Golden Gate Gardener

New Biofungicides Pit Bacteria Against Garden Fungi

March 21, 2023 New York Times, Science Times, D5 announced the discovery of compounds made by bacteria that kill pathogenic fungi in both plants and animals by riddling them with holes. It has proven effective against Botrytis cinera, or gray mold, and against Candida albicans, a fungus that cam infect the human body.

            The Times story was about the naming of the new compounds keanumycins, after an actor who has held “many iconic roles in which he is extremely efficient in ‘inactivating’ his enemies, Keanu Reeves. (Mr. Reeves says he thinks the naming is “pretty cool,” though he thinks it might have been more appropriate to name the compounds after John Wick, the killer he plays in a recent film.) While the article contains no information to suggest that keanumycins are available in any commercial product at present, there has been much research in the area of biofungicides recently. However, some new products do protect plants against gray mold.

The strawberry on the left is so badly infected with Botrytis, or gray mold, that it will never enlarge or ripen.

            This disease is common in humid locations, such as in a greenhouse or near the coast in and near San Francisco. You may have seen it on strawberry fruits, where it makes a very obvious gray mass. It also grows on leaves and flowers of susceptible plants such as tomato, rose, German primrose, and painted tongue (Salpoglossis). I used to tell gardeners that their best defense against the disease was to pick off all traces of infected plant material before it could spread spores. This is still excellent advice that you should act upon whether or not you have another tactic. You can also select plants for a humid garden that have smooth or waxy leaves and fruit that is not soft. (This is easy unless you have your heart set on growing tomatoes, roses, or strawberries.)

 

Botrytis shows itself as colored spots on the petals of roses. To reduce its spread, pick up all fallen rose petals and deadhead spent roses. 

            However, you may also want to try products currently available that promise to kill Botrytis cinerea. The ones I know of contain the soil bacterium Bacillis amyloliquifasciens D747. One formulation that contains it is sold as Revitalize. You can get it as a concentrate or in a ready-to-use spray bottle. It can also be used as a soil drench to control a number of diseases that start there. Also on the label of products containing this bacterium are anthracnose, bacterial leaf blights, black spot of roses, various leaf spots, and powdery mildew. Those diseases are controlled by the product. Only suppression, not control, are promised for downy mildew, early blight, fire blight, and scab. In all cases, it is best to apply the product before the disease shows up or in its very early stages.

            The main point is that a considerable amount of research is taking place in the area of biofungicides, some that has resulted in products already on the market, others in the pipeline. So, it is a good idea to start studying the offerings of your local, environmentally responsible garden center and reading the labels. You will already be pleasantly surprised, and more, even better surprises are likely to come soon.

Garden Tip

Got Pests? Try Botanical Oils

            Into every beautiful and productive garden a little nasty pest activity may fall. Aphids may infest the kale, powdery mildew coat the leaves of zucchini, black spot mar the rose leaves, or little white flies flutter while their nymphs are sucking the sap from a shrub.

            In the early days of modern pesticides, incredibly toxic chemicals were sold to home gardeners to manage pests. These days, the products we use are more likely to kill pests without threatening our health as well. A good example is oil-based pesticide.

            Petroleum oil in water, with a sticker-spreader to keep it from settling out of solution, was long used to spray woody plants in winter. It was called “dormant oil.” If you sprayed it when leaves or flowers were present, it burned them. Because of this, other, often less environmentally friendly, chemicals were used in the summer.

            However at some point, researchers learned that it was sulfur impurities in the petroleum oils that made it toxic to leaves. So they refined the sulfur out and sold the new products as “superior” or “summer” oils. You could safely spray them on leaves and flowers all summer, as long as the temperature was below 90 degrees F when you sprayed.

            Oil kills by clogging the breathing pores of insects or actually exploding the spores and other cells of fungus. And as research continued, It was found that many kinds of botanical oils will also do the job. Products based on oil of canola, soy, linseed, sesame, even jojoba (a desert plant) began to appear (read the active ingredients list). Some of these sprays include aromatic oils, such as thyme and peppermint, which might offer some repellant action.

