Creating a wildlife haven one plant at a time

Wednesday, September 19, 2012

Hibiscus are under attack!


Yikes, My beautiful hardy hibiscus are under attack!


The beautiful dinner plate size blooms are no more and the leaves are being eaten down to the veins.
This looks like damage from an insect with chewing mouth parts, but which one?


Upon closer inspection, there are loads of caterpillars happily eating away at the Blue River and Swamp Hibiscus. Hmmm...I wasn't aware that the hibiscus was a host plant for any butterfly or moth larva. Since this is my first time growing hibiscus I'd better figure this out. So off to my resource books I go to research...


Well, it turns out that these caterpillars won't turn into butterflies or moths. These caterpillar-like larvae are from the hibiscus sawfly, a plant feeding wasp. And I am hosting a party for hundreds! They feed on hibiscus, rose of sharon, hollyhock and mallow. My book Garden Insects of North America (The Ultimate Guide to Backyard Bugs) by Whitney Cranshaw (by the way, this is a very comprehensive book with lots of photos) says that these larvae can defoliate a plant in a very short period of time. No kidding! Look at my poor hibiscus, it certainly isn't the life of the party anymore!


Hand picking all these caterpillars off the leaves is a daunting task but if I am to save the plant the tedious work must begin quickly otherwise this plant will be at even more risk. After hand picking I sprayed the leaves with a soapy mixture to kill any larvae that I missed. The book tell me that sawflies can produce up to six generations in one season (May-October) so the infected plant will need to be sprayed multiple times.

Are these their egg sacks? This must be removed immediately!


There is a little new growth so I am hopefully that this plant will survive.


Has anyone else experienced an infestation of sawflies? What did you do and what where your results?

40 comments:

  1. That is awful. I can't even imagine having to pick all those off there. Hopefully next year won't be a problem with them.

    Cher Sunray Gardens

    ReplyDelete
    Replies
    1. It did take some time to pick them off and they hung on pretty well but hopefully I got them all.

      Delete
  2. That is a lot of damage! I never saw that up here and I have two hibiscus and my neighbor has four Rose of Sharon. None are ever affected by insect damage. It is probably the hibiscus variety though. You grow the tender ones and we can not.

    ReplyDelete
    Replies
    1. My two hibiscus are hardy, not tropical. I am not sure what the range of the hibiscus sawfly is, but I read an article from the Connecticut research station so I assume it does go further north but maybe not so common. Apparently the sawfly is related to bees and wasps and not so much flies.

      Delete
  3. I live in Michigan and nothing has eaten my Rose of Sharon. I like your approach to killing the insects and thank you for the book recommendation.

    ReplyDelete
    Replies
    1. I highly recommend this book. It describes more than 1,400 species and includes lots of pictures which I find really helpful!

      Delete
  4. I applaud your approach to controlling these guys, hard as it must be not to reach for the spray as you see your plants being skeletonized.

    Based on my experience, though, carefully check out any eggs you see before removing them. It could be that those eggs have been laid by a predator species that looks upon the sawfly larvae as a great food source for its young. When I looked up the hibiscus sawfly (which was new to me), the sources said that they insert their eggs INTO the leaves, near the tip or the leaf margins, so I'm pretty sure that the eggs you picture aren't sawfly eggs. (I have no idea what they are, though.)

    I've noticed lacewing eggs, for example, halfway through washing aphids off milkweed (oops!). Later research taught me that milkweed aphids are species specific to milkweeds and weren't going to spread to the rest of my garden plants anyway. Live and learn!

    Good luck!

    ReplyDelete
    Replies
    1. I think you are right. I will have to wait and see who those eggs belong to. As much as I dislike that my plant is being obliterated the learning opportunity is welcomed. These sort of situations is how I learn more and more about the insect world. As much as I support wildlife sometimes human intervention needs to take place so that I don't loose all my plants. I do hope those eggs belong to someone beneficial :)

      Delete
  5. We have a few hibiscus trees in our garden but I have never seen them suffer like yours. :(

    ReplyDelete
  6. Karin,

    I had the same problem about 8-9 years back lost all of my plants, white, pink and red blooming dinner plates. Best of luck on these pests.

    ReplyDelete
    Replies
    1. That doesn't sound so encouraging...I did read that if you don't get them under control it is easy to loose the plant entirely. Thanks Randy for sharing your experience.

      Delete
  7. Ouch! Those are some hungry little worms! I haven't had that problem - yet - but it's good to know about! Good luck!

    ReplyDelete
  8. Mine looked like that earlier this year. Lacey leaves. They have come back nicely ....will have to check to see if there are any more caterpillars on it again.

    ReplyDelete
    Replies
    1. Janet, did you do anything to control them or did your plant just survive and come back? I've never had such an infestation of pests on any plant like this before.

      Delete
  9. Oh, I'm sorry--mine looks exactly the same. Plus, I just won a hardy hibiscus, haven't planted it yet--and within two days, the leaves are reduced to lace! I must admit--I've been working on the kitchen gardens and ignoring the ornamentals, so it's my own fault. Must take care of this ASAP--I had no idea how prolific those pests are! Good luck!

    ReplyDelete
    Replies
    1. Julie, I should have noticed this earlier too. I was preoccupied with other things too (so easy to do with out busy schedules)! I hope your hibiscus survive!

      Delete
  10. Hmm, I wonder if horticultural oil like dormant oil or neem oil might work without being too toxic.

    ReplyDelete
    Replies
    1. Yes, I think they would! Just have to be careful not to spray blooms but since I don't have any right now because the plant is so stressed it should be easy to do. Thanks for the suggestions!

