1. Check the Plants
for Infestation - Inspect the bottom of leaves and
look for damage starting in mid-spring. In cases of
light infestation, you can simply remove the critter
manually or spray with an insecticidal soap which will
melt the waxy coating on its soft skin making it
dehydrate and die.
Natural Enemies - Predaceous beetles, certain
parasitic wasps and a few fungal diseases help to keep
rose and pear slugs in line. Of course, like all natural
approaches, this will not totally eliminate the
problem...just mitigate it. You will need to minimize
the use of stronger
insecticides (soaps are o.k.) to
avoid killing these good guys too.
3. Use an Insecticide - In cases of severe
infestation, it might be necessary to use regular
pesticides for the control of these insects. This should
be the rare case, however.
4. Bt Won't Work - Even though these critters
look like caterpillars...they are NOT. Since they are
the larval form of a sawfly (like
sawfly), the insecticide, Bacillus thuringiensis
(Bt) will not work on them. Bt kills caterpillars
that become moths or butterflies.