Grape leaf skeletonizers can be a nuisance for grape growers, as they have a tendency to damage grape leaves, which in turn affects the overall health of the vine. These pests, particularly the larvae of the grape leaf skeletonizer moth, Harrisina americana, feed on the leaves, leaving only the veins intact.
There are several methods to control and prevent grape leaf skeletonizer infestations. One popular method involves the use of insecticides, particularly when dealing with larger grape growing operations. For small-scale gardeners and organic vineyards, natural predation and biological control methods can be explored.
While grape leaf skeletonizers may prefer some grape varieties over others, it is still crucial for grape growers to keep an eye out for any signs of infestation. By staying vigilant and applying the appropriate control methods, it’s possible to protect grapevines from these destructive pests and maintain a healthy, thriving crop.
Identifying Grape Leaf Skeletonizer
Life Cycle
The Grapeleaf Skeletonizer (Harrisina americana) belongs to the Lepidoptera order and Zygaenidae family. The life cycle starts with tiny white eggs laid by the adult moth. These eggs are found on the leaves of grapevines and hatch into larvae, which are yellow with transverse bands of black dots1. They grow into the adult moth form after going through several stages of development.
Symptoms and Damage
Skeletonization
Larvae of both Grapeleaf Skeletonizer and Western Grapeleaf Skeletonizer are known for their skeletonizing feeding habit on grape leaves. Some key differences between the two include:
- Grapeleaf Skeletonizer (Harrisina americana): Young larvae feed on leaf undersides, eating through some layers but not all, giving the leaf a skeletonized appearance. As they grow older, they eat completely through the leaves.
- Western Grapeleaf Skeletonizer (Harrisina metallica): They prefer to skeletonize the leaf tissue, leaving the large veins intact. Their feeding may lead to sun-damaged fruit and bunch rot.
Photo Examples and Damage Impact
Examples of the damage caused by Grapeleaf Skeletonizers can be seen in these photos. Heavy infestations can lead to:
- Complete defoliation
- Serious yield losses
- Damage to fruit
Prevention and Control
Effective control measures include:
- Use of biological control agents like Bacillus thuringiensis to target the larvae
- Hand-picking in smaller areas due to gregarious feeding habits
- Regular treatments for important grape pests to prevent skeletonizer problems
Prevention Strategies
Cultural Conditions
One way to keep grape leaf skeletonizer at bay is to maintain healthy grapevines and proper growing conditions. Some tips include:
- Plant grapevines in well-drained soil
- Choose a location with good sunlight exposure
- Take care to properly prune and train the vines
Maintaining a healthy grapevine is essential in preventing pest infestations. Additionally, consider planting resistant varieties such as Virginia Creeper or Muscadine grape, which are less prone to skeletonizer infestations.
Handpicking
- Handpicking is an organic method to control skeletonizers
- Check grapevines regularly for any signs of skeletonizer larvae
- Remove and destroy larvae manually
By handpicking the pests from the vines, you can help control the infestation without the use of chemicals. Handpicking is most effective when done regularly.
Organic Actions
Implementing integrated pest management (IPM) techniques is another approach to managing grape leaf skeletonizer populations. There are a few organic actions you can take:
- Introduce natural predators: Certain insects, such as parasitic wasps, feed on skeletonizer larvae. Encouraging these natural predators to inhabit your grapevines can help control populations.
- Use organic insecticides: Products like neem oil and insecticidal soap can help manage infestations without harming beneficial insects or the environment.
- Crop rotation: Rotating your grapevines with other crops can reduce the chances of pest populations becoming established in your garden.
| Method | Pros | Cons |
|---|---|---|
| Handpicking | Chemical-free, low-cost | Time-consuming, labor-intensive |
| Natural predators | Environmentally friendly, promotes biodiversity | May take time to establish |
| Organic insecticides | Less toxic, safer for beneficial insects | May require multiple applications |
By combining these prevention strategies, you can create a comprehensive plan to protect your grapevines from the grape leaf skeletonizer and maintain a healthy, productive vineyard.
Control Methods
Biological Pesticides
One effective way to control grape leaf skeletonizer is by using biological pesticides. A popular option is Bacillus thuringiensis (Bt), a naturally occurring bacterium that specifically targets caterpillars like the grape leaf skeletonizer. Bt poses minimal risk to beneficial insects, humans, and the environment.
Pros:
- Targets specific pests
- Environmentally friendly
- Safe for beneficial insects
Cons:
- May require multiple applications
- Not effective on non-caterpillar pests
Another biological pesticide option is the use of granulosis virus. This virus infects caterpillars, resulting in a viral infection that disrupts their feeding and eventually leads to their death. Like Bt, the granulosis virus has a low impact on non-target organisms.
