Fertilizer which generated NH₃ was detrimental to Criconemoides xenoplax grown in the greenhouse. The fertilizer was lethal to the nematodes in vitro only when it was accompanied by urease-positive bacteria or partially purified urease. The detrimental action of the fertilizer-urease mixture was ntore rapitt at pH 8 than at pH 7.
Ring nematotles; urea
Preplant soil applications of granular phenamiphos effectively reduced Pratytenchus penetrans in soil during the seeding year and 1 year after, and in the roots of birdsfoot trefoil 2 years after seeding. Forage yields were increased in the season following application of phenamiphos, but stands of plants/m² were not greater (P = 0.05) than those in the checks 1 and 2 years after treatment. Additional spring applications of phenamiphos 1 and 2 years after seeding further reduced numbers of nematodes in the soil but did not improve forage yields or plant stand over that of a single application. Broadcast preplant soil sprays of oxamyl followed by several foliar sprays at different rates and frequencies of application over a 3-year period restricted populations of P. penetrans in the soil and roots of birdsfoot trefoil but did not consistently result in increased forage yields. Stands of birdsfoot trefoil continued to decline each year even with oxamyl treatments.
Lotus corniculatus; root-lesion nematode
The pathological effects of Pratylenchus scribneri on susceptible snap bean and resistant lima bean were studied. In a pathogenicity test, the nematode increased nearly 75-fold on snap bean and suppressed top growth. On lima bean, P. scribneri reproduced slowly and did not significantly affect top growth. Discreet lesions formed on lima bean roots, but no lesions developed on snap bean roots. Paraffin sections taken 2, 5, 13, 25, and 32 days after inoculation showed little cellular necrosis in snap bean roots, whereas cells surrounding the nematode in lima bean were extensively necrotic. Cortical cells of infected snap bean roots were almost completely invaded and killed 25 and 32 days after inoculation. The cortex of lima bean tissues was intact, although localized necrotic areas remained at sites of nematode invasion.
host resistance; lesion nematode; Phaseolus lunatus; Phaseolus vulgaris
American boxwood, Buxus sempervirens var. globosum, was tolerant of Helicotylenchus dihystera [in field microplots] as measures of plant growth were similar to the control and nematode densities were maintained at high levels (1,705-1,810/500 cm³ soil after 29 months). Boxwood was intolerant of Pratylenchus vulnus at initial densities of 163, 281, or 475 nematodes per 500 cm³ soil. In comparisons with those of controls, vigor ratings of boxwood after 14 months were much lower at all densities of this nematode. Nematode density was not directly related to vigor rating. However, initial nematode density was directly proportional to growth suppression of boxwood as measured by the difference of the product of final plant height × width or by the difference of the plant surface area determined from a standardized photograph as compared to those of controls. A nematode density of 160/500 cm³ of soil was found to suppress growth by 50%. Populations of P. vulnus declined, according to a linear function, with time after reaching over 7,100 nematodes/500 cm³ of soil taken from the root zones of boxwoods. Ninety-five percent of the P. vulnus population died between 15 and 20 months after soil infestation.
semilogarithmic transformation; Buxus sempervirens var. globosum
Rate of passage through the digestive systems and effects of ingestion on viability of contents of cysts of Heterodera rostochiensis were determined in feeding trials with pigeons, thrushes, starlings, cowbirds, sparrows, and quails. Depending upon species of birds, 12-82% of the cysts ingested passed through the digestive system within 0.5 h. Pigeons required 6 h for complete evacuation. All other birds cmnpletely evacuated ingested cysts from their digestive systems within 3 h. Contents of cysts were nonviable if they were retained in the digestive system of starlings for more than 1.5 h, pigeons more than 1 h, or other birds more than 0.5 h. Cyst contents were nonviable if they remained in contact with excreta from cowbirds or quails for 4 h, thrushes for 96 h, or other species for 72 h after passage. Viability of contents of cysts was inversely related to exposure to excreta-filtrate concentration. Larvae failed to emerge from cysts that were exposed to a 25% concentration of excreta filtrate from starlings, 50% concentration from pigeons or thrushes, or 100% concentration of excreta filtrates from each of the other species. Cysts that were subjected to 44 C (avg. body temperature of cowbirds) for more than 3.5 h were nonviable. Cysts that passed through birds and collected with excrement on polyethylene or soil produced no infective larvae on potato.
