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Master gardener in training: Battling bugs

Caterpillar 1, bean plant 0.

In the UC Extension Master Gardener class, I've learned about the romance of seeds and seedlings, the chemistry of compost and mulch. Now it's time to face the less pleasant realities of the garden: pests -- more specifically, expert recommendations for fighting them off your vegetable crops.

Some bugs do more than eat my food. In the process they weaken the plant, making it susceptible to disease and environmental stress. The bugs aren't evil, just hungry.

Bugs2 Although pests can include vertebrates such as opossums, raccoons and gophers, in class our primary focus has been on insects, the good and the bad. Of the million species documented so far, fewer than 0.1% are considered pests. And by "insect," I'm only talking about bugs with six legs, three body parts and two antennae. Spiders and mites are arachnids. Pill bugs are crustaceans. Snails and slugs are in a weird little group of their own -- hermaphroditic, cannibalistic and living in a world defined by mucus.

Aphids, white fly, mealybugs and other pests move in gradually, almost invisibly. Most aphids are female and don’t need fertilization; put a meal in front of them and they become a baby factory, dropping eggs on the undersides of leaves and in buds. They excrete dew on the undersides of leaves, a sugary treat for ants that over time can become a petri dish for sooty mold. Psyllids do the same. A tomato horn worm, on the other hand, is not so subtle. It can reduce a healthy tomato plant to a stump overnight, starting at the top and chomping its way down. Caterpillars can be shockingly destructive because the irregular holes in the leaves are often blamed on snails and slugs, delaying proper diagnosis.

That's the first step: identifying the problem. How extensive is it? Then you should decide your threshold: How many aphids are too many? Pest and weed specialist Cheryl Wilen talked to my class about integrated pest management, an environmentally aware and holistic approach promoted by the UC Cooperative Extension. The IPM rules are flexible and friendly to organic gardeners: Set a threshold, identify and monitor pests, prevent if possible, and as a last resort, control.

Identifying your problem is tricky. Here are questions to consider:

Is the source of the problem biotic, caused by something alive? Or abiotic, caused by weather, site location, lack of minerals or poor gardening (usually over-watering)? Is the culprit pest or disease?

Bugs3 Inspect leaves for bugs and check roots for grubs or nematodes. Pests will typically go for the youngest, most succulent new leaves and shoots, so look there first.

If you're battling a bug, which bug? One of the best resources for identification is "Insects of the Los Angeles Basin," available from the Natural History Museum of Los Angeles County. Spider mites will leave a webbing on the leaf. Thrips will hide in the buds. Piercer-suckers such as white fly may leave yellow leaves behind, a sign that dead cells no longer have the potential for photosynthesis. The roly-poly pill bug is good and bad -- indispensable to decomposition and building a healthy soil but also capable of gnawing through the stem of a vibrant pea shoot.

And before you deploy some kind of control, realize that by the time you notice a problem, the pest may already have departed for greener pastures. Get some hanging sticky traps -- not to stop an infestation but to diagnose. Inspect every plant -- leaves and roots -- you bring into the garden. After it goes into the ground, monitor. If you keep an alert eye, you’ll notice pests before they become an infestation.

If you have a garden service, ask workers to use your mower, if possible. Clean tools -- especially clippers -- with a diluted bleach solution (one part bleach to nine parts water) to avoid passing diseases. Keep your garden cleared of refuse where bugs hide, and water early so leaves and stems are dry at sunset. If you’re adding beneficial insects such as ladybugs and praying mantis, remember there’s a lag before you’ll see any effect.

-- Jeff Spurrier

Photos, from top: A caterpillar leaves a telltale pattern on young leaves; pill bugs can enrich soil but also eat tender seedlings; the potato bug, or Jerusalem cricket, looks daunting but rarely poses a threat of infestation. Credit: Ann Summa

RELATED: An early spring talk with bug expert James Hogue

California gardening: Get more advice and follow the scene via our Facebook page.

Comments () | Archives (14)

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I would love to hear some of the solutions you learned in class for dealing with pests. I discovered hornworms on my tomato plants and picked them off by hand, but would love to spray some non-toxic solution to help catch any I missed. Onion water, soapy water, peppermint extract? Thanks.