Chemical Insecticides
If biological pesticides are not enough, chemical insecticides may also be used to control grape leaf skeletonizer infestations. Examples of chemical insecticides include methomyl and spinosad.
Methomyl:
- Broad-spectrum insecticide
- Highly toxic to insects
Spinosad:
- Targets caterpillars and other pests
- Derived from soil-dwelling bacteria
| Insecticide | Pros | Cons |
|---|---|---|
| Methomyl | Broad-spectrum; highly toxic | Greater risk to beneficial insects, humans, and the environment |
| Spinosad | Targeted; relatively low-risk | Less effective on some pests |
When using chemical insecticides, it is crucial to follow all label instructions and precautions to minimize potential harm to humans, beneficial insects, and the environment. Consider integrating biological and chemical controls for a comprehensive approach to managing grape leaf skeletonizer populations.
Additional Considerations
Life Cycle of Skeletonizer
The life cycle of the grapeleaf skeletonizer (Harrisina metallica) consists of four stages: egg, larva, pupa, and adult moth1. Moth species like Harrisina metallica have multiple generations per year2. Some key points about their life cycle are:
- Eggs are lemon yellow and laid in clusters on lower leaf surfaces3.
- Larvae feed on grape leaves, skeletonizing the leaf tissues1.
- Pupa stage occurs before adult moths emerge2.
Effects on Other Plants
Grapeleaf skeletonizer larvae mainly affect grapevines (Vitis spp.)4. However, other plants may also suffer from similar defoliation problems caused by insect pests. For example:
- Roses can be affected by the Japanese beetle5.
- Other plant species might experience damage from different moth larvae species6.
Here’s a comparison table of these pests:
| Pests | Main Target | Symptoms |
|---|---|---|
| Grapeleaf skeletonizer | Grapevines (Vitis spp.) | Skeletonized leaves, defoliation |
| Japanese beetle | Roses (and more) | Skeletonized leaves, defoliation5 |
| Other moth larvae species | Multiple plants | Varying levels of damage6 |
It’s important to understand the life cycle of a grape leaf skeletonizer and its effects on other plants when planning to control them. Being aware of the various insect pests in your plant will help you implement the most suitable treatment methods.
Footnotes
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Grape Leaf Skeletonizer
little worms on grapevine
I think you guys are great. I would love to know what these little worms are. They really don’t seem to move, but I’ve found evidence that they’ve been around. Where did they come from and do they need to be destroyed or do they turn into something good? I found them on my grapevine. Thanks,
Lois Cain
Lois
These caterpillars are Grape Leaf Skeletonizers, Harrisina metallica. The caterpillars are a major defoliator on grape vines.
Letter 2 – Mystery from Thailand: Leaf Skeletonizer Caterpillar
The truth is out there – 07.05.10
May 6, 2010
Hi Daniel,
Greetings once again from sunny Phuket.
How are you ?
Some staff of mine have run into this curious little oddity and asked me if I could assist in identifying it.
To me it’s clearly alien – possibly from alpha centuri or the crab-stick nebula. Its no surprise that a week after Stephen Hawkins informs us that aliens are amongst us that we find him (her, it or them).
What do you think ?
With kind regards,
Mark.
Hi Again Mark,
How is the Atlas Moth population doing? We presume this is a caterpillar, but that is just a guess. It surely is a strange looking creature. We haven’t the time to research this at the moment, but we hope our readership will kick in and assist.
Dear Daniel,
Thanks for your quick reply.
Atlas moths have been quiet of late – lets see if they come by later in the year.
Have had a few snake cases recently. One was a Bungarus Kraits which I had to encourage gently with a house broom into a bucket before throwing her over the wall. Give me caterpillars any day !! Also one case of a 2.5 metre King Cobra that was dispatched with a single shot by one of our Security Supervisors using a home made catapult and glass marble – one shot, one metre away straight in the centre of his head. Turns out he used to be Thai Special Forces. Not my preferred method but the on-site team had to act fast as we have families and kids present.
Fingers crossed your readers will be able to assist.
With kind regards,
Mark.