Spread of nematodes; pigeons; thrushes; starlings; cowbirds; sparrows; quails
Cultures of C. elegans containing a high proportion of males were subjected to chemotactic tests by using the method of countercurrent separation. The responses of males and hermaphrodites were determined. Both types of worms preferred Na⁺ over 1/2 Ca⁺², Cl⁻ over NO₃⁻; they were attracted to NaCl, OH⁻, cyclic AMP, pyridine, CO₂, in borate buffer (pH 8.8); and avoided CO₂ in phosphate buffer (pH 6.0), D-tryptophan, and acid. It was thus concluded that male C. elegans have the same chemotactic responses that hermaphrodites of this species are known to have.
attraction; behavior; nematode; repulsion
When Guinea yam, Dioscorea rotundata Poir, was inoculated with Pratylenchus coffeae and Scutellonema bradys together, there was a 53% suppression of top growth, but when plants were inoculated separately there was a 29% suppression with P. coffeae and a 21% suppression with S. bradys. The reproduction of S. bradys was greatly inhibited when both nematode species were together on the same plant in comparison with that on plants inoculated with S. bradys alone. Scutellonema bradys apparently did not affect the reproduction of P. coffeae. Storage-root quality was reduced 72% by P. coffeae but only 20% by S. bradys. The two species together resulted in a reduction in storage-root quality of 84%. Although the Guinea yam is a good host of P. coffeae and S. bradys, our results indicate that P. coffeae is responsible for most of the storage-root deterioration and dry rot of yam in Puerto Rico.
storage-root quality; lesion nematode; yam nematode; deterioration; nematode-nematode interactions
The distribution and density of Pratylenchus minyus and possible relationships of several environmental components, including ammonium nitrate, were investigated in a wheat field in South Australia. Seasonal variation as measured every 2-4 weeks was eliminated from the observations by periodic regression. Correlation and regression analyses were then used to investigate the association of host plant, rainfall, temperature, and the fungus Gaeumannomyces graminis with P. minyus. Other than seasonal effects, soil moisture and G. graminis were the only components associated with P. minyus. Ammonium nitrate usually was correlated with fewer P. minyus in wheat roots. Much higher numbers of P. minyus were observed in seminal than in crown roots of wheat.
Gaeumannomyces graminis; seasonal variation; ammonium nitrate; crown roots; seminal roots; population dynamics
Discocriconemella repleta n.sp. from Brazil is described. The male of Criconemoides inusitatus Hoffmann, 1974, is described here for the first time.
Inoculation of 'Thompson Seedless' grapevines with 500 Xiphinerna index or 1,000 Pratylenchus vulnus alone or in combination suppressed vine shoot and root growth under greenhouse conditions. Pratytenchus vulnus caused greater stunting of roots than X. index. Each nematode species inhibited top growth about equally. Concomitant inoculations caused greater stunting of tops and roots than did inoculations of either nematode species alone. Differences in growth between inoculated and control plants increased with exposure time. Pratylenchus vulnus competed with and gradually superseded in numbers an established population of X. index. Both species reproduced on 'Thompson Seedless' roots, but P. vulnus increased to a much higher level than did X. index. The increase of P. vulnus, together with extensive damage, proves its pathogenicity to grapevines.
Histological changes in roots of Beta vulgaris cultivar 'USH9A' resulting from infection of Meloidogyne hapla alone, Heterodera schachtii alone, or infection by both species on one feeding site were studied. Anatomical changes caused by M. hapla infection were characterized by regions of hypertrophy and hyperplasia. Giant cells were formed within the stele and varied in numbers from 4-7/feeding site; hyperplasia occurred in the form of a large number of relatively small compacted cells generally surrounding the hypertrophied region. H. schachtii-induced syncytia became dense and muhinucleate. Syncytia were formed in the stele and were limited on the side toward the nematode by endodermis or in part by cortical tissue. Histological changes due to the presence of both parasites on one feeding site were characterized by formation of two distinctive pathological tissues typical of both nematodes. In most infections, xylem elements separated the two pathological tissues. In some sections, a single wall separated the two pathological tissues, and no dissolution of separating wall was noted in any sections. Each nematode developed normally and produced its own characteristic pathological tissue independently.
