Houseplant Aphids

(aphids come in many colors and sizes but usually you can identify them by their round or pear-shaped bodies and the two cornicles (little spikes) that emerge from the back of their abdomen. photo credit: Bob O'Neil, Purdue University)

Question:

I enjoyed the houseplants program a few weeks back. I'm still struggling with aphids, I think, on our...? Would the rubbing alcohol work on that? At what dilution would you recommend?

Answer:

If the aphid situation is really bad I would probably go to the next step of control which would be to use an insecticidal soap. If I discover a small population of aphids (i.e. a few) I usually begin by spraying the plant and its foliage with a strong stream of water. If the stream does not knock off the pests completely the hope is that the force of the water breaks their piercing, sucking mouthparts, disabling their ability to continue feeding on the plant. Then I might clean the leaves with a ½ and ½ mix of rubbing alcohol and water, physically removing as many pests as possible before placing the plants back on display. If the population is larger, but still isolated to a specific part of the plant, such as the tips of new growth, then sometimes it is best is to pinch off and remove that part of the plant to the garbage. As long as the rest of the plant is healthy and has plenty of foliage to photosynthesize pinching off a damaged shoot should not be the death of the plant. If anything pruning or pinching back your plant should promote new growth to follow. Lastly, if the plant is seriously infested, then buy yourself some insecticidal soap. As with any chemical, follow the instructions explicitly. I would place the plant somewhere safe so you can really coat the entire plant with the spray solution. I place my infected plants in the bathtub and spray them to the point of the soap running off the tips of the leaves. I let them sit and dry before putting them back into an area of direct sun, if applicable, then continuing to keep an eye on them. Because female aphids can give birth to live young in only a week’s time I would check again and potentially re-spray after a week or so. Again, follow the instructions on the bottle. Safer Soap, or some such insecticidal soap, you should be able to find at a decent florist or garden center/supplier. I usually go to either the Flower District on 28th Street or Chelsea Garden Center on 11th Avenue at 44th Street.