Karl provides a Family
May 20, 2010
Hi Daniel and Mark:
Judging by the number of people who liked this post there seems to be considerable interest in this strange and lovely creature, so it would be a shame if it goes unidentified. I have to believe that it is a slug caterpillar, a moth in the family Limacodidae. The slug-like appearance and the fact that the head is invisibly tucked under the first thoracic segment are characteristic of Limacodid caterpillars. It’s one of my favorite insect families because of the amazing and beautiful diversity of their caterpillars, but also because of their nasty reputation for inflicting painful and sometimes dangerous stings when touched. Not all are dangerous but certainly many are (the danger is in the small stinging hairs on their bodies). In Asia they are often referred to as Nettle Grubs. It is a very large and globally distributed family, but unfortunately they are often difficult to identify because of the general lack of information, particularly in the case of tropical species. The “Thailand Nature Explorer” site (Siamensis.org) has posted a nearly identical photo of a Phuket caterpillar (scroll down to Answer #14) that is tagged as a Limacodidae (Answer #30). You can hit the ‘Translate’ button at the top of the page, or if you can read Thai you may get better information than I was able to get from the dubious translation. I wish I could have found a better answer but this one will probably require an expert. Regards. Karl
Hi Karl,
We had faith that you might eventually come through on this one. Mark may be able to get the locals to translate the Thai, or I may walk up the hill to talk to my neighbor about the information.
Correction: June 6, 2014
Thanks to a comment from Erwin, we now know that this is a Leaf Skeletonizer Moth Caterpillar.
Letter 3 – Grape Leaf Skeletonizer
I didn’t know where to begin to look on your site for this one. Not among your flies. Interesting black cloak with orange collar whe’s wearing. Recognize her ?
David
Hi David,
This is a Grape Leaf Skeletonizer, Harrisina americana, a moth. Caterpillars feed side by side, devouring an entire leaf before moving to the next leaf. They range over most of the Eastern U.S. This is a new species for our site.
Letter 4 – Grape Leaf Skeletonizer
This beautiful graceful looking ……?
Dear Bugman,
This beautiful graceful looking ……? was flying from bloom to bloom on the privet here in northeastern PA. The orange band around the neck reminds me of chenille, and the antenna of fringe. Please help with a name for it so I can learn more about it. Thank you for your help.
Denice
Hi Denise,
The Grape Leaf Skeletonizer, Harrisina americana, is one of the Smoky Moths in the family Zygaenidae. The caterpillars feed in groups on grape leaves, leaving only the veins, hence the common name.
Letter 5 – Grape Leaf Skeletonizer
Subject: Black Flying Insect
Location: West Texas, Lubbock County
July 28, 2014 9:16 am
Hello,
We have seen these very pretty black insects just this summer in our yard and have tried to use on-line searches to identify them, but to no avail. I would like to know whether or not they are harmless, as I have had one land on me several times. They seem to flutter around and also do not seem to be very stable in the wind. Thank you for your help!
Signature: A. Melugin
Dear A. Melugin,
We suspect you may have grapes growing nearby. This is one of the Grapeleaf Skeletonizers, a moth in the genus Harrisina. According to bugGuide, there are three species in Texas, and we can eliminate the Eastern Grapeleaf Skeletonizer as it has an orange collar behind the head. The other two species, Harrisina coracina and Harrisina metallica which is commonly called the Western Grapeleaf Skeletonizer, look quite similar. Caterpillars feed on the leaves of grapes, and according to BugGuide: “Larvae are a major defoliating pest of grapes – Vitis spp., and also feed on creeper – Parthenocissus spp. (Vitaceae).”
Thank you so much! We do not have grape vines, butI looked it up, and found they also feast on Virginia Creeper, which you mentioned and we have. When I went to inspect the plant, sure enough they have been eating the leaves! I really appreciate your help. Thanks again!
April
Letter 6 – Grapeleaf Skeletonizer
Subject: What’s this bug?
Location: East Texas
April 5, 2013 10:07 pm
I found this bug by my front porch.. Not sure what it is
Signature: Thanks, Erika
Hi Erika,
This is actually a moth, even though it resembles a wasp. It is a Grapeleaf Skeletonizer, Harrisina americana, or a closely related species in the same genus. According to BugGuide: “Larvae feed on grape foliage, and can be pests; may also feed on Redbud, Virginia Creeper.
Adults take nectar.”
Letter 7 – Grapeleaf Skeletonizer
Subject: Beautiful black bug
Geographic location of the bug: Illinois, USA
Date: 06/19/2021
Time: 10:07 PM EDT
Your letter to the bugman : This bug was on my car today and I found it sooo neat! I’ve never seen something like this before! It body from head to tail? Butt? Ending? Was about at inch at most. I didn’t get to see it fly but it almost looks like it has a second smaller set of wings under the large ones.
