Date of Award

12-2005

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Andrei V. Alyokhin

Second Committee Member

Randy Alford

Third Committee Member

Gregory Porter

Abstract

Potato is one of the most important crops in the North-eastern United States. Aphids comprise a group of its economically important insect pests. Although aphids are known to cause direct damage by sap feeding, the major concern is their role as vectors in transmitting several important diseases, such as potato leaf roll virus (PLRV) and potato virus Y (PVY). Significant proportions of aphid population in the field are mobile, thus creating new disease foci or enhancing the existing ones.

Although integrated pest management is a well-known concept, there are several limitations for a successful implementation of it among commercial growers. Lack of comprehensive knowledge about the insect behavior is one of the important reasons for the lack of its adoption. Understanding insect behaviour, including host selection and movement within the field in general, can aid in enhancing the efficiency of the present control measures and development of new strategies.

To better understand the mechanism of host finding, we tested aphids to host odor and synthetic host volatiles attractive to the Colorado potato beetle in Petri dish and olfactometer arenas along with the field trials. The odor of potato foliage was found to be attractive to wingless potato aphids without any aid of visual cues. Winged aphids did not show a statistically detectable response. Aphids did not respond to the synthetic Colorado potato beetle kairomone formulation in the olfactometer. In Petri dishes, aphids avoided leaflets treated with both kairomone formulation and its blank carrier.

We did not detect any build-up in aphid populations or virus transmission on field plots treated with the kairomone formulation and blank carrier. Our second objective was to understand the factors that may stimulate aphid movement within the field. Obtaining thorough information on the within-field aphid dispersal will allow fine-tuning control techniques, so that they are directed towards disrupting aphid movement, not just towards reducing aphid numbers. We have conducted experiments in greenhouse experimental arenas that simulated a small segment of potato field. Effects of simulated rain, wind, mechanical raking, fungicide application, reflective mulch, and predator (lady beetle, Harmonia axyridis Pallast) on the interplant movement of wingless adult potato aphids were studied. The number of aphids migrating from the central plant in the arena following tested perturbations was recorded. Studies were conducted with plants of different age and canopy structure. We found that rain, wind, and mechanical disturbances are major environmental factors that can cause significant movement of aphids.

Our third objective was to understand circadian rhythmicity of potato aphids in regard to host finding. We conducted experiments in Petri dish and olfactometer arenas to find if aphids have the ability to find their host plant under light and dark conditions of the 24-hour cycle. Our results suggest that circadian rhythm in host-finding behavior of the potato aphid is regulated by both exogenous and endogenous mechanisms.

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