What about Earwigs? The wet newspaper idea did not wok, after two days we still had not captured any.

to Sarah, if you find more hornworms please consider placing them into a tray or shallow dish and putting it somewhere that the Jays might swoop down for a free meal. They seem to relish those things and you might feel good enough about "recycling" your garden pests for a good purpose in such a manner that all thoughts of spraying are gone.
I have chickens, they make quick work of the hornworms but their favorite meal is right up there in the photo - a big juicy Jerusalem Cricket. My husband nicknames those ugly things "Land Lobsters" because of how excited the chickens get when they see one put into their feeder. I wish I could figure out a way to get them to eat the earwigs that are so plentiful right now....

I work for Garlic Barrier, which is based in Glendale CA, and we have a 100% organic Garlic solution which can be diluted with water and sprayed on your garden to prevent pests. We've been around for 20 years, and offer a money-back guarantee if you aren't completely satisfied with the product. Check us out at www.garlicbarrier.com. Our product repels pests, but doesn't repel bees(beneficial insect) or ladybugs, and is safe for birds as well.

Why the photo of a Jerusalem cricket? Scary-looking as they are, I have never known them to be a pest.

I've found that for the the most part, if you keep your plants relatively healthy (right amount of sun and water), they do a pretty decent job fighting off pests themselves, with the help of some beneficial insects (ladybugs, lady lacewings) that already are in your garden. Occasionally hand picking off caterpillars, scales or the like takes care of most of the rest.

Any infestation that gets beyond this system is usually squirted with homemade, natural insecticidal soap!

I would like to here some solutions in regards to gnats (for houes plants). Ive done almost everything i cant think of...

The ONLY effective solution I have found for earwigs is Sluggo Plus, which unfortunately is not cheap. Placing out earwig bait (a concoction mixed up with molasses, recipes abound online) caught many of them but we have so many that even setting out new bait nightly did not stem the tide. I also tried getting up every night and going out to spray them with insecticidal soap, but like I said the only thing that has been largely effective is Sluggo Plus.

My chickens also adore eating hornworms and any other plump bugs we catch.

Diotomaceous earth works really well on insects.

Sal - those gnats in your houseplants are called fungus gnats and they are a pain! I've tried everything and the only thing that helped was to spray the soil with Bayer Advanced Dual Action Rose and Flower insect killer. It actually lists Fungus Gnats on the pests it controls and after trying everything natural and organic I gave up. Spray 1x a week for 3 weeks and they should be gone. Fungus gnats come in the soil and they will die when the soil is allowed to dry out - but will come right back when you start to water again.

To control ants I use corn meal. I just sprinkle it in the affected areas and within a day or so no more ants. Apparently they eat it and it expands and the ants explode. I especially use it around my fruit trees and veggie garden to keep pesticides from leaching into my veggies and fruits.

Orange guard uses oil from oranges and lemons and works great on flying insects as it removes their protective layer.

Home Depot carries an organic concentrate pest control that is sulphur and pyrethrins. Stinky but effective!

Thanks Jeff for the excellent article summarizing how IPM works. If any of your readers want more information, they can use the UC IPM website at www.ipm.ucdavis.edu. Choose "Home, gardens, landscapes, and turf" near the top under "How to manage pests."

Whoops - just found that one of your hyperlinks got the the UC IPM site.

Does anyone have ANY solution for squirrels, who pilfer and eat ALL of my fruit from 7 different fruit trees in my yard. , ,

Hey, Shawn. I bet others chime in with their solutions, but I wanted to pass along a tidbit from an L.A. Times article (http://articles.latimes.com/2005/apr/14/home/hm-deterrent14) and follow-up (http://articles.latimes.com/2005/apr/21/home/hm-letters21) by Tony Kienitz that we published back in 2005. (Ah, squirrels: a perennial problem.) Tony's suggestion: Give the squirrels something else to eat. He writes, in the only the way Tony writes: "I was studying the effects of black sunflower seed shells as a weed inhibitor, refilling a bird feeder (a.k.a. squirrel feeder) almost daily for weeks, when I noticed that the nectarine tree, usually plagued by squirrels, had fruited quite nicely. The tree had been netted, but the difference was feeding the pesky beasts. Seeds, peanuts, old Doritos or a wild rice pilaf with currants and pine nuts accompanied by a crisp Sauvignon Blanc will keep your squirrels happily fed and out of your fruit trees."


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