ALBUQUERQUE, N.M. — Q: How should I treat for those little green worms that harm my geraniums? I’ve got lots of chewed spots on the leaves and it looks like perfect small holes have been drilled into the flower buds! I get them every year but this year seems worse than ever.
A: If the pots have the same soil that grew your geraniums as last year and you just planted anew, you can bet some of the critters you’re seeing wintered over in the soil. That and you might have seen light-colored, fairly small moths hovering around the geraniums who mated and laid eggs that have hatched and are pestering your geraniums.
I know of one bee-safe pesticide that is meant to hunt these worms. It’s called Bacillus thuringiensis kurstaki. You can find it sold on the retail market as B.T. or BTK. Bacillus thuringiensis is a form of bacteria that when eaten by worms and caterpillars upsets their insides to the point where they don’t want to eat anymore and in turn die. The wormy creatures do have to ingest the product so you will lose a bit more of the plant before you notice success from treatment.
Then, too, I’ll suggest that you deadhead any of the blooms your geranium is wearing now to be sure to get rid of this crop of worms. I have one brave gardener that said she hand-picks the offending worms off the plants, disposes of them and has far fewer to deal with, too. Brave gardener for sure!
I do have a couple of additional cautions about the spraying, too. First, this pesticide degrades quite rapidly once it gets hit by the sun. So spraying once and thinking you’ll have solved the problem, you’ll be disappointed. It’ll take several spraying to get a really good hunt when using the BTK for pest control.
Second, I’ve been reading a lot about bees and the one thought that keeps resonating in my brain is to please do any spraying in the evening after all the bees have gone home for the night. I want us to become a community of nighttime sprayers. Granted the BTK is listed as a “bee-friendly” pesticide; I’m just advocating that you never spray ANYTHING while you have bees about!
Then, too, aim to not spray any plant you have in full bloom so any visiting bees won’t happen to pick up any residual pesticide. That goes for any and all pesticides, not just a biological control like BT.
Now controlling caterpillars and worms can get weird. I got a question from one novice gardener quite recently asking what she should use on her butterfly garden because she’d gotten lots of butterflies but now is seeing lots of caterpillars. Wait … what?!
My brain tilted that she wanted to kill the offspring of the butterflies that she had attracted and I had to be politically correct when I begged she not do a thing as butterflies are a great pollinator and caterpillars are butterflies in a younger form. Yes, they are eating her flowers but without allowing them food this life cycle, next year there could very well be fewer and fewer butterflies!
It’s a tough decision I know when it comes to the “to treat or not to treat” question but the older I get, the more I want to stop using broad-spectrum, kill-everything pesticides! So if you’re not brave enough to hand-pick worms, at least spray a pest-specific pesticide – in the late evening hours – and you should have fairly healthy, worm-free geranium plants! Happy Diggin’ In!
Tracey Fitzgibbon is a certified nurseryman. Send your garden-related questions to Digging In, Albuquerque Journal, P.O. Drawer J, Albuquerque, NM 87103, or to email@example.com.