Golden Gate Gardener

More on the Chard Leafminer

After a series of posts on really pretty plants, I thought it was time to show something no less important but not as charming. I have written several times about Swiss chard leafminers and their management. These pests are starting to emerge from pupae and lay eggs on the undersides of my chard leaves now. The little brown pupae have been in the soil all winter, either in your garden or one nearby. The adult insects, which are small flies, have emerged from the pupae, flown away, found flies of the same species, but the opposite sex, and mated.

There are the eggs that the females lay on leaves. They are quite tiny and white, elongated, arranged in parallel rows.

And here are the larvae, which, because the insect is a fly, are correctly called maggots. When I opened the leaf, they tried to crawl back betweeh the opened layers.

Yeah, I know, they're kind of disgusting, but now you know. These are not, by the way, the maggots that live in garbage. This insect only lays eggs on Swiss chard, beets, and spinach. They are active between late March and about mid October here in San Francisco.

If you see their damage on your plants, your first defense is to brush off the eggs, or pick off any leaves on which you see the blotches that show they are feeding inside. If you are vigilant, you can prevent them from maturing to pupae and dropping to the soil. If they get ahead of you, they will repeat their life cycle several times a summer. Summer oil sprays (choose one based on an edible oil, such as canola or soy) or a bacterial extract spray that is sold under the brand names Bull's Eye or Spinosad, used according to the directions on the label, can help. However, in my college garden, the critters got ahead of us over the past few years, so my strategy this year is to remove all susceptible crops from the garden during the summer. I will replant chard only in late August or September, and protect it with a row cover (a white polyester sold for this use in gardens) until cool weather has killed any adult flies. I plan to start the plants inside about six weeks before I plant them out, to give them a little bit of a boost, and hope for a good harvest until the following March, when out they will come.

Curious to see the blotches on chard leaves? Use the legit search feature on the right side panel of this blog to search for "chard" and you can see other posts on this subject.

Finding Golden Gate Gardening in December 2007

Larry wrote a comment after my last entry about the fact that he has been waiting for some weeks for a copy of Golden Gate Gardening from Amazon.com. I called the publisher today (Sasquatch Books) and they told me that the book is definitely in print and in stock. The problem seems to be a new owner for their distributor. Books are being moved from one warehouse to another in a different state, and so are in limbo. The problem will be solved by early January. Sorry.

Although books aren't flowing into the Bay Area as they should be at the moment, I know there are plenty of them already in Bay Area stores. If you are having trouble finding the book, try local bookstores and nurseries. The San Francisco Sloat Nursery (www.sloatgarden.com) has a few, and they can send them to their stores in other cities. Flowercraft Garden Center in San Francisco (www.flowercraftgc.com) is also well stocked.

The book would make a great holiday gift for anyone gardening in the Bay Area or from Mendocino to Monterey, since right at the end of the year is a great time in our area to be starting some seedlings for planting. Broccoli, cabbage, cauliflower, leeks, lettuce, Florence fennel, and celeriac are the seeds I'll be sowing in the Christmas to New Year week or with my spring class in mid January. In February, I will be sowing radish, peas, mizuna, arugula, fava beans, carrots, beets, and a few other crops directly in the ground.

The Florence fennel and celeriac that we start inside early in the year will be part of an experiment to see if we can avoid damage by a most annoying garden pest. These crops and others at the college garden have been falling prey to some rodent. It has been eating off the roots, leaving the plant standing. When you pick up the plant, it has a gnawed base. Could be a gopher, but I suspect a rat, since I never see the aboveground mounds of a gopher and gophers are more likely to pull the whole plant into their tunnel.

We have taken action. Students removed the soil to a depth of 18 inches from one of our raised beds. In the fall, we lined it with 1/4 inch mesh galvenized fencing (also known as hardware cloth). In February, we will plant that bed and the neighboring, unlined bed with Florence fennel, celeriac, parsnip, leeks, and parsley, all favorites of whatever is eating the roots. Then we shall see if the lining will stop the damage. When we emptied the soil out of this bed, we found a tunnel entering from the side of the bed that was wide enough to stick an arm in up to the elbow. It was just under the wood of the frame. Stay tuned to see if we can outsmart the critter this year!

Bur Clover

Sometimes, when I send a photo to go with my column (for the SF Chronicle, at www.sfgate.com), there isn't room for it. I guess I had too much to say. So when that is the case, I will try to put those photos on my blog.

