Hidden Valley Hibiscus Forum

My Simple Pleasures is trying very hard to get bigger (it's in a 6" pot). Unfortunately something happens to the new growth as soon as it emerges. Is it insects or too much water? The poor plant is getting so bushy from losing all its tips and then trying to grow new branches, which is nice, but I'd just like the branches and leaves to grow.

Occasionally I see it on a few other plants too :(

I had this on my BonTemps shortly after I received it. It has corrected itself on my BonTemps. I think it is a fungus.

Uh-oh, fungus always sounds so bad to me. I'm glad it corrected itself for you, hopefully my problem will do the same.

I see a little of this from time to time and, like on Doll's Bon Temp, it goes away as mysteriously as it arrives.

You could try changing the conditions - mainly more sun or less sun or more or less wind - since a lot of micro-organisms (which I think are involved in this) have a narrow range of conditions that they flourish in.

Charlie

Thanks, Charlie. I put the pot in the afternoon sun, hopefully that does the trick.

I finally caught the evil-doer in the act. I've seen him around, usually after I pinch off the affected tips. I noticed that if I don't pinch down far enough the stem is hollowed out. Also, and I don't know if it is just from the dried up new growth, but it seems I find poop-like grains in the area.

So, here he is...all 5mm of it.

Btw, Charlie, one of the new plants I brought home from open house had a tip like this also. So you might want to look out for these guys too :( Hopefully we can id what it is and find a good spray.

Great pics. I've never seen any literature about stem borers in hibiscus.  I wonder what it is a larva of?  Can you get a side view pic showing the legs or have you already pulverized the little monster?  Wonder if it's an imported pest.

dave

Stem borer? Thank you so much, Dave, it's so much easier to google for it if you have something else besides larva and hibiscus.

Yup, you guessed it...I squished him. I found this picture with a bit of a side view though. Funny, in all shots I only see the front 3 pairs of legs, this shot shows them the best.

That's fascinating, although a little scary, too. I never saw anything like that. How did you happen to catch him in the act? Did you cut into the stems to look or?????

If I learn anything about this I will surely share it. In general, the standard and least toxic way to treat for caterpillars is to spray any product containing BT (Bacillus thuringiensis), a bacteria that only effects certain insects like caterpillars. I have no idea if this creature will be susceptible to it but hopefully it would. Spinosad might also work. However, if the creature lives inside the stems it might be protected from sprays. In that case Safari might get to it if it feeds on plant sap.

Uli, thanks for these great photos!

Charlie

Those are fantastic pictures, Uli!  Wow!  I just sent them off to an entomologist at UC Davis. Hopefully we'll be able to find out what they are.

Now I'm going to start inspecting every growing tip with a magnifying glass! Yikes!

Cindy

I agree, Charlie, it's a bit scary. My little bit of research has not come up with much other than that stem borers are not good and that researchers are still trying to find a way to get rid of them.

When I notice newly growing tips to change color I usually pinch them off. I noticed that often the remaining stem will be hollow and I pinch off a bit more. As I said earlier I have seen these larvae crawling around (my young plants are on a glass table which made it possible for me to spot the larvae that must have fallen off during pinching). When I inspected the pinched off tip today I noticed the little guy inside :(

Oh, and I should mention that the plant I brought home from open house which had the same  died off tip was a 4" Confection Perfection. So maybe you should keep an eye out where ever you had those and the 4" Simple Pleasures.

Cindy, I really hope this doesn't turn out to be a big problem...for you guys more so than me, of course. Keeping my fingers crossed this entomologist knows what it is and more importantly, what to do about it.

In the meantime I keep pinching...and creating some nice bushy bushes ;)

Well its obvious that everyone loves hibiscus :)

Uli, thanks for the additional info. As I mentioned earlier, I've seen unexplained die-off of the newest growing tips occasionally for years now. It's never been more than a few plants out of thousands which makes me think it is something like a moth that flies in, lays eggs on a single plant, and then dies. Larvae feed on whatever they hatch on and then build a cocoon and fly off as they emerge as moths. They don't spread from plant to plant and increase in numbers the way something like spider mites does. Also, I've not seen plant tip growth death progress into death of the host plant, instead we have seen the plant recover as mysteriously as the problem occurred. Our pesticide program creates an environment that is not hospitable to moths or other such insects sticking around. I've seen moths fall from the air dead when a spray of Conserve (for thrips usually) is directed at them.

Doing what you did seems the best answer. Pinch off the growth tip and a little of the stem to find the larvae and then dispose of it. Please keep us informed and with this new info I will watch out for anything resembling it in the greenhouse.

Charlie

I checked all the known scary insects for our area, and this larva is none of them at least. I'll keep searching, and we'll keep a close eye out for more of those little critters. I had a little outbreak of bigger green larvae a few years ago in my house too. They were on only 2 plants that were together in a window, and I have never seen them again. So I think Charlie is right that moths or other flying insects fly in, lay eggs, they hatch and fly away. In the greenhouse they won't be able to survive as flying insects to start a new life cycle. The best they can do is fly in from outside and lay eggs for one cycle. I was afraid that they might survive in my house where I don't really use a pest control program, but they just flew away and didn't come back. Hopefully you can cut all yours off, and never see them again, Uli! We'll inspect every plant in the greenhouse for more of them too!

