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Posts Tagged ‘Organic Pest Control’

Of all the organic products we can use to eliminate pests in the garden Spinosad (spin-OH-sid) has perhaps the most curious back story.

A scientist who was part of a team that was searching for new naturally occurring pest controls was on vacation in the Caribbean in 1982. He was poking around an old abandoned rum distillery and decided to take a few soil samples home with him. Back at the lab they fermented the samples and three years later found that the products of the fermentation had insecticidal activity. To make matters even stranger, this new species of soil dwelling bacterium called Saccharopolyspora spinosa, a rare actinomycete, has never been found anywhere else in the world. It is one of those things you read and think, “What are the chances?”

Spinosad is safe for use on ornamentals, vegetables and fruit. It must be consumed by the insect to be effective. It can be used to control a variety of pests including:

  • Cabbage worms
  • Caterpillars
  • Coddling moth
  • Corn borers
  • Fruit flies
  • Leaf beetle larvae
  • Leafminers
  • Rose slugs (sawfly larvae)
  • Sawflies
  • Spider mites
  • Thrips
  • Tomato hornworms

A note of caution here: Spinosad is highly toxic to caterpillars. That means that it will kill good caterpillars as well as bad. If you have a butterfly garden or plants that attract butterflies, DO NOT spray Spinosad when these caterpillars are feeding. You will kill them.

Spinosad is mildly toxic to fish so be careful spraying it around ponds. It can be toxic to bees and other non-leaf feeding insects if they come into contact with it before it has dried on the leaf. That means that you should spray the product only in the recommended amounts (READ PACKAGE DIRECTIONS!), at the recommended intervals, and at dusk when bees and other beneficials are less active. This gives it time to dry on the leaves where it will still be ingested by pests, but where it will not affect the beneficials.

Spinosad has a very low toxicity for mammals and non-leaf feeding insects including sucking insects like aphids, scale, or mealy bugs. Here’s a link to more information from Cornell University’s Resource Guide for Organic Insect and Disease Management.

Remember, just because a product is labeled “organic” doesn’t mean that is without risk. This is a product that can kill living creatures, albeit pests; use it only if you must and with care. The goal is always to keep the garden in balance so pull this trigger only when things are beginning to get out of control, not when you see a few ragged leaves. We need some of the bad bugs around so that the good bugs that eat them will stay in our gardens.

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We are deep into spring and on our way to summer though it sure doesn’t feel like it in Southern California. We’ve got cool temps, wind and rain which is unusual for this time of year. What’s not so unusual are the garden pests that have started to make their appearance in my garden and which will soon be plaguing Mary Beth and the rest of you in somewhat cooler zones. So we thought that for the next few weeks we’d look at organic ways to deal with the bugs and diseases that bother us in the garden.

We’d like to point out first of all that some nibbling of leaves, flowers and fruits is normal. Bugs are supposed to be in your garden. Live with it. Insects are part of the whole wonderful cycle that makes this all work. We are not striving for a bug-free zone, we are looking to create a balance in the garden. That said there are times when you need to get the upper hand especially when something is devouring your herbs or, perish the thought, your beautiful tomatoes.

This week we’ll be looking at Bt or Bacillus thuringiensis. The most commonly used form of Bt, the one you’ll likely see at your nursery, is Bacillus thuringiensis kurstaki. It is used for controlling leaf-eating caterpillars like cabbage worms and tomato hornworms (although they are called worms they are really caterpillars). Another form, Bacillus thuringiensis israelensis, is used to control certain fly larvae like mosquito larvae which can be a problem in ponds.

Here’s what Colorado State University Extension has to say about Bt:

“The most commonly used strain of Bt (kurstaki strain) will kill only leaf- and needle-feeding caterpillars. In the past decade, Bt strains have been developed that control certain types of fly larvae (israelensis strain, or Bti). These are widely used against larvae of mosquitoes, black flies and fungus gnats.

More recently, strains have been developed with activity against some leaf beetles, such as the Colorado potato beetle and elm leaf beetle (san diego strain, tenebrionis strain). Among the various Bt strains, insecticidal activity is specific. That is, Bt strains developed for mosquito larvae do not affect caterpillars. Development of Bt products is an active area and many manufacturers produce a variety of products. Effectiveness of the various formulations may differ.

