Dealing with Petunia Budworms
By Jean Shildneck, Marketing Lead, Kennedy’s Country Gardens
I don’t mind a few holes in my petunias, so I usually ignore them until later in the summer when “all of a sudden” every blossom looks like Swiss cheese, and then I finally decide it’s time to fight back. A couple of years ago, I waited until early August, and my petunias were almost barren of color. Suspecting that the tobacco budworm was the culprit, I went out into my back yard at 9:00 pm one night with a flashlight to investigate. I was right, and I captured a photo of one of them on a purple petunia blossom. You can see the offender in one of the accompanying photos.
Tobacco budworms (actually caterpillars) are the greenish larvae of the Helicoverpa virescens moth. They hide during the day around the base of the petunias and emerge at dusk to begin feeding on the buds and petals of your petunias. Symptoms of a tobacco budworm infestation include: ragged petals, holes in the petals at the base of the flower, failure of buds to open, and black specks of frass (aka caterpillar poop) on your plant.
The tobacco budworm is resistant to many insecticides, and using insecticides can kill beneficial insects that help keep the budworms under control. One way to control these caterpillars is to remove them from your plants by hand and drown them in soapy water. If that method is too tedious (or you are too squeamish!), there are two organic pesticides that are effective against tobacco budworms that you can try.
Bonide’s Thuricide contains Bacillus thuringiensis (BT) which is a microbial agent that only harms insects that are actually feeding on the plant. It is safe for bees since they are not eating the plant itself.
Bonide’s Captain Jack’s Deadbug Brew contains spinosad which, while approved for organic gardening, is harmful to bees. If you spray at nightime or early in the morning before pollinators start foraging, you will limit the damage to these beneficial insects.
Remember – as with all pesticides, read the instructions carefully and apply only as directed.
Two years ago, when I first wrote this article, I had some Captain Jack’s on hand, and it was already late at night, with no bees about, so I decided that I would give the spinosad a try. I remember wishing that I hadn’t been so sanguine, and had treated my plants earlier in the season when I first noticed the holes in the flowers; it probably would have been a lot easier to control the beasts if I had fought back against them when they were smaller! I remember thinking “better late than never!” and asking my readers to wish me (and my petunias) luck. I was successful in reducing the budworm infestation that year, and my petunias did bounce back.
A couple of days ago I started noticing holes in the blossoms of this year’s crop of petunias. I am going to take my advice to myself and spray them tonight. You might also want to check your plants and consider taking action.
Some of the material for this article came from a piece by Judy Wolfe on hunker.com. You can find the article here.