Instead, black rot bacteria have gained a foothold in the phloem and xylem of your cabbage. As they populate and block these important vascular tissues, wilting and dieback occur. ​

Managing black rot in the garden

Since this disease is most likely to occur in warm, humid weather, planting your cole crops after any chance of Indian summer has passed can help prevent it from occurring. The moisture left behind from overhead watering can also create the perfect conditions for black rot to take hold, so water your cabbages at ground level. There are some resistant varieties available, so shop for those if you have had problems with black rot in the past. Also, it’s a good idea to use crop rotation with cabbages and cauliflower in particular, as these two crops are the most likely to be affected. Since this bacteria can survive on cruciferous weeds, be sure to keep your cabbage patch weed free.​

Glyphosate is an herbicide. It is the active ingredient in RoundUp and other popular broadleaf weed and grass killers. And recent scientific research has shown us that glyphosate may be killing honey bees along with plants.

Glyphosate and GMOs

Glyphosate use walks hand-in-hand with genetically modified plant development. GMOs are designed to be resistant to glyphosate and other weed-killing chemicals, making it possible to grow more food for our ever-increasing global population. It certainly has its appeal. It’s so simple - just aim, squirt, and you’re done. No more weeds. But at what cost?


Glyphosate and overspray

If you (or your neighbor) use a glyphosate product, you need to be aware of the overspray risk. Since none of us is perfect, and breezes do happen, these chemicals can be carried on the wind to places where they are not welcome. That delicate, well loved exotic, handed down from your great-grandmother, is just as vulnerable to death by glyphosate as the dandelions. Also, since glyphosate products kill all the plants it touches, indiscriminately, many plants important to local biodiversity are being lost. We do not yet know the full extent of that domino effect.


Glyphosate and bees

Beekeepers have long suspected that glyphosate is, at least partly, responsible for the recent decline in global bee populations. [Did you know that China now must hand-pollinate their apple and pear trees because there are not enough bees?] New research from the University of Texas at Austin shows that glyphosate kills some of the beneficial bacteria found in a honey bee’s gut, making the bees more susceptible to infection. [Maybe we need to start feeding our bees some type of probiotic? I’m guessing.]


Glyphosate use

Glyphosate first came on the market in 1974. It provided an easy way to kill weeds with just a squirt. Glyphosate is used in agriculture and forestry, and to control aquatic plants. It is sprayed along railroad tracks, between orchard trees, and in public parks. According to the National Pesticide Information Center, there is a sodium salt form of glyphosate that is used to regulate plant growth and ripen fruit. So, it’s very useful and convenient. There are over 750 products on American shelves that contain glyphosate, including RoundUp, Bonide KleenUp Grass and Weed Killer, and Kleeraway Grass & Weed Killer. Tragically, glyphosate is also found in many oat products on grocery store shelves, according to the Environmental Working Group (EWG). The worst offenders the EWG listed include Giant Instant Oatmeal, Back to Nature Classic Granola, Quaker Dinosaur Eggs Oatmeal, and, I hate to say it, Cheerios. I urge you to read through their entire list and shop accordingly. The FDA was/is aware of glyphosate in our foods, but has failed to release its findings to the public. More recently, glyphosate has been linked to the development of Parkinson’s and Alzheimer’s diseases, and may also cause cancer in humans.


Herbicide safety

As with any herbicide, always follow the package directions EXACTLY and COMPLETELY. This is not a time to be careless. You can harm other plants with overspray, or you expose yourself to dangerous chemicals. This can occur by breathing it in during the application process, eating or smoking after applying it, if you don’t wash your hands, or by touching plants that are still wet from the spray. If exposure occurs, follow the first aid directions on the product label. For more information about risks and treatments, contact the Poison Control Center at 1-800-222-1222. Pets are also susceptible to herbicide poisoning.


Instead of using toxic chemicals to rid your garden and lawn of weeds, be industrious and put out the effort to pull them before they go to seed. While you’re out there, use it as a time to take a closer look at the other plants and the soil, and listen for the birds and insects that share your yard space.

