What is this eating my zinnias?!

Metairie, LA

I am a first-time gardener in New Orleans, and planted various wildflowers from seeds in late April.
Tiny caterpillars or larvae (less than an inch long) are chowing on my zinnias.
The larvae are skipping over other plants (cosmos, sunflower, etc) and destroying the zinnias, leaving a lacy skeletal plant in their wake...any suggestions of what these might be? The best I can find is they may be armyworms, but they don't really look like any photos I can find of armyworms.
I don't want to kill them if they will become butterflies...but I don't want them to kill off the plants I planted for the pollinators!
Also, if I should knock ‘em off, what is the best thing to use that won't harm beneficial bugs?
The forum isn't allowing me to attach photos for some reason, so if you'd like to see the photos of the larvae and their damage, please email my username at yahoo dot com.
Thanks in advance!!

Metairie, LA

Kept trying...here are some photos. I have more if needed!

Thumbnail by sea_change Thumbnail by sea_change Thumbnail by sea_change Thumbnail by sea_change Thumbnail by sea_change
Northern California, CA(Zone 9b)

It took me a bit, but I think I found your culprit and sadly no pretty butterflies! Plus it is a really bad world wide crop pest. I went a bit overboard.

Here is an easy read on your problem and you can skip the rest. LOL.
https://homeguides.sfgate.com/problems-caterpillars-zinnias-71216.html

I wanted to make sure it was not a sawfly larvae which I just recently learned about on here.

I found many separate websites with photos so similar it must be true!
Spodoptera eridania – Southern Armyworm Moth

Here a site with a photo of Spodoptera eridania actually on a zinnia leaf!
https://bugguide.net/node/view/658147/bgimage
https://bugguide.net/node/view/188654
Another
http://mothphotographersgroup.msstate.edu/species.php?hodges=9672
https://www.discoverlife.org/mp/20p?see=I_MPG33024&res=640


I would try Bacillus thuringiensis, Bt. It is not a poison so safe to use. The caterpillars have to eat the sprayed leaves to be effective.
https://wimastergardener.org/article/bacillus-thuringiensis-bt/
Though I am not positive now that it would be totally effective after reading (or tried to read) several scientific papers only, like https://www.sciencedirect.com/science/article/pii/S0022201112002790
But it would not hurt to try it.

I found this page which laudes the use of neem oil. I thought neem acted by smothering but evidently it also can interrupt the feeding.
"Neem-based insecticide
A lot of research has been done on neem-based insecticides. There has been growing interest in the agricultural sector in using plant and botanical insecticides as alternatives to restore a biologically base equilibrium in insect populations. Neem has been shown to be a feeding deterrent for insects. The primary active ingredient in neem is azadirachtin, a steroid-like tetranortriterpenoid, that exhibits a wide range of bioactivity to hundreds of phytophagous insect species from different orders. There has been shown evidence that neem based products interfere with the regulation of feeding and metabolism as well as with anatomy and function of midgut tissues.[5] Neem-based formulations of pesticides reduced the amount of food ingest by S. eridania larvae. The growth that is disrupted by neem is determined not only by feeding inhibition but also by digestibility, as the S. eridania larvae showed reduced efficiency in converting ingested food. These setbacks in growth and food ingestion and digestion extend the development time of larvae. Neem-based pesticides are exceptional in having broad range of bioactivity against herbivores that include toxicity, growth regulation, repellency, feeding deterrency, and disruption of metamorphosis.
Pure neem oil has been found to be the most effective antifeedants by the third instar. Pure neem oil and azatrol are most effective feeding deterrent for the second and fourth instars of southern armyworm. Although these products worked in laboratory experiences, it was found that the magnitude of the negative effect on the larval mortality and pupal ecdysis varied considerably among neem-derived insecticides tested.[6]"

You might just want to pull the effective plants ASAP and discard the troublemakers!