Insects Controlled by Bt

Kurstaki strain (Bonide Thuricide, Safer Caterpillar Killer, Greenstep Caterpillar Control, etc):

  • Vegetable insects
    • Cabbage worm (cabbage looper, imported cabbageworm, diamondback moth, etc.)
    • Tomato and tobacco hornworm
  • Field and forage crop insects
    • European corn borer (granular formulations have given good control of first generation corn borers)
    • Alfalfa caterpillar, alfalfa webworm
  • Fruit crop insects
    • Leafroller
    • Achemon sphinx
  • Tree and shrub insects
    • Tent caterpillar
    • Fall webworm
    • Leafroller
    • Red-humped caterpillar
    • Spiny elm caterpillar
    • Western spruce budworm
    • Pine budworm
    • Pine butterfly

Israelensis strains (Vectobac, Mosquito Dunks, Gnatrol, Bactimos, etc.)

    • Mosquito
    • Black fly
    • Fungus gnat

San diego/tenebrionis strains (Trident, M-One, M-Trak, Foil, Novodor, etc.)

    • Colorado potato beetle
    • Elm leaf beetle
    • Cottonwood leaf beetle”
We (back to Bees and Chicks now) have used Bt for years and find it very effective and safe when used according to package directions. It is not harmful to humans, pets, or beneficial insects like bees. It can be used up to the day before harvest (I’d still want to wash sprayed fruit before eating).
Nonetheless, you shouldn’t go spraying everything willy-nilly. Be sure first of all that a caterpillar is what is eating your plant. Some insects that look like caterpillars are really worms, most notably rose slugs, and Bt will not kill worms. (Note that these are called slugs, but are really worms! For info on how to identify and control rose slugs click here.)  If it is a caterpillar eating your plants, spray just the affected plants/area. You must be very thourough because the caterpillar needs to eat the BT for it to be effective. You may need to repeat the application every 5 – 7 days while the insects are active. We have usually gotten good results with just a couple of sprays.
A note of caution here: Bt will kill good caterpillars as well as bad. If you have a butterfly garden or plants that attract butterflies, DO NOT spray when these caterpillars are feeding.
Bt is but one tool in the organic arsenal. Next week we will take a look at more.

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Today’s tips are meant for gardeners in Southern California, but will apply to those of you in cooler climates in a month or so.

We’ve been having a spell of wet, cool weather. Normally things are growing at a rapid pace by now, but because the night-time (and even the day) temps have been unseasonably cool our gardens are a bit behind where they would normally be. Still, that’s ok because it gives us a chance to catch up if we’ve fallen behind.

March Garden Maintenance

  • Fertilize lawns. I use GroPower Plus and it seems to work well. It has humic acid which is really good for conditioning the heavy clay soil in our area.
  • Fertilize roses. This year I’m trying Dr. Earth Organic 3 Rose and Flower Fertilizer. It’s got lots of great ingredients, like fish bone meal and kelp meal, that should help my roses be strong and healthy.
  • Check new growth for pests. Staying on top of pests in your garden is key to keeping plants healthy. Succulent new growth attracts sucking insects like aphids.
    • My roses have aphids. I washed them off with a stream of water and I’m going to pick up a container or two of ladybugs to help keep them under control.
    • Snails and slugs. We’re likely to notice a big increase in their numbers because of all the rain we’ve had. If you garden organically, you’ll have help in controlling snails and slugs. Lizards will eat them, as will opossums and birds. You can lay down barriers of diatomaceous earth, sand or crushed eggshells to keep them from your plants. Copper barriers on tree trunks will keep them from climbing up and eating fruit (they love citrus). You can capture them by watering an area they frequent and laying down a board or a piece of old carpet. You can also use dampened tubes of rolled newspapers. — anything that creates a dark, damp space. Wait a day or so and pick it up in the morning to capture these pests. Seal them in a plastic bag and throw them in the trash. You can also put some beer in a shallow pan or can. They’ll come for a drink and fall in and drown.
  • Pinch back fuchsias. Cut them back by two-thirds or so, leaving 2-5 leaf buds for new growth.
  • Divide perennials like agapanthus, callas, day lilies, rudbeckia and daisies.
  • Pruning – many books will tell you it’s time to prune ornamentals, but it’s best to wait a while until the spring nesting season is over. Otherwise you might inadvertently prune away a nest with eggs or baby birds. (Speaking of which, check out Thursday’s Garden Journal for an exciting surprise!)
  • Stay on top of weeding. The rains will make weeds pop up, so get them out of your beds while the damp soil makes it easy and before they disperse seeds for a whole new round of weeds.
  • Finish cleaning up storm debris in your flower beds. Put down some compost or other organic fertilizer (see last week’s tips on improving your soil) and mulch.

We’ve noticed in our search terms that a number of people are looking for information about digging fresh manure into soil. Be careful. Some manures must be aged before you use them. If you are preparing new beds and will be able to leave it to mature for at least couple of weeks, you can dig in fresh horse or cow manure. However, don’t dig these manures into soil near plants. It will heat up as it decomposes and it will burn your plants’ roots, possibly killing them. Chicken manure also needs to be aged – at lease three months.