​Brown marmorated stink bug lifecycle

Each autumn, these pests gather along fences, tree trunks, and buildings. From there, they move to a protected area where they overwinter in a resting stage called facultative diapause. In the spring, these adults become active again and start feeding. Within two weeks, they mate. Soon after, females begin laying the 200 to 500 eggs she will deposit in her lifetime. In the mid-Atlantic states, there are two generations each year. Here, in California, we do not yet know the extent of the brown marmorated stink bug’s reproductive capabilities. It is safe to assume that there will be even more generations here, where winters tend to be mild.

Lifecycle of Xylella fastidiosa

This particular bacterium is what’s called a fastidious mollicute, which means it must live within a plant’s xylem to be able to reproduce. The diseases they cause occur because they get so overcrowded that they block the flow of water and nutrients through the xylem.


Not all plants are negatively affected by this bacterium. Clover, blackberry, goldenrod, and many grasses can host this pathogen, acting as a way station without suffering any consequences. Unfortunately, when a sharpshooter feeds on one of these plants and then moves to your garden, trouble can start.


Symptoms of bacterial leaf scorch
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Scorch diseases are characterized by the same symptoms you would see as a result of environmental conditions, such as herbicide overspray or too much fertilizer, or other diseases, such as verticillium wilt. Initially, you will see wilting and/or chlorosis. Leaf edges look, well, they look scorched! Then leaves start dropping. Fast. Before you know what happened, the plant dies. Except when it doesn’t, because sometimes it won’t. Scientists are still trying to sort it all out.

Disease vectors

The bacteria that cause scorch diseases are carried into your garden by leafhoppers and spittlebugs. Actually, it’s in their saliva. Sharpshooters are the biggest carriers of the disease, as far as we know. These insect pests have a wide host range of their own. As sapsuckers, every bite they take infects the plant on which they are feeding. Because their host range is so large, they are spreading diseases to plants that have never been exposed before, so they have no defenses in place.


There are no known chemical treatments for scorch diseases, so controlling the disease carriers is your best bet. If the disease appears, remove the infected plant completely and put it in the trash.

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Mulching and proper irrigation can help your plants protect themselves.

Curly top host plants

This viral disease can strike beets, beans, ground cherries, peppers, pumpkins, chickpeas,  tomatoes, squash, spinach, melons, horseradish, watermelon, and more. Scientists have identified different species of virus that cause similar symptoms. For lack of better ideas, those viruses are called Beet curly top geminivirus (BCTV), Beet mild curly top virus (BMCTV), and Beet severe curly top virus (BSCTV).

Curly top virus lifecycle

The virus overwinters in annual and perennial weeds. From there, beet leafhoppers (Circulifer tenellus) carry the disease to your garden plants. Symptoms don’t start to appear until long after the leafhoppers are gone, but they are the disease vector, so controlling leafhoppers goes a long way toward preventing this disease. Unfortunately, insecticides are generally not effective against leafhoppers. Leafhoppers have many natural enemies, so make your garden hospitable to beneficial insects. You can do this by avoiding broad spectrum insecticides, planting a variety of umbellifers, such as dill, carrot, and fennel, and providing a water source.


The symptoms and host plants of curly top look too much like other viral diseases, such as spotted tomato wilt, to be identified by the casual gardener. Laboratory tests are needed to know for sure. In the case of viral disease, it is simpler to yank the plant and toss it in the trash, rather than spreading the infection to other plants.

Plants may not have an active immune system, but that doesn’t mean they just roll over and take whatever hits them. When pathogens strike, plants can respond in two different ways to resist becoming infected: they use pre-existing structures and chemicals, and they can use responses that are induced by the presence of a pathogen.


Pre-existing defenses

Just as our skin blocks many pathogens from entry, a plant’s skin, or epidermis, does the same thing. That's why insect feeding and mechanical damage can increase the chance of a disease taking hold - the plant’s first line of defense has been breached. Plant cell walls also block viruses, bacteria, and fungi. Unlike our human immune system, which uses white blood cells to actively hunt down and destroy invaders, plant cells have antimicrobial defenses built right in. These defenses take the form of saponins, glucosides, and antimicrobial proteins. Enzyme inhibitors can also stop some pathogens from feeding on the plant. Plants also have chemicals that can neutralize toxins created by a pathogen. Finally, receptors can recognize a pathogen and alert the plant to take further action.