            I encourage you to try these products, based on renewable, even edible, oil sources, in your garden. I have permanently stopped an aphid infection of kale with a single, thorough spray of a botanical oil product. However it is usually necessary to respray every week or two to continue the protection. Also, to control diseases, oils are most effective as a preventative or at the very first signs. If you spray early, you can kill spores on plant surfaces, but once a fungus grows deep inside the plant, where sprays can’t reach, it is often too late. Follow directions on labels and watch your plants.

            Another oil product that kills insects and some disease spores is Neem oil. It also is toxic for insects to eat and kind of disgusting to them, so reduces feeding and even egglaying. However, the ingredient, azadirachtin, is a growth retardant for bees, so I prefer to try other oils first, or save neem oil for pests not listed on labels of botanical oil products. Azadirachtin breaks down in sunlight in 100 hours. Follow directions on label, including about interval between spraying food crops and eating them.

           

Fruit Growing Resources

Here are my recommendations for sources of information on growing fruit and nuts in San Francisco and the Greater Bay Area. Also search this blog for info on citrus HLB disease and on wooly apple aphid, both problems for which you should keep a lookout: 

Golden Gate Gardener: Third Edition, Pam Pairce, Sasquatch Books, 2010. The chapter on fruit is a good primer on selection of fruit-bearing plants for Bay Area gardens, with a discussion of microclimate adaptation and summaries of the care and possible problems involved in growing specific fruits. Suggested varieties included.

ANR University of California Publication 8261 Selecting Fruit, Nut, and Berry Crops for Home Gardens in San Mateo and San Francisco Counties, by K. S. Jones and Laurence R. Costello. https://anrcatalog.ucanr.edu/Details.aspx?itemNo=8261#FullDescription

Grow a Little Fruit Tree, Ann Ralph, Storey Publishing, 2104  This is my favorite book for current and prospective fruit tree owners. She covers choosing, planting, harvesting, pests, but most importantly, pruning. The most important information in the book is how to make the first cut and prune the tree in the early years to create trees that you can harvest without having to use a ladder. The illustrations are attractive and useful. 

California Rare Fruit Growers: This California-wide organization has local chapters that often give workshops or hold scion exchanges. They are on the web at crfg.org. Especially useful is the fruit facts Wiki, https://crfg.org/wiki/fruit/, which includes fact sheets for many kinds of fruits, especially subtropical ones. They also now have  YouTube programs, at https://www.youtube.com/results?search_query=crfg.

 

A New Protector Against Burrowing Animals

This spring I found that a burrowing animal was eating plants, roots and tops, in my small front garden. I know it was not a mole, because moles don't eat plants, just insects and earthworms. Could have been a gopher, but by the amount it ate in a night, I thought maybe something smaller, maybe a RAT! (The rats that burrow are called sewer rats; the ones that don't, roof rats. Rats have burrowed in my backyard before so this seemed a good guess.)

Whatever it was, my Chinese forget-me-nots, the ones I grew lovingly from seed and transplanted into the garden, were disappearing night by night. Then whatever it was started in on the primroses I just bought and set out, and the large 'Moonglow' yellow yarrow was losing branches, then roots. Then it ate most of the tops off of two x kellereri yarrows!  These were divisions of my original plant-which is one of my favorites. Something had to happen.

I dug out all of the yarrow, both 'Moonglow' and  Kellereri, and what was left of the primroses and put them all in pots on the back porch. Then I cleared away and found the place the varmint had blocked up the opening of its burrow. I dug it out, exposing the hole. The varmint had replugged it the next morning. I repeated. It repeated. I repeated. After many repeats, over several days, I decided I had to escalate. I have heard that water down the burrow can discourage a burrowing pest, but doubted it in a large garden, but in my 10 x 12 foot front garden, maybe it would work. I wanted to tell the varmint that this was not a good place for a home, before it ate everything left there. At this point about a quarter of the tiny space was a wreck. My husband was beginning to ask whether maybe I should be looking for a trap. I said hold on, let's see if this works.

So, the next day, I dug the plug out again, got the hose, attached a jet nozzle, and put it down the hole. Turned on the water. Most of it stayed in the hole. But the next say, the plug was back.

Over the course of a week or so, I dug out the burrow plug 8 or 10 times, used the hose 3 times. And then the varmint stopped replugging the hole. 

