think I have spider mites on some of my plants. How can I tell that
they are, in fact, spider mites, and what can I do to get rid of
because each individual creature is so tiny, are some of the most
difficult-to-identify garden pests. And note that I said creature,
not insect, because, in spite of a superficial similarity, mites
are not insects.
Mites are more closely
related to spiders than insects. In fact, the two-spotted mite,
the pest that is most often found infesting our garden plants, is
sometimes known as 'red spider' because, like a spider, it has eight
legs, and because its body changes to an orange/red colour in winter.
This confusion of common
names sometimes causes innocent spiders to be falsely accused of
being a garden troublemaker. A suspicious gardener, on sighting
a tiny red spider, is likely to wonder if this is the dreaded pest
about which he´s heard so much. The easiest way to resolve
this is to point out that, if the spider is easily seen with the
naked eye, it´s not a two-spotted mite (and is more likely
to be a garden friend).
Two-spotted mites are
very tiny. So tiny that they´re quite difficult to see with
an unaided eye. But if you have good eyesight, in good light the
two dark spots on the body stand out clearly.
What to look for
Usually the first sign
you´ll see of mite presence is the damage they cause. The
two-spotted mite is a sapsucker that works from underneath the leaf,
sucking out the leaf´s green cells. Damaged leaves turn yellow
or brown and their surface has a papery, slightly gritty feel.
As mite numbers build
up, their damage becomes more obvious. A layer of fine webbing appears
on the underside of affected leaves and may eventually cover the
entire leaf. The tiny mites can be seen scrambling on the webbing.
How to control two-spotted
Wet them: Like
many other garden pests, two-spotted mites flourish in warm, dry
conditions. One of the best ways to keep numbers under control is
by spraying water over the plant material. A regular mist spray
can discourage up to 50% of a population of two-spotted mites.
Oil them: White
oil is registered for control of mites. Good spray coverage is essential
because white oil works by smothering the pest and blocking its
breathing processes. Avoid spraying any type of oil when temperatures
insecticides (but not all) will control mites. Mavrik is a very
low toxic insecticide/miticide that is doubly effective because,
as well as controlling on contact, it has a good repellent (i.e.,
it makes the leaf surface unpleasant for the mite) action.
As with any other form
of garden pest control, prevention is better, and more desirable,
than cure. Avoid growing plants in constantly dry situations (such
as beneath overhanging eaves) and keep plants well-fed and free
from water stress.
by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor
of Resource Management.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH