Garden Friends and Foes – Part 2

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Good morning and welcome to this weeks installment of Garden Friends and Foes!

If you’ll remember, last time we talked about the flea beetle and the lady beetle. This week we’ll be discussing two insects that actually have a relationship to each other in the garden: the tomato hornworm (foe) and the braconid wasp (friend).

Let’s kick things off with the bad, shall we?

Hornworm

Chances are you’re going to see the damage these guys have done to your plants long before you notice what the problem is, as it camouflages really well since the color of it’s skin is the same color as the foliage on your plants. Because of this, it’s very easy to assume that it’s some kind of fungal or bacterial issue causing parts of your plant to fall off, but trust me, it isn’t. If you ever do see parts of the plant missing that didn’t turn yellow and brown first, search long and hard because you’ll find out what’s doing it and once you see it, you’ll be amazed at the size.

Identification

As previously mentioned, they are a very similar green to plant foliage. Once hatched, they start off fairly small, but they’ll grow in size very quickly to about 4 inches long and a half inch in diameter, and this is when they’ll do the real damage. The tomato and tobacco hornworms are very similar, but you’ll be able to differentiate by the amount of white stripes along the side of the body (8 tomato, 7 tobacco) and the style of the horn at it’s back end (tomato straight and black, tobacco curved and red).

A hornworm can easily wipe out an entire plant in one to two days, so while massive defoliation is typically the first indication that you have a hornworm problem, you may also notice their black droppings all over the ground beneath the plant.

Prevention + Treatment

Since hornworms are a fairly decent size and don’t usually infest like other insects, the easiest treatment is to hand pick them. Once you’ve pried their iron grip from your plants, you can either relocate them as they generally don’t find their way back, or you can drop them into soap water which will kill them fairly quick. If you’d like to take preventative measures to eliminate the issue before they even become worms, tilling in the fall will generally disrupt the overwintering pupae that are in the soil.

If you’re practicing no-till gardening or don’t mind using biological or chemical controls,  you can also use a bacterial insecticide such as Bacillus thuringiensis kurstaki or Sevin, but be aware that the latter will also likely effect the beneficial insects in your garden as well.

One last form of treatment is actually the perfect segue into mentioning this weeks garden friend.

Braconid Wasp

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Occasionally you’ll find a hornworm that is littered with small, ovular white eggs on it’s back. These are the eggs of the braconid wasp, which not only means that the host hornworm will soon meet it’s demise, but other hornworms in the area will be targeted and hunted down as well. This is the ultimate form of organic pest control because it’s simply the circle of life taking place.

Identification

The beautiful thing about the braconid wasp is that they don’t sting, which means that you don’t really need to identify the actual insect because there isn’t a bad thing about them. In the event you’re curious, they’re not too different in appearance than other wasps, usually dark bodied with four clear wings and generally reach no more than half an inch long. there are over 15,000 species, so it’s a little tough to identify unless you see one on top of a hornworm.

The other beautiful thing about braconid wasps is that they don’t just feed on hornworms. They go after aphids, caterpillars, squash bugs and stink bugs as well, so remember that if you see a hornworm with these eggs on it’s back, leave it alone. You’ll be happy you did.

Prevention + Treatment

None necessary! Leave them alone and not only enjoy the fruits of your labor, but the fruits protected by the braconids labor!

Be sure to stay tuned next week when we talk about the garden foe, the aphid, and it’s adversary, the aphid midge!

What is your experience with hornworms? Have you had the pleasure of finding braconid eggs on them?

 

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