The Asian tiger mosquito, Aedes albopictus (Skuse), is a worldwide nuisance pest that is capable of vectoring several viruses of public health concern. This invasive mosquito has recently expanded its habitable range through its utilization of artificial breeding sites, often due to the activity of humans. These factors, combined with additional expansion due to global changes in climate, have led to invigorated efforts to mitigate the impact of Ae. albopictus. Because it is a diurnal species, standard mosquito control efforts utilizing spray trucks or planes to administer insecticides offer little control, as these methods are directed towards crepuscular species. Barrier spray applications, however, have been shown to achieve a significant reduction in local mosquito pressure while requiring less insecticide application. The design behind barrier sprays is to apply insecticide treatments only around areas of interest, instead of trying to eradicate the local population of mosquitoes.
These studies were conducted to evaluate the efficacy of different pyrethroid barrier treatments against Ae. albopictus mosquitoes, and to examine the impact of the most effective treatment on local mosquito populations when applied to suburban residences. Three pyrethroids were examined in these studies: Demand® CS (lambda-cyhalothrin), Talstar® Professional (bifenthrin), and Suspend® Polyzone® (deltamethrin). The following factors affecting pyrethroid barrier treatments showed significant impacts on the knockdown and mortality rates of Ae. albopictus mosquitoes: the plant species, the label rate at which treatments were applied, the active ingredient used in the treatment applications, the time of exposure to the treated foliage, the presence/absence of a blood meal in the mosquito, and the time after treatment. Demand CS treatments showed the highest proportions of knockdown and mortality in adult female Ae. albopictus mosquitoes and did so for the longest amount of time, regardless of the length of the exposure time. Because the Demand CS formulation of lambda-cyhalothrin was shown to be the most effective treatment in the previous studies, it was applied as a barrier treatment to suburban residences in Roanoke, Virginia, in a field trial. Applications of Demand CS as a barrier spray were shown to significantly reduce mosquito catch numbers inside the treated barrier throughout the 8 week study, as compared to the control properties. The findings of these studies indicate that many factors, pertaining to both the insecticides used and to the environment in which they are applied, play a role in influencing the efficacy of a pyrethroid barrier treatment for the control of Aedes mosquitoes. Thus, it is important to gather relevant information before the application of a barrier spray treatment to design the most appropriate program for the situation. / Doctor of Philosophy / Mosquitoes in Virginia are capable of transmitting many different diseases to humans and livestock. Many different treatment options are available to protect humans from these populations of mosquitoes. Some of these options can be performed for a whole community, such as area-wide fogging or treatments from truck-mounted sprayers, while others are applied to properties individually, like mosquito misting systems or barrier sprays. Applying long-lasting insecticides to the edge of an area can help to protect the inside of the area from mosquitoes, and this is called barrier spraying. Barrier sprays, in particular, have become a popular choice for homeowners, and they are successful at limiting human exposure to local mosquito populations. The experiments conducted here looked at three different insecticides used in these treatments and compared them for their ability to inhibit and kill Asian tiger mosquito. Other factors that potentially influenced effectiveness were examined, such as the plant type, the length of time since the treatment was applied, and whether or not the mosquito had taken a blood meal. These experiments examined three commonly used pyrethroid insecticides to determine their efficacy against the local Asian tiger mosquito. Suspend Polyzone lasted a long time but did not produce sufficient mortality, Talstar Professional killed large numbers of mosquitoes, but for a short period, and Demand CS lasted a long time and showed a high mortality rate. These studies showed that the three different insecticides lasted on the plants for different amounts of time, but also that the insecticides needed different amounts of contact time to kill mosquitoes. This information is essential because understanding how a treatment loses effectiveness over time can help with deciding when retreatment is needed. It was also found that the different insecticides were affected by the plants that they were sprayed onto, meaning that certain insecticides did better when sprayed on specific plants. Results from these studies revealed that Asian tiger mosquitoes that had just fed on human blood were more likely to die from insecticide treatments. Thus, even if a mosquito should bite an infected person, barrier spray treatments of their property will lower the chances that the mosquito can spread the disease to other people.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/106635 |
| Date | 21 May 2020 |
| Creators | McMillan, Benjamin Eugene |
| Contributors | Entomology, Paulson, Sally L., Brewster, Carlyle C., Gross, Aaron Donald, Kuhar, Thomas P., Gallagher, Nicola T. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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