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organic pest control

What’s Eating My Swiss Chard?

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Of all the greens I like to grow in summer, Swiss chard is usually the one that is most trouble-free. It doesn’t get bitter or tough in the summer heat. It produces leaves for months on end, without sending up a flower stalk that triggers an end to leaf-production. The crop also, usually, attracts very few pests. However, this summer, something started eating my Swiss chard.

Damage in the Swiss chard patch

Holes in Swiss chard leaf, characteristic of caterpillar feeding damage

When I first noticed the damage to the Swiss chard, I figured it was caterpillars because of the kind of damage I saw on the leaves. There were big holes in the leafy parts, but the thick middle stem, or midrib, was undamaged for every leaf.

However, when I examined my patch of Swiss chard, I did not find any caterpillars, even though I found plenty of frass (caterpillar poo). I looked under the leaves, down the stems, and around the bases of the plants in my search.

University of Minnesota Extension offers several possibilities for which pests might be eating my Swiss chard, but I did not find any of the named pests. The list includes cabbage loopers, slugs (which also make holes in leaves as they eat), diamond back moths, flea beetles (which make smaller holes), and cabbage worms.

Dark wad of caterpillar frass (poo) on edge of damaged Swiss chard leaf.
Dark wad of frass on damaged leaf.

Some caterpillars are harder to find than others, so I sprayed all the chard plants with Bt for caterpillars (Thuricide, organic-approved) and figured that would stop the problem.

It didn’t. When I rechecked the patch a couple of days later, some leaves had been stripped completely down to the midribs. Caterpillars were still feasting on my plants. Since I didn’t find any caterpillars in the daytime, I changed the plan.

That night, before heading to bed, I went out to my chard patch with a flashlight and a tub that contained soapy water, prepared for a hunt.

I found caterpillars.

Caterpillars at night

Drowned caterpillars

That night, I found seven caterpillars on the Swiss chard, and I dropped them all into the soapy water. The caterpillars were on the Swiss chard variety ‘Perpetual spinach’, which is my favorite. The variety ‘Verde de taglio’, which has less tender leaves, also had some damage, but I did not find caterpillars on that variety.

The two groups of caterpillars most often identified as night-feeders are armyworms and cutworms.

Cutworm caterpillars

I think of cutworms as those little lumberjacks that cut down garden seedlings in the night. It didn’t occur to me that cutworms might eat bigger leaves until I saw an article about the winter cutworm, Noctua pronuba, at AskExtension.

The winter cutworm is found all across the U.S. The AskExtension article notes that the winter cutworm can be controlled with Bt for caterpillars, which is what I use on caterpillar pests, but only when the caterpillars are small. The caterpillars I found were large enough that, if they had been winter cutworms, they would have been unaffected by the Bt/Thuricide.

However, my caterpillars do not look like winter cutworms.

Armyworm caterpillars

One of the caterpillars that is eating my Swiss chard

A couple of nights after the big hunt, I went back out with the flashlight to hunt again, because leaves of my Swiss chard were still being eaten.

I found a couple more caterpillars, this time on both varieties of Swiss chard. To get a better look, I brought one of the little pests inside before drowning it in soapy water. I am pretty sure the caterpillar is an armyworm, possibly a yellow striped armyworm.

When the armyworms are as big as this — longer than an inch — handpicking and drowning the caterpillars may be the best organic option for stopping the damage in a small garden. As with the cutworms, larger caterpillars are not killed by the organic-approved Bt.

Worse, it sounds like (from reading multiple articles), a particular form of Bt is needed to get rid of the armyworms. My Thuricide won’t work on these pests. The special variation is in a product called XenTari BT. This is still an organic-approved Bt, but the strain of bacteria used to produce it is slightly different.

When I checked the product page for XenTari on amazon.com, it says the product is currently unavailable. I am guessing that is because armyworms are causing problems in more gardens than just mine, here in September.

