GENEALOGY
Original source for U.S.
release was Italy. First U.S. releases made in 1977. Established in
the Pacific Northwest, including Idaho, Oregon, and Washington.
Established in Stevens County.
LIFE
CYCLE
Eggs are microscopic
(0.04mm). Adults usually cannot be seen with the naked eye. Each of
the tiny females may deposit 60-100 eggs within the gall they share.
After hatching hundreds of the minute worm like nymphs feed on the
green gall material around them. The nymphs pass through several
developmental stages to become adults. Whenever the gall dries out
there is a mass exodus of all mobile stages.
In the Pacific Northwest the female mites form a dark brown
overwintering stage called a deutogyne. The deutogynes move down the
stem in fall to crevices in the plant at or below the soil surface
where they become quiescent until spring.
When the weed starts to bolt in the spring the mites invade the
shoot buds. Adults live up to 4 weeks. The mites feed and continue
to reproduce on a roughly 10 day cycle until fall.
EFFECT
Mite feeding causes the
buds to contort into galls which look like miniature cauliflower.
Both nymphal and adult stages damage the plant. Mite feeding
decreases plant vigor, helps reduce or eliminate seed production,
hinders formation of rosettes, reduces shoot production, and
sometimes results in the death of the plant.
REDISTRIBUTION
Collect infected plants
from July to mid October. Bind the galled plants together into
"Teepees". Wedge these bundles into plants that are not
infected. Cooler weather, evening releases, and high humidity helps
the chances for establishment.
COMMENTS
This mite disperses well
within the weed patch, and is known to colonize any biotype of Rush
Skeletonweed found in our area. It is considered the most effective
agent released on Rush Skeletonweed to date in our area. The agent
is well established in Stevens County.
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