To BT or not to BT...sigh

10 years ago

Our backyard has a very terrible cabbage worm problem. We have a whole geranium bush, as well as a couple of trees, and the whole section of nasturtiums that have become yellowed, spotted, holey and munched up by those critters, which tons and tons of tiny black specks left behind as evidence, not to mention actual little white moths fluttering about the garden and hanging out on leaves.

There are even holes in some of the large aeoniums' leaves.

I've tried to hand pick the worms out but there are just too many and I don't always see them. So I got some BT to combat these critters, but today when I was in the yard (I haven't used it yet) I saw an orange and black butterfly hanging out. This is not the first time I've seen them there, as I have seen at least a handful fluttering about and always pleased to see them. It's not a monarch, but I just know it's orange and black and not the pesky white moths.

So I am now loathe to use the BT, because even though it's a 20 to 1 problem, I really don't want to risk killing the orange and black butterflies.

Am I being silly? Or should I just take out the infested nasturtiums and call it a day? It just makes me not want to put any other plants out there knowing that they're all going to get ruined by the cabbage worms.

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Comments (6)

rhizo_1 (North AL) zone 7
10 years ago
I'm suspecting a case of incomplete or misidentification. Cabbage worms come from pretty white butterflies, not small white moths. Your nasturtium pests are likely cabbage worms of some kind....I'd get rid of those pest magnets in a flash.

The problems with the geranium and trees are likely unrelated. If you post pictures of the orange and black butterfly, we could take a shot at ID.
Kimmsr
10 years ago
There are three cabbage worms, the Imported Cabbageworm, Cabbage Looper, and the larva of the Diamondback Moth. The Imported Cabbageworm is a known pest of Nasturtiums and is one reason whyt they are grown as trap crops.
The Bacillus thuringiensis - Kurstaki dusts and sprays will, if applied at the right time in the life of the leaf eaters, kill them but it has limited affect on older larva. When applying BtK , as with any other pesticide, due care is necessary to the target pest is reached but none others, ie. spray the plants the pest is to be found on but not the plants that pest is not likely to eat.
Proper identification of the pest is also necessary.

Here is a link that might be useful: Cabbage pests
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ken_adrian Adrian MI cold Z5
10 years ago
crikey ...

CABBAGE worms do not eat TREES.. else they would be called TREE worms ...

if your nasturtiums are heavily infested.. GET RID OF THEM .. and be done with it.. its late OCT ... why go the bug kill route ...

if per chance your zone is so warm.. they last all winter.. of something else foreign to me... then cut them back HARD ... and remove the vast majority ...

NEVER treat anything.. in any manner.. chemical nor organic ... UNTIL you have a full and complete ID ... i suspect you are throwing around guesses.. and we might be reading such as gospel ...

provide pics... or take examples to a good nursery.. and get the ID ... then lets talk about remedy ....

bt.. if i am not mistaken.. kills nothing.... in the short term ... it can take a long time.. to take its course... but i WILL DEFER on that... its awful early to be thinking straight on a product that i dont use.. because .... i have no faith in it .... return it and get your money back ... IMHO ......

plagues come and go .. you may see none next year ... so dont go thinking you have to napalm the yard for NEXT YEAR ...

can we work on that ID for you ...

ken
a_shau
Original Author
10 years ago
Hi all, thanks for your responses. Here is a picture of a worm on one of the small trees out back. I think it's a citrus tree:

I have also found these worms on the Flowering Kwanzaa

as well as this unidentified potted tree:

I have hand-picked worms off *all* the trees mentioned above as well as the nasturtiums - the same worm. It is light green, about an inch long and not hairy. I have actually seen one that had grown really fat and was perhaps about 2 inches. Same exact worm, but just bigger. You can always tell where a worm will be because the leaf is completely curled up and when you open it up you see a bunch of silk and then the worm wriggling around inside. This is the condition of the geraniums:

I'll try to get a photo of both the white moths as well as the orange and black one if I see one.
a_shau
Original Author
10 years ago
Well, it looks like the nasturtiums also have a serious black aphid problems. Sigh. So I'm holding off on the BT for now.
Kimmsr
10 years ago
Nasturtiums are grown by many gardeners as a trap crop because they are so attractive to so many insect pests.
There are a number of moths and butterflies that produce larva that look kind of somewhat similar to the cabbage worms. Or is it there are a number of larva that look similar to the cabbage worms that produce different moths and butterflies?

This post was edited by kimmsr on Sat, Oct 12, 13 at 6:31