Today's photo is of bur clover, a weed that is related to other clovers and to peas and beans. The bur is a little pod, like a bean pod, that is curled up and has prongs along the edge to catch on fur or clothing. I've picked them up on cloth shoelaces. The plant has tiny yellow pea-type flowers and, like beans or white clover, each leaf has three leaflets. At the base of each leaf there are a pair of little wing-like structures called stipules. (If you see this plant, get out a hand lens and check out some of these details. They are really interesting when seen larger.) The plant lies fairly flat to the ground, so mowing often doesn't do much to control it. In fact, if you have it in a thinly covered grassy area, and mow the area, you will favor it over the grasses. If the grasses were to remain unmowed and grow over its top, the bur clover would be shaded out.

The writer whose question I answered in the column today had been told to pull bur clover out. This can work if you keep at it, since it is an annual plant, growing only from seeds. Pulling when the plant is small or when soil is moist or both works best. It seems to sprout at different times of year. I have the mature plants in the photograph in the garden now, but I see it in summer as well, from seeds that germinated in the spring.

The solution I gave in today's column was for a property that was not going to be actively gardened. Judith Lowry, of Larner Seeds (www.larnerseeds.com) suggested a cardboard mulch covered with purchased soil. In the purchased soil, she suggested sowing seeds of red fescue. This is a solution intended for California, near the coast, where red fescue is native. I'm sure there would be other best choices of grass for other parts of the world.

Chard Leafminers

My Golden Gate Gardener column in the Home Section of the SF Chronicle this morning (accessible at www.sfgate.com) was about the leafminers that attack Swiss chard, beets, and spinach. I thought you'd like to see a photo to help identify this Swiss chard pest. Leafminers are larvae of a fly. They lay tiny white eggs on the leaf undersides. When the maggots hatch, they eat a hole in the leaf surface and start eating out the leaf--the part of the leaf between the upper and lower epidermises (epidermi?). Some leafminers, like the ones that infest columbine, eat winding trails in the leaf, but the one shown here usually creats big ugly blotches.

What to do? I have been fighting these critters for several years, removing leaves with damage, spraying with summer oils (purchased at nurseries) to kill the eggs. (The oil product I use is based on canola oil, with a sticker-spreader, so should be nontoxic to people.) Even tried Spinosad, a new product, containing an exudate of a bacterium, that is registered for use by organic farmers. Some neem oil products are also registered for use on this pest and crop.

But the problem is that the maggot isn't damaged much by chemicals unless they penetrate into every cell, and products that do this would render the plants inedible. The catch 22.

What else to do? You can try to kill the pupae. They fall to the soil and later emerge as adult flies. The life cycle repeats about monthly from the end of March to mid October in San Francisco's climate, with the winter generation overwintering as pupae. I plan to keep the chard I am growing until March (may as well, it won't have the damage then). In March, I will take it all out and dig the soil to turn up any pupae it contains where they are likely to dry out or be damaged, or maybe (hopefully) eaten by birds. (In summer, when the soil is warmer, you could apply beneficial nematodes to the soil. They are a bit pricy, but should eat this and other pests.)

Then, no chard, beets, or spinach all summer. (There is plenty else to grow.)

In late summer, I shall start some chard seed indoors. When it is a month or two old, I will plant it in the garden. If it is ready to plant, but still before mid-October, I will cover it with row cover (a thin spun-polyester material that lets light and water through) making sure it is secured at the ground so flies can't fly in. When the weather turns cool enough to kill the flies, off will come the row cover. Then I should have chard unmolested until the following March.

Has anyone had any better ideas for dealing with this annoying pest of chard, beets, and spinach?

Battling a Swiss Chard Pest

Every year, the leaf miners ruin my Swiss chard all summer. Maggots in the leaves, with their accompanying frass (bug doo) render it rather unappetizing. In past years, I have sprayed with summer oil every week, or as often as I can remember to do it, but the improvement has been only slight.

I have been reading about a new product, called Spinosad, and have finally tried it on my Swiss chard. About a week and a half after the first spraying, there seem to be fewer new injuries. I also sprayed spinach that was being damaged, with similar results. Tomorrow, I will clean up the plants and spray it again.

Spinosad (also sold as Bulls-Eye), is made by fermenting the bacterium Saccharopolyspora spinosa. Two of the metabolites of this bacterium (that is, products of its metabolism) are highly toxic to a number of insects. It is said to stop susceptible insects from feeding in one hour, and remain toxic to newly arriving insects for the next week or two. It is also said to spare lady beetles, lacewings, and minute pirate bugs, all creatures that eat pest insects in our gardens. It breaks down in sunlight and does not persist in soil. The amount of time to wait after spraying before you harvest varies, but for Swiss chard and other leafy greens, it is one day. It is OMRI, meaining approved for use by organic farmers.

