What’s Eating My Petunias?

This container was an impulse purchase from my supermarket around July 4th.  It has weathered the unseasonably hot temperatures we’ve had for the month of July, but suddenly it’s looking very peaked–yellowing, chlorosis in some of the leaves, and definite holes in many of the flowers.

Since I’ve grown petunias before, I knew just what to look for–see if you can spot the little guy in this next photo.

The nearly invisible worm chomping his way into the bud of this next flower is commonly known as the “petunia/geranium” bud worm, for obvious reasons.  He’ll also eat nicotiana flowers should you happen to have those around.  He is the larva of a type of tobacco moth that tunnels into buds of flowers and then eats his way out, leaving the holes I showed in the second photo (or worse).

Now because the worm spends so much of its life inside the bud, control can be difficult.  Most of the organic sprays actually have to hit the pest to kill it so if you’re going to spend that much time hunting down the little pests, you might as well do what I do–hand pick them and throw them in a place where you know you have a lot of birds, or just squash them.

If you have no concerns about chemicals, some of the systemics will work–but again, it will take awhile because the worms have to eat the chemical and then die so there will still be some damage.

Finally if you’re not quite sure that you have these worms but you see this

doubt it no further.  This is worm excrement–you have the worms.

20 thoughts on “What’s Eating My Petunias?

  1. Laurrie August 2, 2010 / 8:43 am

    Hmmm, this was very helpful, especially the close ups of the evidence. I think I have these critters in my petunias.

    • gardendaze August 2, 2010 / 9:01 am

      Laurrie,
      I’m glad this was helpful. Sadly, these little guys are very common. And I love the old-fashioned petunias. While I grow the newer “million bells” type, they’re just not the same– they don’t have the deep saturation of color or the fragrance!

  2. katie June 14, 2012 / 7:54 am

    thanks for posting this info … i just went out this morning to care for all of plants on my little balcony and found the evidence, holes in the flowers and little worm poops on the leaves, these little critters are destroying my gorgeous petunias. will they spread to my other plants? i have blanket flower, dahlias, daisies, geraniums, palms, marigolds, philidenrons, ferns and new zealand impatiens. i have worked hard to create a little garden in a very small space and it will break my heart if these little critters destroy my little garden.

    • gardendaze June 14, 2012 / 9:49 am

      Hi Katie,
      I’m glad I was able to help. Never fear–most of your garden is quite safe. You’ll want to keep an eye on those geraniums, however. They are prone to the same little worms. A bit of insecticidal soap ought to protect both–and be a non-toxic answer for you, loved ones, pets, and wildlife. Just be sure to spray when the plants are in the shade, and try to avoid bees! Thanks for reading!

      Karla

  3. Sally July 7, 2013 / 12:51 pm

    Thanks for sharing this info! This is exactly the problem I’m having and after reading your article, I hunted several of these suckers down! My guess is that I won’t be able to control the situation by the hand-picking technique, though.

    • gardendaze July 7, 2013 / 1:27 pm

      Sally,
      Glad I was able to help! If you have a lot, hand picking can be impractical. I get decent control with insecticidal soap. If you want to try something slightly stronger but still organic you can look for something with pyrethrins in it. Just be sure to spray in the coolest part of the day, and not when the plants are in the sun. Good luck and thanks for reading!

      Karla

  4. sandra kean August 22, 2013 / 3:30 pm

    Are the moths in my arborvitae shrubs going to turn into bud worms? Or are they the moths that turn into the worms hanging from the maple trees and eat the leaves in the spring? Will a treatment from Lawn Dog get rid of these?

    • gardendaze August 23, 2013 / 8:44 am

      Hi Sandra,

      It’s a little hard to guess what might be in your arborvitae but I can tell you that they’re not the moths that are in the maples. Each tree has pretty specific host insects.

      Lawn Dog will certainly tell you that they’ll cure everything that you have, I suspect, but without identifying your moths, I don’t know that I’d ask them to treat. For example, right now, I have lots of different moths “hanging out” so to speak, on my Japanese maple. That’s all they’re doing. They rest there in the cool shade of the day and in the evening they fly off to other places.

      Arborvitae are most susceptible to a nasty looking pest called bag worms which makes a cocoon of the arborvitae needles and sucks the juices out of the tree. The also get lace miners and mites and a few different fungi. They don’t get bud worms and there are no known moths that infest them.

      Here’s a great fact sheet from the Cornell cooperative extension service which might help you:

      Click to access e225_arborvitae_probs_oct00.pdf

      Thanks for reading and commenting!

      Karla

  5. sandra kean August 23, 2013 / 9:37 am

    I’m assuming that I should make sure I throw away the soil that is in my window boxes if that is where the larvae live through the winter. Those worms drive me crazy…..I pick them off two to three times a day.

    • gardendaze August 23, 2013 / 10:49 am

      Sandra,
      What’s happening is a moth is coming and laying those worms every year. And now that the moth knows that you have petunias in the same spot, it knows its young will have a reliable source of food, so it comes and lays its eggs, which hatch into young (the caterpillars, or worms that you’re seeing) and you go crazy.

      Insecticidal soap does a nice job of controlling the critters if you get tired of hand-picking. You sound like me, like you don’t like to spray.