A fun morning, if one is into insects, detective work and photography ;)

On my first quick walk around my cv's this morning I noticed an affected tip on Arabian Princess. Whatever this borer is, it gets around. I rubbed off the tip and saw that there was still a hole which means I have to pinch off more. The strange thing was that the hole was angled into the big top leaf.

I decided to have my coffee and breakfast first and think about whether I wanted to sacrifice the beautiful leaf. When I went back the hole was almost completely covered by these little pulp balls. So now I know there's definitely something still inside...the leaf will have to go. Trying to catch the larva in the act I blew off the balls and wait when suddenly...

...some slight movement catches my attention out of the corner of my eye (something I developed when I started nature photography). Sure enough there's a larva crawling on the new growth of my Saffron. UGH!!! As you can see in the pics the head is not quite as dark as the other one's, but close enough?

Back to AP: 2 new balls at the entrance to the tunnel. I will see what I can find inside once I'm done posting this.

Ok, I'm not going to post the pics I took because I accidentally sliced the little guy open when I cut the stem in half lengthwise and his guts were spilling out. Gross!

However, it was the same type as the one in the previous photos, the one I found on Saffron, and he had already drilled a 1" tunnel into the stem of the leaf.

I'm not liking this  :'(

Uli your third photo has a great side view of the larva showing the 3 pairs of thorasic legs, 4 pairs of prolegs, and one posterior proleg which is typical of lepidoptera larva (moths and butterflies) so Charlie is likely correct in that it is a moth larva. Hopefully that eliminates beetle, fly, wasp, and bee larva as possible culprits.  Lets hope the entomologist at UC Davis can come up with a specific identity.

I've yet to find any mention of stem boring larva as a pest of hibiscus anywhere in my online research.  I've found mention of caterpillars that feed on its foliage and even sawfly larva that are foliage feeders, but nothing about stem borers.   This is quite a mystery.

dave

Dave, the 3rd photo was for you :)

I agree, I think its some type of moth. The fact that I just chased one off of Saffron kind of supports that theory. Too bad I wasn't able to catch it, but I did get 2 more larvae. If the whole food chain is suddenly out of whack, blame me  ;)

Oh, I found mention of 'tip borers' and hibiscuses. Nothing detailed, but it's out there:
http://www.hibiscusworld.com/BeersBook/6-Pruning.htm (below the pruning pics, the paragraph starting with 'once'). There are others, though nothing helpful as far as I can tell.

Uli, thanks for the link.  It would be nice if one of these articles would provide some useful info about the tip borers.

dave

I just got email back from the UC Davis entomologists. Two of them tried to identify this larva, and then sent it on to a California pest expert. None of them had seen it before and said it it "something not common."

Charlie searched through all plants in the greenhouse yesterday trying to find more of them and couldn't find any more of them. But we'll keep looking.

Cindy

Oh sweet joy! Does that mean i can get a pest named after me...pestus ulii? Lol :)

Cindy, thank you so much for your help, and thank you to the UCD entomolofists as well. I will email you one of the gruesome photos with the larva inside the leaf stem so you can see the damage it can do.

I'm so glad you haven't found any trace of this in the GH. I'm keeping my fingers crossed it stays that way!

Pestus uli! That's funny.

I think what they need in order to ID it is to have a larvae in their possession that they can grow to an adult. Easier said than done, and I'm hoping you have seen the last of any live ones of these.

Charlie

They want a live one? and here I go stabbing them  ::)

Hmm, if they would like me to send them one (or more) I don't think there would be a problem on my end.

I went to Armstrong this morning and scared the guy there with my pics, but no solution other that "you could try this or that". He was leaning towards Ortho Tree and Shrub with something starting with M. At the price of that container I can hire somebody to sit and catch all moths flying around my cv's.

BT should take care of any newly hatching larva.

dave

Uli, how's it going with this problem now?

I have a few other questions about it if you don't mind.

You mentioned seeing moths or butterflies around the hibiscus. What color were they and how big?

Is the only obvious symptom dead tip growth until you cut into the stem?

Do you think you have eliminated all the larvae infested stems?

Did you find anything in the Confection Perfection that had a dead terminal growth tip?

Thanks,

Charlie

Dave, nice ID of the larvae. Moths we can deal with, said with a hopeful smile.

Uli, that book you linked to is the old Les Beers hibiscus book from Australia. Les is still around (I think) and I'm going to try to ask him about it or someone else in Australia for more details. I've never heard of this in the US but suppose it could be happening and no one noticed.

Charlie

You mentioned seeing moths or butterflies around the hibiscus. What color were they and how big?
Earlier this "summer" I had a lot of Gray Hairstreaks sitting on buds, which made me think they were the culprits of the "bud worms". I haven't noticed any in the past month though. The little moth that flew away the other day when I was larva hunting was about a cm in length, wings were folded in when it sat, and it was dark

Is the only obvious symptom dead tip growth until you cut into the stem?
dead tips and the crumbly stuff, which I now think is the pulp balls that the larvae throw out

Do you think you have eliminated all the larvae infested stems?
crossing my fingers, knocking on wood! I haven't seen anything abnormal since the other day when I killed 4 larvae

Did you find anything in the Confection Perfection that had a dead terminal growth tip?
no, but I didn't look for it either because at that point I still thought it was some kind of fungus. Unfortunately it did look identical, down to the crumbly stuff