and thus vector control strategies can frequently be implemented
as an effective means of disease management. Some epiphytotics
have resulted from the introduction of a new vector into a
region where the pathogen is already present. For example, Citrus
tristeza virus (CTV) became an economically important pathogen
in South America after the introduction of an efficient aphid vector
(81; Toxoptera citricida (Kirkaldy)). Little cherry virus 2 eliminated
sweet cherry production from important growing areas of
British Columbia after the introduction of the apple mealybug (31;
Phenacoccus aceris Signoret). Similarly, Pierce’s disease, caused
by the bacterium Xylella fastidiosa, became more prevalent in
California vineyards after the introduction of the glassy-winged
sharpshooter (18; Homalodisca vitripennis (Germar)), whereas
grapevine leafroll spread more rapidly in California after the introduction
of the vine mealybug (Planococcus ficus Signoret) due to
its rapid, proliferative reproduction in comparison to native mealybug
species (91). Vector exclusion or control on a regional or national
level can be an important consideration when managing the
spread of vector-transmitted pathogens in nurseries and production
fields.