Browsing by Author "Neff, Stewart E."
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- Biology and natural control of the white pine weevil, Pissodes strobi (Peck), in VirginiaHarman, Dan M. (Virginia Tech, 1966-06-05)Ovariole development and termination of diapause in the white pine weevil were studied by dissecting weevils at various intervals throughout the winter. Old-generation adults brought into the laboratory November produced viable eggs within 5 days. New generation adults brought into the laboratory on November 4 produced viable eggs during November. Viable eggs were deposited by other new-generation adults after 10 to 15 day. at room temperature in winter. On each of the 3 collection date studied, new generation adult produced viable eggs without copulating after collection from hibernation indicating that capulation occurs in the fall. There was no evidence of progressive ovariole development throughout the winter. New generation adults which were isolated as soon as they emerged from the shoots and maintained at constant room temperature had poorly developed ovarioles by November 20 and produced no eggs. Weevil flight and dispersal through a white pine plantation was studied by releasing 409 marked weevils at a central point within a l431-tree plantation and checking every tree at 5-day intervals. Weevils flew readily at the time of re1ease. Marked weevils were recorded throughout the plantation. which extended as far as 330 feet from the release point. A few weevils were observed on scattered white pines 200-300 yards from the release point beyond a hardwood barrier. Total numbers of weevils present on the leaders increased from April 26 to May 5, after which numbers steadily decreased. By June 15, only 20 weevils were observed on the leaders.
- The effect of pumped-storage reservoir operation on biological productivity and water qualitySimmons, George M. Jr.; Neff, Stewart E. (Water Resources Research Center, Virginia Polytechnic Institute, 1969)With the increased utilization of our water resources by a growing population, intelligent management of these resources, giving full consideration to all the relevant factors, becomes essential. Pumped-storage hydroelectric projects have been developed giving primary emphasis to the factors which relate to the generation of electricity. These projects can also provide a means of reducing stream pollution effects through stream flow augmentation and by lessening the effects of thermal stratification...
- Hymenopterous parasites of lps spp. bark beetles (Coleoptera:Scolytidae) in VirginiaBerisford, C. Wayne (Virginia Tech, 1968-06-19)The pine engraver beetles (~ spp.:Coleoptera:Scolytidae) may be serious pests depending on certain prerequisite conditions. In their secondary or "normal" role they breed in slash and damaged, dying, and dead trees. The broods emerging from these sources normally attack similar material. When such material is scarce due to cessation of cutting operations in mid-season or when conditions are especially favorable for brood development, an excess of beetles is often produced which, due to the lack of more suitable material, attack healthy trees. Repeated attacks cause these trees to succumb and die. When normally healthy trees are weakened by fire, flood, defoliation, drought, stagnation, etc., then they become more acceptable host material for successful engraver attacks. When the production of a very large number of beetles in "normal" breeding material coincides with physiological stress in "healthy" trees, then population explosions can occur. When large numbers of beetles and low host vigor do not coincide, spot kills cornnon1y occur. According to Thatcher (32), spot kills, although not conspicuous, add up to large volumes of timber loss each year.
- Mineral requirements of selected species of aquatic hypomycetesHickman, Don Winston (Virginia Tech, 1966-01-05)This study was undertaken to investigate the mineral nutrition of aquatic Hyphomycetes by determining the mineral requirements of several species. On the basis of rapidity and renroducibility of growth, four species were selected, These were Heliscus lugdunensis Webster (Nectria lugdunensis webster), Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni), Clavariopsis aquatica DeWildeman, and Lunulospora curvula Ingold. These were grown in liquid culture on a rotary shaker at constant temperature. The containers and other equipment were cleaned by acid washing. When necessary to establish a nutritional reguirement for an element, the nutrient salts were purified by the phosphate adsorption and dithizone methods. In addition to nutrient salts and purified water, the media contained only glucose. Since all the species except Clavariopsis aquatica DeWildeman grew well for many transfers and approximately two years on this completely defined medium, without vitamins or amino acids being provided, it is concluded that they do not require these nutrients. Whether an element was required, and in what concentration, was decided on the basis of the amounts of growth obtained with various concentrations of the element in the initial media. Growth was measured as the dry weight of the mycelium from 100 ml of medium and the values from four replicates were averaged. Phosphorus, calcium, nitrogen, zinc, iron, magnesium, and sulfur requirements were demonstrated for all four species. Efforts to demonstrate requirements for potassium were unsuccessful. Manganese toxicity was demonstrated for Clavariopsis aquatica DeWildeman and a manganese requirement was suggested for Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni). The results suggested a molybdenum requirement for Heliscus lugdunensis Webster (Neetria lugdunensis Webster) and Lunulospora curvula Ingold, a boron requirement for H. lugdunensis and toxicity for C. aquatica, and a copper requirement for F. penicillioides. Approximately 0.50, 0.25, 0.50-1.00, and 0,.05-0.10 milli-moles per liter of phosphate were required to obtain maximum dry weight yields of Heliscus lugdunensis Webster (Nectria lugdunensis Webster), Flagellospora penicillioides Ingold (Nectria penicillioides Ranzoni), Clavariopsis aguatica DeWildeman, and Lunulospora curvula Ingold respectively. Calcium concentrations of 7.5, 50, 7.5, and 25 milli-moles per liter supported maximum growth of these species in the same order. All four were able to utilize ammonium nitrogen, nitrate nitrogen, or ammonium nitrate to produce about the same amounts of growth. C. aquatica was apparently able to use nitrate nitrogen only in the presence of an unidentified nutrient and this is interpreted as indicating a role for that nutrient in the nitrate metabolism of this species. Fifteen milli-equivalents per liter of ammonium nitrate, ammonium, or nitrate nitrogen was adequate to obtain maximum dry weight yields of H. lugdunensis. Five milli-equivalents per liter of ammonium nitrate, 15 of ammonium, and 35 of nitrate nitrogen supported maximum growth of F. penicillioides. As little as 5 milli-equivalents per liter of ammonium nitrate or ammonium nitrogen was optimal for C. aguatica and 5 milli-equivalents per liter of any of the three nitrogen sources was optimal for L. curvula. The optimal nitrate concentration for C. aquatica was not determined. There is an obvious advantage to a single medium on which a great number and wide variety of species may be grown. The author is of the opinion that a far greater advantage lies in the use of a completely defined medium on which one or more organisms may be reproducibly grown, Such media are suggested and their employment is strongly urged. Only in this manner can considerable morphological and physiological variations be avoided.