How you want your letter signed: Alicia
Dear Alicia,
This is a Grapeleaf Skeletonizer moth, and you may compare your individual to this image on BugGuide. According to BugGuide: “Found on flowers in fields, etc. Adults are diurnal and nocturnal, and come to light.”
Letter 8 – Grapeleaf Skeletonizer Caterpillar
Subject: Caterpillar
Geographic location of the bug: West Michigan
Date: 08/23/2019
Time: 05:43 PM EDT
Your letter to the bugman: Curious what kind of caterpillar this is.
How you want your letter signed: Sincerely The Crow
Dear The Crow,
Were you near a grape vine? This looks to us like a Grapeleaf Skeletonizer Caterpillar, which is pictured on BugGuide.
Letter 9 – Grapeleaf Skeletonizer Hatchlings
Whats this?
Hy, I am Don from Franklin, La, and I have a second year growth of Thompson White Seedless grape vines that have and still has this pocket of caterpillars, they start with a group of egg pockets cluster about the size of a quarter and grow to small caterpillars and eat away at the leaves, I sprayed with daconil and also use seven dust (which is better) than daconil. What is it and what is the best control? I also saw a leafhopper.
Don
Hi Don,
These are Grapeleaf Skeletonizers, Harrisina americana. The caterpillars will eat the leaves to the veins. We don’t provide extermination advice.
Letter 10 – Grapeleaf Skeletonizers
Subject: Grapeleaf Skeletonizer?
Location: coastal North Carolina
July 18, 2017 9:46 am
These small moths were feeding from mountain mint and rattlesnake master on July 15th. I suspect they are Harrisina americana, the grapeleaf skeletonizer, but a friend from the facebook group “Pollinators on Native Plants” suggested they might be the orange-collared scape moth, Cisseps fulvicollus. Since I do have a few grapevines in the yard, I suspected the former, and I don’t believe the latter species habitat range extends to this region. Thanks for any input.
Signature: Dave Hobbs
Dear Dave,
You and just about everyone in North America lives within the range of the Orange-Collared Scape Moth according to BugGuide data, however, we agree with you that these are Grapeleaf Skeletonizer Moths based on this and other BugGuide images. The BugGuide description is: “wings narrow, completely black, held spread out and away from body at rest; collar orange/red, complete (not broken, as in Clemen’s False Skeletonizer); tip of abdomen has prominent tufts of scales; antennae pectinate in both sexes, and plumose in male.”
Letter 11 – Leaf Skeletonizer Moth from Japan
Subject: Red-headed tiger moth (?)
Location: Tsuchiura City, Ibaraki Prefecture, Japan (about 60 km northwest of Tokyo)
July 6, 2012 4:17 am
Hello Bugman!
This moth came up to say good morning the other day. He landed on me as bold as can be and then flew off. He did stay put long enough for me to get a picture, though.
I always try to find a bug before I post to you, and usually I’m not successful. But this time I think I’ve got it! I guess this beautiful moth is some kind of tiger moth. From his wing shape and red head, I think he must be a ctenucha moth or a clymene moth. I think the ctenucha is most likely, but I couldn’t find any pictures on-line with the same markings as this one has. Can you confirm?
Thank you so much!
Signature: Melissa in Japan
Subject: red-headed moth submission classification
July 6, 2012 5:37 am
Hi Bugman!
I just uploaded a picture of a black-winged moth with a white stripe on its wings and a red head for an identification. A Facebook friend just identified it as ”zygaenidae chalcosiinae pidorus glaucopis‘.
Don’t know the common name, though.
Melissa in Japan
Signature: Melissa Noguchi
Subject: red-headed moth (last one I promise!)
July 6, 2012 6:11 am
Hi again,
We can’t find the common name in English for the moth I submitted, but apparently it’s called a ホタルが (hotaru-ga) in Japanese. A direct translation of the name would be the Firefly Moth.
Melissa (still in Japan)
Signature: Melissa Noguchi
Hi Melissa,
Thanks for all your emails regarding this lovely moth. We learned on BugGuide that the family Zygaenidae is commonly called the Leaf Skeletonizer Moths.
