IMPORTANT IS VECTOR CONTROL?
This is a hard question to answer because the benefit of vector
control depends on many factors including 1) the sources of virus
inocula, 2) the size and activity of the vector population and 3)
the type of virus.
airborne vectors of virus entering a dahlia planting will not be
carrying dahlia viruses. Therefore the most likely and important
source of virus is your dahlia collection. Did you plant infected
dahlias? If so there will be a greater need for vector control.
level of vector activity (numbers, types, amount of migration) varies
from year to year. Temperature, rain, predator populations, length
and severity of winter, daylight length, types and quantity of vegatation
in the area and many other factors influence vector activity. Some
years vector populations will be so large and active that protection
of dahlias from virus will fail. For example, in the Palouse region
of Eastern Washington 1 year out of about 7 the aphid population
is so active in the spring that field peas can not be adequately
protected from virus and serious loss results. It is not possible
to predict that 1 year ahead of time. Most other years aphid populations
can be controled and plants protected from virus.
viruses differ considerably in the rate of spread. Viruses such
as CMV can rapidly spread short distances quickly. CMV is efficiently
spread by many species of aphids but is nonpersistant in those aphids.
In contrast, DMV is transmitted by fewer aphid species but aphids
retain the virus longer and can move it farther. It is semipersistant.
However, it is not certain that all strains of DMV are aphid transmittable
(see section on DMV). Another example of differences are seen with
the thrip transmitted viruses. Tobacco streak virus is transmitted
less efficiently than tomato spotted wilt virus. Problems with tobacco
streak are rare in part because large populations are needed to
spread the virus.
answer to the original question is that vector control is important
and can help protect the dahlias from virus but it will fail at
times and will have no effect on the incidence of some viruses.
Because there are 2 stages to any epidemic (introduction of the
pathogen and local spread). Eliminate virus sources, and control