|
Question: When is a worm not a worm?
Answer: When it’s a
caterpillar.
I was recently asked to investigate a problem lawn. Despite
being well watered it was suffering from brown patches. And what was worse,
the patches were getting bigger!
As I walked across
the lawn, a number of small brown moths flew out of the grass away from my
feet. This was my first clue.
I took a hosepipe and
left it to flood an area of the lawn. A close inspection of the flooded
grass revealed a host of wriggling caterpillars.
The moths were a type
of willow moth (Spodoptera ciliata), which prefers to use short grass as a
host plant in which to lay its eggs.
The moths of the
Spodoptera genus lay eggs in batches of more than a hundred at a time and
the resulting caterpillars are known as armyworms and are major pests of
many crops around the world.
Lawn armyworms live
in the thatch of the lawn and emerge after nightfall to eat the grass back
to bare earth. As the army devours an area it marches ever onwards until all
the lawn is eaten.
Of course, in the
natural environment, grass does not have a very long season in the Cretan
climate, which makes the moths seasonal, too.
However, at home we
expect our lawns to be green the whole year around. This means that the
caterpillars never go hungry, making it is possible for the moths to produce
many generations over the course of a year.
It is hard enough to
grow a decent lawn in such a hostile climate (for grass) without having to
engage in a war with an army!
I have read about
nematodes that will destroy the caterpillars, and, also, of wasps that use
the caterpillars as a host for their eggs. But I have no experience with
them, and I doubt if they are readily available on Crete. |
If you insist on having a lush green lawn, you
will, unfortunately, have to use chemicals, and a number of suitable
insecticides are available here.
The one that I have
used to some success contains the ingredient chlorpyrifos and will
keep the lawn clear for up to two months.
The brand that is
available in the farm shops here, however, is not labelled for use on turf,
therefore I would recommend that you get the help of a professional to carry
out any pesticide treatments.
Remember not to allow
any animals to graze on a treated lawn and any clippings should not be used
for composting.
If you have fruit
trees growing in the lawn, obviously you would not want to use any chemicals
under these at fruiting time, if at all.
By the way, just what
is this “thatch” mentioned earlier?
It is a layer of both
living and dead plant stems that build up between the soil surface and the
green grass blades. It’s what gives a lawn the springy feel underfoot, and
provides an ideal home for many of the lawn pests and diseases.
On the whole, it is
considered to be detrimental to the well being of the grass if it is deeper
than about 1cm.
Thatch can be
physically removed from a lawn. On a small scale, this can be done with a
wire-tined lawn rake, but a better job is achieved by using an electric or
petrol-powered machine.
This job is generally
carried out annually on a high quality lawn, whilst the grass is growing
well.
Aeration also
encourages the breakdown of thatch and should also be carried out at least
annually (more often for sports pitches and areas of heavy wear and,
therefore, compaction).
If you want to
comment on this article then please visit my blog site at:
http://www.quality-gardens-crete.blogspot.com.
 |
