My work involves biological control of weeds, so that’s
using insects to control weeds in
Hawaiian forests. So our targets include
strawberry guava and many other ecosystem
altering weeds in the Hawaiian Islands. Some of our worst invasive weeds in Hawaiian forests include
strawberry guava (this tree), miconia, clidemia. This plant here, in the
family Melastomataceae. There are many serious
invaders in that family. This is very typical of the
way strawberry guava invades in thickets of small stems
shooting up all over the place. And so they’re blocking out the
light for the native understory. So we get very little
native regrowth of native plants
in the understory. It’s just all strawberry guava. The young stems are
slender and they fall over and they will take root in the
ground and send up new shoots so you develop a very thick
tangle of stems over time. Essentially it becomes
impenetrable. So, our intent with the
biocontrol is essentially to restore the balance
to the system with a natural enemy
for strawberry guava. Here in Hawaii it has
no natural enemies. So, bringing in that specialized
agent will help limit the invasiveness of strawberry
guava. Some invasive species are
valued in Hawaii and elsewhere. For example, plants like
strawberry guava create fruit that some people eat,
so there is concern that biocontrol might
wipe out strawberry guava and eliminate that fruit source. But, the biocontrol we
developed for biocontrol of strawberry guava is not
going to kill these trees, it’s just going to limit their
fruiting and limit their growth, their availability to
spread into native forests. The biocontrol for strawberry
guava is an insect that’s native to Brazil. It forms galls on the new
leaves so it would be feeding on this part of the plant,
and as the leaf grows, the gall grows and that
slows down the overall growth and reproduction of the plant. In Brazil, you don’t see
strawberry guava being invasive, it’s very limited
in distribution. It still produces fruit there
and some people enjoy the fruit but it remains a harmless native
plant in its native range. Our work involved is
developing the biocontrol agent, so that means doing the research
to demonstrate the specificity and impact they have on
the plant, and then we turn over that information
to the state and the regulatory agencies who evaluate whether the
biocontrol is suitable for introduction. If they decide it is okay
to release it in the state, then we help them
with that process and do the follow-up monitoring
which is really critical to understand whether the
biocontrol is having the effect we intend. We are not in every case
going to solve the problem. A weed like strawberry
guava is going to persist in the areas it has already
invaded, so it is going to take other management
approaches combined with biocontrol to
solve the problem. For example, in a thicket
of a forest like this, these trees will not be
killed by the biocontrol, but their growth will be slowed
and if resource managers do come in and cut the trees, then
their ability to respond and regrow will be
limited by the biocontrol. Hopefully by combining these
different strategies over time, we will be able to
actually restore forests and really beat back
the invaders, so that’s the long-term goal.