Battle Against Tobacco / Tomato Hornworms

Well-camouflaged tobacco hornworm can be a garden menace!

Time to talk about the nasties. This bugger is a vicious defoliator, mostly attacking plants in the Solanaceae (nightshade) family – tomatoes, potatoes, eggplant, peppers, and of course, tobacco. The specimen above was first assumed to be the tomato hornworm, but a master gardener from Colorado State clarified the difference between the two caterpillars. They’re the larval stage of the “hawk”, “sphinx” or hummingbird moth – begrudgingly beautiful – but can wipe out your tomato plantation in no time.

These critters added to our tomato heirloom woes (notably “blossom drop” from the very high temps) just yesterday when Roy discovered them feasting on the leaves. In the evening, he applied Bt, Bacillus thuringiensis – an effective natural pesticide against caterpillars. In less than 48 hrs, we put on our “pattern identification lenses”, and picked about 20 of these nasty buggers. Picking them off the leaves is like pulling velcro apart, and they seem to fight back by bending backwards and grabbing you with their vicious little jaws. (Actually I don’t think they bite and people will handle them with bare hands … but these critters still gross me out!)

The Bt was effective almost overnight, but we still found a half dozen or so lively, fat beasties today.

Bt already took effect in less than 24 hrs. for some caterpillars

The happy ending to this story is that we get a whole lot of entertainment feeding these caterpillars to our chickens. The chooks will come to you eagerly, snatch the beasty from your hand, and fight over the gourmet meal. They were pretty subdued in the video, but you do see the Buff Orpi do an Olympic sprint well away from the competition!

A more informative video on tomato and tobacco hornworms to watch is from GardenForkTV.

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Addendum to Vegetable Garden Boxes

After our post on how we built our new vegetable garden beds/boxes, we invited our readers to send us pictures of their garden boxes. Here are a few of them. It is *amazing* to see how much can be grown in containers. We applaud you for your love of growing your own food, and the creativity and beauty that often comes out of this endeavor!

Here’s a box set up right on top of a lawn. What an excellent use of space!

Marigolds surround array of veggies - toms, cabbage, et al

Or how about a delightful collection of containers that can be moved around as needed? This is particularly important in areas where drastic changes in temperature may occur. Containers are also gopher-proof!

Wendy's delish greens in containers

Love these container-grown herbs!

We love this innovative “double decker” garden box with its varmit-proof roof!

@Badgerpendous' double decker veggie box

Varmit-proof garden box

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The netting is to prevent squirrels, racoons, cats, and the occasional chicken from digging into da goods!

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Here’s another garden w/ a funkily-dressed scarecrow in the center of the beds. And check out that awesome climbing bean trellis in the background, too:

@napaosak's veggie garden boxes - wow, look at those cabbages!

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Finding & Identifying Pests In Your Veggie Garden

Ahhh, summer!  You’ve probably harvested several lbs. or meals of your favorite tomatoes, lettuces, beans, potatoes, and those lovely cole crops – broccoli, cabbage, radishes, chard!  The garden even looks glorious basking in that August sun.  But wait, there’s warfare going on in this idyllic scene.  WAR, you say?

Oh yes, just because you can’t see it, it doesn’t mean it’s non-existent.  The soil-bearing fungi are whetting their appetite to get those sugars from the leaves or roots and decompose the plant, but even more obvious are those critters you DON’T but CAN see … ONCE YOU TURN OVER THE LEAVES!

Check what's going on under the leaves.

Yes, you’ve worked on the preparation, the maintenance, weeding, etc., but do not rest on your laurels as veg garden work is not complete till it reaches your mouth!  And that is what many new gardeners neglect:  touching the leaves, turning them over, trying to ID what critters are munching on THEIR dinner, and what they’re going to do about them.

Cabbage caterpillars (not loopers) devastating broccoli leaf; aphid on right.

So hear’s an example of Roy looking under the leaves of the Calypso bean plant.  Hm, not snails.  Probably a caterpillar.  He looks for the culprit.  Gets out a book (see below) for ID.  Reads prognosis and treatment.

Moves on to the next plant. Broccoli. Ewww, found the critters. Caterpillar stage chewing up the leaves. A sole aphid in the corner. Roy’s thinking, maybe BT will take care of that, insecticidal soap for aphid or lacewing treatment.

To help you ID and do something about these garden pests, here’s a suggested list of references for the veggie garden:

• Garden Insects of North America by Whitney Cranshaw
• Pests & Diseases: The Complete Guide to Preventing, Identifying, and Treating Plant Problems by DK American Horticultural Society
• Gardens Alive – One of better pest/disease references in their catalog.
• UCDavis Statewide Integrated Pest Management Program – Lists vegetables with common pests.  Includes photos.
• Cornell University Integrated Pest Management Program – Photos and detailed descriptions of pests
• Texas A&M Integrated Pest Management Program – Excellent vegetable insect management information

And if all fails, just send us a tweet with photo on Twitter and we’ll try to help you ID your pest!

P.S.  Roy’s solution to the cabbage caterpillars is smushing them and applying BT tonight before the infestation gets worse.

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Companion Planting, Part IV: Putting It All Together

This last section on companion planting (CP) sums up practical ways to cultivate a healthy garden with some “built-in” natural protection.