Northern California, CA(Zone 9b)

I just reread your post and see you thought of armyworms. Gee, had I read that carefully, I might not have had to look thru so many sawfly larvae photos then caterpillar ones. Shoot! LOL

Ottawa, KS(Zone 5b)

Hi Kell,

I agree with your recommendation of a Bt containing product against the armyworms. I would not recommend neem oil, because it contains Azadirachtin, and it is questionably safe. In fact, neem oil is outlawed in the UK. I think that prohibition now includes Canada.

https://webarchive.nationalarchives.gov.uk/20151023223913/http://www.pesticides.gov.uk/guidance/industries/pesticides/topics/pesticide-approvals/enforcement/products-containing-azadirachtin-also-known-as-neem-oil

ZM

Northern California, CA(Zone 9b)

Geez, I read your link page twice but can't see what Neem does to humans. It almost sounds like it has not been approved yet but is still under consideration.

I used to literally bath in it when I would spray my 10 feet mite infested brugs with it. I think they used to tout you could brush your teeth with it. It was the organic, safe approach to insect control. It never worked btw, LOL. Eventually I switched to incredibly expensive miticides and wore a space suit to spray them. Then 1 day, I said I am living in a toxic dump with 1000 brugs and stopped growing them en masse. What I discovered is if you do not have such a leafy abundance of mite food, they disappear. I also stopped force feeding the few brugs I kept thus reducing the lush constant new growth that was a mite calling card.

Amazon literally has 3 pages full of Neem/Azadirachtin insecticides for sale here.

I found this on Wikipedia "Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the LD50 in rats is > 3,540 mg/kg making it practically non-toxic)." https://en.wikipedia.org/wiki/Azadirachtin

Oh I just found this on E X T O X N E T Extension Toxicology Network: "Azadirachtin is registered in the United States as a general use pesticide with a toxicity classification of IV (relatively non-toxic)." Along with a page of how even after feeding it to rats daily for 80 days no ill effects. Not that this makes it safe for humans but seems nothing bad has been found. http://pmep.cce.cornell.edu/profiles/extoxnet/24d-captan/azadirachtin-ext.html

And then I read this page at the National Pesticide Information Center which makes it sound pretty benign for humans and exposed animals. And I was right, it is used in toothpaste! LOL "It has been used for hundreds of years to control pests and diseases. Components of neem oil can be found in many products today. These include toothpaste, cosmetics, soaps, and pet shampoos." http://npic.orst.edu/factsheets/neemgen.html

I did find this about bees, azadarichatin and England. "The issue came to light after a study released by the European Commission on Monday suggested that azadarichatin – which is commonly used elsewhere in Europe – was fatal to the majority of bumblebees exposed to it, even at concentrations far lower than those generally used by farmers." https://www.telegraph.co.uk/news/earth/environment/11679681/Soil-Association-approved-use-of-unauthorised-pesticide-on-organic-crops.html

I bet this is more than you ever wanted to know about it. LOL

Brookfield, WI

Quote from Kell :

I did find this about bees, azadarichatin and England. "The issue came to light after a study released by the European Commission on Monday suggested that azadarichatin – which is commonly used elsewhere in Europe – was fatal to the majority of bumblebees exposed to it, even at concentrations far lower than those generally used by farmers." https://www.telegraph.co.uk/news/earth/environment/11679681/Soil-Association-approved-use-of-unauthorised-pesticide-on-organic-crops.html


Ahhh, I bet this, and not potential toxicity to humans, is the reason behind any bans or restrictions in the U.K. If I remember correctly, they are pretty serious about their bees over there!

As for Sawfly larvae, which I agree these look like, I have had good luck with insecticidal soap. Depending on the type of larvae, you may need to retreat every few days for a bit. Two doses did all of the sawfly larvae on my roses this spring. The annoying thing is trying to make sure you spray every part of the plant, under leaves and above leaves. My thorny roses made doing that a big chore.

I caught the outbreak early, and after the first spray I used my fingers and a lint roller to carefully remove anything that looked like an egg. I also clipped the badly damaged leaves, especially if I was unsure about whether I hit them well enough with insecticidal soap. It has been one week since my last spray down. So far, so good!


This message was edited Jun 27, 2019 10:36 AM

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