Masters Theses

Date of Award

12-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Reid R. Gerhardt

Committee Members

Jerome Grant, Charles Pless

Abstract

Container-inhabiting mosquito oviposition activity and the influences of three oviposition treatments were examined from three Knox County, Tennessee sites May - October 2000 and March - October 2001. Species composition, seasonal distribution and relative abundance of mosquitoes were examined in a ten county region in eastern Tennessee. Due to the increase in La Crosse (LAC) encephalitis cases and the potential for West Nile (WN) virus in eastern Tennessee, there is now a greater need for information regarding the biology and ecology of the exotic species, Aedes albopictus (Skuse), and the native species, Ochlerotatus (= Aedes) triseriatus (Say).

Weekly oviposition, larval, pupal and adult collections of Oc. triseriatus and Ae. albopictus were conducted at three sites in Knox County. Oviposition activity was sampled using five sets of three cup treatments at each site: 1) replenished cups had water replenished and oviposition strips exchanged, 2) replaced cups had the cup, water and oviposition strips exchanged and 3) returned cups had water replenished and the strips were taken to the laboratory, where eggs were counted then the strips were returned to their respective cups. Host-seeking adult collections for Oc. triseriatus and Ae. albopictus were made using a CO2- baited Centers for Disease Control (CDC) miniature light trap, with the light removed. More overall oviposition activity was detected in replenished cups (62,351) than replaced cups (40,141), while returned cups were not analyzed due to complications. Ochlerotatus triseriatus and Ae. albopictus both had more oviposition activity in replenished than replaced cups. This indicates that Oc. triseriatus and Ae. albopictus both have more oviposition activity in cups with greater organic content and aged water that may contain larvae or pupae. Surveillance programs that need large numbers of eggs for laboratory rearing and disease testing activities should only add water as necessary to increase levels of oviposition activity by both species.

Biweekly oviposition activity and host-seeking adult collections were conducted at ten counties (Anderson, Blount, Grainger, Hamblen, Jefferson, Knox, Loudon, Roane, Sevier and Union) from May - October 1998, April - October 1999 and 2000 and March - October 2001. Adult collections of all mosquito species were made using a CO2-baited CDC miniature light trap. Average temperature and average rainfall variables were obtained for Blount County and were analyzed for any effect on Oc. triseriatus and Ae. albopictus oviposition and Ae. albopictus adult activity. The average temperature during, two and four weeks prior to the sampling periods had significant (p < 0.0001) impacts on the oviposition activity of Oc. triseriatus. Aedes albopictus oviposition activity was significantly (p < 0.0001) explained by the average temperature during and two weeks prior to the sampling periods. Adult Ae. albopictus activity was best described (p < 0.0001) by the year, the average rainfall and average temperature four weeks prior to the sampling periods.

Trends for Oc. triseriatus peak oviposition, overall oviposition and Ae. albopictus adult activity were seen in both studies. Ochlerotatus triseriatus peak oviposition activity occurred approximately one month earlier than Ae. albopictus, beginning in late May and early June and tapering off in late summer. Aedes albopictus peak oviposition activity began in late June and steadily continued into fall. In both studies, more oviposition activity was seen by Oc. triseriatus than Ae. albopictus except for Hamblen and Sevier Counties in 1998 and 1998 and 1999 respectively. Although more Oc. triseriatus eggs were collected than Ae. albopictus, there were a greater number of Ae. albopictus adults collected from all sites in the ten counties. This may be due to sampling design or differences in the survivorship of eggs and larvae in field conditions at these sites.

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