Browsing by Author "Ravlin, F. William"

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    Aspects of the biology, behavior, bionomics, and control of immature stages of the cat flea Ctenocephalides felis felis (Bouche) (Siphonaptera: Pulicidae) in the domiciliary environment
    Byron, David W. (Virginia Polytechnic Institute and State University, 1987)
    The larval stage of the cat flea, Ctenocephalides felis felis (Bouche), was found to exhibit behaviors that were conducive to its security in carpet. Larvae exhibited positive geotactic, and negative phototactic behaviors. This resulted in the larvae spending greater than 80% of their time at the base of the carpet pile. Cat flea larvae also exhibited a positive hydrotaxis, and appeared to exhibit undirected movements when foraging. Larva were observed to respond to disturbances by coiling their body longitudinally. Cat flea hatched and unhatched eggs, and larval exuviae were found to be dispersed in a contagious fashion within carpet. The spatial pattern of the immature stages and remains was influenced by the habits of the pet host within a given room. First-instar larvae do not move far, if at all, from the location of eclosion. The movement of the larval stage is influenced by biotic and abiotic factors in the environment. Areas of high pedestrian or pet traffic are not conducive to successful eclosion from the egg or for successful larval development. Various methods of control exist for controlling an indoor infestation including both non-chemical and chemical tactics. A method for the physical control of immature stages in carpet is vacuuming. A beater-bar vacuum removes about 50% of the eggs but less than 30% of the larvae from a carpet. Chemical control tactics indoors are normally conducted using a compressed-air sprayer. Pressure within the application system is critical for creating spray patterns which can be overlapped to allow even insecticide coverage of the substrate. A compressed-air application system is not capable of delivering pesticides in a manner that will completely penetrate the carpet substrate to reach the base of the carpet. No significant differences in carpet penetration were observed over a range of 20 to 70 psi. Regardless of pressure, more than 93% of the solution applied to carpet was deposited in the upper third (6 mm) of the carpet. Pet owners were surveyed about their knowledge and perceptions of household infestations of the cat flea, and also about financial expenditures and their willingness to pay for a flea-free environment. The importance and the pest status of flea infestations were determined to be based on physical, psychological, and economic impacts on homeowners. Respondents' perceptions of infestations on their pet were associated with infestation levels in the house. The respondents were willing to pay more for flea control in July, the onset of the flea season, than they were at the peak or decline of the season. They were also willing to pay more as their perception of the intensity of the problem on the pet or in the home increased. Household income was not shown to affect a respondent's actual financial expenditures or his willingness to pay for flea control on the pet or in the home.
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    Ecology of the stalk borer Papaipema nebris (Guenee), (Lepidoptera:noctuidae), in the southwestern Virginia no-till corn agroecosystem
    Highland, H. Brett (Virginia Polytechnic Institute and State University, 1986)
    The stalk borer (SB), Papaipema nebris Gn. exhibited from 7 to 9 instars when reared on a meridic diet in a control-led environment. Both sexes went through variable numbers of instars before pupation. Head capsule width measurements did not form discrete sets, and overlap occurred between adjacent instars. In feeding preference tests with first instar larvae using either leaf disks or stem sections, higher numbers of larvae fed on grasses, such as orchardgrass, Dactylis glomerata L. or fescue, Festuca arundinacea Schreb., compared to numbers feeding on other plants. In no-choice laboratory and field tests, larvae tunnelled into plant stalks at the same frequency by which they would feed on foliage, showing a tendency to tunnel into plants they accept as hosts. Third or fourth instar larvae preferred to tunnel into orchardgrass and rye, Secale cereale Lover the other plants present in field cage tests. The SB prefers to oviposit on narrow leaved, perennial grasses, such as fescue and orchardgrass, over wide leaved annual grasses or broadleaf plants. Significantly higher numbers of eggs were laid on upright over prostrate plants in cage studies. The SB also preferred ovipositing on desiccating or dry plant material. Higher numbers of SB infested corn seedlings were found next to field margins compared to numbers found within fields. Contour and transect maps of SB infested fields showed considerable aggregation over three years, and this distribution was confirmed by high variance to mean ratios, and small k values. SB distribution in no-till corn can be adequately described by the negative binomial model. Field collections of SB in corn stalks showed 2, 3, or 4 instar larvae infesting the youngest seedlings. Variation existed in larval development from year to year. Linear regression covariance analysis showed that larval development was different between field collected larvae from year to year.
