Controlling flea beetles in the fall garden (help wanted)

I didn’t get row cover on my beans in time this spring, and the flea beetles found me.

tired beans

Flea beetle is something of a catch-all term used to describe several species of beetles (not all of the same genera), all of which are tiny (1/16 to 1/10 of an inch long), that live in the soil and cause mayhem in North American gardens. They adore feeding on your vegetable plants, and can reduce a favorite crop to smithereens if not dealt with promptly. One treatment won’t suffice: They can produce four generations or so in a warm-climate growing season. Overwintering adults typically emerge when temperatures hit about 50 degrees (10 C). In recent years, it’s been 50 degrees at Christmas.

Here is my quandary: Their preferred cuisine is cruciferous, which happens to be what I need to get planted soon. Most winters are mild enough here that greens and root crops may be harvested year-round if grown under horticultural fabric, but that means getting seedlings and transplants off to a good start, starting now.

Row covers can be effectively employed to exclude flea beetles from pristine soil, but (clearly) that’s not what I have. Installing row cover where an infestation has already occurred just traps the beetles inside, keeping them safe from predators while they devour your spinach. Row cover must be sealed tightly all the way around to be effective, by the way.

Trap crops come highly recommended. “Plant a crop of mustard greens!” the gardening literature exhorts. Alas, the trap crops are what I want to eat this winter. Kale, collards, mustard greens, broccolini, radishes, tatsoi, arugula. These are the seed packets sitting on my desk, awaiting my decision. I fear that planting a trap crop, even far away (relatively speaking) from the vegetable bed, will only encourage more of the little punks to move in and feast upon everything in sight.

The garden literature also recommends scouting newly planted beds and counting the beetles as they arrive. This presumes the gardener can count insects best differentiated from dirt with a hand lens before they jump to the safety of the earth. Anyone who has brushed against a plant infested with flea beetles has seen a spray of tiny bugs fleeing the scene of the crime. Who can possibly count them in situ? Even if the gardener manages to hunker silently down and get a view of the action, must she hold her breath to avoid disturbing them? What if she needs to sneeze? (It’s fall pollen season, you know.)

Flea Beetle Management for Canola, Rapeseed, and Mustard in the Canadian Northern Great Plains. Graphic by the Government of Saskatchewan.

I don’t want to spray if I can avoid it. I have been known to pull out the neem oil from time to time, but it’s only moderately effective against flea beetles.

What to do, then?

Possible solutions to flea beetle infestation

I’m tempted to try one or a combination of the following. Have you had success with any of these?

1. Diatomaceous earth. DE is a fine powder made of fossilized remains of diatoms, a kind of algae. When used as an insecticide, the powder absorbs components of the waxy coating of insects’ exoskeletons and causes them to dehydrate. It’s critical to obtain food-grade DE for this application to be effective.

2. Interplanting with garlic. Garlic is a moderately effective insect repellant when sprayed on plant surfaces. I have to plant my garlic somewhere; I suppose it may as well go between my rows of kale.

3. Parasitic nematodes. To read about parasitic nematodes is to discover another of Mother Nature’s horror shows. Employing them can be a bit tricky, because the gardener must get the correct kinds of nematodes (families Steinernematidae and Heterorhabditidae, and some species are picky about who they infect); time the application to coincide with a larval stage of the target species; and keep the soil moist, not too hot, and not too cold.  On the plus side, they don’t infect birds or mammals.

Parasitic nematodes. Photo by Penn State University Extension.

Given my warm climate, and extrapolating unscientifically from the graphic above, I guess I might be able to interrupt a larval cycle if I went out tomorrow and applied the nematodes…maybe?

Please send your advice, post-haste.

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Comfrey: A plant’s smelly, magical wonder food.

Using commercial fertilizers, particularly sustainable or non-synthetic ones, can get really expensive. Compost and manures add important organic matter to the soil, which helps to build the subterranean ecosystems that support plant health, but they don’t add much in the way of major nutrients.

Fortunately, nature has provided a means to make our own sustainable fertilizers. Comfrey (Symphytum officianale), a plant that grows well in most gardens, provides nutrient boosts when added to compost or used in liquid fertilizers. And once you’ve bought the plants, it’s free.

Comfrey plants (Symphytum officinale) photo by Trish Steel [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)%5D, via Wikimedia Commons

Comfrey is a borage relative. Hardy to Zone 3, it has large, broad leaves like those of Pulmonarias, to which they are related, and small clusters of blue or white pendulous flowers. Comfrey’s fuzzy, sometimes prickly leaves discourage insect pests. It grows in a range of soils in sun to part shade, and uses its impressive root system, which may grow anywhere from 6 to 10 feet deep, to mine minerals from the subsoil, aerate its surrounding soil and break up the heaviest clays. It will regrow from tiny slivers of root, though, so be sure to plant it where you want it. If you are as indecisive as I am, grow it in a container. You won’t get quite the same level of benefits as compared to comfrey grown in the ground, but at least you won’t have it permanently installed.

