On fighting pests with pests

16 May 2007

Got questions about the environment? Ask Umbra.

Dear Umbra,

I have a pest problem in my backyard -- specifically, some tiny (but apparently hungry) insect is making lace out of my basil leaves. I do not want to use pesticides for many reasons, not the least of which is that I cook with the herbs I grow.

I think I have found a "natural" solution, but I wanted to consult you first. My garden-supply store sells praying-mantis egg cases ("The natural pest control solution! Over 200 insects inside! Hang on a tree and eggs will hatch when temperatures stay above 70 degrees for three weeks!") The store also sells bags of dormant ladybugs for the same purpose. My question is: should I buy these bugs? Or will unleashing them just upset the natural balance and biodiversity of my rather small backyard?

Bugged,
Lindsay Ratcliffe
Helotes, Texas

Dearest Lindsay,

It's common to see these entrapped insects in garden stores now, and sustainable farmers often use beneficial insects for pest control, but they are not a cure-all. Before you do anything to deal with your basil perforator, you need to take the official First Step of natural pest control: positively identify the pest. Without knowing what is causing the holes, you can't take an effective step to stop it/them. Let's identify together, and then I'll get to your main question.

Pray tell, which way to the buffet?

Photo: iStockphoto

Usually I would use a pest and disease book I got at a used bookstore, from the Rodale Organic Gardening imprint, but today the internet will connect us all. Before looking it up in any book or computer, one should go out and look closely at the plant. One may actually see the pest in action. If not, note where the damage is happening -- on all leaves, on the oldest leaves, on the stem, etc. -- and hazard a guess as to whether it looks like an insect or a disease. Next, on to the internet. I'm entering "basil pests" first and getting several websites describing major pests of basil, which include aphids, slugs, Japanese beetles, white flies, grasshoppers, and flea beetles. Further limiting the search with "Texas" gets me to Texas Extension, and they only suggest Japanese beetles, then I'm on to "Japanese beetle damage" -- whoa. Ick. That's pretty dang lacy. You get the idea. After you have identified which pest is damaging your plant, find out what its predators are. If neither ladybugs nor praying mantises consider your pest to be dinner, part of your question is answered ("no").

As an aside: step two of natural pest control is to do a series of less-toxic interventions. These include habitat modification (killing the host plant, removing the places where pests nap, etc.), mechanical control (this includes squishing and picking off), barrier techniques (deer fence is an example), and less-toxic pest controls (this is where the ladybugs come in). Last resort would be the toxic interventions.

Ask Umbra continues below

ADVERTISING POLICY

Back to your question.

If ladybug or mantis dinner is in your garden, we have the larger question of whether buying insects and releasing them is worth the money, and your concern about destroying your yard. I don't think it's worth it. Mantises are general predators. Although they might eat your mystery pest, they might also eat the various unsung beneficial insects already in your yard (aka, destroy the yard, although destroy is too strong a word), and they might eat each other, completely defeating your primary purpose. Ladybugs eat aphids and a few other soft-bodied insects. The Asian multicolored ladybug is an introduced species that is displacing native ladybeetles -- you may have Asian lady beetles infesting your home. Here are some tips to avoid such a fate, and photos to help identify your own ladybugs. If you release ladybeetles, a few might land, eat, and breed, but it's likely that the bulk of them will fly away, and this is why I think ladybug sales are hokum. If you have aphids, any ladybeetles already in the vicinity will eventually come find them and eat them. I don't know how they find them, maybe smell.

A big part of pest control is creating a yard (and neighborhood) in which natural predators and beneficial insects such as spiders, beetles, and ladybeetles live and reproduce, adding to the yard's diversity. This won't mean you have no pests, alas, and when you find out what is eating your basil you'll still have to find out how to stop it. For your sake, I hope it isn't Japanese beetles.

Preyingly,
Umbra

Yours is to wonder why, hers is to answer (or try). Please send Umbra any nagging question pertaining to the environment -- but first check out her FAQs!

The claims made in this column may not reflect the views of this magazine. Neither the magazine nor the author guarantees that any advice contained in this column is wise or safe. Please use this column at your own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals Unit, floors 2B-4B.

Comments: (12 comments)

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Lady, bugged

Part of creating an environment that is diverse and naturally protective against pests is to build healthy soil. Many unseen natural pest controls exist in the soil. Most pest insects have a larval stage where they are more vulnerable to natural pest controls and frequently that stage occurs in the soil where those unseen critters can get at them. Also, healthy soil provides plants with the nutrients they need to be healthy and able to fend off pests.

Birds are great natural pest controls that eat insects so creating a bird-friendly habitat can also help. Use of toxic pesticides is a real turn-off for birds. Better than using pesticides to eradicate the problem is, as Umbra suggests, removal of the distressed plant - at least for this year. Work on building your soil and your environemnt and try basil again next year. Or try planting it in pots in another part of the yard. Or trading what you have growing well with someone else who has a good crop of basil.