- Natural regulation of coprophagous Diptera in VirginiaBurton, Ralph Peterson (Virginia Tech, 1968-07-10)Larval mortality of the face fly, Musca autumnalis De Geer, due to the biotic environment in Virginia was determined to be approximately 62.7% during the sumer of 1967 in preliminary studies. This was based on the difference in numbers of pupae resulting from an insect~accessible tray and an insect~proof tray, Each was filled with bovine manure and both contained approximately equal numbers of eggs or new first—instar larvae when placed in the field, Pupae of the major species of coprophagous Diptera resulting from pasture droppings of bovine feces were collected in sandboxes and furnels from three areas of Montgomery County, Virginie during 1967. The pupae were separated according to species, incubated, and examined afterwards to determine the fate of each pupas, Special emphasis was placed on the parasites involved and the portion of total porasitization contributed by each species, Primary interest was in biological reculation of face fly populations, Other flies were studied for comparison and to determine natural reservoirs of parasites, Comparisons of data from sandboxes with those from funnels showed a higher over-all rate of parasitism in the sandboxes than in the funnels. Other techniques for attempting to obtain new parasites of the face fly were also employed, Adult face flies were examined for nematodes, Heterotylenchus autumnalis Nickle. Approximately 16% of the natural population were infested during 1966-7. Available data for mortality during different life stages were combined into a preliminary life table for the face fly. Muscidifurax raptor Girault and Sanders, a pteromalid parasite, was recovered in low numbers from face fly pupae during 1966 field studies, It has been successfully propagated in the laboratory on face fly pupae by mechanically cracking the fly puparia to aid emergence of the parasites, Parasitism is normally accomplished by penetration of the ovipositor throush the posterior spiracles of the host, The ovipositor of one female was observed to penetrate the anterior spiracle of a face fly pupa. Muscidifurax ravtor is not limited to the spiracles for penetration of house fly pupae. Muscidifurex raptor was found on several hosts in nature. Eucoila sp., Xyalophora quinouelineata (Say), Aleochora tristis Gravenhorst, and A. bimaculata Gravenhorst, which are parasites of coprophagous Diptera, were hyperparasitized by M. raptor. Studies on the biology and behavlor of M. raptor were conducted in the laboratoiy, Its effectiveness in parisitizing different hosts was compared on house fly and face Fly pupae.
- A revision of the neotropical genus Erilophodes Warren (Lepidoptera, Geometridae)Covell, Charles VanOrden (Virginia Tech, 1962-05-05)The Geometrid moth genus Erilophodes Warren was redefined, using morphological characters of the wings, abdomen, hind tibiae and genitalia. Two new species, E. Spinosa and E. toddi, were described on the basis of male characteristics. Females of these species are indistinguishable from each other and from those of E. colorata Warren, the type species. Ischnopterix Wagneri Le Moult was treated as a junior subjective synonym of E. colorata Warren. Three species referred to Erilophodes Warren were removed from the genus. E. indistincta Warren was transferred to the genus Ischnopterix Hubner. E. marmorinata Bastelberger was placed as a junior subjective synonym of Neodesmodes semialbata Warren. E. arana (Dognin) was transferred to the genus Neodesmodes Warren. Erilophodes Warren was found to occupy an area from Espirito Santo on the southern coast of Brazil to Montevideo, Uruguay, westward through the northeastern tip of Argentina into southeastern Paraguay. There seems to be considerable overlap in the ranges of the three species. Placement of Erilophodes Warren in the subfamily Ennominae was verified. With some reservations the genus was retained in the tribe Nacophorini.