Spider Mites on Potted Orange Tree

2012 June 16

We once had a small potted orange tree as a houseplant. But while it started out well, over time it started doing poorly. Some branches would die back, and others would keep producing buds but the buds would wither and fall off before becoming leaves. Looking more closely, we noticed that the buds, leaf bases, and surfaces of the developing fruits had a thin coating of webbing, andon October 18, 2010 I photographed the culprits:

We had spider mites. These are a large group of mites in the family Tetranychidae

Spider mites are plant parasites, sucking juices out of their host plants. They are pretty tiny (these were less than a millimeter long), and spin thin sheets of webbing to protect themselves and their tiny, spherical eggs (which are visible in this next photo).

There are about 1250 known species of spider mites, and a lot of them are agricultural pests. They cause exactly the problem we were seeing: stunting and killing new growth. They breed like crazy, too: under appropriate conditions, the eggs hatch out in a couple of days, and the adults are sexually mature within less than a week. The female can lay up to 20 eggs a day and can keep it up for almost a month, so with the fast hatching rate the numbers can get completely out of hand very quickly. And since they are so tiny and hard to see, they are likely not to be noticed until they are already pretty far along.

We tried controlling them by applying alcohol to the infested parts of the tree, but it was a losing battle. Most of it died back, and what was left was so deformed that it couldn’t recover. Ultimately, we moved the tree outside and let the elements take their course once winter rolled around.

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