During the battle, I decided to replant a couple of plants in gopher baskets. And here is where my problem led to a discovery that will be useful to other gardeners. When I went over to San Francisco's Flowercraft nursery, they offered me a new kind of basket, made of a soft stainless steel wire mesh. So this is what I have used, and have written about it in my May 8th, 2016 SF Chronicle column.They are called Grow Master Baskets. To learn more about them and see who sells them, see westernplantingsolutions.com or call 530-751-3366.

These baskets are less expensive than the old kind, easier to handle, and come in many sizes.  The company suggests fitting a basket over the rootball like a glove, but I have used baskets that are a bit larger than present rootballs, spreading the baskets in a wider planting hole, and putting some soil in them, then setting the plants in the soil.That way the plant has room to grow more roots and still be protected.

'Moonglow' yarrow plant in a Grow Master anti-gopher basket

When I first used the basket, the varmint was still active. Because I had used a somewhat larger basket than the rootball, there was enough of it to roll up over the plant and secure with some plant-tie that I ran through some of the openings in the mesh. This protected the top of the plant as well as the roots while it got re-established, and while I figured out what to do next.

But now I have uncovered all of the protected plants. The 'Moonglow' yarrow is about to bloom. The x kellereri yarrows are still recovering in pots, but they shall return. And one Chinese forget-me-not survived to bloom beautifully!

 

 

Bay Area Citrus in Great Danger

If you have citrus trees in your garden, or know someone who does, listen up. A pest insect that has wiped out half of the citrus crop in Florida is spreading in California and has reached the Bay Area. Last year, a new quarantine area was created in the San Jose region, because the pest was found in trees there. Now the most recent quarantine area covers the northern peninsula and a swath of the southern part of San Francisco.

Lemons on a Healthy Lemon Tree in San Francisco

The insect itself will not kill the tree, but it often carries a deadly disease, and if a particular individual insect is carrying that disease, it will infect the tree while it is feeding. And then there is no cure. Other Asian citrus psyllids will pick up the disease from that infected tree, and will spread it.

So far, none of the insects found in our region have been carrying the disease, but it seems like only a matter of time till one does. Scientists are looking for a cure, or a way to breed resistance to the disease into citrus trees, and would like to buy as much time as they can by keeping the problem in as small an area as possible.

What to do? Inspect your trees. Spring is a good time to do it, since it is a time when there is much active growth on citrus. Look carefully at as many of the growing tips, with their small, new leaves, as you can. The insect, which is called the Asian Citrus Psyllid, or ACP, lays very small yellow-orange eggs in new growth. They will be easier to see with a magnifying glass. The eggs hatch into yellow nymphs that average sesame seed-sized. They are also distinctive in having long, white "tubules" with bulbous ends that extend from their bodies. The adults are aphid-like, mottled browns, and stand with their rear in the air, heads down, sucking sap.

Asian Citrus Psyllid Nymphs

Asian Citrus Psyllid Adult Feeding on Citrus Leaf

If you find the insect on your tree, and are not in an area already quarantined, you should call the California Food & Agriculture (CDFA) Exotic Pest Hotline at 800-491-1899. If you are within  the quarantine area already, you should try to kill the pest.

To see an interactive map of the quarantined areas and more photos and learn the best ways to control the pest, see the following UC  website: http://ucanr.edu/sites/ACP/Homeowner_Options/

Also, be sure to buy citrus only from responsible sources. (Major citrus tree growers are now growing trees for the market only in covered production areas that the pest can't get into.) Don't accept plants, cuttings, or grafting material from other gardeners.

And if you are in a quarantined area, don't take any leafy branches outside of it. (You can share your fruit outside of the quarantined area if it doesn't have any stems or leaves attached.)

The insect can also infest some plants that are related to edible citrus, like calamondin (xCitrofortunella microcarpa), box orange (Severinia buxifolia), orange jessamine or orange jasmine (Murraya paniculata), and Indian curry leaf (Murraya koenigii). They should also be inspected and are subject to the same quarantine rules.

The disease we are trying to avoid, and that I hope we never see, is Huanglongbing, or HLB. It is also known as yellow shoot or yellow dragon disease. The leaves of infected trees have yellow blotches, usually starting in one section of the tree. The blotches don't look like most nutritional deficiencies in that they cross the leaf veins, and are often arranged asymmetrically on the leaf. Fruit develops unevenly, asymmetrically, ripens poorly, with little juice and a bitter flavor. The disease will kill the tree. If it appears, the only recourse at this time is to remove the infected tree before the disease spreads to other ones.