      What you could try next year is a different plant–maybe million bells? They look very much like petunias but don’t get the worms. Or something entirely different–angelonia, (summer snapdragon) is a nice long blooming annual for sun.

      That would throw the moths off the trail.

      Karla

      • sandra kean August 26, 2013 / 10:07 am

        I will make sure I get rid of the soil in the planters and now I wish I could find a way to get rid of the moths. I will ask Lawn Dog if they have a treatment for them. It seems I may just have to plant something else. I planted red salvia and they did beautifully.

  6. gardendaze August 26, 2013 / 10:49 am

    Sandra,

    Next year I would definitely try something else. This year, you could see what Lawn Dog proposes. I’m sure they’ll have some sort of spray or remedy.

    Your other options, as I think I mentioned before, would be to spray yourself with insecticidal soap. If you prefer something with a chemical component, Bayer makes a Flower & Garden (or perhaps it’s rose & garden or rose & flower–I don’t use it so I’m not quite sure what they call it these days) spray.

    You’d want to spray in the shade rather than in the sun. And if you–or Lawn Dog–choose something with neonicontinoids (the Bayer sprays would have that pesticide) try to spray at a time when there are few bees around since bees are particularly susceptible to this pesticide.

    It will tell you that on the label. I’m not sure Lawn Dog, having a business to run, will care as much.

    Good luck!

  7. Coleen July 14, 2014 / 2:50 pm

    Thank you for helping me to figure out what these worms are. My petunias have been doing great until about a week ago. I know from past experience that when I start seeing holes and/or the entire bloom is eaten down to the nub, time to track them down. They are expects at camouflage! This morning their damage was so obvious because they cleared the entire top of a very large plant. I filled a container with a couple inches of water and went hunting. Your best indication of where to look is just above the excrement found on the leaves. Today I found 27 of them in various sizes which I simply plucked from the plant and dropped in the water. They drown very quickly and it seems more compassionate than squishing them. Today I am going to put them in a shallow container under the bird feeder. Thanks!

    • sandra kean August 20, 2014 / 7:58 pm

      It’s August 17, 2014, and my beautiful hosta with the white centers are turning into rusty leaves and it looks like they are dying like it was November!! What’s happening? Any one??

  8. gardendaze August 20, 2014 / 9:16 pm

    Hi Sandra,
    It’s always frustrating when a plant sort of “up & dies”–or appears to. This sounds a little more mysterious than most. I presume your not seeing any evidence of insects chewing that would cause this.

    That leaves two other possibilities. What is happening weather wise? Are you having abnormally dry conditions? Could the plant literally be going into early dormancy to protect itself from drought?

    The other option is less pleasant because it means that the plant has some kind of blight. I’m not a horticulturist by training but again, these are usually brought on by some sort of environmental stresses. Unfortunately they are also usually incurable.

    So I hope it’s an early dormancy thing. I know I am seeing lots of trees here in Connecticut shedding leaves already because of dryness.

    Hope I reassured you somewhat. Good luck.

    Karla

    • sandra kean August 21, 2014 / 2:22 pm

      Hmmmm, might possibly lack of water. It has been very dry and i haven’t purposely watered the plants. I’m thinking to cut the hosta back to the ground and hope they come back next year.

      sandra

  9. gardendaze August 21, 2014 / 2:43 pm

    Sandra,
    Yes that sounds like a good idea. Once a leaf has yellowed, there’s no saving it. And you certainly don’t want to look at those sad looking plants from now until they would go into actual dormancy.

    A single summer like this isn’t going to do them much harm–hostas are tough. But next year, if you notice that we’re not getting 1″ of rain a week or so (that’s what established perennials like, generally) you might want to give them a bit of extra water.

    If, for whatever reason, you’ve got watering restrictions–or if you try to be conservation minded, which is great–there are still some things you can do. Consider installing a rain barrel. If you don’t want to do that, take some buckets with you into the shower. You’ll be surprised how fast they fill up. Then you can always use those to water the plants.

    Hope these tips help a bit.

    Karla

  10. Merrie Hupp July 31, 2016 / 5:21 pm

    Karla,
    Thank you for this information. I have found two of these worms on my petunia plant. (I bought it at Lowe’s as a hanging basket about a month ago and did not repot it.) I removed them both, but have a feeling there are more that I cannot see. They are so small and look exactly like the stem of the plant. Is there a home made insecticidal soap that you use or can you recommend a brand?
    Thanks,
    Merrie

    • gardendaze July 31, 2016 / 5:33 pm

      Hi Merrie,
      In a pinch, you can use a drop of liquid dishwahing detergent (the kind for hand wahing dishes) in a small spray bottle of water.
      I prefer Safer insecticidal soap, or another brand specifically made for plants. Lowe’s should sell one if you have time to run over there. I think Bayer makes one. It should be in a blue bottle. What you are looking for is the active ingredient of potassium salts of fatty acids.
      The reason I prefer something made for plants is not because I like to spend money, but because it’s less likely to damage the plants. Liquid dish soap isn’t made to be used on plants. It actually can wash away the protective coating on the leaves and then they can burn. So you can damage the plants–and the bugs are already doing that. No point in helping them.

      Hope that I have helped you. Good luck and thanks for reading and commenting.

      Karla

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