Q: I have a bougainvillea that’s been growing in my big south-facing window for 45 years. Occasionally, it gets aphids and more recently red spider mites.
Though I have used a systemic on occasion, my usual solution to pests has been to get rid of all the leaves and prune back the spindly limbs so they have nothing to eat. I’ve done this twice in the past six months, but the spider mites seem to persist. The nursery lady told me that root systemic poisons do not work on spider mites, but recommended Bayer Advanced Insect, Disease and Mite Control, which I applied as soon as the plant began to leaf out again. Although I have yet to see a mite, I see the little webs, so I know they’re lurking. Any thought on how to get rid of these guys?
A: Mites are microscopic and especially hard to see when they are young. You can manually wipe off the webbing, and that will help reduce the population. Natural enemies may keep spider mites in check to some extent, and so it is sometimes a bad idea to use broad-spectrum products that kill all insects and mites. It is better to use something labeled specifically as a miticide. Mites may also be managed a bit with water. They do best in very dry conditions and simply spraying the leaves with a hose periodically can help reduce their numbers. Be careful not to overdo the water, since bougainvilleas don’t respond well to overwatering.
Keeping the plants in good health is important, and removing all the leaves is contrary to that idea. The mites might also feed on the spindly limbs. Don’t overdo the fertilizer as it makes the plants more attractive to the mites.