Early fall sleuthing

It won’t be too long now before gardens in south-central Connecticut get nipped by frost, and that will be the end of juicy tomatoes such as these Sweet Million cherry tomatoes soaking up any last season sun.

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When I went out to check this plant a couple of days ago I found a late and unwelcome visitor had taken residence.  The visitor left signs, so I knew what to look for, but new gardeners might not.

What first caught my eyes were a few small brown droppings scattered on the stone edging directly below the outreaching vines.

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Then I looked up at the vines above and noticed stems with no leaves.

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When you come across these two indicators look for a tomato hornworm happily munching away. They eat tomato, pepper, eggplant, and potato plants. Find one and you’re likely to find more. Here’s a close-up, but if you were really sharp you might have noticed him on the left side of the plant in the previous photo.

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Tomato hornworms can quickly defoliate plants and will also munch away at the plant’s fruit. Throughout the growing season you should keep a watchful eye for their droppings and the defoliated stems they leave behind. When spotted, take time to inspect the three inch long caterpillars before sending them to their demise. If you see tiny white oblong objects projecting from the back of a tomato hornworm it is already on its way out.  These white objects are cocoons of the braconid wasp. This wasp lays eggs on the back of hornworms. Once hatched, wasp larvae feed on the inside of the hornworm. Since braconid wasps are beneficial insects in the garden, it’s good to let them complete their life cycle on the back of the nasty caterpillar dining on your plants. Don’t worry much about parasitized hornworms feeding further … they won’t eat much once they become a braconid nursery.

If a hornworm has not been found by braconid wasps, then hand pick and drown them to prevent further damage. Just make sure to bring really sharp sleuthing eyes to this task … it can be difficult to spot the well disguised caterpillars.

A quick read of a tomato hornworm bulletin from the University of Rhode Island offers a peak at a parasitized hornworm plus more on the lifecycle of hornworms and the adult sphinx or hawk moths from whence they come.

The last act of my hornworm – it had no braconid wasp cocoons – was to serve a photo model for my favorite photographer … even a hungry caterpillar can have a stunning portrait.

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4 comments for “Early fall sleuthing

  1. September 29, 2010 at 6:25 pm

    My alternate method of disposal for the bugs and caterpillars: give them to my kids. They have a little bug cage that they stuff the poor, doomed critter into and shove in a bunch of things they think it would like. Then like clockwork, they check on its status about once a fortnight or so. Works like a charm.

    Christine in Alaska, no tomatoes, no hornworms

  2. joenesgarden
    September 29, 2010 at 9:27 pm

    Christine in Alaska ,
    I’d do the same if my kids were little enough. Alas, they are all adults. My granddaughter holds promise though … she just needs a couple more years of growth. No hornworms here anymore either.

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