Comfrey has been used in the past as an herbal medicine, but research proves comfrey contains poisonous chemicals called pyrrolizidine alkaloids (PAs). The roots contain up to 10 times the amount of PAs than the leaves. Its toxic chemicals can be absorbed through the skin, though, so it is advisable to wear gloves when handling comfrey. Do not take comfrey internally, as it is extremely toxic to the liver and may also be carcinogenic.

Comfrey (at right, with large leaves) and stinging nettle (Urtica dioica, at left, with serrated leaves) grow together in a barrel in my garden.

Comfrey (at right, with large leaves) and stinging nettle (Urtica dioica, at left, with serrated leaves) grow together in a barrel in my garden.

For plants, though, it’s a wonder food.

Comfrey contains high levels of the macronutrients nitrogen (N), phosphorus (P), and potassium (K), as well as calcium and vitamin B12.  Comfrey also contains allantoin, a chemical compound that stimulates cell growth and regeneration. It may be the allantoin that makes comfrey so effective as a fertilizer. Extracts from comfrey’s leaves have antifungal properties, and have been shown to effectively combat powdery mildew.

It’s good to know the specific epithet of the plant you’re getting. Symphytum officianale, the species, will seed prolifically and may become problematic in the home garden. The Bocking 14 strain of comfrey (Symphytum x uplandicum) contains the high nutrient levels of the species, but it’s also sterile, so it won’t self-seed and become invasive. Bocking 14 is difficult to track down in the United States, but is available from a few Internet sources.

Comfrey leaves can be used as a mulch or buried in the garden bed at planting time. As they rot down, they’ll enrich the soil. Take care when using them as a mulch, though: The decaying leaves can be attractive to slugs, so don’t mulch with them around leafy greens or ornamentals like hostas.

A more versatile way to use comfrey is as a liquid fertilizer or tea. To make the tea:

  1. Chop up a handful of fresh leaves (use gloves), and place in a container with a well-fitting lid.
  2. Add water to cover, submerging the leaves with a rock if necessary.
  3. Let the mix rot down for 3-4 weeks. At this time, the comfrey will have been reduced to a stinky black goo.
  4. Dilute the comfrey liquid concentrate at a rate of approximately 1 part comfrey to 15 parts water. The final product should be light brown in color, like weak tea. Water it in around your plants that need a boost, particularly fruiting plants, or use the tea as a foliar spray on plants that are susceptible to mildew.
  5. You can seal up the rest of the concentrate for use at a later time, or bury it in the compost pile to supercharge your compost.

Comfrey tea is higher in phosphorus and potassium, so you may wish to blend it with nettle tea to get a better nitrogen boost. This tea will feed the soil as well as your plants, ultimately making your plants more resilient. For a gentle, natural fertilizer, comfrey is hard to beat.

Dear Friend and Gardener: August 1, 2014

Dear Friend and Gardener,

How on earth can it be August? The summer is flying by, and I must start thinking about my fall garden. Already I am somewhat behind (what else is new?).

This past week I planted baby bush lima beans and pulled out the ‘Contender’ bush beans. The flea beetles abused the ‘Contenders’ horribly; next year I’ll do a better job of protecting them at the outset. I have two small eggplant growing, but something’s making eyelet out of the leaves. I do hate to spray but it may be time to pull out the neem oil. Oh, how it smells!

flea beetle damage beans

Flea beetle damage on ‘Contender’ bush beans

The tomatoes, however, are performing well. We’ve had cooler weather lately, in the mid-80s, which means the plants have a better chance of setting fruit. While the fruits do taste better when they ripen hot, I have to wonder, how hot is hot? What’s the optimal temperature for good-tasting tomatoes? The other challenging factor is that we’ve had lots of rain. I have to really keep an eye out and harvest the ripened fruits before they split.

I got my first fig on Wednesday! It was, I tell you, the best fig I have ever eaten. Do you grow figs? I intend to plant another one this fall because I have heard that they set better when there is another fig close by. And I also have ambitions to grow some more blueberries. Well, I have lots of ambitions.

One of my lingonberries died during a heat wave but the other is chugging along nicely. I’m starting kale this weekend and some lettuce as well. I should make room for carrots, garlic, and shallots. I’m fortunate to be able to harvest food year-round here, if I get organized in late summer and through the fall. How long is your harvest season?

Hope the weather is treating you well and the late blight stays at bay.

Best,

Amy

 

Tropical punch: Ground cherries offer strong flavor in a tiny bite.

ground cherries (Physalis pruinosa)

Related to tomatoes, and more closely to tomatilloes, the ground cherry (Physalis pruinosa) goes by many names, including ground tomatoes, husk cherries, and cape gooseberries.