Once these “hot” manures have been aged for three months, you can use them as you would other fertilizers. Other manures like rabbit or llama poo are ok to use straight, both for digging into new beds and as top dressing on established beds. Just be sure you find out how much to use. Too much of anything will cause big problems.

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Barbara: Summer garden doldrums — I’ve noticed that I’m a little less enthusiastic in my garden lately. I’m pretty content to wander about doing nothing more than a little grooming here and there. But that’s all right because besides deadheading and keeping the garden tidy there’s not that much to do. The exception is keeping a sharp eye out for garden pests, because the sooner you deal with them the better off you’ll be. One of the pests that bedevils us this time of year is the rose slug.

Rose slugs are tiny, green worms that are the larvae of the rose sawfly. Heaven knows why they’re called slugs. They don’t look like a slug and they don’t leave a slime trail. Both the name and their appearance cause a great deal of confusion when you want to find a way to get rid of them. The most important thing to remember is that they are not caterpillars and you’ll see why this is an essential bit of knowledge in a minute.

When you’ve got rose slugs, you know it. These little creepies will skeletonize your rose leaves seemingly overnight (they don’t eat the buds or flowers) — one day you’ve got beautiful green, glossy leaves and the next day the plant looks like it was hit by a bomb. It is not pretty!

In Southern California the rose slugs have hit in a big way in most of my neighbor’s and client’s gardens. They are voracious and can make a mess of a rose bed in just a few days. As with most garden pests it’s important to treat for them as soon as you notice any leaf damage. Here, following the principles of Integrated Pest Management, are methods of control in ascending order of potency and potential harm to the beneficial insects in your garden.

Remember that the rose slug feeds on the underside of the leaf, so this is where to look for them and where to spray.

Mechanical

  • Search & destroy — a great release for your aggressive tendencies. Flip rose leaves every morning and squish, or pick off the little worms. Not for the squeamish. This method can work, but you’ve got to be persistent and if you’ve got a big infestation this is a stopgap at best. So the next step is…

Sprays

  • Water — this is a safe and effective method for many garden pests (works especially well for aphids). Dislodge them with a strong stream of water. Frankly, I haven’t found this to be effective for rose slugs, but it’s worth a try.
  • Insecticidal soap. You should spray in the early morning or in the evening when the wind is calm so that you don’t get drift and it won’t harm the good bugs who are not out and about at these times. Aim your spray on the underside of the leaves, it needs to hit the bugs to work.
  • Neem Oil works by suffocating the pest, so be sure you cover the underside of all the leaves.
  • Spinosad works by excitation of the bug’s nervous system. It must be ingested, so it affects only chewing and sucking insects. That said, be aware that it is toxic to honeybees for 3 hours, so spray in the evening when bees are back in the hive. It will take a couple of days to see any results and you may have to spray more than once.

Now for the bit about sawfly larvae not being caterpillars. The reason this is important is that it means that Bt (Bacillus thuringiensis) will not work. I can’t tell you how many times otherwise knowledgeable gardeners have recommended Bt for this problem. Even our local nursery swore that it would work. It won’t and you’ll be wasting your money if you use it for this purpose.

If you have exstensive leaf damage it might stress your plant, but it’s not fatal. Simply strip off all the leaves and they’ll grow back again in a few weeks. Also, it helps to know that if you’ve just planted some new rose bushes this year they were probably raised in a nursery using non-organic methods. The transition into an organic garden will make them more susceptible to pests than your other plants for the first season. Don’t despair, just give them time to get adjusted.

Here’s where I extol the benefits of organic gardening — again. Boosting your soil with compost and feeding your plants with rose tea (click here for the recipe) will make them healthy enough to resist most pests. And organic gardens will attract all kinds of good creature who will help you with your gardening — beneficial bugs and birds especially. (Every afternoon the birds come by to pick bugs off my plants.) So I’m not aiming to have a completely pest-free garden. After all there needs to be a little bit of bad stuff to feed the good guys.

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One of the most common garden pests is the earwig or pincher bug, a nasty-looking little bug that actually is not all bad.

Earwigs eat living and dead material in your garden, doing a lot of cleanup work. They love to eat soft-bodied bugs like mites and aphids and they’ll eat insect eggs too. In some respects they can be a beneficial force, but past a certain number they are very destructive. They are especially fond of soft fruits, sweet corn and seedlings. They can also do lots of damage to leaves and flowers on mature plants as this photo that Mary Beth took in her client’s garden shows.