Luckily, the batteries in my flashlight are still good. If the damage continues, I will just keep on hunting through the Swiss chard at night, until I’ve removed all of the pests.

Planting Dates for Summer Garden Vegetables

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As spring advances and weather warms, the urge to plant the summer garden becomes almost overwhelming. Knowing which crops can stand a bit of cooler weather and cooler soil can help us make good choices about what to plant when we just can’t wait any longer.

Understanding the last frost date

Most of the garden vegetables that we grow in summer are frost tender, which means that they won’t survive freezing weather. This is why most seed packets use the “last frost date” — the expected date of the last freezing temperatures — as a marker for when to plant summer crops.

Where I live, the average date of the last frost in spring is in mid-April. The date is not exact; we estimate the date based on the dates of the last frost in previous years. Annoyingly, we won’t know the exact date of the last frost for this year until we are well past it. Some years, the last frost in my yard is in March, and one year my yard had a frost on April 23rd.

The role of soil temperature

Cucumber seedling with three true leaves, already planted in the organic home garden.
Cucumber seedling transplanted into the garden in April.

Part of finding the best time to plant vegetables is knowing the best temperature for seeds to sprout and for plants to grow. Texas AgriLife Extension points out that these two temperatures are not necessarily the same. For example, bean seeds may sprout best at a soil temperature of 85 degrees F, but that temperature isn’t best for plant growth and productivity.

The AgriLife article lists reasonable, “compromise” soil temperatures for planting many crops:

  • cucumber (64°F)
  • cantaloupe (68°F)
  • okra (73°F)
  • pumpkin (75°F)
  • squash (70°F)
  • watermelon (72°F)
  • beans (72°F)
  • beets (45°F)
  • tomato (55°F)
  • turnip (50°F)
  • corn (55°F)

From the list, you can see that beets and turnips (cool-season crops) can do well in cooler soil, corn and tomato plants slightly warmer, and cucumbers and cantaloups a bit warmer still. This information can help in planning your schedule.

Recommended date ranges from University Extension programs

UGA publishes a Vegetable Planting Chart that shows suggested planting dates for garden vegetables. The dates are for middle-Georgia (a line through Macon across the state), which means that the dates need to be adjusted for areas north and south of that line.

Tomato transplants for the organic home garden, indoors under lights on a cold day.
Tomato transplants for the organic home garden, indoors under lights on a cold day.

For my area, just north of Atlanta, I would add about two weeks to the ranges in the UGA planting chart to get a reasonable planting date range for my garden.

North Carolina State University Extension publishes a planting chart for Western North Carolina. The dates are similar to those that I would use for my garden.

You may notice that the recommended date-ranges in the linked publications for spring planting can be quite large – up to six weeks for some vegetables. The whole range of dates might be good theoretically for a particular crop; however, for organic home gardens, there are some good reasons for choosing to plant either at the early end of the range or the late end.

Reasons to consider dates at the edges of the recommended ranges

For both bush beans and pole beans, I usually plant as early as I think the plants can survive the experience. The early planting — as early as the first week in April, if the weather forecast looks ok — means that I start harvesting beans before the end of May. By the time the Mexican bean beetles show up to demolish the plants, I will have harvested plenty of beans.

I also choose an early planting date for cucumbers, squashes, and melons. Those plants all are attacked by mildew diseases in late summer and an assortment of pest insects in mid to late summer. Early planting allows a larger harvest, before the plants are affected by whichever problem attacks first. For these crops, planting seeds in the first week in April, or transplants a week or two later (when the soil is warmer), can make a big difference in how much food I can harvest before the plants die.

Okra and sweet potatoes are two crops that I plant at the later end of the recommended planting date range. Both of those two crops grow slowly in cool weather, and I have found that keeping ahead of the weeds, which grow faster, is more work when these two crops are planted early. When okra and sweet potatoes are planted later, in early or mid May in my yard, they grow fast enough to shade the ground sooner, and weeds have less chance to take hold.

