The ratio of Octomyomermis muspratti to the host mosquito at the time of exposure had little effect on the ratio of male to female parasites that resulted. However, the ratio of males to females increased as the number of parasites/host increased. Hosts with a single nematode produced fewer than 1% males in comparison with hosts with 8 parasites which produced about 40% males; hosts with 10 or more nematodes generally produced more male than female nematodes. Males of O. muspratti usually emerged before females because of the earlier death of multiply-infected mosquitoes. The size of the host at the time of invasion bad no significant influence on nematode sex ratios. Since mating is apparently necessary for reproduction in O. muspratti, the low male to female ratios that occur will be important in developing successful mass production techniques.
sex ratios; Mermithidae biological control; parasitism; mass production
A system that uses microbeads for the culture of bacteriophgic nematodes is described. Glass-bead culture was found to simulate a soil microcosm more closely than did agar culture i n terms of CO₂ production , number of nematodes produced, and nematode size.
bacteriophagic; natural environment; glass microbeads
Nematodes were prepared for scanning electron microscopy by cryofracturing in ethanol and then by critical-point drying in carbon dioxide. Cross sections of Caenorhabditis briggsae and Xiphinema americanum showed the arrangement of the intestine, ovaries, muscle cells, and some layers of the cuticle. The technique is complementary to transmission electron microscopy and facilitates the interpretation of results from thin sections.
Caenorhabditis briggsae; Xiphinema americanum
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.
grapes; apples; walnuts; Pratylenchus vulnus; P. penetrans
Growth and yield of 'Veebrite' tomato were studied in 20-cm (i.d.) clay-tile microplots containing initially 260, 1,840, 6,120, or 27,950 Meloidogyne hapla larvae/kg of soil. Low nematode numbers stimulated, and the highest nematode population suppressed, vegetative plant growth. More tomatoes, with a higher total weight, were harvested from plants infested with 260 and 1,840 nematode larvae at planting than from those with initial densities of 6,120 and 27,950 larvae. At the two highest densities, the cumulative fruit production (weight) was suppressed by 10% and 40%, respectively. The increase in growth and yield at the lower densities appeared to be due to an increase in the size of the root systent. However, at the higher densities, yield was no longer directly related to root weight. The reproduction factor of M. hapla was negatively correlated with initial density; for the lowest and highest initial densities, it was 96X and 7X at midseason, and 354X and 3X at harvest, respectively. The equilibrium density was 63,000 larvae/kg of soil; initial densities larger than 2,000 larvae/kg of soil may require control.
root-knot nematode; crop losses; Lycopersicon esculentum
A procedure for treating crop seeds with aqueous solutions of the systemic nematicide oxamyl is described. Seedlings from treated seeds were more resistant to attack by parasitic nematodes. Leachate from treated seeds reduced the number of free-living nematodes in the surrounding soil.
control; oxamyl; bean; corn; cucumber; soybean; watermelon; Helicotylenchus dihystera; Meloidogyne incognita; Meloidogyne arenaria; Paratrichodorus christiei; Rotylenchus sp
The reproductive abilities of four races of Heterodera glycines were compared on soybean cultivars by using single cyst or mass inoculations. Progeny transfers were used to determine changes in reproduction of H. glycines. Reproduction of all races (1, 2, 3, 4) was best on 'Lee' and poorest on P1 88788. The size of females produced and numbers of eggs/female of the different races varied with the cultivar. Races 1 and 3 appeared to contain low populations of Races 2 or 4. Races 2 and 4 were best selected by a series of transfers on 'Pickett' soybean.
Soybean-cyst nematode; Glycine max; races; resistance
The development of the DD-136 strain of Neoaplectana carpocapsae was studied on three food sources at 10, 15, 20, 25, 30, 33, 35, and 37 C. No growth occurred at 10 or above 33 C. At 15, 20. and 25 C, growth and reproduction occurred. The most favorable growth occurred at 25 C. At 30 C, N. carpocapsae developed to adults but did not reproduce. Key Words: temperature-growth effects, DD-136 strain.
Qualitative and quantitative differences in population growth patterns of Aphelenchoides rutgersi from Florida, A. sacchari from Jamaica, A. dactylocercus from Great Britain, and A. cibolensis from New Mexico were assessed on 28 species of fungi. The patterns of population growth of A. rutgersi and A. sacchari were statistically similar although not identical, and they differed considerably from those of A. dactylocercus and A. cibolensis. It is suggested that A. rutgersi and A. sacchari, from Florida and Jamaica respectively, may be more closely related to each other than to either A. dactylocercus or A. cibolensis.
