Many aphids live on a a wide range of host plants, including orchids. Photo: Ron Parsons, youplants.com
Question: I recently discovered aphids on 2 of my 6 orchids. I’ve had them for almost 2 years and I inspect them regularly. Plus, they’ve always been indoors. Where do these insects come from? Will my other orchids be infected?
Yen Doan
Answer: Aphids can reach indoor plants in several ways.
Since they have a winged phase that usually appears at the end of the summer or in fall, the most obvious thought is that they might have flown in through an open door or window. In fact, though, indoor aphids most often hitch a ride on us (or on our pets)!
When you work outdoors in your garden, or even just rub against an outdoor plant, you can accidentally pick up a few aphids and carry them indoors on your hands or clothes. Since aphids enter diapause (a state of near-dormancy) in the fall, they’re often not noticed at first, but when the days begin to lengthen, they wake up and begin to reproduce. That’s why aphids suddenly seem to appear out of nowhere in midwinter, a situation that has led more than one gardener to believe in spontaneous generation!
Yes, your other orchids can become infected. Ideally, you’d put the affected plants in quarantine in another room until the problem is resolved. And be careful when you handle them! Aphids are easily moved from infected plants to healthy plants when watering, not only on via clothing, but through contaminated tools. For example, they’ll readily hitch a ride on the spout of a watering can.
To control aphids, weekly treatments with a solution of insecticidal soap or neem will be effective provided that all insects, even those hidden in the leaf axils, are reached. It’s therefore important to carefully spray the product on all plant surfaces, even the undersides of the leaves.
And don’t expect the treatment to give instant results. It usually takes 4 or 5 treatments to completely wipe out an aphid infestation.
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