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Clover mite populations are composed
entirely of females. Red eggs are deposited in protected areas with sunny
exposure. They hatch from September to April when temperatures rise above 30o
F. during the day. Tiny bright red six-legged larvae
crawl down into the grass and begin to feed. They soon change color to
reddish-brown. After 3 to 6 days with favorable temperatures, the mites change
to the next stage of development. When they are ready to molt or shed their
skin, the mites travel upward to a protected location. In the second stage
mites, now with eight legs, move downward and begin to feed.
Clover mites repeat this procedure two
or more times for the third and adult stages. Under ideal conditions, the life
cycle can be completed in 1 month. A sudden drop in temperature may kill all
mobile forms, and only eggs and resting stages survive. If winter starts with
mild temperatures and becomes cold gradually with no warm periods, adult mites
can hibernate and survive from September to April – a situation which signals a
population explosion in the spring. Cool summers favor clover mite survival;
while hot, dry summers cause aestivation or a period of inactivity.
Adult clover mites live for about 2
weeks outdoors; unless moisture is available, they seldom live longer than 24 to
48 hours in dwellings. There is an overlapping of mite stages in the spring and
fall, so all stages may be present at the same time. Some host plants include
lawn grasses, weeds (especially dandelions), legumes, ornamental flowers,
daffodil, salvia, alyssum, primrose, bleeding heart, phlox, clover, and poppy.
Plants that clover mites do not attack include geranium, chrysanthemum, and
zinnia.
Lush, newly established lawns and
heavily fertilized lawns serve as ideal locations for clover mite build-up.
Possibly, predator-prey imbalances account for initial, huge populations of
clover mites in housing developments beginning in the 3rd
year and continuing for 5 or 6 years. Natural
predators include other species of mites, spiders, and an anthocorid bug.
Clover mites are dispersed in various
ways. They can crawl from yard to yard, be blown by the wind on soil particles,
or be washed from one place to another by heavy rains.
Houses with highly reflective
surfaces, such as glass panes, light colored paint, or aluminum siding are
preferred for “invasion.”
In many instances, only the sunny
exposure of a dwelling become severely infested. When mites reach a warm
surface, they roam about until they find a protected area, such as: crevices in
the bark of a tree, wall voids, under siding and shingles, and cracks and
crevices in brick veneer. If surfaces become too hot or too cold, mites search
for a more favorable location.
George C. Hamilton, Ph.D.,
Specialist in Pest Management & Louis M. Vasvary, Ph.D., Specialist in
Entomology, (deceased)
Control
Control treatment sites include lawn
areas and foundation walls. Lawn areas adjacent to foundations should receive an
insecticide application. The base of the outside foundation and outward to a
distance of 10 to 20 feet should be treated. However, the distance form the base
of the foundation depends upon the degree of infestation. The insecticide should
also be applied form the base of the outside foundation up to windowsills on the
first floor. Some pressure is required to force insecticide into crevices under
shingles, siding, pits in mortar and around window frames, and where pipes or
other utilities enter the dwelling. Where large populations of clove mites have
been a constant annoyance, Drione or Dri-Die can be placed into wall void areas
by drilling tiny holes into stud voids and introducing micronized dust. In
general, residual insecticides are most useful for clover mite control because
overlapping stages exist during periods of activity. Resting stages and the egg
stage are relatively tolerant to most insecticides.
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