" Mites may
hibernate
in an empty indoor garden area for
many months, only to reemerge when
warmth and new plant material is
available again, so regular scouting
needs to be carried out once a new
crop has been established.”
Insecticide sprays need to be used with caution. While they
can be highly effective in the early stages, mites can build
up genetic resistance if the same spray is used repeatedly on
the crop. There are several spray compounds and products
used for mite control (acaricides) in commercial horticulture,
but, on a smaller scale, the main miticide compounds contain
the active ingredients abamectin (a derivative of a toxin
originally found in soil bacteria) or synthetic pyrethroids.
These may only be used for a limited number of applications
per year and chemical control compounds should be
rotated within a spray program to prevent pest-resistance
development. Azadiractin (derived from the neem tree) is
a botanical insect growth regulator available in a number
of products that can work with other control options to help
reduce mite numbers, but it does not destroy mite eggs.
Various horticultural oil and soap sprays are often used as a
smothering agent for mites. Excessive or repeated use of oil or
soap sprays can cause crop damage, particularly on sensitive
plants and those grown in highly protected conditions. Oil
and soap spray damage typically shows as irregular brown
spots with a darker border or a water-soaked appearance that
is often mistaken for a foliar disease.
78
Maximum Yield
Biological Warfare Against Mites
Biological control options include the predatory mites
Phytoseiulus persimilis; Amblyseius californicus, which
has more tolerance to lower humidity, and Amblyseius
fallacis, which is resistant to some pesticides. Predators
need to be introduced when there are already some mites
present for them to feed on. If there are no mites present,
the predators will rapidly die out, so there always needs
to be a carefully controlled balance between predator and
prey maintained for biological agents to be successful.
P. Persimilis also requires specific conditions to control
mites, including temperatures in the 68-79˚F range. Once
temperatures reach more than 86˚F and humidity is less
than 60 per cent, the predators become ineffective, but
mites will thrive under these conditions.
If a mite infestation becomes uncontrollable, removal of all
infested plant material is essential, as is the cleaning and
sanitation of all surfaces. Mites can survive on non-plant
surfaces such as walls, floors, around heating pipes, and
inside vents, so a thorough cleaning is required to prevent
infection. Mites may hibernate in an empty indoor garden
area for many months, only to reemerge when warmth
and new plant material is available again, so regular
scouting needs to be carried out once a new crop has been
established.
Mites in an indoor garden may seem like a formidable foe, but
some knowledge of their life cycle and infestation methods,
as well as simple prevention measures and effective sprays,
make this pest controllable in many cases. Scouting and
early identification (as soon as the first signs of damage is
visible) are essential for successful control. A wide variety of
control options, combined with careful application of spray
compounds to prevent pest resistance, is vitally important
when dealing with mites.