Earwig damage

Earwig damage looks similar on leaves. You will find irregular holes or chewed edges. Signs that it’s something other than earwigs are frass or webbing which indicate caterpillars, or slime trails which are left by slugs and snails.

Once you know that earwigs are your problem it’s time to get things under control. Earwigs like dark, moist hiding places so you can take advantage of this habit to trap and eliminate them. There are several techniques that you can use.

  • Roll up dampened newspapers and place at the base of the affected plants in the evening. In the morning shake the earwigs which will be hiding in the rolls into a pail of soapy water.
  • Another trick is to use cut lengths of old hoses. Follow directions above.

You’ll probably have pretty good results with those two options, but here’s the very best way to trap earwigs.

  • Fill tuna fish or cat food cans 2/3 full of vegetable oil and a few drops of molasses. Earwigs love this concoction. In the morning they will have climbed into the cans and drowned.

Keep setting traps until you stop finding earwigs in them.

This is so much better and more direct than any chemical methods which will introduce toxic substances into your garden killing beneficial insects and making your plants less healthy. Organic is better!

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We’ve been a little busy this week — more like crazy busy. Mary Beth is settled in Colorado, but her spring is just happening.  Her garden got by for five years while she lived on Block Island with a minimum of care, so now she’s got lots of work to do replacing plants that didn’t make it and cleaning out overgrown areas.

I’ve been helping a client whose husband is an ace at starting seedlings, but then wants to plant every last one of them — heaven help us! I’ve been building trellises for vines and tomatoes and trying to figure out where we’re going to tuck in the peppers, okra and watermelons. (Though “tucking in” the watermelons is kind of laughable.) Meanwhile, my garden is lost under a blizzard of eucalyptus litter. Hopefully I can get around to cleaning it up in the next day or two.

Today we’ll give you some organic pest control tips and next week we’ll talk about how to identify the pests that are munching your plants. This is backwards I know, but the i.d. part takes visuals and MB and I are still working on that part. Be sure to check out next week’s post. It should be a good one.

The most important concept in dealing with problems is to use the least harmful technique first. For instance, you could spray aphids (and spider mites) with insecticidal soap, but that can also kill beneficials who, in sufficient numbers, can keep pests in check. Spraying them off with a strong stream of water is a good first step and a surprisingly effective way to control bug populations. If that doesn’t work, your next move might be to release beneficial insects. If you still have a serious infestation then you could spray with an insecticidal soap.

One other thing to keep in mind is that stressed plants are much more vulnerable to all kinds of pests and diseases. Be sure your plants have the proper amounts of light, water and fertilizer. Encourage and support beneficials and birds by growing plants that attract them. Set up a fountain or birdbath, which will encourage birds to stick around and eat bugs and provides water for beneficial insects too. Birdhouses will also entice birds to stick around. In a healthy environment all things work together to keep pests in check.

Handpicking

Picking insects and egg masses works well with chewing insects such as bean beetles, potato beetles, Japanese beetles, hornworms, squash bugs and snails.

Traps

Earwigs:

Roll up newspapers and put the rolls at the base of pots or wherever else they congregate.

Slugs:

Method #1 — newspaper rolls again, but this time dampen them. It’s so easy to toss the rolls in the morning. You never have to touch the creepy, slimy little buggers.

Method #2 — place boards on the ground and sweep the slugs that gather underneath them into the trash.

Method #3 — place a small can filled with beer flush with the ground. Slugs and snails will fall in and drown.

Grasshoppers:

Sink  jars into the ground and fill halfway with a mixture of  1 part molasses and 10 parts water.

Barriers

Diatomaceous earth repels earwigs, slugs and snails.

Copper tape (at least 2″) repels snails and slugs. Lay it in your beds around vulnerable plants. Wrap it around tree and shrub trunks to keep snails off.

Earthworm castings and tea are also great at repelling sucking insects like aphids and they are said to provide protection against fungus as well.

Releasing Beneficials

Release beneficials in your garden to control pests. Ladybugs, praying mantises, green lacewings and trichogramma wasps, which control a number of pests, can all be ordered online or bought at your local nursery.

Spraying

As a last resort you can mix a number of concoctions that will kill soft-bodied insects. But, and this is a BIG but, these sprays will kill the good along with the bad, so don’t use them until you have to.

Mix one tablespoon of vegetable oil with a few drops of mild soap in 2 quarts of water. Spray both sides of leaves. The oil coats and smothers insects. Add 2 tablespoons of baking soda and it will help control fungal disease as well. (If fungus is your only problem, stick with just baking soda and water and spare the bugs.)




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