Two-spotted mites are tiny creatures (about the size of a full stop) that damage plants by feeding on the
chlorophyll in the leaves. They are yellowish-green with 2 large dark spots on their back. In autumn they
turn reddish-orange, hence their other common name, red spider. The first symptom that your plants are
under attack is usually a white spotting on the surface of the leaves. In heavy infestations the mites
remove nearly all the chlorophyll and the leaves turn yellow and drop off. Similar symptoms but with the
addition of black marks on the underside of leaves are not mites but probably thrips.Two-spotted mites feed
on a wide range of plants, particularly cucumbers, tomatoes, capsicums, beans, roses, orchids, strawberries,
berry fruits and, apple and peach trees.
Suggested Organic Strategies:
- Common organic practices such as making compost, mulching the soil and avoiding chemical insecticides
help to encourage predatory mites, a major predator of two-spotted mite. A healthy garden will have a
resident population of predatory mites to keep pest mites under control.
- Try a high pressure hosing in the early morning, 3 days in a row.
- An unlikely pest control device is a hand-held vacuum cleaner! After vacuuming, tip the contents
immediately into a plastic bag and place in the freezer for a few hours.
- Keep your plants healthy by feeding, mulching and watering.
Organic Strategies for Two-Spotted or Spider Mite Control
© Frances Michaels
Mites secrete a very fine, silk-like webbing which protects the mites from enemies and contact with chemical
sprays. When large populations have been present for a few weeks webbing may cover the whole plant. Females
leave plants on threads of webbing blown on the wind or they may drop off a plant and crawl to a new plant.
Female two-spotted mites over-winter in the soil under leaf litter, tree bark, or cracks in greenhouse walls,
they emerge in late spring and lay eggs. At a temperature of 30°C their life cycle can be completed in 8 days,
giving 12 to 20 generations over summer. Mite numbers build fastest in hot dry weather with low humidity.
Organic gardeners have an advantage regarding spider mite control. Common organic practices such as making
compost, mulching the soil and avoiding chemical insecticides help to encourage predatory mites, a major
predator of two-spotted mite. A healthy garden will have a resident population of predatory mites to keep
pest mites under control. Predatory mites are abundant in the top layers of soil, in humus and animal manures.
Two types pf predatory mites are available commercially Phytoseiulus persimilis
. They are best introduced when pest numbers are low. More information and commercial
producers of 'good bugs' can be found at:
Gardeners who spray a pesticide such as carbaryl to control caterpillars will unfortunately kill all the
predatory mites present as they are very susceptible to pesticides. So the gardener may have controlled a few
caterpillars only to find that the population of a much more serious pest, the two-spotted mite may then
explode. In this case, the organically acceptable caterpillar control, Bt (
), would have been a much better
choice as it would have not affected the beneficial predator at all.
Other predators of two-spotted mite include hoverflies, a tiny black ladybird Stethorus spp.
the 'spider mite destroyer'; green and brown lacewings, damsel bugs, predatory thrips, spiders and tiny
Physical and Cultural Controls
There are some easy things you can do that will have a big impact on spider mite numbers. Try a high pressure
hosing in the early morning, 3 days in a row. An unlikely pest control device is a hand held vacuum cleaner!
After vacuuming, tip the contents immediately into a plastic bag and place in the freezer for a few hours. You
can control whiteflies doing this as well. Pruning back affected plants and removing infested leaves will
reduce pest numbers. Try to control weeds that harbour the pest such as plantains, black nightshade and
marshmallow. Keep your plants healthy by feeding, mulching and watering.
Least Toxic Chemical Controls
Two-spotted mites are not insects and are highly resistant to many chemical insecticides. There are several
organic controls that work well, as their mode of control differs from that of a chemical insecticide.
Remember to coat the undersides of the leaves well with spray as this where the mites primarily are.
can be very effective to
smother the mites and mite eggs. Avoid using it at temperatures higher than 35°C as it may cause leaf burn.
One or two follow-up sprays should be applied at 5 - 7 day intervals to kill new mites.
Insecticidal soap sprays such as
are a good choice of
control for the home gardener. They should be applied at least 3 times every 7 - 10 days. Wettable sulphur
or dusting sulphur can only be used in cool weather as otherwise it will cause leaf burn. You should avoid
using an oil product for at least a month after applying sulphur as in combination it can cause phytotoxic
problems for plants.
Control of Two-Spotted Mite on House Plants
Pest problems on indoor plants often increase rapidly due to the absence of 'good bugs' inside our homes
as conditions are simply unsuitable for them to survive. Always treat all susceptible house plants at the
same time. Trim, bag and remove heavily infested leaves and discard severely infested plants. Take the
plants outside and spray with an organically acceptable oil or soap spray. Re-apply the treatment at one
to two week intervals as long as the pest persists. If plants are able to be easily lifted, a regular
rinsing under the shower, will help prevent mite problems occurring.