Inducible plant defenses

Once a pathogen is recognized, cell walls are reinforced and defensive chemicals, such as hydrogen peroxide, as well as antimicrobial enzymes and proteins, are manufactured. In some cases, plants have evolved a behavior called a ‘hypersensitive response’ in which the tissue surrounding an infection is killed off, to block further infection to neighboring cells.

Disease resistant varieties

Rather than treating a disease after it occurs, it is far easier to grow plants that have built-in defenses. This reduces the need for pesticides and fungicides. When shopping for plants, look at the plant label to see if that particular plant is resistant to diseases that tend to appear in your garden. Plant labels use the following codes to designate specific disease resistances:

• A      Alternaria stem canker
• F      Fusarium wilt
• N      Nematodes
• T      Tobacco mosaic virus (TMV)
• St     Stemphylium gray leaf spot
• V      Verticillium wilt

So, if you see a plant label with the letters, V, F, and N, that means that particular plant is resistant against verticillium wilt, fusarium wilt, and nematodes. This does not mean the plant is guaranteed to not get these diseases, but it does mean the chances are significantly lower.


You can help your plants fight disease by selecting resistant varieties, spacing plants properly, employing crop rotation, and providing adequate water and nutrients. Also, be sure to sanitize your tools regularly, to halt the spread of disease from one plant to another.

Carrot root fly control

The best way to protect young plants from carrot root flies is to use row covers as soon as seeds are planted, and to leave the cover in place until it is time to harvest. Some people use window screen panels around raised beds to block this pest, while others use window screen material to create protective cones for individual plants.


There are resistant varieties of carrot, specifically ‘Flyaway’, which claim to thwart these pests, though I can’t vouch for its effectiveness, personally. Research has shown that intercropping alfalfa with carrots and other host plants, or mulching with alfalfa works to reduce carrot root fly infestations. Crop rotation can also be used to interrupt the carrot root fly lifecycle.

Melon flies could end up costing California farmers over $4.5 billion if they ever get a toe-hold in the state.


Melon flies (Bactrocera cucurbitae) are a type of fruit fly. Native to India and Asia, melon flies were first seen in Hawaii in the late 1800’s. They have now become a devastating pest on the Islands. Quarantine stations have worked long and hard to prevent this pest from entering the Continental U.S. The melon fly was first seen in California in 1956, and several other times since, but whenever melon flies are identified stateside, eradication programs immediately go into affect. These programs use pheromones to attract male melon flies. These males are then sterilized and released. This messes up melon fly breeding. So far, this method has been effective. So, why would a gardener care, if the pest isn’t even here? Because maybe it is.

White mold (Sclerotinia spp.) can remain dormant in the soil for a very long time. It takes a significant amount of cool moisture to wake one of these fungi up from its dormant sleep, but the underside of a head of lettuce, or a cabbage, provides just the sort of humidity needed to trigger an awakening and the ensuing infection. This disease is also known as Sclerotinia stem and crown rot and it is caused by two different fungi, depending on the host plant.

How to avoid white mold in the garden

Since prolonged moisture is needed for this fungus to come among us [sorry, I couldn’t resist], keeping things dry is a good defensive plan. These specific steps can help you avoid a white mold problem in your garden:

• use raised beds
• irrigate to the side of plants, rather than directly on them
• space plants in such a way as to provide good air flow
• apply only as much nitrogen as is needed
• inspect senescent flowers and leaves for signs of infection
• remove and destroy infected plants immediately
• monitor plants closely after 60° to 70°F days with high relative humidity (95–100%)
• inspect nearby ornamental plants and weeds for signs of infection
• employ crop rotation with non-host plants
• in really bad cases, fungicides and soil solarization may be needed

As prevalent as white mold is, it’s a good idea to know what to look for ahead of time.

How to prevent and control Johnson spot

Moisture is a key ingredient to this fungal growth. If leaves are wet and temperatures are between 77 and 82°F, Johnson spot can quickly take hold. To break this disease triangle, be sure to space plants in such a way that supports good air flow, avoid overhead watering, allow the soil to dry out between waterings (without causing water stress), and only apply the minimum amounts of nitrogen needed by the plants.


Of course, that advice is only partially useful when it comes to lawn care. To help your lawn avoid becoming infected with Johnson spot, water as early in the day as you can. This will allow plants to dry off before evening comes around.