Tomatoes are another crop that I plant later than almost every other gardener I know. My experience is that later-planted tomatoes, like at the end of April or early May, are less troubled by blossom-end rot than earlier-planted tomatoes. They also are more likely to survive whichever soil-borne wilt disease is in my yard, and infection by the ever-present early blight disease is usually less severe.

Organic gardeners won’t use the chemicals that are available in garden centers to control all the above problems. Instead, we have be a bit wily about getting around the diseases and pests that can reduce the productivity of our organic home gardens. I have found that adjusting my planting dates to the edges of the date ranges, for some crops, is all the “control” I need.

Of course, keeping a good attitude about the vagaries of the natural world also helps.

Amy’s planting schedule

In case you are curious, this is when I plant the standard summer crops, most years, in my garden, zone 7B, just northwest of Atlanta:

  • first week in April – plant seeds for bush beans and pole beans if forecast is ok; if a freeze is in the forecast, I start these in a flat or tray, to transplant to the garden after a couple of weeks. I also start squash-family plants – cucumbers, zucchini, winter squashes, melons – in little pots this week, to transplant to the garden when the soil is warmer.
  • mid-April – plant corn, if any is planned. For me, that is usually popcorn. Early planting for corn reduces problems with corn ear-worm. Later plantings almost always have more ear-worms. Plant the transplants (beans, squash family plants) when the first true leaf is a couple of inches across.
  • late-April – plant pepper plants, and seeds for Swiss chard (if planned).
  • early May – plant tomato and eggplant transplants, seeds for okra.
  • mid-May – plant sweet potato slips.
  • mid-summer – plant Southern peas when one of the earlier crops comes out of the garden (bush beans or cucumbers are usually the first to go). After bush beans have been gone from the garden for a couple of weeks, if there aren’t any pole beans also in the garden to harbor more Mexican bean beetles, plant a new patch of bush beans.

What the above schedule doesn’t show is that I start tomato and pepper plants from seed, indoors, in early March. It also doesn’t include annual herbs, like basil or borage, or flowers, like nasturtium and Zebrina hollyhock, that I plant most years.

Protecting early-planted crops from frost

The summer crops are frost-tender, but I plant some of these crops early enough that the risk of frost is high. A couple of different strategies can be used to protect your crops.

The first strategy is the use of transplants to allow an early start for some crops, like beans and cucumbers. This strategy takes some planning, and it takes space in your house. It also, though, protects plants from cooler weather, since they are indoors. The plants can be planted into the garden when the risk of frost is lower.

The second strategy is the use of row covers to protect tender crops in the garden from a light frost. If a hard freeze happens and the row cover does not fully protect a crop, some replanting might need to be done. The good news here is that most seed packets contain enough seeds to replant a small home garden.

For further reading, my older post about planting seeds in the garden contains reminders about planting depth and plant spacing that might be helpful.

(If this post is helpful or interesting, please “like” or “share” it. Thank you!)

Snails in the Garden

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We are in December, with below freezing temperatures at night, but there are still a few snails in the garden. Their continued presence among the greens (chicory, kale, lettuce, rocket) tells about the long season of rain leading up to winter here in north Georgia.

Snail on a chicory leaf, early December in Georgia.

I haven’t seen any serious damage to my plants, so I am not concerned about the snails. To be honest, I am amazed by their persistence in the cold.

If there were very many snails, and a lot of damage to crops, I would set out some organic-approved iron-phosphate bait. The one I have used most recently is called Sluggo, but there are many similar baits, with the same active ingredient, that work.

When I have used the iron-phosphate bait, it was actually for roly-polies, many years ago. For some reason their population had boomed, and roly-polies roiled every square inch of ground in the garden. These critters usually eat decaying organic matter, but there were so many of them that they started eating seedlings in the garden. That was a problem, but the Sluggo iron-phosphate bait for slugs and snails works on roly-polies, too.

It took a couple of years of persistent use of the bait to beat back the roly-polies, but my garden hasn’t been invaded like that again.