I would also go for the praying mantises and ladybugs - they do help, they are fun to watch, and they change the habitat for the better since they do start to get established if you've created good conditions for them. They are also a strong incentive not to be tempted to use toxics cause once you have a resident population of mantises or ladybugs you won't want to spray.
Barbara

Barbara

by BMendenhall at 9:49 AM on 16 May 2007

no such thing as a pest

Build a healthy environment in your garden and you'll create a place where life of all sorts will want to be.

Our garden is full of life, and yes, it includes slugs, aphids, and earwigs and other critters that vendors of toxic chemicals love to portray as pests to extract millions of dollars from us that could be better spent on compost bins, bat boxes or backyard beehives. You do not need to expose yourself, your family, your neighbors, and the other equally important life forms that inhabit the planet to long-lived poisons that are unneccessary for a healthy garden.

Bugs of all sorts play an important role in achieving the type of balance that allows everything else to flourish. Do they occasionally nibble a tender shoot? Sure, but they also provide a food source for the other birds and insects that you want spending some time in your yard. Overtime, and as the balance of your yard improves (improved soil, variation in type, size, and density of plants, sources of water, places for insects to reside) you'll see a greater range of creatures taking up residence. And you'll see your garden with new eyes and find yourself thrilled that the basil has been munched, knowing that your actions have made a contribution to the health and well-being of your garden, your neighborhood, and the planet.

Tom Kelly

by kyotousa at 11:05 AM on 16 May 2007

organic pest management

I agree that a healthy ecosystem in the garden is desirable, but if you're raising fruits and veggies to eat, you may want find out how to SAFELY control the pests that want to eat them first.

I'm in Texas too (Austin), and I LOVE J Howard Garrett's "Texas Organic Vegetable Gardening." In addition to really helpful info about growing specific fruits and veggies, there is a chapter about organic pest control.

The book includes info on beneficial insects - ladybugs, ground beetles, fireflies, lacewings, nematodes, predatory mites, praying mantises, spiders, and wasps... some of these amy already be in your backyard! You can introduce others, but most will leave. Those that stay will work on keeping pests in check, but they'll never really be able to eliminate them.

SO - If you have a pest infestation (which it sounds like your basil plant has), you may want to use some kind of organic pesticide on the specific plant. Depending on the pest, there are several non-or-less-toxic solutions that you can apply to the plant. Molasses, citrus oil, diatomaceous earth, garlic-pepper tea, Bt, compost tea... which one you use totally depends on the pest, so as Umbra said, it's important to identify it correctly.

If you have trouble identifying your basil chomper online, you can put a few leaves and bugs in a sealed plastic sandwich bag, and take it to your county Cooperative Extension agent(s). He/she/they should have no problem identifying it, though they may counsel heavier-duty pesticide solutions. Just nod your thanks, and then go home and use something a little safer for you, your soil, your plants, and all of the little critters - good and bad - that enjoy your backyard too.

P.S. Bexar County's Extension Office can be found online here: http://bexar-tx.tamu.edu/

P.P.S. I have no connection with J Howard Garrett, I just really like his book. Promise.

by atlasgrrl at 11:46 AM on 16 May 2007

Patience is also a weapon against pests

One of the principles of natural pest control is that you have to have pests in order to have natural pest predators. So, paradoxical as it may seem, patience is often one of the most important weapons a gardener can use against pests.
Insect outbreaks follow a typical pattern: The population of pest insects skyrockets, which eventually attracts predators. Once the predators are assured of a reliable food supply, they breed, which produces a lot more predators. The pest outbreak then begins to subside as pest insects are gobbled up. But this process takes time. If it's disrupted (for instance, by an impatient gardener who decides to resort to pesticides), it may never happen at all.
Sometimes predators can't keep up with an insect outbreak, of course, which is why Umbra is quite right to say that it's best to know what you're dealing with. However, it's amazing how often patience pays off. Your friendly local predators will come to the rescue--but you have to give them a chance!
Incidentally, Umbra is also quite right to warn people off importing insects to the garden. If you provide good habitat and avoid using pesticides, most likely there are plenty of local predators, from lady beetles to wrens and other birds, that will be more than happy to control pest insects for you.

Wild Flora http://www.wildgardeners.blogspot.com

by Wild Flora at 12:24 PM on 16 May 2007

Be Careful with those Praying Mantis!

I work in the great state of Washington, and some of my job includes educating elementary schools about the fast fading prairie ecosystem. One of our projects?? Collecting those praying mantis egg cases and keeping them OUT of the prairie (they usually end up in school science labs for the kids to watch).
The Praying Mantis is an invasive species in our region, and is killing many of the bugs that are neccessary to a healthy praire. Make sure to do research, and keep them out of your region if they shouldn't be there! Invasives can do a lot of damage, especially if you are trying to restore landscapes!