Aphelenchoides rutgersi; A. sacchari; A. dactylocereus; A. cibolensis; population; fungi; host range; taxonomy; evolution
Seeds of 'Coker 68-15' wheat and 'Maton' rye were immersed for 5 min in acetone solutions of oxamyl, carbofuran, or phenamiphos containing 0, 0.25, 0.5, 1.25, 2.5, or 5.0% (w/v) nematicide; after drying, seeds were planted in pots containing 500 gm of sandy loam naturally infested with Hoplolaimus galeatus and Tylenchorhynchus claytoni. In sterilized soil, only the 5% concentrations of all nematicides were toxic to rye, whereas both the 2.5 and 5% concentrations were damaging to wheat. Phenamiphos was generally the most phytotoxic compound. Numbers of T. claytoni in soil declined sharply in response to seed treatment with all nematicides. In soil planted with wheat, numbers were reduced 80% by the 1.25% treatment; little additional control was shown with higher concentrations. Soil with rye showed a 40-60% reduction in numbers of T. claytoni with the 1.25% solutions and little change at higher concentrations. Hoplolaimus galeatus developed only in pots with rye; root populations were suppressed (30-50%) by treatment with 1.25% or higher concentrations of all nematicides.
control; oxamyl; carbofuran; phenamiphos; Secale; cereale; Triticum aestivum; Hoplolaimus galeatus; Tylenchorhynchus claytoni
Japanese hollies were itttolerant of Meloidogyne arenaria in field microplot experiments. Ilex crenata var. rotundifolia was relatively more tolerant than I. crenata var. convexa or I. crenata var. helleri. When M. arenaria was added at various itfitial population densities to soil containing plants of "Helleri," "Convexa," and "Rotundifolia," respectively, 91, 75, and 25% were killed by the end of the third growing season. No control plants died during the same period. Initial numbers of M. arenaria larvae and eggs were the only population densities that were correlated (negatively), regardless of cultivar, with plant growth over the three growing seasons. A linear relation was found for initial density of M. arenaria and growth of I. crenata rotundifolia. Increasing nematode density by 10-fold suppressed the growth of this cultivar by 23%.
Ilex crenata var. convexa; I. crenata var. helleri; I. crenata var. rotundifolia; population dynamics; root-knot
Howardula dominicki n. sp. is described from specimens collected from the tobacco flea beetle, Epitrix hirtipennis (Melsheimer), at Oxford, North Carolina , and is distinguished from other members of the genus . Parasitism by H. dominicki sterilized female flea beetles and often led to the death of larvae.
Allantonematidae; entomogenons nematode; taxonomy
The effects of Pratylenchus penetrans upon yields of 'Veebrite' tomato were studied at initial soil population densities (Pi) of 360, 2,010, 4,580, and 14,360 nematodes/kg of soil in 20-cm (i.d.) clay-tile microplots. The lowest Pi appeared to stimulate fruit production. Higher Pi's suppressed fruit production (total weight of marketable tomatoes and numbers of intermediate- and large-sized fruits), in comparison to control yields, the highest Pi resulted in 38% fewer fruits which weighed 44% less. These losses were at least partly due to a delay in fruit ripening, caused by the nematodes, which did not become apparent until the fourth week. Nematode populations in the soil increased at all but the highest Pi; final populations were around 7,000/kg of soil. Nematode populations in roots ranged from 230-590/gm of root at the completion of the experiment. Nematode control by fumigation would definitely be warranted at soil population densities of 2,000/kg or higher; with 500-2,000/kg, the decision to fumigate would depend on soil type and economic and hiological factors.
root-lesion nematodes; populations; Lycopersicon esculentum
Five new records of Paratylenchus, including P. pandus n.sp., are reported from Korea. An amended key to the genus is included on the basis of these findings. Macroposthonia tulagonovi is also reported with additional descriptions and illustrations.
