- Leaves become speckled, as though covered with hundreds or thousands
of pale yellow dots giving a rather ill-looking and "dusty"
appearance. Heavily infested plants may become covered with fine
webs. The red spider mites themselves are eight legged animals less
than 1mm long and can be difficult to see.
Leaves dry up and fall leaving only young leaves at
the ends of shoots. More often affect plants under glass, but will also
attack many ornamental plants outdoors in a hot dry summer.
Damage - Sap feeders which
weakens the plant. Usually a problem in house and greenhouse plants
as they like a dry atmosphere, can be a problem outside in hot, dry
Treatment - Red spider mites
breed in hot and dry places. If you can increase the humidity around
the plant you decrease the pest's reproduction rate. In greenhouses
and patio areas the floors can be damped down. For house plants a short
holiday somewhere cooler and more humid - the bathroom or even outside
in the warmer months may help get rid of the infestation.
You could try giving
them cold water baths, they hate them. Spray them with water that
is between 0°C and 5°C (make sure the plant won't also
hate it though!). If you find an infested plant, attack it with ice
water. Keep a spray bottle in the refrigerator and mist once or twice
a day until the mites are all gone.
|I've been having trouble with Red Spider Mite
in my conservatory for a couple of years, using conventional
and biological pest control. I then tried your idea of spraying
infected plants with ice water. Brilliant results! - Thanks
Jon Willis - by email
The rapid reproductive rate and the existence of pesticide
resistant strains makes control difficult. Insecticidal soaps sprayed
every three days may help control infestations if not eradicate them.
Another option is to go for biological control.
Biological control of a pest relies on introducing a predator species
so "fighting nature with nature", if chosen carefully, the
predator will stop damage to your plants without damaging the environment.
Such biological controls are safe for the user, children and pets. They
will not harm other beneficial garden insects and are biodegradable.
They do rely on the predator always having some food
though, or they will die out, so like other organic practices it is
a question of maintaining a small population of pests to allow the predators
to be ready for them, in this case though the balance is skewed away
from the problem.
Biological control for red spider mites is a predatory
mite; Phytoseiulus permilis. This insect reproduces at
twice the speed of red spider mite at 18°c (64°f). The
Phytoseiulus mite eats only Red spider mite and each can eat many
hundreds of them. Whilst feeding on Red spider mite, Phytoseiulus
will also reproduce laying many eggs which will hatch into more predators.
Phytoseiulus is similar in appearance to red spider mite but
is more red in colour and moves much faster.
is suitable for glasshouse or conservatories and can be used on strawberries
and fruit from May to August outside.