Thursday, July 19, 2012

A caterpillar to watch for!

In a rather freakish lepidopteran coincidence (?), two of my co-workers brought me specimens of the above caterpillar yesterday. One of these colleagues resides in southern Franklin County, and one of the cats in the photo is her specimen. When she brought it in, the caterpillar was new to me - I had never seen one, and had no idea what it was. I did, however, know the plant that it was eating: wild blue indigo, Baptisia australis. Using the plant as a clue, it took nearly no time to pin a name on the mystery caterpillar. It is the larva of the genista broom moth, Uresiphita reversalis.

In what is either a remarkable coincidence or evidence of an expanding genista broom moth population, another co-worker waltzed in about an hour later with yet another of these caterpillars. He lives 40 or 50 miles north of the other caterpillar collector, in Morrow County. His caterpillar is the other specimen in the photo. After determining that my two colleagues weren't pranking me, I set about learning a bit about this moth and its larvae.

Photo: Wikimedia Commons, photographer unattributed

Several species of Baptisia, or indigos, are commonly sold and planted in gardens and yardscapes, including this wild blue indigo, Baptisia australis. In Ohio, it is primarily a species of gravelly river bottoms, and now is known but from one site in the wild and is listed as endangered. We've got two other native indigos in our flora: white false indigo, B. alba (white or creamy flowers), and yellow false indigo, B. tinctoria (yellow flowers). While both of these species are rather rare in the wild, they both are sold at least sparingly in the nursery trade. The genista broom moth caterpillar could turn up on any of them, as well as other pea family plants in the genera Genista, Lupinus, Sophora and perhaps others.

The caterpillar is quite striking and very distinctive. It's also easily noticed, as genista broom moth cats are active during the day, and highly gregarious, sometimes forming colonies of dozens of caterpillars. As they defoliate their host plant, the caterpillars lay down lots of filmy silk, creating a rather messy look sure to catch the eye of any gardener or casual observer.

I conferred with Dr. David Wagner about this species, and he tells me it does seem to be on the move and has turned up recently in new east coast sites (the species is principally a westerner). The caterpillars apparently can assimilate toxic alkaloids from their host plants and sequester them, thus they are chemically well protected. Thus, their daytime habits as most birds won't fool with them.

In spite of Internet maps showing dots in Ohio, there apparently is no validated record of genista broom moth for the state, or at least of larval infestations. This species may be an up and comer in our neck of the woods, and it bears watching for. If it increases and jumps from the garden Baptisias into the small, local and widely scattered native Baptisia stands, there could be trouble.

If you've seen this caterpillar, let me know, and ideally take a photo and send that too. The adult moths are rather plain and would be far more likely to go unnoticed than the conspicuous caterpillars.

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14 comments:

Vincent Lucas said...

Are you sure there are no records for this moth in Ohio? I think you should consult Eric Metzler about this as he would be the one to give you a definitive answer . . . .

Jim McCormac said...

Hi Vince, didn't check with Eric, but I did consult Dave Horn and he didn't know of it and his Ohio list of thousands of species doesn't include it.

It may be that adult moths have been trapped once or on occasion. It seems they are strong flyers capable of wandering. I'm really interested in larval colonies and possible reproduction in Ohio.

Jim McCormac said...

The following is a Facebook exchange with Brian Parsons of the Holden Arboretum near Cleveland (I had posted info about this caterpillar there as well):

Brian Parsons: Yes, the Genista Broom moth is having a banner year with outbreaks all over the greater Cleveland area. BugGuide.Net calls it a native species and what throws many people off is the use of the term Genista since it likes many other legumes. The ones most upset are the perennial gardeners who are having their Baptisia plants eaten. I have had a bout 5 samples brought to me over the past month. My guess is that the moth is moving with the perennial Baptisia 'Purple Smoke' as 2/3 of the reports I have seen are associated with that one cultivar. We have it in 3 spots at Holden and I recorded the sightings with Butterflies and Moths of North America.

Jim McCormac: Thanks, Brian! Have you known of this thing up that way for a while, or just in recent times? I'll be curious to see if there are other reports.

