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Global Invasive Species Team listserve digest #013
Wed, 20 Jan 1999 16:53:19 -0800 (PST)
--CONTENTS--
1. Dangers of Photomonitoring Results of Leafy Spurge Biocontrol
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1. Dangers of Photomonitoring Results of Leafy Spurge Biocontrol
From: David Hanna (dhanna(at)3rivers.net)
After 5 years, we are seeing significant results from our biocontrol
releases for leafy spurge. The quantitative data from our release sites
clearly shows that the beetles are impacting the spurge. However, the
photomonitoring portion of our monitoring has turned out to be somewhat
problematic. The phenology of spurge affected by the flea beetles is very
different from non-affected spurge. At our sites, spurge affected by the
flea beetles flowers 4-6 weeks later than spurge in non affected areas.
Thus, the visual impact of the beetles impact in photos varies by season.
Photos taken in late June show non-affected spurge in bright yellow flower
while with affected spurge just coming up, producing fairly stiking visual
evidence the beetles are working. However, photos taken in late July show
non-affected spurge senescing, with affected spurge in peak flower, making
the impact of the beetles appear much less dramatic. So, if releases at
other sites use only photomonitoring, we recommend taking these
differences in phenology casued by the flea beetles into account when
setting up the monitoring protocol. If photos are taken only once in a
season, the full picture of the beetles' impact will not be captured--the
impact will likely be over or under represented.
David Hanna
Pine Butte Swamp Preserve
HC 58 Box 34B
Choteau MT 59422
406-466-5526
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