Date of Award:

1950

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Advisor/Chair:

G. F. Knowlton

Abstract

Virus diseases of stone fruit orchards have existed in Utah for more than a quarter of a century and are seriously diminishing the peach and cherry fruit production. Western X of peach, rusty mottle of cherry, wilt and decline of cherry, and little cherry constitute the most economically important stone fruit virus diseases in Utah. Many orchards, particularly in Davis County, have 50 to 83 percent of the trees infected with one or more of the yellow-red viroses. Surveys have shown that the diseases are spreading from 3 to 5 percent each year. It is believed that certain insects are responsible for the natural spread of the virus diesases of stone fruits. Some inconclusive evidence points to leafhoppers as the potential vectors since many cicadellidids are capable of transmitting virus to plants during the feeding process. They have maintained a reputation for being efficient vectors of plant viruses for many years, as well as inducing other types of plant injury. Their adaptable, piercing-sucking mouth parts inoculate plants with filterable viruses taken in from infected plants. They inflict other types of damage to the host by injecting toxic substances. The most sever type of damage, however, is that caused through the virus infection which generally is systemic. The purpose of this investigation was to determine the occurrence, seasonla abundance, and host preference of leafhoppers occurring in the stone fruit orchards of northern Utah. Leafhopper occurrence in plant environs adjacent to the stone fruit orchards was also studied. Studies were made to determine if any correlation existed between leafhopper abundance and percentage of diseased trees in the orchards. Trap studies and surveys seemed to be the most appropriate technique in approaching this problem. The trap studies were conducted in fifteen stone fruit orchards in five counties of norhtern Utah. Surveys were undertaken in most stone fruit growing areas in the northern part of the state.

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