At this point, I don't know every detail about this material, but if the leafminers desist from mining in my Swiss chard leaves, I will find out the ones I don't know yet and report them. It is also said to kill thrips, caterpillars, sawflies, and a number of other pests. (A critter called a rose slug is a sawfly larva. I see it on San Francisco roses often. Summer oil is relatively effective against it, but for serious infestations, Spinosad may be just the ticket.)

By the way, the leafminer in the chard and spinach is the larva of a fly (therefore it's a maggot) that eats out the inside of leaves, causing ugly blotches.The fly lays eggs on the leaves of chard and spinach; the larvae hatch out and enter the leaves. When they have eaten their fill, they drop to the ground to pupate. When they emerge from the pupae, the flies breed and lay eggs again. This goes on in the warmer part of the year here in San Francisco, from late March until mid-October. (Chard and spinach growing October to March are safe, but you have to start them earlier than mid-October for good winter production.)

The fact that the pupae live in the soil means that beneficial nematodes watered into the soil might help as well. I am thinking of getting some this year. These microscopic creatures that you can purchase are only effective when the soil is warm, so I will wait a few more weeks before adding them.

Moth Pheromone Lures

I just read the comment seeking information on moth pheromone lures to control light brown apple moths in home orchards (see previous post, with comment). I haven't checked to see if the right lures are available in California, though Peaceful Valley would be a good place to look. However, it has been my understanding that these lures work best in a larger planting. In just a few trees, the lures will confuse a few male moths, leaving nearby females unfertilized, but females ready to lay eggs are likely to just fly in from the next yard. In larger orchards, they even recommend putting the lures not only throughout the orchard, but also outside the margins of the orchard all around, so that nearby moths won't be fertilized.

The CDFA is using traps to monitor for the moths, I think that have some pheromone in them and catch the moths on a sticky surface. This is a good idea of you want to know if they are around, and IF you can identify what you have caught. In Australia, grape growers use a homemade trap to catch insects and see what they have. They use (cheap) port wine, in a 10% solution, in a container that is about 6 inches wide and 8 inches deep. They put a wire mesh with half-inch holes in it over the container to keep the birds out. Then they inspect it at least twice a week, so that freshly caught moths may still be floating, so easier to count and identify. Again, both of these kinds of traps are for monitoring, rather than control, but we are in the monitoring phase right now, for the most part. And both traps depend on your being able to recognize the insect--or take it to a County Agricultural Commissioner who can.

What you are more likely to see than adults is the yellow green caterpillar with a brown head, and some webbing around young leaves, and maybe involving the young fruits. They say the caterpillars are more common low on the tree, which is good, since that is where you are most likely to be looking. If think you see one, you can bag or bottle it up, with some of the plant, and consult your local ag commissioner.

As I say, very few of these moths are being spotted so far, so noticing them is probably more important than combating them. You are far likelier to have damage from ordinary pests, such as codling moth, than this still quite rare moth.

If you want to do something to decrease the likelihood of damage to backyard trees, thin your fruit properly, since the critter is more damaging when it is able to web several fruits together, and pick up fallen fruit.

Moth Invaders?

I've spent the past few days researching the light brown apple moth, an insect that has recently appeared in the Bay Area. It is native to Southeast Australia, and has escaped to New Zealand, Great Britain, Ireland, and Hawaii. Now a number of them have been found here in California. There is a map on the California Department of Food and Agriculture site showing where they have been found. It's at: http://www.cdfa.ca.gov/phpps/pdep/Map_of_LBAM_Detections.pdf

The Chronicle had an article about the pest in the Business Section on Thursday, April 5th, and will be running more stories in the Home Section. I have written an article for the Chronicle about the biology of the pest; Ron Sullivan and Joel Eaton will be reporting on the steps being taken to contain it. Look for at least one of these stories on Saturday, April 14th--and part of the matter might be carried forward to Wednesday, April 18th.

It is a tiny moth, with a small caterpillar that is mostly a leafroller. That is, it rolls itself up in the leaf to feed. One important fact to know abot it is that it eats over 200 kinds of plants, so once we had it, it would be almost impossible to get rid of.  Another is that it damages grapes, including the fruits, when it gets them tied up in its webbing early in the season. Another is that some of California's trading partners would demand special treatment of crops for export, and others might refuse to trade with California. You can see why the California Department of Food and Agriculture wants to keep it out of the state's agricultural areas, or, preferably send it packing out of the state.