Intercropping vs. monoculture

By this time, you should be convinced that intercropping to create a diverse vegetable garden “habitat” is most effective to naturally protect your garden from pests, and can potentially enhance the yield of your favorite crops. Monoculture not only makes your valuable veggies more susceptible to pests in one season; sometimes, despite your efforts to work in rich, organic fertilizers, the same family of plants grown in the same area will fail in later seasons.

We learned this the hard way as we were initially concerned about having too many different veggies with too little yields.  As it turned out, yields started falling in later years as our broccoli became more susceptible to pests (BTW – brassica family, unlike tomato plants, generally like to be moved around).  So be daring, be bold, and experiment with different veggies – even those you think you’d never like!

Not a thriving veggie habitat

Intercropping creates a healthy, diverse garden habitat

Exploiting garden warfare

Your lovely spring garden or the woods near your home may look “serene”, but in truth, there’s constant warfare going on at a physical and chemical level.  So why not take advantage of it?

For instance, sunflowers may be great weed deterrents as they were found to be strongly allelopathic to weeds like wild mustard, jimsonweed and ragweed (Ref 1, p. 310).  Or what about selecting a “sacrificial plant or soldier” to protect the more valuable crops?  For instance, kale can be planted at borders of other more valuable cabbage family plants to draw pests away.  Or black nightshade can be used as a decoy plant to attract Colorado potato beetles away from your potato plants.  This may not be the best option for those of you with tiny gardens, but try to think of creative ways – even using containers which can easily be moved around – in deploying “soldiers” to protect your cash crops.

And while we’re on the subject of war, keep in mind that CP is not necessarily a mutually beneficial combination.  Some gardening experts believe that it is almost one-directional, though this can be difficult to ascertain.  For instance, you might consider that if carrots were planted next to peas or tomatoes (as our comparison of CP guides suggest), would yields from peas or tomatoes be greater at the expense of the carrots?

Using ornamentals to attract beneficials and help control pests

Many gardeners certainly deploy ornamentals like nasturtiums and marigolds to protect plants from pests like aphids, detrimental nematodes, white flies, and other pests.  But having herbs and flowering plants (esp. daisy and parsley families) also benefits the vegetable garden by attracting beneficial insects and birds that eat nasty bugs or pollinate plants.

We have had success growing tomatoes and beans with marigolds in containers, but have yet to attribute the yields/health of the plants to the marigolds. Some CP guides will suggest different varieties of marigolds for different pests (African, French and golden marigolds appear to be the best varieties).

Nasturtiums (whose flowers are a mildly peppery but delicious and attractive addition to your salad!) do have to be kept in check as they can take over an entire area, and are an incredible snail magnet on the West Coast.

Recording your own companion planting results

If you’re really intrigued by companion planting and want to put it to work for your garden, then record your observations.  Your best CP guide is your own gardening experience, though keeping in mind that results may not always be reproducible (see Part I).  A simple notebook or spreadsheet works perfectly well (of course, there’s Plangarden, too )  Some variables to keep in mind are the yield and planting distance in the control vs. experiment plots.  For the die-hard garden geeks, we refer to Anna Carr’s excellent book (Ref. 1, pp. 332-355) that offers experimental techniques.

Good luck and may the companion forces be with you!

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CP, Part III: Comparison of Companion Planting Guides

Avid gardeners like ourselves have sometimes been stumped by the conflicting information you’ll get from different gardening pros and horticulturists.  Sometimes they’ll even contradict themselves.  Or worse, you’ll set up a companion planting scheme and discover that the insect repellent properties of, e.g. garlic to repel red spider mites from tomatoes, was completely ineffective in your particular garden habitat.

So we created a survey of plant companions from four sources to ascertain which combinations they generally agree/disagree on, with the understanding that observing and documenting our own results is really what matters in the end … though may not always apply every season!

Click here for PDF version of summary tables. © 2009 Plangarden

A PDF of the tables appears on the right.  More details are in the slideshow below this post. 

Here are some useful terms often used in the context of CP: allelopathy and phytotoxins. Allelopathy (allelo- “one another”, and -pathy “disease or suffering” from Greek) refers to how plants find ways to stake out their territory, often by harming nearby neighbors.  They may release phytotoxins (phyto- meaning “pertaining to plants”) which essentially attempt to knock out nearby competitors.   Phytotoxins can sometimes also repel insects and other animals.  

Some notoriously allelopathic plants harmful to the vegetable garden (though may be great at deterring pests which we’ll discuss in Part IV) are the eucalyptus, black walnut, and absinthe wormwood.  Make sure you know what lies just outside your property line if you decide to grow vegetables in that area.

Limited research has gone into subsoil fungal activity and its respective role in companion plants.  Some speculate that both beneficial and harmful compounds may be transmitted through the mycelial network – though it’s impossible for everyday gardeners to ascertain “fungal contributions” to the companion plant ecosystem.

In the end, what we suggest is to “not get overwhelmed” on which combination of plants will produce the ideal garden.  Our “strategies” post offers a starting point in figuring out what to grow.  Perhaps the initial approach in using these tables would be to scan those combinations least likely to yield beneficial results (the red circles), and then move on to the good companion pairings.

Is owning a book on companion planting an absolute must for the gardener?  Personally, we feel that you can get sufficient information to jot down notes from library books or from the Web.  However, if you love to experiment and collect gardening books, then look through the book reviews on Amazon.

In our next post, we’ll cover companion planting as it relates to the contribution of flowers, herbs, and insects to your overall vegetable garden.

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