This fungus has developed resistance to chemical treatments, so cultural practices are your only option. These practices include crop rotation, selecting resistant varieties, and disposing of infected plant material in the trash.


Johnson spot is the most significant disease of rice in the world. Experts estimate that this disease destroys enough rice to feed 60 million people every year.

California red scale is a citrus pest found throughout California, except in Coachella Valley, where an eradication program is in place. These insects may be tiny, but California red scale is a serious pest of citrus trees.

Like other armored scale insects, California red scale (Aonidiella aurantii) have piercing, filamentous mouthparts that are inserted into stems, fruit, and leaves, and suck life-giving sap from your tree. These particular scale insects prefer lemons, limes, Valencia and Navel oranges.


Red scale lifecycle

You will probably never see a tiny, flying male red scale. They only live for about 6 hours and have only one purpose. The females, however, attach themselves to your citrus trees, where they feed on your tree and give birth to 100 to 150 crawlers. Two or three crawlers are born every day to each female. These crawlers leave to their own feeding site. They can also be blown to nearby trees by the wind, or move from place to place by catching a ride on a bird in a practice known as phoresy - though I don’t know if they do it on purpose. Once they settle on a new location, both males and females begin to grow a waxy dome over themselves. Male covers are more elongated, while female covers are more round. Females molt two more times, while males molt under their first dome four times before taking to the air.

Damage caused by California red scale

Chlorosis, twig and branch dieback, fruit loss, and, in severe cases, tree death can all result from California red scale infestations. This damage most commonly occurs at the end of summer, when trees are water stressed and scale populations are at their peak.


How to control California red scale

Scale insects are naturally protected from pesticides. And California red scale has developed a resistance to many insecticides, so, unless you are a commercial farmer or city government, you do not have access to chemicals powerful enough to kill off California red scale. [And would you really want to spray that stuff on your food?] Keeping your trees healthy with regular, deep summer irrigation will reduce water stress. And avoiding the use of broad spectrum insecticides will allow natural predators to do their thing against scale populations. Parasitic wasps and several varieties of lady beetles can provide significant control of scale insects. 

Because ants, dust, and poor air flow all make it more difficult for these beneficial predators to find and catch their prey, be sure to prune for good air flow, wrap tree trunks with sticky barriers to block ants, and give your trees an occasional rinse with the hose during the dustier parts of summer. In winter, apply dormant oils.


The next time you go water your citrus trees, take a closer look to see if California red scale has made an appearance.

There are three different bean mosaic diseases that occur here in California: bean common mosaic, cucumber mosaic, and bean yellow mosaic. These are all viral diseases that cause downward cupping and wrinkling of leaves, especially as leaves get older, along with the telltale mosaic pattern. Bean leaves that develop a bright yellow mosaic pattern may be infected with the bean yellow mosaic virus. There are several strains of bean yellow mosaic (BYM). In addition to beans, bean yellow mosaic can infect peas, peanuts, soybeans, black locust, and fenugreek.


Bean yellow mosaic symptoms

You can differentiate between bean yellow and the other mosaic infections because bean yellow has a yellow mosaic, rather than a light or dark green mosaic. Bean yellow mosaic also exhibits as bright yellow spots on leaves. Plants infected at an early stage of development can become severely stunted and should be removed from the garden and tossed in the trash.


Bean yellow mosaic lifecycle

The bean yellow mosaic pathogen is called, very unimaginatively, bean yellow mosaic virus, or BYMV, for short. This poorly named virus commonly overwinters in legume crops, such as fava beans, alfalfa, clovers, and vetch, as well as in certain weeds and gladiolus. The virus moves from plant to plant in aphids. When an aphid feeds on an infected plant, it becomes a carrier, transporting the disease to every plant it feeds on from that point forward.


Since resistant cultivars are not yet available, these tips may help prevent bean yellow mosaic in your garden:

• buy disease-free seeds from reputable suppliers [Do not use grocery store dried beans!]
• avoid using broad spectrum insecticides that kill aphid predators
• start seeds early enough that they reach flowering stage before aphids become a problem
• heavy aphid populations can be treated with insecticidal soap or neem oil
• plant different legume crops as far away from each other as possible
• remove legume weeds from the area
• reflective mulches may reduce the number of aphids attracted to your plants

Finally, if you see an infected plant, trash it.