So let's get out there and look now, before it's too late!

Yellow-blotched Leaves of a Citrus Tree Infected with HLB Disease.

Roly-Poly Problems

I got the following question through my web site. I'll answer it below. I was trying to wait until I had a good photo of these little critters, but I don't seem to have very many of them these days, so there's no photo for this post.

The Question:
My veggie garden has been besieged by roly polies.  When I check gardening blogs, most answer that roly polies do not eat live plant tissue but they are definitely eating the base of my cucumber and squash plants. I caught most of them early and taped the base of the stems so they couldn't continue to gnaw away...but they have!!!  They continue to move up the stem even though the stem is tougher than when they were small seedlings.  I have lost a few plants to them. My vegies are mulched with my homemade compost which is a cold one and probably supports the rolly pollies.  How do I rid my soil of them?  They are everywhere!!  BTW I live in San Rafael, Marin County.  Should I solarize the soil?

The answer:Too many garden how-to books and other guides are researched by reading what others have written, so we get the same information over and over. And wrong information over and over is frustrating.

Roly Polies will generally eat any living or dead plant matter that is soft enough, inlcuding much dead, decaying plant matter. If there are only a few of them, they may not damage crops much, but when their populations build up, they do significant damage. While I've never seen sow and pill bugs eat squash stems, I have watched them chew up the blossom ends of summer squash fruit and eat into ripe tomatoes.

"Roly Polies" is a general common name for both sow bugs and pill bugs, which often occur together in gardens. These are two different species of animal, both more closely related to shrimp than to insects. We call the species that can't roll up sow bugs, the ones that form a tight ball when disturbed, pill bugs, but their habits and management are about the same.

Your goal is to make conditions unpleasant for them and to reduce their numbers if they get so numerous that they are becoming pests. Start by pulling the mulch back from your squash plants, leaving a bare area a few inches wide around them. Try to keep this surface, especially, but all of your garden soil or mulch surface, as dry as possible, since these creatures need to stay moist to survive.

I doubt that solarizing the soil will help with sow and pill bugs. They would tend to run out of the hot area under the plastic. You might get eggs, but the adults are very mobile.

Sow and pill bugs tend to congregate in moist dark places in the day time. You have to move fast, but if you know where they are hiding, and see a lot of them in one place, you can scoop them into a plastic bag, seal it, freeze it, and compost them. Or you can leave out traps, in the form of anchored opaque plastic sheeting or cardboard, remove it fast, and start scooping. Try using a kitchen scoop or a deep trowel.

If you have many sow and pill bugs in an area you are about to clear and replant, try to reduce the population before you plant seeds or set out new seedlings there. Waiting a couple of weeks may be enough, but if you have many of the creatures, you may want to use mechanical means, as just described, or chemical means, as follows, to reduce the population.

I never use chemical means as a first resort, but you may want to supplement your cultural and mechanical methods by using a product called SluggoPlus. In addition to the iron phosphate that kills snails and slugs, it contains Spinosad, an extract from a soil microorganism, that is toxic to sow and pill bugs, earwigs, and cutworms. Use it according to directions, including not spreading it any more thickly than the directions indicate, as it is toxic to pets. (If spread according to directions, very thinly, it is less likely that a dog might eat enough of it to harm it, but do read the directions.)

Good luck reducing your roly poly problem!

 

 

More on Early Blight of Potatoes & Tomatoes

(See photos in the previous post)

In my last post, I reported having seen some potato plants in San Francisco with what looked like early blight, a disease caused by the fungus Alternaria solani. I remembered from my research for the book Controlling Vegetable Pests, which I wrote in the early '90s, that this disease is not common here in California, but much more so elsewhere in the US. I wrote then that it is "less common in arid regions of the West, although overhead irrigation and frequent heavy dew promote disease in these areas." It showed up the week after we had an unusual June rain, and in a garden that has frequent fog. But the question is: Where did the spores come from?