Letter 12 – Leaf Skeletonizing Moth from China: Histia flabellicornis
Subject: A black-winged pink-headed bug
Location: Jiangsu province, China
July 31, 2015 7:11 am
Hi, Could you help me identify the species/ name of this bug? thanks
Signature: a bug lover
Dear bug lover,
This request had us confused for a bit at first. Though it looks decidedly mothlike, the antennae had us believing this might be a Fishfly in the Subfamily Chauliodinae, which delayed our ability to quickly find an identification. Then we found a similar looking diurnal moth from China on FlickR that is identified as Cyclosia midamia in the family Zygaenidae and we resumed our search, eventually finding a side view of Histia flabellicornis on the Digest of Taiwan Lepidopterology page. A dorsal view on FlickR has us confident that your moth is indeed Histia flabellicornis, a Leaf Skeletonizing Moth in the family Zygaenidae. Insect Creations describes it as: “A wonderful and some what rare moth. The wing shape is very unique.”
Letter 13 – Mating Forester Moths from Israel
Lepidopteran love
April 12, 2010
Hi WTB,
Here’s a lovely couple of Zygaena graslini moths working on the next generation.
Ben
Eastern Samaria, Israel
Hi Ben,
Zygaena graslini is in the family Zygaenidae, which according to Wikipedia are called Forester Moths or Burnet Moths. In North America, the Grape Leaf Skeletonizer is in this family.
Letter 14 – Mating Grape Leaf Skeletonizers
Subject: Bug ID
Geographic location of the bug: Michigan
Date: 07/08/2019
Time: 10:20 AM EDT
Your letter to the bugman: I found these insects mating on a dutchman’s pipe leaf. They are black with an orange head – similar to love bugs found in the south; but wings look different and the antenae are longer.
How you want your letter signed: Anita Kittel
Dear Anita,
Have you any grape vines nearby? These are mating Grape Leaf Skeletonizer moths, and you can verify our identification on BugGuide. According to BugGuide: “Found on flowers in fields, etc. Adults are diurnal and nocturnal, and come to light.”
Reader Emails
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Mating Grapeleaf Skeletonizers
Subject: Love Bug look alike
Location: New Orleans, LA
August 20, 2015 8:03 am
I see these in my backyard a lot I know they aren’t love bugs because they’re antenna is long and thick and there wings are more opaque than translucent, I can’t find info on them anywhere
Signature: Amanda
Dear Amanda,
These mating Grapeleaf Skeletonizers are actually moths.
Thanks so much, Daniel. I have to say that I like the Japanese name better! On the other hand, you may have solved the riddle of who’s been eating my almond tree leaves!
Melissa
Thanks Melissa,
Leaf Skeletonizer Moths is just the common family name.
French or garden sorrel, with its long single leaves and reddish-green flowers (June
and July) is that which will be found cultivated but
grows wild also and will usually be juicier and with a little
less of an acidic kick than wood sorrel. It is a very nutritious recipe made of chickpeas and garlic.
On the first summer weekend in June alone the Kansas City Barbecue Society is
sponsoring no less than 16 BBQ competitions in California, Oklahoma,
Kansas, South Dakota, North Carolina, Illinois, Missouri, Wisconsin,
Tennessee, Maryland, Colorado, Minnesota, and even staid old Massachusetts.
French or garden sorrel, with its long single leaves and reddish-green flowers (June
and July) is that which will be found cultivated but
grows wild also and will usually be juicier and with a little
less of an acidic kick than wood sorrel. It is a very nutritious recipe made of chickpeas and garlic.
On the first summer weekend in June alone the Kansas City Barbecue Society is
sponsoring no less than 16 BBQ competitions in California, Oklahoma,
Kansas, South Dakota, North Carolina, Illinois, Missouri, Wisconsin,
Tennessee, Maryland, Colorado, Minnesota, and even staid old Massachusetts.
Hi there this is kind of of off topic but I was wanting to know if blogs use WYSIWYG editors or if you have to manually code with HTML. I’m starting a blog soon but have no coding knowledge so I wanted to get advice from someone with experience. Any help would be greatly appreciated!
Hi Daniel, this refers to a three years old post “Mystery from Thailand: Slug Moth Caterpillar” posted by Mark. I now know that this caterpillar belongs to Zygaenidae and is something like Callizygaena or very near. On facebook there exists a group called “caterpillars of Thailand” where an entomologist, Paradorn Dokchan, posted photos of a caterpillar which -except for color- looks exactly like Mark’s caterpillar. So it is clear that this is not the larva of a slug moth…:https://www.facebook.com/photo.php?fbid=10152458938483252&set=pcb.536052519836727&type=1
Kind regards, Erwin
Is the Grape Leaf Moth with the red/orange band on its neck, found in Arizona?
BugGuide reports the species as far west as New Mexico, but it could be in Arizona as well, just not reported.
I also see a catterpillar like this earlier when we were in the beach forest. I have photos and vidoes of it but i think i can’t post it here. Btw, I’m from Philippines.