Preventing and controlling pink root

Keeping plants healthy and employing crop rotation are the two best ways to avoid pink root from causing too many problems. A note on crop rotation: do not follow a cereal crop with onions, as it creates conditions that promote this particular pathogen. Severe infestations can be eliminated with soil solarization, but that’s a pretty drastic measure for the home gardener.


If you see pink, purple, or black shriveled roots on your onions, try growing them in a different area, in fresh soil, and be sure to feed, weed, and water them properly, and protect them from insects, to ensure that they stay healthy enough to protect themselves.

Symptoms of lower limb dieback

This disease normally appears in late April or May, on trees that are 7 or 8 years old. It starts out with the leaves on lower limbs yellowing, and then turning brown. Eventually, the entire branch becomes girdled by cankers and dies, right up to where it attaches to larger, scaffold branches, or the trunk. If you scrape the bark off of an affected limb, you will see brown spots in the wood. [Sorry, but I couldn't find an image I could use.]


Susceptible varieties

Some almond varieties are more susceptible to lower limb dieback than others. Padre almonds are the most likely to get this disease, with Butte being a close second. Almond varieties that show some resistance to lower limb dieback include Aldrich, Carmel, Fritz, Mission, NePlus Ultra, Nonpareil, Sonora, and Wood Colony. If you are shopping for an almond bare root tree, you might consider one of these more resilient varieties.


Preventing lower limb dieback

While research is currently underway, it is believed that overly wet soil, low light levels, and root exposure to herbicides or excessive fertilizer may weaken trees, making them vulnerable to whatever it is that causes this problem. This is just the opposite of shade tree decline, in which severe drought slowly kills a mature tree, with the early symptoms being a lack of leaf cover in the upper canopy, or crown, of the tree.


Lower limb dieback occurs most often in years with a cool, wet spring, followed by high temperatures. Soil compaction and low infiltration rates are also believed to play a role in lower leaf dieback. Trees with hull rot also appear to be more likely to develop this condition. In this case, fumaric acid and other toxins are believed to accumulate in larger branches when multiple spurs are infected. In this weakened state, these trees are also more likely to be infected by fungal opportunists, such as Botryosphaeria dothidea and Phomopsis amygdali. Phomopsis amygdali causes the stoma to stay open, desiccating the tree. Botryosphaeria dothidea causes cankers on a wide variety of plants.


Keeping your trees healthy is the best way to prevent lower limb dieback.  This means proper irrigation, reasonable applications of fertilizer (only after a soil test shows a need for it), and control of scale insects, which may play a role in the spread of this disease. Fixed copper, sulfur, and fungicide treatments have not been shown to be effective.

Native to China, Japan, and Korea, these invasive, wood boring beetles love to hitch overseas rides on wood-related packing materials: shavings, pallets, that sort of thing. In 1996, an infestation of Asian longhorned beetles (Anoplophora glabripennis) was discovered in Brooklyn. Two years later, a second sighting occurred in Chicago. Then, they were found in New York, New Jersey, and Illinois, where they are responsible for the removal of thousands of trees. These pests have already cost state and federal government (our tax dollars) over $168 million and that number looks to rise exponentially, now that they have expanded their range into California and Washington. 


​The potential economic impact was first estimated to be more than $41 billion. That number has increased to nearly $700 billion, and that’s before you factor in the damage to breakfast morale when the northeast’s sugar maples are attacked! Eradication efforts got into affect each time these invasive pests are found, sometimes successfully, sometimes not. The U.S. Customs Department is working hard to halt the importation of these pests. Eradication in the U.S. is still possible, but it’s an uphill battle. And they need our help.

Trees susceptible to ALB

Many popular hardwood trees are vulnerable to ALB infestation. These trees include alder, ash, beech, birch, boxelder, elm, hackberry, hornbeam, horse chestnut, mimosa, planes, poplar, sycamore, and willow. And blueberries! And members of the Prunus family, which includes apricots, peaches, nectarines, cherries, and almonds! We do not yet know what the impact will be on California’s native hardwood trees.


Experts predict that this pest could cause more damage than gypsy moths, Dutch elm disease, and chestnut blight combined, destroyed millions of acres of trees across the country, in parks, along streets, in backyards, and in agriculture. Dead and dying trees are more likely to cause fires and they are unable to support the biodiversity that keeps a region healthy. If you consider all the wood-based products we use every day, ALB could cause many prices to increase significantly. All because of an insect.