My first thought was that someone had planted potatoes from the grocery store. These could carry the spores, even without symptoms, or could have had dark lesions with underlying brown or blacky corky rot from spores that grew on their surfaces. However, the gardener assured me that these were purchased at a nursery as certified disease-free.

So the spores must have blown in from a nearby garden or were carried in the rain. Then they landed on potato leaves that had some injury, at a time when the temperature and amount of hunidity were right for them to start growing, and the rest is history. The ideal temperature for early blight spore growth is 75-80 degrees F, but the symptoms develop fastest at 70 degrees. 

This disease can also infect tomato, and, occasionally, eggplant or pepper. Wild relatives of these plants are also susceptible. On tomato, the leafe symptoms, the bull's eye spots, are the same as on potato, and there may be sunken lesions on older stems. In additon, there may be excessive blossom drop (common here anyway due to cold nights) and leathery, sunken, dark brown lesions on the stem end of the fruits.

If this disease shows up in your garden, take the plants out of the garden. (In San Francisco, they can go in the Green Bin, since the municipal composting system will heat up enough to kill the spores.) If potato plants have formed tubers, eat them up soon, as they may decay in storage. Don't store them where you will kep other, healthy, potatoes later.

The spores can germinate in plant material from infected plants as long as it has not completely decayed, so pick up every bit of the plant and dig up most of its root. Do not save seeds from tomatoes that ripened on infected plants, as the spores can hide in the seeds.

Remove any solanum weeds that are growing in your garden, as they can harbor the disease. (They have flowers similar to those of tomato, but usually with white or pale lavender petals, and have clusters of small, inedible berries that turn black when ripe.)

Plan not to grow tomatoes or potatoes in the place where infected plants grew for two to three years.

When you do plant potatoes or tomatoes, provide your plants with adequate water and fertilizer and avoid getting water on the leaves of tomato'potato family plants. Start examining them when they are about a foot tall to be sure they do not have symptoms. Prevention is more successful than cure when it comes to plant diseases, but if you have had the disease, or if you see the first lesions it is causing, you might try the fungicide Serenade, which is based on a soil bacterium. Follow directions on the label, including repeated sprayings as it directs. (If you are spraying after seeing lesions on a leaf or two, pick off those first infected leaves before you spray.)

May early blight of tomato or potato not darken your door, or the leaves of any plants you are growing to produce food!

Early Blight Appears on Local Potatoes

When I saw these symptoms on some potatoes in a local garden, I thought they looked like early blght of potato and tomato, a disease caused by the fungus Alternaria solani. But I thought it unlikely, because this is not a common disease in our region. I tried to return to get good photos of the diseased plants, but when I arrived, the plants had been pulled, so my photos show leaves I selected to show the symptoms.

The most diagnostic symptom is those dark brown lesions on the leaves with concentric rings visible in them. Those are from repeated growth of the fungus and release of spores. Symptoms are similar on tomato. Also susceptible are a number of wild potato/tomato relatives and other members of this plant family.

Eventually, the brown spots coalesce so that the entire leaves become brown and die.

(This is an entirely different disease from Late Blight, which is Phytophthora infestans. Search this blog for more on that disease, with photos of its symptoms.)

Potato/tomato early blight is spread by spores, as are most fungi. I sent a sample of the diseased leaves, through the Cooperative Extension, to Brenna Aegarter, a UC potato expert in Stockton to ask for help identifying the disease. She lifted spores from the leaves with Scotch tape and put them under the microscope. Here is what she saw, followed by her reply:

"There is clearly Ulocladium and Cladosporium (which are common “molds” on senescing/decaying leaves) as well as some Alternaria spores. However, the challenge is that there are two types of Alternarias in the world. One type is a common mold and would often be found on dying leaves. The other type are pathogens of plants and infect tissue that is living (and includes Alternaria solani cause of early blight). The ones that are not pathogens have short “beaks” while the pathogenic ones have long beaks (the narrow section of the spore that extends out).  Under the microscope I saw Alternaria spores with beaks, but the beaks were not so long as to entirely convince me that they are spores of Alternaria solani. But I have sent my photo to a colleague to see what he thinks. Stay tuned!"

Later, I heard from her to the effect that her colleague had confirmed that the beaked spores are Alternaria solani. If you look at the slide, you will see the ones with a long point on one end. There are the other, decay bacteria spores also, and I think the large, long objects are probably plant hairs.

