For the last 15 years, the focus in our laboratory
has been on classical biological control by the introduction of
a small eulophid egg parasitoid, Oomyzus gallerucae [D].
These small wasps may parasitize 50 - 90% of the eggs in a cluster
in addition to host-feeding on other eggs, essentially destroying
the entire egg cluster.
Program Overview 1984-1999:
- We have released approximately
400,000 O. gallerucae in 28 locations in California, representing
at least seven strains from several European sources (Fig. 3)
et al 1998).
- Studies with the egg parasitoid
have been frustrating. · Parasitism during the year of release
may be as high as 95% of ELB eggs. However, the parasitoids apparently
do not overwinter well in California, as they are normally not
recovered the year after release.
- Parasitoids have occasionally been recovered
in years subsequent to field release, indicating that enough parasitoids
survive to keep populations established, but not to impact ELB
levels significantly. ·
- Laboratory studies have confirmed that
a low percentage of parasitoids possess the longevity to successfully
overwinter in our climate. (Dreistadt
and Dahlsten, 1991).
[D] Oomyzus gallerucae parasitizing elm
leaf beetle eggs.
Fig 3. Release sites in northern and central California
for different strains of Oomyzus gallerucae, 1984 - present.