The fruits grow under the plant’s large leaves, encased in a thin calyx that dries to a crispy, papery husk. The husk and fruit fall to the ground when they are ripe (hence the name).

husks and fruit

Ground cherries grow encased in calyces that turn brittle when the fruit is ripe.

Large fruits measure about the size of an adult woman’s thumbnail, with a texture resembling a firm grape, and taste strongly of pineapple. I look forward to experimenting with them in cooking, if I can stop eating them by the handful, like popcorn.

In my Zone 7b garden, I transplanted seedlings about one month after the average last frost, or mid-May, and got my first fruits about six weeks later. This plant does like it hot–it seemed to double in size every day the temperature hit 90 degrees or higher.

For those who practice permaculture, this plant seeds itself easily and seems to require no inputs except for hot sunshine and whatever rain may fall. Do allow space for them–halfway through the growing season, mine are five feet tall and wide–or were, before the 8-year-old ran over a few inconvenient stems with a bicycle. The stems are rigid but not woody, a bit like basil in mid-season, and may crack or break under their own weight. Because my space is limited (and shared with bicycles), my plants are now supported with slings of garden twine, tethered to a bamboo pole.  You could perhaps grow lettuce beneath them, or root vegetables, if you wished to implement companion planting.

This is a fruit that has made it into my garden’s permanent rotation. I’ll share recipes later in the summer–assuming I can quit snacking.

ground cherries physalis fruits in bowl

Dear Friend and Gardener: June 27, 2014

Dear Friend and Gardener,

It was another hot and dry week in the garden. I fed the beans with some nettle tea to perk them up. I’m starting to see flea beetle damage but the plants are big enough to be able to withstand it, I think. I have also sown a second crop elsewhere in the garden in case these do surrender their fight before long.

The tomatoes are showing signs of ripening, particularly the Principe Borgheses. I am so ready for them! I love dried tomatoes, particularly in the dead of winter, but have never tried drying any of my own. Another kitchen adventure awaits. The basil tastes splendid and there is plenty of it.

I noticed a little mildew on one of my honeyberries the other day. I shall spray it with a little milk spray if it gets truly bad, but I’m willing to let a lot go for the sake of avoiding toxic sprays. It doesn’t look terrible unless you get up close, and if you get that close, well, you shouldn’t be walking on my garden beds to begin with.

I transplanted a few Blue Hubbard squash seedlings sown from the packets I got at the seed library. I have heard that nasturtiums planted with squash will help deter squash bugs. Do you know if this is true?

Hope your garden is giving you joy and lots of tomatoes.

Best,

Amy

 

 

 

Cooling it: Helping your veggies through intense summer heat

Getting a good harvest through the summer, particularly in areas where temperatures regularly rest above 90F (32.2C), can be challenging. Today, it’s 97 (36.1C) and still. I watered early in the morning. A thick layer of straw mulch covers the ground around all the vegetables, and shredded bark mulch protects the ornamentals, but it doesn’t feel like much help.

Seeing my plants droop in the heat makes me depressed. More importantly, heat-stressed plants are more susceptible to viruses, fungal diseases, and all sorts of nasty stuff. So today, in anticipation of these ghastly temperatures, I went spelunking in the shed and found the old patio umbrella and cast iron stand. I set them up on the southwestern corner of the raised bed, where the umbrella shades the beans, tomatoes, and some of the peppers from noon until sunset. They do get morning sun, as well as reflected light all day from the gravel paths close by.

It may sound ludicrous, but providing your vegetables just a tiny bit of shade, particularly from the afternoon heat, can make a big difference in their resiliency over the season. Give it a try.

 

Digging Durham: Is this a great library, or what?

As I mulched the vegetables yesterday before the temperatures hit 93 (34C), I thought about the second sowings I need to get started.  And I remembered that while I’d donated some seeds to the Digging Durham Seed Library back in the early spring, I hadn’t been by since the collection launched to see what my fellow citizens brought forth from their seed shoeboxes to share.

seedDigging Durham Seed Library vegetable packets

Free veggie seeds for the taking: Eggplant ‘Listada di Gandia’; squash ‘Blue Hubbard’ and ‘Waltham Butternut’; bush baby lima beans; bush bean ‘Contender’; and two packets of drying beans ‘Lazy Housewife.’

What incredible luck! This covers just about everything I had planned to grow but the sweet potato slips, which can’t fit into the little envelopes, and the Malabar spinach. If I had found Malabar spinach in the seed library, I would have fainted in surprise and been roused only by the echoing choruses of “Shh!!”

I’m still a bit giddy.

“Checking out” the seeds means taking them from the drawer and taking them home. I didn’t even have to flash my library card. As part of the deal, I will grow the crops, save some seeds at the end of the season, and return them to the library for next year’s growing season. What a fantastic way to try out new vegetable varieties.

Digging Durham seed library

The seed library’s baby photo

If your local library doesn’t have a seed library, consider starting one. I can tell I’m going to be a patron of ours for as long as I can.