I will, in my next post, explain this disease and what to do about it.

Email as an Aphid Managment Tactic

I planted broccoli in my community garden last fall, and this spring, as it neared bearing age, it was overrun with aphids. The worst was the largest plant, which tipped over in a winter storm. (It is often the case that a plant with damaged roots becomes most attractive to aphids.) What to do?

I began by crushing as many aphids on leaves as I could find, and washing the leaves with the hose as I went. I looked over the plants carefully, checking the undersides of leaves and in curled over leaves.

When a leaf was heavily infested, I sometimes broke it off and took it away to a green bin (our municipal composting container here in San Francisco). As it began to bear heads, I removed them too, as they were so full of aphids I didn't want to try to get them clean.

I also noted that there were many lady beetles (ladybugs) on my African blue basil plant (a perennial that was coming back from winter), so I assume some of them were eating aphids on the broccoli, though I never saw one there. And, some of the aphids were turning brown and puffy, since they had been parasitized by the miniwasp that preys on aphids.

But after 2 weeks, with the problem not going away, I used a different pest management tactic, the email. I sent an email to a gardener in an adjacent plot to say that there were so many aphids on the Russian kale in that plot that it was certainly inedible, and so many that they were surely flying over to my broccoli in search of more to eat.

I think this tactic turned the tide. The next time I looked, the infested kale was gone (thank you!) and within a week, the infestation of my broccoli was much lower. I still searched and found pockets of aphids on inner leaves, but it was so much better.

Then, in a couple of weeks, presto, clean broccoli heads! I have been enjoying them ever since. I like to steam a few lightly and refirgerate them to cut up and put on a salad!

 

Healthy Schools Information

I am giving some classes about pest management for some school garden coordinators in San Francisco. Because of this, I have been researching the legalities of pest management in California schools. Below are some links to information that explains the Healthy Schools Act, including lists of pest management chemicals that can be used in schools without posting, and explanations of how to post use of a chemical that isn't on the list.

Note that the rules were set up mainly for inside and landscape usage, rather than for food gardens. The active ingredients that are exempted from the Healthy Schools Act are all basically food products, so are permitted in food gardens, but there are inert ingredients that aren't, so to find out which these are, see the EPA list of inert chemicals that can be used in "food use sites". (Pesticide labels also indicate whether the product is legal to use in food gardens.)

http://apps.cdpr.ca.gov/schoolipm/   This is the main page of the CDPR School IPM Program. It provides overall info on regulations that  apply to schools, and allows you to link to the next two useful pages: 

http://apps.cdpr.ca.gov/schoolipm/overview/hsa_faq_color.pdf  This document provides FAQs on the Healthy Schools Act.

http://apps.cdpr.ca.gov/schoolipm/school_ipm_law/exempt_products.pdf   Here you can read about Pesticides & Inert Ingredients that are exempted from the Healthy Schools Act (The actual lists start on page 3--scroll down) (This document also includes links to the EPA minimal risk pesticide list and to the list of CDPR exempted products) 

http://www.epa.gov/opprd001/inerts/section25b_inerts.pdf  This is the list of inert ingredients permitted for use on food crops.

www.cdpr.ca.gov   To see if a pesticide is registered (legal) in California (Click on: Look up pesticide products.)

www.npic.orst.edu. Use this site to research a pesticide ingredient through the National Pesticide Information Center, sponsored by the EPA, go to  Look for Active Ingredient Fact Sheets.There are technical or general Information Sheets, depending on your interest and technical background. There are also sheets on inerts and much other useful information on this site. You can also call them to ask for information in person.

www.ipm.ucdavis.edu  Click on Home and Garden Turf and Landscape, then on Pesticide Information, then on "Home & Landscape Active Ingredients Database." Also, within the pest management writeups, there are comparison charts for various pesticides, telling you what parts of the environement they might harm and other health and environmental factors you might consider when choosing among alternatives. 

See also my book, Golden Gate Gardening. The chapter on IPM includes much information about choosing and using pesticides. In addition, the book's Appendix IV, pages 390-397,  explains pesticides in greater detail, including how to read a label and detailed analyses of common active ingredients you may be thinking of using in your garden, so you can make informed choices among your options.