Watch for quarantine information. It is important not to carry the pest accidentally into uninfested areas. It can live on a number of garden flowers and vegetables, so expect some upcoming crimps in your usual gardener's generosity. You know, the "Here, take a bouquet home with you. And would you like some Swiss chard."

Stay tuned to learn more about this invading pest.

A rose cane may die--should you worry?

In last week's column for the S.F. Chronicle (September 27, 2006), I wrote about the fact that roses are prone to occasional dying canes and that this can be caused by many different stresses. Cold winters can cause canes to die, but so can botrytis (gray mold), powdery mildew, black spot disease, soil that is too wet, too much fertilizer. Less commonly, there are insects borers or canker diseases that can kill canes. Many cane deaths start with an injury that isn't lethal in itself, but allows a fungus in that kills the cane. And these fungi aren't ones that cause a specific disease, just opportunistic fungi that attack weakened plant tissue. And the injury could be just normal deadheading or pruning.

With all of these causes, one begins to feel it must be the exception that rose canes survive, and yet, survive they mostly do. The bottom line is that a few may die, you cut them out and try to figure out if you can do anything else to prevent it from happening again.

I think that learning to grow plants is often a process of learning when to worry and how much to worry. New gardeners often worry when a single leaf turns yellow, a single twig dies. It is right to worry when rose canes die, but, like an occasional yellow leaf, it might not have an underlying cause you could have anticipated, or, it might.

Read my columns on www.sfgate.com. You can find them by searching for my name (Pam Peirce) or for a specific topic.

Thoughts on Snails in Gardens

I have been thinking about how best to deal with imported brown garden snails in the garden. I was out early this morning, and I found one medium-sized one and maybe a dozen tiny ones in my small front garden. I pay special attention to which plants they are climbing. And I also pay attention to which plants they eschew. (That is, they don't chew.)

If I plant a dahlia, any snails in the vicinity are all over it right away. But they aren't at all interested in Mexican sage (Salvia leucantha), feverfew (Tanacetum parthenium), or Jupiter's beard (Centranthus ruber). They never touch my California fuchsia, which is blooming like crazy in the garden right now, or the matilija poppy, the California poppy, or the blue-eyed grass. They aren't interested in the leaves of Pacific coast iris, but will eat the flowers. I planted Oenothera odorata, and they do not like it, but they do like the flowers of gazania.

This morning, I found all of the little snails on the stems and flowers of an Erysimum 'Apricot Twist'. I found the bigger one on Gazania. Duly noted, though, the erysimum has been blooming all summer and hasn't attracted many snails before this.

In zoos, in the areas where vegetarian animals are living, they have to plant things they won't eat. Otherwise, the animals would simply eat up the plants right away, and the results would look depressing and ugly to the human zoo goers. So zoo landscapers are forced to put the animals in compounds with plants that look like they are from the right habitat, but which the animals actually rather detest. (But before you feel sorry for them, remember they get fed stuff they like. So, for example, the Koalas get branches of fresh eucalyptus leaves brought to them as needed.)

Taking a clue from the zoo (the landscaping, not the feeding part) we can plant a garden that snails don't much like. It is already done to avoid deer damage, but many gardeners just keep planting anything they like in gardens where they haven't planned to put much energy into eliminating snails, and are then surprised when snails eat plants up.

So that is part of the equation. If you don't plan to meticulously control snails, don't plant their favorite food. Another important part is that if you do plant something they will eat, snail bait alone is unlikely to be adequate to eliminate snails from a garden. You probably will have to remove some of them by hand. They are, after all, are slow-moving creatures. And in the daytime, they don't usually move at all. They have predictable daytime hiding places where they generally sit quietly. So why not remove them? They hide in places that are rather dry, dark, and have a smooth surface to cling to. Once you find their favorite daytime hiding places, you will find that there are usually some there (as long as there are any left in your garden.) And night or early morning hunts find them right out in the open, and also show you which plants they really like.

When you have taken a snail out of your garden (or returned it to the soil as fertilizer) you have stopped its damage. I can't see why anyone wouldn't want to do this before, and as an adjunct to, beer traps, Sluggo bait, or any other method that depends on the snail finding what you left for it and preferring it to your plants. There has to be a lag time, during which the snail is eating a garden plant. (Bothers me to lie awake wondering if the snails found my new viola transplants first or the snail bait I left in the garden.)