      Delete
  11. Yikes! I just planted some hibiscus this year, but so far they are doing well. I am going to look at them to see if I see any signs of this sawfly. I hope your plants survive the trauma.

    ReplyDelete
  12. My native hibiscus are usually attacked by Japanese beetles but I have never had these critters...it is the delicate balance of nature and gardening...looks like you may have saved the plant.

    ReplyDelete
    Replies
    1. I hope so! It is hanging on but I think I will know better next year.

      Delete
  13. Oh no. I thought the main pests Hibiscus had were Japanese beetles.
    There's always something!

    ReplyDelete
    Replies
    1. Isn't that the truth! Some plants just can't win!

      Delete
  14. I've never had those bugs. At first I thought you had Japanese beetles, too. Hand picking bugs can be gross but it's so much better than a pesticide. It sounds like there are some good bugs that should be eating these critters that are falling behind on the job.

    ReplyDelete
    Replies
    1. I agree. I have searched in my books and on the internet and have been unable to come up with their predator. In this case human intervention was necessary. The Japanese beetles were not as bad this year in my garden (knock on wood).

      Delete
  15. Wow, I've never had those bugs. Although I've never grown Hibiscus either...even though I LOVE them!!! I do have Hollyhocks, though, and they do have bug problems--mostly from Japanese beetles. Darn pests! BTW, I posted about your "Lessons Learned" this weekend. Thanks!

    ReplyDelete
    Replies
    1. It is a love/hate relationship! I like to leave it up to the beneficial insects to take care of any pests that are in the garden but when you get an outbreak like this some human intervention is necessary otherwise, the plant will die. Always a fine balance :)

      Delete
  16. Oh no..I hope it does survive...Michelle

    ReplyDelete
    Replies
    1. Me too. The Blue River hibiscus was attacked more than the swamp hibiscus and it is hanging on. I hope it will survive. Sometimes it is hard to tell until the next year.

      Delete
  17. I had no clue this could happen...I have just been driving by and enjoying my neighbor's three huge hibiscus plants all summer. His plants apparently escaped this plague. Glad you found out what it was.

    ReplyDelete
    Replies
    1. Hibiscus are really impressive and such tropical looking blooms. I love them in the summer. If your neighbor's plants are ever attacked you will be able to advise him :)

      Delete
  18. We'll be back in the warm south in a few weeks (Jack Frost is already nipping at our plants up north). Will have to check to see if we have these when we get down south - thanks for the heads up - hope yours recover.

    ReplyDelete
  19. Good Morning, Karin

    How awful for your poor hydrangeas and the extra work for you. I have a few, but nothing bothers them here. I wish that held true for all of my other plants.

    -Karen

    ReplyDelete
  20. Hi Karen, just wanted you to know that I nominated your blog for the beautiful blogger award. This is one of those awards bloggers give each other for mutual recognition and promotion. There's a little homework involved, see my site for details. If you'd rather not bother, it's no problem. I do enjoy your blog - the photography is outstanding.

    ReplyDelete
  21. I Live in Pennsylvania and I have the hardy Hibiscus with huge flowers.
    I had 4 plants each was about 3 ft across with gorgeous flowers.
    Long story short, I went on vacation for 1 week, when I got home I actually thought someone stole the plants there were sticks sticking out the ground and just the veins hanging of the branches I almost cried.
    Someone told me the sawfly would lay the eggs and then come the worms that would eat a plant in 2 days.
    However, next year I was like a shark as soon as I saw the saw flies I would spray down the plants with soapy water. It helps a lot.
    Every morning and evening I would pick off all the worms if there is any.
    A task of course but I save my beautiful flowers.

    ReplyDelete
  22. This comment has been removed by the author.

    ReplyDelete
  23. Thanks so much for posting this. One of my Hibiscus plants just got infested with very similar caterpillar / larvae. In addition, there were a lot of tiny webs on the new leaves, so at first, I thought it was spider mites. However, when I opened up the leaves, which had been pulled together by the webbing, I found the pests resting there in their self-made shelter, one caterpillar inside each webbed leaf. The pests were about two centimeters long and looked just like yours pictured, except without the yellow underbelly. Did you have any success with your pest removal efforts, Karin? Did your pests also make webs?

    ReplyDelete
    Replies
    1. The sawfly larvae hatch out of the eggs and then begin eating. Often, especially when smaller they hide on the underside of the leaves. I've never known them to make webbing. I suspect you either have two different things going on or the larvae you are seeing is something different than what I found. I have sprayed the larvae with a horticultural oil and a homemade spray. Both were effective since the larvae have very soft tissue and absorb the spray. The past two years I have found the larvae but fewer of them and I just let them be so that they would be food for birds or other prey. My hibiscus leaves looked ragged for a while but in a few weeks after the larvae finished hosting on the plant they grew new leaves and looked fabulous. The larvae won't harm the plant however it may be unsightly for some gardeners.

      Delete
  24. This comment has been removed by the author.

    ReplyDelete
  25. Thanks, Karin. I'm so glad your plants survived. I did some more research and have learned that my caterpillars are not sawfly larvae because they don't have the rows of tiny black dots on their backs. I have observed them making the webs that they use to pull the tips of leaves around themselves, like a taco, to hide in. So far, I'm just removing the pests daily by hand. Hopefully that will work.

    ReplyDelete

"Don't wait for someone to bring you flowers. Plant your own garden and decorate your soul"

Thanks for taking the time to leave a comment...I love hearing from you!