Some insects are eating the leaves of my bougainvilleas

February 25, 2018 8:09 PM

Something is eating little bits out of my bougainvillea leaves (not the entire leaves, just whittling them away). Over the course of weeks, they're getting a lot of my foliage. Fairly new plantings (about 4 months) fairly mature plants, otherwise healthy. What can I use to stop them (and what might it be)? I'm in southern California.
posted by arnicae to Home & Garden (3 answers total)

Look closely at the leaves, under them, on the stems, etc. If you don't see caterpillars or aphids, it is likely leaf cutter bees. You can spray the bush with something containing capsacin to make it less tasty to critters, but you would need a lot of it since mature bougainvillea tend to be pretty big. Anything else you put on the plant will kill the critters which is not beneficial for the ecosystem. Can you just let them have their bit?
posted by eleslie at 6:18 AM on February 26, 2018

Exactly the same thing happened to me! (also in Socal). All the sources said "Bougainvillea Loopers", so I looked and looked and looked for them, at nighttime too. Couldn't find enough of the little boogers for them to be the culprit. If you find them, you want BT spray. Based on this, and the fact that the chewing was from the outside of each leaf, I decided it was some sort of leaf cutter bee or other flying insect, so I had to up the chemical ante to Cypermethrin. This is bad for any insect though and definitely not organic, if you are trying for that. The Cypermethrin spray worked wonders for me though. Instead of being chewed off the second they emerged, the new leaves can now grow! I spray once every 2 weeks. It lasts longer than that, but I want new leaves to be protected. I got this one.

Just letting them have their bit doesn't work when "their bit" is every single leaf. ;-)
posted by bluesky78987 at 7:12 AM on February 26, 2018

So, to not answer your question, my approach is: if a plant pest is not literally swarming across the surface of a plant, and the plant visibly dying by the second, and I am just getting a few aphids here, a few chewed leaves there, I just leave it and let god sort it out. Every insect on earth is prey to something else and if the pest insect numbers increase too radically, the predators will arrive soon enough and take care of them for you. It can take a week or so after an infestation starts for e.g. ladybugs to turn up, but I pretty much guarantee they will.

And if they don't, and the plant packs it in...well, I'll grow another type of the same kind of plant, or just another kind of plant altogether.

However, I work with different plants, with different pests, in a different environment. bluesky78987 has direct experience with your exact problem and therefore more relevant advice. I will say, though, that cypermethrin is absolutely toxic deadly stuff that kills the total crap out of literally everything. Neem oil - concentrated, from an Indian supermarket, not the garden store - diluted with water might be a better thing to try out first.
posted by turbid dahlia at 5:50 PM on March 1, 2018