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.
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.