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    Impact of the microbial pesticide Bacillus thruingiensis Berliner subsp. kurstaki on Hymenopterous parasites of the imported cabbageworm, Pieris rapae (L.) (Lepidoptera: Pieridae)
    McDonald, Richard C. (Virginia Tech, 1990)
    Three formulations of Bacillus thuringiensis Berliner subsp. kurstaki (Dipel 4L, Dipel 2X, and ABG-6167) were compared with the synthetic pyrethroid perrnethrin ( common name Pounce 3. 2 EC) for insecticidal activity and impact upon parasitism of the imported cabbageworrn, Pieris rapae (L.) (Lepidoptera: Pieridae) in field broccoli (CV Packrnan) from fall 1986 to spring 1988. Perrnethrin, Dipel 4L, and ABG-6167 were not significantly different in their efficacy towards imported cabbageworm larvae. Parasitization of P. rapae by the larval parasite Cotesia glomerata (L.) (Hymenoptera: Braconidae) and the pupal parasite Pteromalus puparum (L.) (Hyrnenoptera: Pteromalidae) continued after spraying in the B. thuringiensis plots, but was not significantly different from perrnethrin. However, 100% of the P. rapae chrysalids recovered were parasitized by P. puparum. The impact of seasonal hyperparasitism was compared between .Q. glomerata, and a Yugoslavian strain of Cotesia rubecula (Marshall), an exotic larval parasite of the imported cabbageworm. Four hyperparasites, two of them attacking both~. glomerata and~. rubecula, were found in field plots from 1986-1988. The level of hyperparasitization for the two primary parasites was significantly different. Hyperparasitization averaged only 8.1% for C. glomerata from 1986-1988, but was 37. 9% for C. rubecula from 1987-1988. During the early- to mid-season of 1988, hyperparasite activity was not detectable and C. rubecula outcompeted C. glomerata for hosts; but by mid-season, hyperparasite activity against C. rubecula increased to 100%, causing its populations to crash. C. glomerata then became the dominant parasite of P. rapae. C. rubecula was not recovered in 1989. Hyperparasites may be a limiting factor in establishing C. rubecula in southwestern Virginia. Mortality and successful pupation of P rapae fourth instars parasitized by C. rubecula to B. thuringiensis endotoxin at dosages of 850, 85, and 8.5 I.U./ml was examined. After day two, the LC50's of parasitized fourth instars were approximately thirty times higher than that of unparasitized larvae and by day four, the LC50 response of parasitized fourth instars was 180 times higher than unparasitized larvae. Twenty-five percent of parasitized fourth instars exposed to a concentration of 850 I.U./ml successfully pupated, compared to 76% at 85 I.U./ml and 69% at 8.5 I.U./ml. Parasitized fourth instar P. rapae consume less food and are therefore less susceptible to B. thuringiensis than unparasitized larvae at the same dosages.
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    Insect Identification Laboratory Annual Report 1983
    Hilburn, Daniel J.; Ravlin, F. William; Weidhaas, John A. (Virginia Cooperative Extension Service, 1984)
    This report summarizes the activity of the Insect Identification Laboratory ad Virginia Tech for 1983.
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    Insect Identification Laboratory Annual Report 1984
    Hilburn, Daniel J.; Ravlin, F. William; Weidhaas, John A., Jr. (Virginia Tech, 1984)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1984.
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    Insect Identification Laboratory Annual Report 1985
    Hilburn, Daniel J.; Ravlin, F. William; Weidhaas, John A., Jr. (Virginia Tech, 1985)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1985.
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    Insect Identification Laboratory Annual Report 1986
    Day, Eric R.; Ravlin, F. William; Weidhaas, John A., Jr.; Rutherford, Susan L. (Virginia Tech, 1986)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1986.
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    Insect Identification Laboratory Annual Report 1987
    Day, Eric R.; Ravlin, F. William; Weidhaas, John A., Jr.; Rutherford, Susan L. (Virginia Tech, 1988)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1987.
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    Insect Identification Laboratory Annual Report 1988
    Day, Eric R.; Ravlin, F. William; Weidhaas, John A., Jr.; Rutherford, Susan L. (Virginia Tech, 1989)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1988.
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    Insect Identification Laboratory Annual Report 1989
    Day, Eric R.; Ravlin, F. William; Weidhaas, John A., Jr.; Rutherford, Susan L. (Virginia Tech, 1990)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1989.