interrelationships; cyst; root-knot; sugar beet
Population densities of Belonolaimus longicaudatus, Pratylenchus brachyurus, and Trichodorus christiei were determined from soil samples taken weekly in Tifton, Georgia during a 14-month period (except for April and May) at 15-cm increments to a depth of 105 cm. Belonolaimus longicaudatus predominately inhabited the top 30 cm of soil that was 87-88% sand, 6-7% silt, and 5-7% clay. No specimens were found below 60 cm where the soil was 76-79% sand, 5-6% silt, and 15-19% clay. Highest population densities occurred during June through September when temperature in the top 30 cm of soil was 22-25 C and soil moisture was from 9 to 20% by volume. Pratylenchus brachyurus was found at all depths, but population densities were greatest 45-75 cm deep where the soil was 78-79% sand, 6% silt, and 15-16% clay. In the months monitored, highest population densities occurred during March, June, and December when the soil temperature 45-75 cm deep was 14-17 C and soil moisture was 22-42%. Trichodorus christiei was found at all depths, but population densities were highest 30 cm deep where the soil was 83% sand, 5% silt, and 12% clay. Highest population densities occurred during December through March when the soil temperature 30 cm deep was 11-17 C and soil moisture was 18-23%.
seasonal fluctttations; Belonolairnus longicaudatus; Pratylenchus brachyurus; Trichodorus christiei
The fine structure of the esophagus of Pratylenchus penetrans is described. The gland lobe is syncytial and contains two types of nuclei: three large nuclei with little chromatin, and more numerous smaller nuclei with large amounts of chromatin. Some of the smaller nuclei are associated only with glandular tissue, whereas others are part of nerve ceils within the esophagus. Clusters of free ribosomes, rough endoplasmic reticulum, and numerous mitochondria occur in the lobe region where the secretory granules are formed. No Golgi bodies were observed. On the basis of these observations, possible differences in the mechanism of secretory granule formation between plant-parasitic nematodes are discussed. Several other minor differences between the fine structure of other plant-parasitic nematodes previously examined and that of P. penetrans are also noted.
Two efficient, senti-automatic elutriators for assaying soil samples for nematodes are described. The first apparatus is a four-unit elutriator which combines conventional extraction methods with the following major features: atttomatic mixing of 500- to 1,500-cm³ soil samples with water (± air); "turbinate" sample splitters from which fractions of 1/15 or greater are passed onto 26- or 38-μm sieves for collection of larvae and adult nematodes; the capacity for collecting roots, intact egg ntasses, and cysts on 250-425-μm sieves; and a variable speed motorized sieve-shaker. Nematodes, after being collected on 38-μm sieves, are separated from debris by centrifugation or by Baermann trays. Secondary features include: air cylinders, solenoid valves, and time clock for atttomatic dumpittg residual soil and water; relay-controlled coarse spray nozzles activated for 5 sec every 30 sec for washing nematodes through 250-425-μm sieves; adjustable rates of water amt air flow, and tinting. The second type of elutriator operates on similar principles but costs less to construct. It requires somewhat more operator participation; sieve spraying is carried out by the operator, anti elutriators are dumped manually. Both elutriators also show promise for monitoring populations of certain other soil microorganisms.
population dynamics; techniques
Variability of morphological characters used to separate Pratylenchus penetrans from other species of the genus was studied in a population originating from a single gravid female. Pronounced heteromorphism was observed and characterized. About 30% of females had a crenate-tail terminus. Several shapes of stylet knobs were characterized; 50% of them were anteriorly flattened to indented. The outer margin of the cephalic framework extended into the body from one-half to two annules. The shape of the spermatheca varied from round to oval. A fifth lateral line was observed in many specimens. Environmental factors, and particularly the host plant, influenced such morphometric characters as body length, width, esophagus length, stylet length, V value, a and b' ratios, as well as qualitative characters such as tail terminus, growth of ovary, and shape of median bulb. Nematodes reared on pea and cabbage had a higher percentage of females with a crenate-tail terminus than those from tomato, rye, beet, and alfalfa callus culture. Nematodes from peas were longer and wider; they often had gonads that extended to esophagi, but they had shorter esophagi amt stylets than those from callus culture. Populations from different geographical locations also exhibited variahility in morphological characters, as did the Cornell population. The validity of many characters used in species identification is discussed, and the possibility that other related Pratylenchus species are conspecific with P. penetrans is suggested.
taxonomy; crenate tail; smooth tail; host effect; selective response
A computer-simulation model (MELSIM) of a Meloidogyne-grapevine system is developed. The objective is to attempt a holistic approach to the study of nematode population dynamics by using experimental data from controlled environmental conditions. A simulator with predictive ability would be useful in considering pest management alternatives and in teaching. Rates of flow and interaction between the components of the system are governed by environmental conditions. Equations for these rates are determined by fitting curves to data from controlled environment studies. Development of the model and trial simulations have revealed deficiencies in understanding of the system and identified areas where further research is necessary.