If you see it, catch it! Report it!

If you see an Asian longhorned beetle, catch it. Period. Just do it. They don't bite or sting. While they can fly, they don’t do it very well and only for short distances. You can do this.


Your efforts could save millions of trees and billions of dollars. Seriously.

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Put your captive in a glass jar [they chew through trees, remember?] and place it in the freezer. Be sure to label the jar with where you found it (GPS position, if possible), the date you found it, and your contact information. These reports are critical if we are to protect our trees. Using this information, experts can create quarantine zones and implement eradication programs most effectively.


If you live in California, call the CDFA hotline at 1-800-491-1899. In fact, put the number in your phone now, so you’ll have it if you ever need it. I did. If you live outside of California, report it to your state’s Department of Agriculture. Together, we can save millions of trees.

Pierce’s disease control and prevention

This disease triangle consists of the host plant, the feeding insect carrier, and the disease-causing bacteria. Break the connection between any one of those three and you can reduce the chances of disease. The easiest ways to prevent Pierce’s disease is to keep host weeds out of the area and treat for the sap-sucking insect pests. Since insect-eating birds, such as bluebirds, along with several predatory insects, love to eat sharpshooters, keep your garden welcoming to these natural helpers.


Monitor your plants for signs of Pierce’s disease so that you can act quickly, reducing the spread of the disease. Most of the vector insects are low fliers, so physical barriers can be used to quarantine potentially infected plants. During the dormant season, remove any vines that have been infected for more than one year. They will not recover and they will spread the disease to other plants as vector insects feed on them and then move to nearby plants for more feeding.

Mole management

If you cannot tolerate moles in your garden or landscape, trapping will be necessary. While there are dozens of repellants, scaring devices, home remedies, and plants that claim to offend moles, research has not shown that any of these methods actually work. The only exception is castor oil solutions, which have been shown effective on eastern moles. Flooding tunnels wastes water and does not rid an area of moles. [They’ve dealt with floods for far longer than we have been gardening.]


Trapping always works. Underground harpoon traps and scissor-jaw traps are the most effective methods. Of course, this means dealing with a dead mole and a messy trap. Some new mole baits are showing limited effectiveness, but then you have to worry about children, pets, and local wildlife also suffering a horrible death. Plus, if your landscape was appealing to a mole before, it probably will be again, to a different mole. If you have valuable plants that need protection against moles, you can install a hardware cloth barrier 2-feet into the ground, with a 6-inch lip bent at a 90° angle away from the plant to thwart mole digging.


Mole trivia

Moles are fascinating creatures. Some of the more interesting mole facts include:

• A mole placed on the ground can burrow out of sight in 10 seconds.
• Moles have a special type of blood that allows them to breath in low oxygen environments.
• Moles have an extra thumb, called a prepollex.
• Female moles have a set of male genitals.
• Moles squeeze the dirt out of earthworms before eating them.
• Star-nosed moles can find, catch, and eat food faster than the human eye can see.
• Moles are the only animal known to smell things in stereo.

If you can tolerate moles, they actually provide many benefits to the garden and landscape.


Did you know that mole saliva contains toxins that paralyze earthworms? Researchers have found underground storage spaces filled with thousands of paralyzed earthworms, for later eating.


Now you know.

Kuno scale control

Since ants protect Kuno scale from natural predators, blocking ants from getting up in your trees is the easiest control measure. To do this, simply wrap the tree trunk with a sticky barrier. You can also apply horticultural oil to twigs and the ends of branches just as buds are swelling, in spring. You can also try drenching the undersides of leaves in early summer, but this is tricky, because it’s not a good idea to spray dormant plum or walnut trees with oil, especially during periods of drought.


​And, let’s face it, spraying the underside of leaves is a royal pain.

Because these viruses can spread rapidly, over relatively great distances, close monitoring and control are in everyone’s best interest. Once a plant is infected with one of the leafroll viruses, it should be removed and destroyed. There is no cure or treatment. When shopping for plants, choose resistant varieties, and be sure to control carrier pests, to reduce the likelihood of leafroll affecting your garden.