The Royal Horticulture Society (RHS), in the UK, where slugs and snails commonly invade gardens and farms and cause a lot of damage, has been studying methods of slug and snail control. Earlier this fall, the BBC reported on an RHS study of home-methods, using things like crushed egg shells, sharp sand, and copper strips to keep the pests away from garden crops.

The study found that none of those things really work, which is sad news for those of us who like to “DIY” as much of our gardening as possible. They had not yet tested beer-traps (beer in shallow saucers, set around the garden, to lure and then drown slugs and snails), so there may be one method left for us to use, other than placing boards in the garden for the pests to hide under, then turning the boards over to pick off the critters by hand to drown or otherwise dispatch.

In another RHS study, effectiveness of iron-phosphate baits and another organic control, nematodes that target slugs and snails, was compared to conventional (chemical) control options. The organic methods did almost as well as the chemicals. Based on my roly-poly experience, I would have guessed this outcome, but it is nice to have that guess confirmed.

Trap Crops for the Home Garden

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Since trap crops take up some space, it never occurred to me that using these was a suitable organic pest control strategy for small home gardens. However, I have unexpectedly gained experience with a trap crop, since that is what my zucchini have turned out to be.

What is a trap crop?

A trap crop is one that is planted as a lure to pest insects, to keep them away from the main crop. Most trap crops are not expected to yield a harvest; instead, they are offered up to pests as an alternative to the main crop of a farm. According to SARE, trap crops are often planted around the edge of the main crop, forming a protective barrier that pests are likely to stay within. Trap crops can also be planted as a block or patch near the main crop.

According to University of Georgia, trap crops to work best when they make flowers before the main crop that they are protecting. When the plants are making flowers and fruits, that is when they are most attractive to most pests.

My zucchini plants function as a trap crop

You may have read the two recent blog posts about pests on my zucchini plants — one about squash beetles and the other about cucumber pickleworms. The squash beetles are really less of a problem, since there are only four or five each day for me to smash and the damage is limited to holes in the leaves. The pickleworms, though, are another story.

They have caused serious damage to the zucchini plants, ruining flowers and boring into main-stems and leaf-stems. The plants are still standing, but all hope of harvesting zucchini from this late-summer crop is gone.

This is the good news: my cucumber patch, planted in early August like the zucchini, has supplied several cucumbers for our meals already. Checking the cucumber plants nearly every day, I have found only a few squash beetles, grand-total, on the plants. It has been easy to find and smash the one-every-few-days beetles as I check on the garden.

In an instance of amazing good luck, my zucchini variety was so fast to mature that the plants made flowers more than a week before the cucumbers did. When the pests first showed up in my garden, the squash beetles and cucumber pickleworm moths flew past the cucumber patch, which didn’t have flowers, and attacked the zucchini plants in the half-barrel planter, where flowers and little squashes were abundant.

Cucumber patch protected by trap crop of zucchini, example of organic pest control. Zucchini are in a half-barrel at left end of garden (not in this image).
My cucumber patch in late September. No leaf mildew diseases, no pickleworm damage. PHOTO/Amygwh

Even better, the cucumbers still do not show any pickleworm damage.

To combat any pickleworms that could be present, I have been treating both sets of plants with Bt for caterpillars (the one I am using is Thuricide), which is an organic pest control product. We have had a lot of rain, though, which washes the Bt away. I am not re-spraying my plants after every rain, so some days the cucumber crop is unprotected other than by the stronger allure of the zucchini plants.

At this point, the three remaining zucchini plants look hopelessly ragged, but they are still alive. I am leaving them in the garden for as long as they continue to work as pest-magnets.

The cucumbers remain pickleworm-free, but they are not perfect specimens. I had forgotten about the uneven pollination in hot weather that results in lumpy cucumbers. These are not headed for a pickle jar, which means the imperfect shapes are not really a problem.

