Predaceous Nematodes Research Articles

The detrital food web in a shortgrass prairie

Several experimental approaches have been taken to demonstrate the importance of soil fauna in nitrogen mineralization, but there have been difficulties interpreting the results. We have supplemented the experimental approach with theoretical calculations of nitrogen transformations in a shortgrass prairie. The calculations incorporate a wide array of information on decomposer organisms, including their feeding preferences, nitrogen contents, life spans, assimilation efficiencies, productio:assimilation ratios, decomposabilities, and population sizes. The results are estimates of nitrogen transfer rates through the detrital food web, including rates of N mineralization by bacteria, fungi, root-feeding nematodes, collembolans, fungal-feeding mites, fungal-feeding nematodes, flagellates, bacterial-feeding nematodes, amoebae, omnivorous nematodes, predaceous nematodes, nematode-feeding mites, and predaceous mites. Bacteria are estimated to mineralize the most N (4.5 g N m−2 year−1), followed by the fauna (2.9), and fungi (0.3). Bacterial-feeding amoebae and nematodes together account for over 83% of N mineralization by the fauna. The detrital food web in a shortgrass prairie is similar to that of a desert grassland. The shortgrass detrital web seems to be divided into bacteria- and fungus-based components, although these two branches are united at the level of predaceous nematodes and mites.

Effect of Water and Nitrogen, and Grazing on Nematodes in a Shortgrass Prairie

Effect of Water and Nitrogen, and Grazing on Nematodes in a Shortgrass Prairie

Predaceous nematodes of the family Mononchidae from the Mackenzie and Porcupine river systems and Somerset Island, N.W.T., Canada

Paramononchus arcticus n.gen., n.sp., Coomansus fletcherensis n.sp., and Mononchus superbus n.sp. from the Mackenzie and Porcupine river systems and Somerset Island are described and illustrated. Paramononchus n.gen. is closest to Mononchus Bastian, differing in having the dorsal tooth opposed by a denticulated rib with two small basal teeth and a transverse rib at the level of the dorsal tooth. Other mononchids from the river and lake samples are described and illustrated including Coomansus gerlachei and Mononchus maduei which are reported for the first time in Canada.A new genus Parahadronchus is defined with Parahadronchus adamanicus (Jairajpuri, 1969) n.comb. as its type species, and generic diagnoses and a key to the 23 recognized genera of Mononchidae are included.

Miconchus kansasenis n. sp. (Mononchidae: Nematoda) from Kansas, United States.

A new species of predaceous nematode, Miconchus kansasensis is named and described. It differs from M. exilis (Cobb) in tail length and position of the vulva. Dimorphism in tail shape within the genus Miconchus is discussed. A taxonomic key to the species is provided.

Relative Efficacy of Different Gil-Cakes on the Incidence of Root-knot Nematodes

Root-knot nematodes (Meloidogyne spp.) have become a serious problem in many vegetable growing tracts of our country. The ubiquity of such nematodes in poor soils particularly those devoid of organic matter is perhaps mainly responsible for the extensive infestation consequently leading to low yield and poor quality of a number of vegetable crops. Unbalanced application of fertilizers not only leads to severe repercussion on plant itself but in many cases it increases the reproductive rates of nematodes (Oteifa and Khalil, 1961). The deficiency of phosphorus and potash in some Bihar soils was reported to be responsible for heavy infestation of the nematodes in tomatoes, brinjal and bhindi (Lall and Hameed, 1965). In recent years, the use of organic matter in different forms has been reported to reduce nemic population in soil (Hutchinson, 1960 and Mankau, 1963). Tho organic matter being either directly toxic to the nematode (Ellenby, 1945), or may interfere with respiration and oxidation processes in the nematode body (Renninger, et al., 1958) or alter the oxygen, nitrogen, and pH status of the soil (Mankau, 1963). Linford et al. (1938) observed reduction of soil populations of root-knot nematodes as a result of decompo- sition of organic matter in the soil which in turn supported building up of large populations of plants and animal forms destructive to nematodes including nematode capturing fungi, non-trapping fungal parasites, predaceous nematodes and predaceous mites. These collectively destroyed root-knot nematodes as well as free living forms in early weeks of decomposition. Recently, a number of soil cakes have been tested by various workers against these nematodes. Lear (1959) tested castor cake against M. javanica Treub. Singh (1963-64) reviewed the role of different organic matters used as biological control agents against different plant parasitic nematodes while reporting the efficacy of karanj (Pongamia pinnata) cake as compared to fumigants, green manuring, etc. against M. javanica. In view of this a pot experiment was conducted at Bihar Agricultural College, Sabour during winter 1964 to study the relative efficacy of different types of easily available oil cakes and the effect of their decomposition against Meloidogyne spp.

Population Fluctuations of Nematodes Associated With Red Pine Seedlings Following Chemical Treatment of the Soil1)

Thirteen genera of stylet-bearing nematodes, two taxonomic groups (Dorylaimidae and Hetero deridae), Mononchus sp. and nonstylet-bearing nematodes were found associated with red pine seedlings in a West Virginia nursery. The most prevalent plant-parasitic nematodes were Paratylen. chus sp., Hoplolaimus galeatus, and a Trichodorus sp. D-D mixture, methyl bromide, Nemagon, and Vapam were evaluated for their effectiveness to control the nematodes. Only methyl bromide gave satisfactory control of the plant-parasitic nematodes; however, after the second growing season, the nematode population levels of all treated plots were less than those for the control. Bacterium-and fungus-feeding nematodes accounted for the rapid increase in the populations following methyl bromide treatment. Population levels of all the nematodes increased after all treatments and reached a peak in October of the first year. The populations declined during the winter months, and rose again the second year. A species of Eucephalobus was the most common nonstylet-bearing nematode, while a Mononchus sp. was the predominant predaceous nematode. A temporary decline in the total nematode populations during the first growing season was thought to be caused by the feeding activities of the high populations of Mononchus.

ABNORMALITIES IN THE REPRODUCTIVE ORGANS OF A PREDACEOUS NEMATODE, PRIONCHULUS MUSCORUM

Two bivulvar females of the predaceous nematode, Prionchulus muscorum, are described and illustrated. Only two specimens exhibiting bivulvarity were found among the several thousand Mononchidae examined.