Meloidogyne; Vitis; population dynamics; pest management
An analysis of the offspring of single smooth- and crenate-tail females of Pratylenchus penetrans indicated the existence of progenies containing only males or females. Of the 80 progenies analyzed, 46 contained females with smooth and crenate tails. In general, regardless of the mother's tail type, most females possessed crenate tails, although more crenate-tail females originated from a crenate-tail female than from a smooth-tail female. Twenty-three progenies contained only females with crenate tails, most of them originating from crenate-tail females. One progeny originating from a smooth-tail female contained only females with smooth tails. No simple interpretation of the inheritance of tail type could be attempted because selection pressure favored females with crenate tails when P. penetrans was reared on Wando pea plants.
Wando peas; sexual forms; genetic nature; selection pressure; adaptive capability
Selected species and cultivars of plants were evaluated for host suitability for Hoplolaimus columbus under greenhouse and fieht conditions. Sixteen agronomic plant cultivars were assayed for infection and reproduction after 2-6 months. Lima bean, soybean, cotton, and sweet corn were most favorable for nematode reproduction, whereas sweet potato was a nonhost plant. Field corn and watermelon, which tolerated H. columbus without significant yield losses, are suited for alternative crops in the southern coastal plain. Populations of H. columbus occurred in 15% of soyhean and 25% of cotton soil samples assayed. Population levels of H. columbus and Helicotylenchus spp. were correlated with fluctuations in various soil nutrient factors, whereas Meloidogyne spp. and Scutellonema spp. were not. No correlation was detected between the presence of H. columbus and populations of other nematode genera stndied.
lance nematode; parasitism; host-parasite relations; ecology
Interrelationships of Meloidogyne hapla and Heterodera schachtii in combinations of several population levels and different inoculation periods were studied. Results indicated suppression of gall development of M. hapla in any treatment in which inoculations of H. schachtii preceded those of M. hapla by 10 days. This interrelationship was characterized by amensalism with M. hapla serving as an amensat and H. schachtii serving as an inhibitor. Conversely, when inoculations of M. hapla preceded H. schachtii inoculations by 10 days, there were increases in cyst development. This relationship was characterized by commensalism with H. schachtii serving as a commensal. In both interactions, the preinvading parasites acted independently and established populations equal to treatments receiving either parasite alone. When both nematodes were inoculated simultaneously, there were no effects on populations of either. Relationships of this nature were characterized by neutralism. Ratios of total soluble/reducing carbohydrates were lower in treatments when M. hapla inoculations preceded those of H. schachtii. Plants inoculated with both nematodes died earlier than those inoculated with either parasite alone. High concentrations of Al and Fe occurred in treatments wherein M. hapla or H. schachtii inoculations preceded each other by 10 days. Generally, noninoculated control plants exhibited higher concentrations of K, P, Mg, and B than other treatments.
Interactions; carbohydrates; mineral elements; amensalism; commensalism; neutralism
Funaria maryanneae n. sp., distinguished by its large size and long prerectum, is described from specimens collected in Bad Sooden, Germany, D. B. R. This nematode was collected also from Fräkmüntegg (Mt. Pilatus), Switzerland. Proleptonchus weischeri n. sp., with short hemispheroid female tail and relatively anterior vulva, is described from specimens collected in Kaufunger Wald near Kassel, Germany, D. B. R. This is the first report of either genus from the continent of Europe. Leptonchus parisii Zullini, 1973, from Chiapas, Mexico, becomes a junior synonym of Funaria obtusa (Thorne, 1939) Goseco, Ferris and Ferris, 1974. Leptonchus acutus Zulliui, 1973 becomes Funaria acuta n. comb., and Funaria rothi Goseco, Ferris and Ferris, 1974 becomes a junior synonym of Funaria acuta.
Pratylenchus penetrans suppressed the tuber yields of potato cultivars 'Katahdin', 'Kennebec', and 'Superior', but did not affect yields of 'Russet Burbank'. In comparison with noninfested controls, all initial nematode densities (Pi) of P. penetrans (Pi = 38, 81, 164, 211/ 100 cm³ of soil) suppressed yields of Superior; a moderate Pi (81/100 cm³ soil) suppressed yields of Kennebec; and on Katahdin, a moderate Pi enhanced yields, but higher Pi's caused a marked loss. In general, yields were related to the tolerance of the cultivars to nematode colonization. Highest nematode densities were found in the roots of Russet Burbank; the next highest, in succeeding order, were found in roots of Kennebec, Katahdin, and Superior. Symptoms of nematode invasion were confined to losses of tuber yield and root weight.
root-lesion nematode; Solanum tuberosum; tolerance