Anyway, that's why these two steps are first on my snail damage prevention "to do list:" 

--watch what they eat. Don't plant favorites where you can't protect them.

--hand pick as much as possible. They have slow life cycles. You really can make a big difference with just a few hunts.

Pardon me, I think I will take a flashlight now and try to get a few more of the small ones, from last summer's hatch, before they find my violas...

Habitat Earth and Our Gardens

An editorial in the July 3rd New York Times under the heading "The Rural Life" is about observing birds. The author, Verlyn Klinkenborg, has begun to notice that birds occupy certain "spacial dimensions" as they live among us. That is, the redwinged blackbird lives in the marsh, the meadowlark hunts from the fencepost, the phoebes hunt bugs low to the ground, the barn swallows higher up, the catbird in the thicket at the edge of the lawn. He (I think the name is masculine) is struggling with the concept of habitat, that a bird can't choose to live a certain place, the way a human chooses to live in a particular city.

I quote: "It takes an act of will on our part to remember how profoundly, and how beautifully, bound to habitat all the other creatures around us really are."

I am struck by more thoughts than I can record. One is that most people indeed, may not understand habitat, and the chain of eaters that make up an ecosystem. I saw a Nature program on KQED Public television a few weeks ago that illustrated the concept beautifully by showing how a fig tree growing in the wild, in Africa, served as a host for many many creatures who depend on it for food. And then some of the creatures on the tree are eating others on the tree. There were the wasps that breed in the figs, pollinating them, the creatures that eat the emerging wasps, the creatures that eat the ripe figs, and the ones that hunt them, ones that eat the leaves of the tree, and so forth. And of course there is all of the life related to other food chains in the same place, and all of the invisible life in the soil and of microorganisms. If this ecosystem is disrupted, some of these creatures will not be able to survive in it. Unlike humans, most creatures are slow to adapt to new conditions and simply die if their accustomed food isn't available.

We think of our gardens as nature, and of course they do contain many of the creatures of nature, but they are highly disrupted nature. They are anthropocentric, human centered, selections from nature. They are not wild ecosystems. Even our native plant gardens are not the same as wild ecosystems. We select what we want in our gardens. We do not invite the poison oak (a major food for the California state bird, the quail) or the rattlesnake. We don't encourage bumblebees to make a nest in our small urban gardens. We want the birds and the butterflies, but not the skunks and the cougars. And humans have also inadvertently brought to our gardens nonnative eaters, like European species of snails, that don't have much in the way of predators native to our gardens.

(If the fig tree of the Nature story were in a garden, along with all of its many eaters, the human would become just one among many eaters, competing for the fruit. And the tree would not be beautiful, but mangy and eaten. Humans would even be in danger of becoming the prey of a larger animal.)

Because we eliminate some of the links in the chain in our gardens, and introduce new creatures, we then have a different proportion of the remaining creatures than would exist in the wild. Because of this disruption, sometimes we have a huge population of eaters that are destroying something we really wanted to enjoy looking at in a perfect state, or that we wanted to eat up ourselves. Here our options are to let the critters have the plants (though if the habitat were completely undisturbed, some other creature might not let them eat as unmolested as they are in our garden), or try to reduce the population of eaters.

Integrated pest management is the best strategy yet devised to deal with the situation. It entails, first, a decision whether the pest damage is intolerable. If not, let it be. If so, you begin a careful logical progression of possible solutions, starting with the ones that are least likely to harm natural predators. If you can't find a way to solve the problem without more harm to natural predators than you want to cause, you can stop short of a solution that might save your plants but might also kill something you want to spare. But often you can find a less draconian solution.

Some people choose to garden following "organic" principles, which means using few or no chemicals.Using IPM logic is a great help to them as well, giving them many many tools that manage pests in ways that improve the balance of the habitat.

Birds are indeed habitat dependent, and a story in the July 4th SF Chronicle by Environment Writer Jane Kay, says that bird extinctions are on the rise. Some birds can use our gardens as habitats, if we plant something that feeds them, like native berried bushes, or use few or no pesticides, so the insects they eat won't poison them, but other birds need marshes or forests, or African fig trees in the wild, so the problem is wider than our gardens.

In the final analysis, we ourselves are not really free of habitat limitations. We have learned to use many different natural habitats, and to ship materials to house, clothe and feed us so we can live in cities and other habitats that don't provide our basic needs on site, but our habitat is the planet earth, and if we make it inhospitable for ourselves, we will not be able to make a living on it.

Not so cheery, eh? But gardening is a way into understanding this stuff, and knowledge, as they say, is power.