The Q&A Archives: Odd Destructive "spider" ?

Question: I have two large flowering shrubs, which are commonly called here "potato bush trees." They have thin very long downward-turning branches; long thin leaves and bloom with small deeply purple flowers. Each summer one of them gets a very destructive pest: looks much like a great many tiny all black spider-like bugs which tend to clump together on the branches. They even form squirming piles at the junction of twigs. The branches and leaves begin to turn yellow and die, though I don't see any eating damage on the leaves or wood. I get the impression the shrub is being sucked to death!

I've not been able to identify this bug so far - in fact I don't even find an identification of the shrub and the nursery I purchased them from is out of business.

Hope you can help solve the mystery. Thanks.

Answer: I think you're on the right track! Based on your description I'll bet your plants are being attacked by black bean aphids. These critters are a charcoal gray as opposed to the green aphids we're used to seeing, but their feeding habits are the same - they suck the fluids out of plant tissues! Beans and nasturtiums are their favorite plants, but it sounds like your trees have fallen victim to their voracious appetites, as well.

You might try hosing the insects off until beneficial ladybugs find your stash of black bean aphids. If all else fails, you can control the pests with insecticidal soap sprays.

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