taxonomy; Macroposthonia tulagonovi
Soil moisture and the nematode population density in aldicarb-treated soil influenced control of the sugarbeet nematode, Heterodera schachtii. Greater numbers of nematode larvae infected 14-day-old sugarbeet seedlings growing in aldicarb-treated soil at 20-30% than at 80-100% field capacity (F. C.), and plant growth was inversely related to nematode infection and the nematode population density. Compared with that of control plants, plant growth increase also was greater at 80-100% F. C. when the nematode population was above 1.8 larvae/gm soil. A nematode population of 1.8 larvae/gm soil did not significantly affect sugarbeet yields. Aldicarb gave less control when soil moisture levels dropped to 20 and 50% F. C. at nematode populations of 3.5 and 6.2 larvae/gm soil. More effective control was obtained wth soil moisture levels at or above 80% F. C. This difference was attributed to continued activity of the toxicant in the rhizosphere at the high moisture level.
sugarbeet; sugarbeet cyst nematode; oxime carbamates; nematicide
The sex ratio of the Arkansas 1 isolate of Heterodera glycines was determined in experiments in which 'Lee' soybean was inoculated with either one or two larvae. A 3:1 male to female sex ratio was established for this isolate under the test conditions used. No influence of one nematode on the penetration and development to adult of another nematode in the same root was detected in double larval inoculations.
cyst nematodes; nematode-nematode interaction; soybean
Extracts of nematodes of the Raleigh, North Carolina (RNC), Waynesville, N. C. (WNC), and onion populations of Ditylenchus dipsaci were examined for pectolytic activity. RNC nematodes contained a NaCl-stimulated endo-polymethylgalacturonase with optimal pH for activity of 6.0, whereas nematodes of the WNC and onion populations possessed a NaCl-stimulated endo-polygalacturonase with pH optimum of 4.0. Nematodes of each population also contained a CaCl₂-activated endo-pectin methyl-trans-eliminase with optimal pH of 9.0. Nematode extracts containing 0.5 M NaCl macerated potato discs. RNC and onion nematodes induced gall formation in Wando pea seedlings, but WNC nematodes induced a resistant, hypersensitive response. Thus pectolytic activity was not correlated with pathogenicity of D. dipsaci on Wando pea.
stem nematode; pea; pathogenicity; resistance
Anguina plantaginis n. sp., parasitic on Plantago aristata, is described and illustrated. This new species is most closely related to A. klebahni, A. millefolii, A. mobilis, and A. moxae and is characterized as follows: moderate body size for the genus; absence of esophageal "storage organ"; postvulval uterine sac extending about 45% of vulva-anus distance; crustaformeria of young females longer than spermatotheca or uterus proper; spicules with 2 sclerotized thickenings; long, conical tail in both sexes, narrowing at about 1/6 of its length to peg-like tip; parasitic only on P. aristata. Two nematode generations that are morphologically similar but differ in body size develop in one plant gall. The postembryogenesis, studied with respect to morphological development of the larval stages, is similar to that of Ditylenchus. The sexes can be differentiated from the second molt on. The infective larva is the third stage, which is morphologically distinct from the regularly developing third-stage larva.
We investigated the role of terpenoid aldehydes in the resistance of cotton (Gossypium hirsutum) to the root-knot nematode (Meloidogyne incognita). Three-day-old, root-knot-resistant ('Auburn 623') and -susceptible ('Deltapine 16') seedlings were inoculated with M. incognita. Comparable portions of inoculated and noninoculated roots were harvested 2, 4, 7, and 10 days later. Terpenoid aldehydes were extracted, separated by thin-layer chromatography, eluted as their phloroglucinol derivatives, and measured colorimetrically. In noninoculated seedlings of each age, the susceptible cultivar contained more total and more of each of five specific terpenoid aldehydes (hemigossypol, methoxyhemigossypol, gossypol, lnethoxygossypol, dimethoxygossypol) than did the resistant cultivar. In both cultivars, the concentration of terpenoid aldehydes increased as seedlings aged. After inoculation, the concentration of terpenoid aldehydes was usually highest in the noninoculated, followed by the infected susceptible, infected resistant, and noninfected resistant seedlings in that order. The changes in concentration that occurred in response to infection, particularly at 7 and 10 days after inoculation, did correlate with host resistance, i.e., there was a net loss of total and each specific terpenoid aldelhyde in tlae susceptible cultivar, and a net gain in the resistant. Our data do not exclude the possibility that localized synthesis of terpenoid aldehydes is involved in resistance to root-knot nematodes.
Gossypium hirsutum; physiology; resistance