Weird shapes from incomplete pollination, but no cucumber pickleworm damage. PHOTO/Amygwh

Because of pest-concerns, I am harvesting the cucumbers while they are fairly small. This is a bit like harvesting tomatoes before they are fully red. I know that if I leave tomatoes in the garden to fully ripen, some pest (stink bug, chipmunk, mockingbird, etc) will notice the beautiful, ripe fruit and take a bite before I get a chance to enjoy the harvest, myself.

Unlike for tomatoes, there is not a flavor-reason to wait for more mature cucumbers. They taste pretty much the same at smaller sizes, and leaving them out in the pest-filled world seems a little like tempting fate.

So, as I ponder my next year’s garden, it is good to know that zucchini plants can use some unseen come-hither chemistry to draw pests away from the cucumbers.

This is the kind of garden-discovery that any of us can make. I have been growing food in this yard for more than 25 years, and I learn more about gardening every year. And even though there are pests, the garden is producing good food. This is part of the joy of gardening!

Fire Ants in the Garden – Organic Control

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No gardener wants to encounter fire ants in the garden, but sometimes we find that they have moved in, unwanted. Getting rid of these pain-inflicting invaders can take some persistence, but options for organic control do exist. Knowing a little about the biology of these ants can help a gardener plan a successful counter-attack.

Flattened fire ant mound with deer hoof print in the middle.
Flattened fire ant “mound” shows deer hoof print. PHOTO/Amygwh

Fire ants do not tolerate freezing weather very well. If you treat a fire ant mound in fall, even if the whole mound isn’t dead within a few weeks, enough workers can be killed that the rest of the colony doesn’t survive the winter.

In spring and fall, too, most of the ants in a colony will be closer to the surface, so that a mound drench type of product has a good chance of reaching all of them.

In other words, both fall and spring are when organic controls are more likely to work well. Killing off smaller colonies in fall will also reduce the number of new colonies next spring, when mated queens that survived the winter will fly off to start new colonies.

The very first control to try, though, doesn’t use any products at all. On a cool day after a rain (when more ants are nearer the surface), pour a few gallons of boiling water on the mound, starting by circling the mound a foot or so away and then pouring the rest right on the mound. If this doesn’t kill the whole colony, move on to “Plan B”, a purchased mound-drench or a bait. (NOTE: Boiling hot water can burn people when accidentally spilled, and it will also kill plants near the mound it is being poured on. Please handle boiling water carefully, and do not use it near trees, shrubs, perennials, bulbs, or other desired plants.)

Another option is called “bucketing”. You gather up a few buckets, dust the inside with talcum powder or corn starch (to keep the ants in), and on a cool morning dig quickly into the mound, dumping shovels full of dirt into your buckets. Dig deep enough to find the bottom of the mound. Add a generous squirt of dish soap to each bucket, and add water to drown the ants. This works on small mounds, but not on old, deep colonies.

Organic-approved products for killing fire ants typically contain either d-Limonene (from orange oil) or a spinosad compound (from special bacteria) as their active ingredients.

One organic produce that contains d-Limonene, to be used as a drench, is Orange Guard Fire Ant Control. The d-Limonene products have worked pretty well in our area community gardens.

An organic product for fire ant control that uses spinosad as the active ingredient is Captain Jack’s Dead Bug Brew by Bonide. Instructions for using it as a mound drench are pretty far down the label, but they are there.

Whatever product you choose, be sure to follow package directions carefully.

Remember to NOT disturb a mound in any way before using a product on or around the mound. If the ants are disturbed, they go into “defense mode”; a whole lot of ants will boil up out of the mound where they can’t be reached by a drench.

Fire ants are not easy to eradicate, and new colonies will continue to move in from surrounding areas if they can, even when old colonies are killed off. It is their way.

However, gardeners can be persistent, too. Knowing the best times to work on the mounds for best effect helps keep our gardens fire-ant free.

For more information and the recipe for a DIY orange-oil-based soil drench, see Fire Ants in the Garden, Part 2.