Brian Parsons: Hi - No , like you - just this year but I have seen larvae from Cuyahoga, Lake, and Geauga this month and several just this week. The are all over it seems and my reports are from perennial gardeners. The larvae are just totally defoliating some Baptisia plants this year. Larvae numbers could have been low in other years, but it is interesting that there are so many reports this year.Who knows - we had a super mild winter this year and those huge winds and warm temps in March that blew all the Red Admirals and Question Marks in may have blown in adult Moths that laid eggs that are only now munching away.

Jim McCormac said...

A few more Facebook comments from the group Mothing Ohio follow (Jim):

Kimberley McRitchie: Jim... I live in Port Clinton, Ohio (Bay Twp. Ottawa County) and discovered several (if not a dozen) of this very caterpillar on my Golden Chain Tree, 3 or 4 days ago. Since that time they have rendered the tree leafless and frankly dead looking, (hopefully not). I spent a great deal of time attempting to ID it through various moth/caterpillar web sites, with no luck. Thank you for posting this info, I now have a name for the culprit but not sure if I need to be concerned about my other trees, shrubs, garden, etc. Any additional tips/info would be most appreciated.

Ronnie Macko: Jim. I looked on my Baptisia and found at least 40 of these caterpillars. Where would you like me to send you a picture? (I believe this is northeast Ohio [Jim])

Anonymous said...

Jim,
I have 2 clumps of Baptisia australis (4ft tall x 3ft wide) at the CJ Brown Visitor Center in Springfield that had these caterpillars show up last year. There were 20 or so on each last year, but this year there are at least 60-70 and they have completely defoliated both clumps. These B. australis are about 100 yards from each other, and one is about 40 yards from a Baptisia leucophea that remains uninfested. A visitor from northern Montgomery County this week saw them and said her australis had been devastated by them too. When I saw them last year, I thought I had seen them before and remembered seeing a similar caterpillar eating Sky Blue Lupine in Hernando County FL, almost 10 years ago. I will dig through my slides and see if they are the same. Thanks for the ID.
Brian Menker

Jim McCormac said...

Thanks for the report, Brian. I've had a number of others since the comments above were made - there's no question that this species has exploded for whatever reason this season in Ohio.

Beth said...

I live in west central Wisconsin and found this caterpillar this year. Beth Shide

Bob Scott said...

I read this post, went out and looked at the Baptisia alba in my wildflower garden, and there they were! So you can add Vinton Co. to the distribution.

Bob Scott

Jim McCormac said...

Thanks for the additional records, Beth and Bob. I've probably got about 12 Ohio counties for this caterpillar now, plus reports from a few other midwestern states.

Anonymous said...

Hi Jim- I don't know if you will to remember me, but weyou met at floraquestthe and I'm on the board of the native plant society of northeastern ohio. Anyway, all 3 of my native batistias (false blue) are covered in these caterpillars. I live in south western geauga county. You can contact me for more info at shootingstarohio@gmail.com. by then i should have pics. - Tracey

Anonymous said...

Found these in GREAT abundance, feeding on my garden lupines, in southwestern VA.

Anonymous said...

I just found these caterpillars later this evening on my false lupine.
I was wondering is a pest thing I need to worry about or are they no harm? Do I need to pick them off my plant and get rid of them or leave them alone. Just wondering how to handle it.
Thanks.

Richard Wendt said...

Richard Wendt - Lincoln NE
Upon returning from a weeks vacation we noticed our blue indigo plant was dying. Upon closer inspection we found it covered with these caterpillars. We cut down the bush, bagged it and sprayed the contents with two kinds of bug spray. Raid seemed to work best. We also sprayed the ground around the bush to eliminate those that fell off. They didn't seem to bother anything other than the blue indigo.

Richard Wendt said...

Richard Wendt - Lincoln NE
Upon returning from a weeks vacation we noticed our blue indigo plant was dying. Upon closer inspection we found it covered with these caterpillars. We cut down the bush, bagged it and sprayed the contents with two kinds of bug spray. Raid seemed to work best. We also sprayed the ground around the bush to eliminate those that fell off. They didn't seem to bother anything other than the blue indigo.