Date: June 14, 2001
Category: Nematodes Subject: Nematode Populations
We are in our second week of June and nematode populations are high in
some greens and moderate to low in others. We know of no good way to predict
what your nematode populations will be at any given time but generally
the populations will increase through to the end of July. A soil assay
is the only reliable way to assess nematode populations. Since nematodes
occur in a "clumped distribution" in the soil, a composite sample
of 15 to 20 cores is preferred over a cup-cutter sample. June and July
is a good time to determine populations of ectoparasitic nematodes such
as stunt, lance, ring, and spiral. Ectoparasites remain in the soil and
feed on the roots by inserting their stylet into root cells. They are
easily extracted from the soil. Lance nematodes may feed from the outside
or move into the root entirely. Endoparasites such as root-knot and cyst
are not easily quantified in June and July because they have moved into
the root and are not extractable from soil. When we find root-knot and
cyst nematodes in the summer extractions we recommend that additional
samples be submitted as soon as the ground thaws in the Spring.
If nematode populations are moderately high to high, June is the best
time of the year in the New England region to apply nematicide for ectoparasites.
An application now will suppress the population through the most stressful
part of the season. Unfortunately, root-knot and cyst nematodes will not
be significantly affected by nematicides during this time of the year
because they are protected within the root.
