Shared information, patience, curiosity prevent a Gardening Oops

It’s the first of the month, the day I share a gardening mistake, oversight, or downright blunder, what I call a gardening oops, or GOOPs. I do this hoping to prevent other gardeners from making the same or similar GOOPs. My August 2012 GOOPs is about shared information, patience, and curiosity, three factors that recently merged to tweak how, after decades of gardening, I control hornworms in my Zone 6 Connecticut garden.

Like many, I  wait anxiously for tomato harvest time after nurturing tiny tomato plants from seed to maturity, and attentively monitoring for damage, disease and predators. This season my biggest tomato problem, so far, has been a voracious but fascinating creature, the hornworm.


There are two types of hornworms, tobacco hornworms (Manduca sexta) and tomato hornworms (Manduca quinquemaculata). Both cause similar damage, have like predators, and matching life-cycles. My hornworms, corralled onto one large tomato branch for a photo op, are of the tobacco variety. If left alone, each will eventually become a Carolina Sphinx moth.


See the hornworm hanging upside down in the middle of the photo? Their color disguises them well until a gardener notices is munched foliage … leaf stalks completely cleaned of foliage … or telltale hornworm droppings, such as these below. The larger the droppings, the larger the hornworm.


Once found, the first reaction is to remove these eating machines which is what I’ve done in the past, unless their back is covered by white, oval-shaped cocoons. These cocoons are likely of braconid wasps which lay eggs on hornworms so wasp larvae can feed on hornworm guts. The presence of cocoons,  like those below, means the hornworm won’t eat much more since it is, in fact, dinner to wasp larvae.

Hornworm With Cocoons 2 Thumb

My GOOPs was in removing and destroying all hornworms without visible cocoons. I would not have known this as a gardening oops without the information shared by fellow blogger and gardener Diane St. John.  Diane told how she captured a hornworm in a jar to watch for a few days and noticed that cocoons appeared where none were previously visible. I mimicked her process and, after three days of emptying the jar of caterpillar droppings and providing fresh tomato stems each day as food, cocoons appeared. I returned the parasitized hornworm to the outdoors so the cocoons can hatch into the garden.

Gardening affords constant opportunities for learning and, thanks to Diane’s willingness to share, and my curiosity in replicating her experience, I now know that removing all hornworms without visible cocoons may not be the best practice. To avoid my GOOPs don’t be too quick to destroy hornworms until you are sure they are not a nursery for the very insects that will help keep them under control. Also, I recall watching a fair number of Carolina Sphinx moths pollinating last summer’s flowers. Now I better understand the link between these moths and future hornworm damage. It’s all part of gardening thoughtfully … keeping your eyes, ears and mind open to new information to better work with nature, and learn a little along the way.

Care to share a GOOPs confession of your own? Just leave a comment below or a teaser comment that links to a GOOPs post on your own blog.

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6 comments for “Shared information, patience, curiosity prevent a Gardening Oops

  1. August 1, 2012 at 8:14 am

    Like many gardeners I have an eversion to bugs, but your post lets us know that getting intimate with them, watching and observing and studying, can really help. It takes the ick factor out when you understand what they are, and how they live and reproduce. Although that parasite on the hornworm is still completely icky….. : )

    My oops is on my blog today and it is about all the repeat mistakes I keep making over and over.

    • August 1, 2012 at 9:10 am

      I’m just the opposite, Laurrie. I’m fascinated by garden insects and their lifecycles. Snakes, however, have a huge ick factor.

  2. August 1, 2012 at 9:40 am

    Thanks Joene! I discovered this by accident and was fascinated by it as well. I would pick them all off but always saved a couple in a jar to feed and show other people when one morning they had the cocoons! Then on another hornworm I learned a new aspect of the lifecycle-this is kind of gross-we observed little “worms” coming out of the hornworm and THEN the cocoons are spun! This is when I earned the name “The Bug Lady” at work…. Nature is quite amazing! It is also amazing any of these hornworms make it to adulthood.

    • August 1, 2012 at 10:39 am

      Diane, I noticed the same on one of my watched hornworms. I’ve noticed cocoons more frequently on hornworms about 1-1 1/2 inch long. I have two such parasitized hornworm of this size on my tomatoes. I also returned my observed hornworm (also of this size) that developed cocoons back outside. The beneficials seem to be winning the hornworm war. I hope other beneficial insects will start attacking all the aphids.

  3. August 3, 2012 at 10:20 am

    Good information on fascinating insects, Joene. I just hope I don’t have to use it. Cheers.

    • August 4, 2012 at 10:15 am

      Lee, I think you are safe this year … all the area hornworms seem to be on my tomatoes and peppers. Picked off another biggie this morning.

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