Updated: Jan 15, 2021
Hello Fellow Wrigglers!
Over the past few weeks, we have gotten several queries regarding broad mite infestation. These are really common in Singapore and to make matters worst, broad mites are invisible!
Okay, they're not really invisible. But what are they and how do we prevent them from manifesting on our beautiful plants?
Broad mites are members of the Tarsonemidae family, known as the ‘white mites’. They are extremely small (< 200 micrometres in length) and they move very quickly.
Broad Mites - Photo's were taken with an electron microscope
Broad mites can spread among greenhouse-grown crops via air currents, leaves of adjacent plants contacting each other, by workers handling infested plant material and then touching non-infested plants or by host insects such as whiteflies.
Broad mites have a relatively short lifespan of approximately 10 days, during which they feed on our plants and reproduce. They have four stages in their life cycle: Egg, larvae, nymphs and adult. The female broad mites lay approximately 30 - 76 eggs over an 8 - 13 day period before they die. In our tropical climate, it takes approximately 5 days before the eggs fully mature and become reproductive. Couple the quick development cycle and the wide range of hosts (e.g. apple, chill, papaya etc.), it's not surprising that broad mites are a common pest in Singapore.
Now we know what they are, how do we spot these "invisible" creatures?
Being comparable to the thickness of a human hair, broad mites are extremely difficult to spot with the naked eye. The female lay single eggs, rather than in clusters, making detection difficult, even when viewed under magnification of at least 10x.
Broad mites primarily feed in groups on the underside of young leaves. They reside and feed on the young, developing tissues of plants that provides an ideal food source for development.
When mite populations are extensive, they will move and feed on the upper leaf surface resulting in severe deformation as their saliva is toxic causing twisting, hardening and distorting growth in the new leaves. Recognising these symptoms is key to identifying broad mite infestation.
If left untreated, the broad mite population would explode and they would feed aggressively on both young and older leaves. This would cause damage to the leaves which would weaken the plant and in extreme cases, kill the plant.
Do also note that they can also be transported to neighbouring plants which would make the infestation harder to control. Hence it is important to treat broad mite infections immediately, the moment you observe wrinkly leaves and deformed new growth.
Controlling broad mite infections
Once the infestation has been identified, the first step would be to remove all infected (wrinkled) leaves and stems. This is a necessary evil that your plant would thank you for several weeks down the road.
Following the removal of the affected parts, daily application of insecticidal soap is surprisingly very effective in controlling broad mites. Similar to the method used to control aphids, we apply sulphur soap every evening via a spray mist bottle.
There are also other methods of controlling broad mites such as introducing natural predators such as the Amblyseius californicus, a generalist predatory mite that primarily attacks spider mites. They will also feed on other leaf inhabiting mites including broad mites!
There are also a number of miticides such as Avid or Forbid that would be applied via a spray mist bottle. These are extremely strong chemicals guaranteed to rid you of your mites issue. But they work by penetrating your plant tissue and killing the bugs that way.
However, we have never tried any of the bio-control methods or the miticides for managing broad mites due to the effectiveness of sulphur soap method which is more natural and friendly to the environment!
We hope that this would help you identify and prevent broad mite infestations from ruining your plants as we understand how frustrating it is to see a healthy plant deteriorate!
All hail the Sulphur Soap and Stay Wriggley!