by sernya at 1:19 PM on 16 May 2007

I remember selling lady bugs and praying manti

I always discouraged customers at the garden center where I worked away from buying lady bugs or praying mantis eggs when I worked in a garden center, not for any environmental reasons, but mainly because they don't work very well, espeically for aphids.
Aphids, usually, will not kill the plants that they infest if they are large plants, like trees and rose bushes, although they are messy and unsightly. Also, they produce a sugary waste that attracts bees, wasps and other creatures that sting and frighten children, which was the biggest complaints about them we got. But, as irritating as they may be, they will most likely all die come winter and will only be a problem for one summer season.
Lady bugs and praying mantis do not work well for the main reason that there are too many of the aphids to eat. For most of the year, each generation of aphids are born already pregnant with the next generation of female aphids, and millions of pregnant aphids are born to the mommy aphid within a few days of her birth. It takes a ton of lady bugs and praying mantis to keep up with that. Most lady bugs do fly away, and although a praying manis egg will hatch up to 200 little, baby mantis (which are very cute, by the way, the sort of dance), most of them eat each other and you only end up with the one or two strongest, who will proceed to fight to the death or mate if they ever run into one another, and if they mate the female will eat the male when they are done! The best way to get rid of aphids, if you must, is to use mildly soapy water. Spray down a tree and wipe down the leaves and branches of a smaller bush.
If you are going to release lady bugs the best time to do it is in the evening. That way they will be more likely to land for the night and hopefully when they see how many bugs you have they will be less likely to leave in the morning, but still many of them proceed to fly off. They do not have logic like we do.
At least, this is what the horticulturist at our garden center taught me.

by jessifromdenver at 3:37 PM on 16 May 2007

if aphids are eating your basil...

I've been experimenting with companion planting. There are some good ideas in Rodale's Organic Gardening book mentioned in the article. I have tried using nasturtiums to attract all the aphids in the yard, and keep them off my other goodies. They are pretty if you don't look at them too closely, and the aphids love them so much, they tend to leave things near them alone. Who'da thunk it? Hopefully the nasturtium gods and goddesses will forgive us the sacrifice.

Correction to the article: toxics are not a last resort. They are not a choice. If it's the wrong plant in the wrong place, change the place or the plant. Period. It's too important- they don't just go away.

-liese

by liese at 7:36 PM on 16 May 2007

Japanese beetle control

There is also a non-toxic, biological control for Japanese beetles called milky spore disease. It comes in a granulated form that you spread in the spring. The larval form of the beetle, called grubs (which can damage lawns from underneath), dies from the disease and thus does not reproduce. The disease is very species-specific, so it doesn't harm other beneficial insects, and can persist and spread for several years, benefiting your whole neighborhood. It is safe and nontoxic, and is the only way I've ever found to reliably protect my roses and grapevines from being reduced to lace.

Trolls, phishers, spammers, etc. you all suck! That's why I ignore you. Hahahahaha!

by nattydad at 8:44 AM on 17 May 2007

Thanks!

Thanks, Umbra, for taking my question! And thanks to everyone for the great recommendations--I can't wait to put some of these strategies to use.

And I'm definitely going to look for the Rodale and Garrett books.

Lindsay Ratcliffe

by Lindsay at 3:22 PM on 17 May 2007

ladybugs

I doubt that releasing ladybugs outside would be worth the money to buy them, but I've used them very succesfully on indoor plants. In the winter we bring in many pots of plants that would not survive outside, and often some of them become infested with some kind of pest. We've had aphids, whiteflies, scale bugs, and thrips. We had very good success with ladybugs eating the aphids; moderate success with the Encarsia formosa wasp on whiteflies (physical removal of whitefly adults such as vacuum cleaner or a tightly woven net, and removal of heavily infested leaves was more effective, I think). I've also used physical techniques on scale bugs such as covering their bodies with various substances or scraping the less mature adults off (removing mature adults may release very tiny little ones, so covering them is a better option). I don't remember what technique got rid of the thrips.

Ordering bugs in the winter should be done during a warm spell. That's been getting easier in recent years. I've had excellent service ordering from www.planetnatural.com many times. This past winter we ordered directly from a ladybug breeder, but a two-week shipping delay resulted in 99% dead ladybugs on arrival, so we went back to Planet Natural when it warmed up again. We had a dense population of perhaps thousands of aphids on our Angel's Trumpet plants, and the ladybugs eraditcated them in about one day.

....

Incidentally, the new internet filter at my state job blocks Gristmill. Apparently it's even banned during lunch and breaks. Oh well.

by Pandu at 6:40 AM on 18 May 2007

Another great web resource

You Grow Girl is another great site (not just for girls) I refer to all the time for my own two urban gardens. They have a ton of DIY ideas for identifying and managing pests, as well as maintaining healthy garden ecology.

Girl on Foot: A regular gal soul-searching the modern day car-free commute.

by girlonfoot at 11:06 AM on 21 May 2007

Japanese Beetles

Last year was a bad year for Japanese Beetles in Colorado. Tons of plants' leaves looked like swiss cheese. The pretty little beetle that was the cause was on several edibles. I looked up companion planting to keep them away in the future. Garlic was listed. I happened to have one of my favorite products nearby - Dr. T's Insect Repellant. It contains Garlic Oil, Mint Oil & Lemon Oil. Since it is an oil, I waited until evening (didn't want to fry the leaves). When I sprayed on the repellant, the beetles ran & jumped away so quickly it was funny. They didn't seem to like anything else nearby, so I never saw them again.

by hankerson at 8:01 PM on 25 May 2007

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Lady, Bugged

On fighting pests with pests