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    Insect Identification Laboratory Annual Report 1990
    Day, Eric R.; Ravlin, F. William; Rutherford, Susan L. (Virginia Cooperative Extension, 1991)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1990.
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    Insect Identification Laboratory Annual Report 1991
    Day, Eric R.; Ravlin, F. William; Rutherford, Susan L. (Virginia Tech, 1992)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1991.
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    Insect Identification Laboratory Annual Report 1992
    Day, Eric R.; Ravlin, F. William (Virginia Tech, 1993)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1992.
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    Insect Identification Laboratory Annual Report 1993
    Day, Eric R.; Ravlin, F. William (Virginia Tech, 1994)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1993.
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    Insect Identification Laboratory Annual Report 1994
    Day, Eric R.; Ravlin, F. William (Virginia Tech, 1995)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1994.
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    Insect Identification Laboratory Annual Report 1995
    Day, Eric R.; Ravlin, F. William (Virginia Tech, 1996)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1995.
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    Insect Identification Laboratory Annual Report 1996
    Day, Eric R.; Ravlin, F. William (Virginia Tech, 1997)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1996.
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    Insect Identification Laboratory Annual Report 1997
    Day, Eric R.; Ravlin, F. William; Pfeiffer, Douglas G. (Virginia Tech, 1998)
    This report summarizes the activity of the Insect Identification Laboratory at Virginia Tech for 1997.
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    A study of factors affecting queen survival, nest initiation, and nest development in the baldfaced hornet Dolichovespula maculata (L.) (Hymenoptera:Vespidae)
    Stein, Kenneth John (Virginia Tech, 1990)
    Mating success and nutrient reserve effects on queen survival and nest initiation were examined with respect to the reproductive fitness of queens of the baldfaced hornet, Dolichovespula maculata. The sperm content of the Spermatheca was examined in queens of this hornet species and in queens of 10 other yellowjacket species collected in spring and summer of 1987, 1988 and 1989. Queens of the baldfaced hornet, D. maculata, were also analyzed for sperm content prior to nest initiation and during colony development. A regression model was employed to determine sperm utilization. Based on total cell counts and adult census, the sperm use efficiency of this species changed from approximately 90-100 sperm released per egg in the initial stages of colony development, to 2-3 sperm released per egg after 1000 eggs had been laid. Near the end of the season the predicted number of sperm released per egg was 0-1. The number of sperm in D. maculata males ranged from 2-2.5 million; a value considerably greater than the mean sperm number (20,223; ±4,669) found in mated spring queens (n=15). Nineteen (18.4%) of 103 yellowjacket queens analyzed in the spring seasons of 1987 and 1988 were uninseminated. The effects of mating success and sperm utilization on colony development are discussed. A significant regression of sperm content on colony size was also found for 8 species of yellowjacket. Queens of D. maculata were collected for studies of nutrient reserves before hibernation in the fall, during nest initiation, and after colonies had produced more than 2 worker broods. Fresh and dry weights were determined for all queens and a seasonal comparison of the energy reserves of lipids, sugar, and glycogen was performed on the thoracic and abdominal tagmata. Total nitrogen was also quantified to estimate protein changes by season. The results show that lipids accounted for 35% of the weight lost during hibernation, sugars 12%, and glycogen 6%. Total thoracic nitrogen remained constant throughout the year, whereas abdominal nitrogen was the same in the fall and spring queens but increased in the summer queens. The results from this study suggest that most queens which survive the winter and successfully initiate nests have similar energy reserve quantities. The implications of these findings to solitary foraging behavior are discussed. The eggs of D. maculata were examined in the spring and summer to quantify the energetic contributions provided by the queen. Mean egg weight was highest in the spring and decreased with progressive nest development. Both egg weight and energy reserves were variable among and within nests. The nutrient reserves for eggs in embryo nests, in order of importance, were lipid (22%), glucose (9.5%), and glycogen (5%). A 10-day egg incubation experiment demonstrated a mean loss of 83 ug dry weight; lipids could not completely account for the weight loss, either quantitatively or qualitatively. A study on egg developmental time failed to provide sufficient data; all eggs eventually died although embryonic larval movement was detected in 2 eggs after 16 days. The energetic contributions which a queen provides to the eggs are discussed with respect to foraging behavior and environmental influences.