what's happening to SP's new growth?

[Pachrian]

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.

[Pachrian]

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 

[roadrunner]

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

[Pachrian]

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.

[roadrunner]

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

dave

[Cindy]

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

[Pachrian]

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!

[Charlie]

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

[Pachrian]

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.

[roadrunner]

BT should take care of any newly hatching larva.

dave

[Charlie]

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

[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

[Pachrian]

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