasmic Inclusions in Schwann Cells of the Marine Nematode, Deontostoma californicum.

Electron microscopy of the photoreceptors in the marine nematode, Deontostoma californicum, revealed numerous lamellated inclusions in the Schwann cells ensheathing the lateral cephalic nerves. Immediately after the axons from the modified bipolar neurons of the photoreceptors enter the lateral nerves, these spherical-to-oval lamellated bodies are observed in the surrounding Schwann cell cytoplasm. These previously undescribed Schwann cell inclusions, approximately 500 nm long and 320 nm in diameter, are lamellated and characterized by the presence of an electron-dense stalk-like process, 80-280 nm long. The lamellated inclusions are bound by a single limiting membrane, 6-7 nm thick, which shows occasional interruptions. The internal structure of the inclusions is characterized by the presence of electron-dense lamellae or bands, 11-16 nm thick, which assume various complex patterns ranging from arrays of parallel linear densities to a reticulate appearance. In addition, the nematode Schwann cell cytoplasm contains the usual organelles, gliosome- and lysosome-like inclusions. Their relationship with lipofuscin pigments is briefly discussed.