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.
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:
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.
Mexican fruit fly larvae travel the world… in infested fruits.
Cousin to the dreaded MedFly, melon flies, and spotted wing drosophila, just to name a few, Mexican fruit flies (Anastrepha ludens), or MexFlies, are a major agricultural pest. Currently, in California, there is one active Mexican fruit fly quarantine in effect in San Diego County, but this is an on-going battle, so it’s a good idea to check the CDFA quarantine listing, or your local Department of Agriculture, regularly to see if your area is included.
History of Mexican fruit flies in California
First found in the U.S., in Texas, in 1903, Mexican fruit flies were seen again in 1927. By 1954, they had spread to Florida, Arizona, and California. It is estimated that these pests have cost farmers $1.44 billion in damages. Mexican fruit flies are subject to eradication programs that include capturing, sterilizing, and releasing males that interrupt the breeding cycle.
Mexican fruit flies have been expanding their range for several years now, and it’s not simply by catching a ride on an infested piece of fruit. Commercial agriculture brings crops to non-native regions, introducing them to local pests and diseases. For example, the mango, from India, only became a popular food of Mexican fruit flies after it started being grown in Central American and Mexico.
Mexican fruit flies prefer grapefruit, oranges, tangerines, mango, apple, peaches, nectarines, avocado, and pear. More recently, they have been found on figs, bananas, prickly pear cactus, cashews, papaya, guava, pomegranate, peppers, tomatoes, squash, beans, quince, Japanese persimmon, passionfruit, pummelo, and arabica coffee. [Coffee?!!?} Not only is the Mexican fruit fly range expanding, but so is their diet.
Mexican fruit fly description
Slightly larger than a housefly, Mexican fruit flies are 1/3 to 1/2 of an inch long. They have a yellow or brown body and distinctive wing patterns. Also, adult females have extra long ovipositor sheathes (egg-laying tubes). The wing patterns include a costal spot (C), an inverted-V, and a sideways S shape. Larvae are slender white grubs with mouth hooks, and a slightly flattened back end.
Mexican fruit fly lifecycle
As far as fruit flies go, this particular species is relatively long-lived. Individuals can survive for 11 to 16 months. Females lay over 1500 eggs in their lifetime. Eggs are laid in groups of 10, on the skin of a fruit, preferably one that is slightly damaged. This provides an easy point of entry for Mexican fruit fly larvae, along with many other pests and diseases. In a week or so, after being deposited, the eggs hatch out larvae that burrow into the fruit and start feeding. As they feed, the larvae take on the color of the fruit their are eating, so you may not notice right way, after taking a bite of an infected fruit.
Larval feeding continues for 3 or 4 weeks, depending on temperatures. Then, larvae drop to the ground, where they pupate in the soil. During this seeming pause in development, the slug-like larva is converted into a winged adult that begins breeding immediately after emerging, starting the whole process over.
Controlling Mexican fruit flies
Because they spend most of their lives inside fruit, insecticides are not effective against Mexican fruit flies in the larval, egg, or pupal stages. There is a tiny, repeated window of opportunity for treatment of adults, but only if direct contact is made with the insecticide. Generally, adults will simply fly away from treated trees and return a few days later, after it has worn off. Commercial growers use complex bait and trap methods that are unavailable to small scale growers.
So, they only thing you can do if you suspect Mexican fruit flies have found their way to your garden is to immediately contact the California Pest Hotline at 1-800-491-1899, or your local Department of Agriculture. It is best to leave controlling these pests to the pros.
If your olive tree has strange knobs forming on the stems, it may be olive knot.
Olive knot is a bacterial disease of olive and oleander. It is caused by Pseudomonas savastanoi pathovar (pv.) nerii and P. savastanoi (=syringae) pv. savastanoi These bacteria are like evil twins that don’t cause serious harm, but they are still a pain to be around.
Symptoms of olive knot
The knobby bit you see is called a gall. Galls are swollen, distorted, woody growths that can girdle stems and twigs. The P. savastanoi pathovar (pv.) nerii bacteria is the one that causes the galls on both oleander and olive twigs. It also forms galls on leaves and flower buds of oleander. The P. savastanoi pv. savastanoi twin only affects olive, causing galls on twigs, stems, and at leaf nodes.
Olive knot lifecycle
The bacteria responsible for olive knot enter the tree through pruning wounds, leaf scars, frost cracks, and sun scald wounds. Infection normally occurs in autumn and winter, but symptoms do not appear until late spring or early summer. The bacteria live in the galls they form, and can all be found on the surface of twigs, leaves, and fruit. The bacteria are commonly spread by wind and rain.
To prevent olive knot in your garden or foodscape, be sure to plant disease-free root stock, avoid overhead watering, and prune off any infected material during the dry season, disposing of infected material in the trash. Be sure to sanitize your tools afterward.
Fixed copper sprays (one in fall, and two in spring) can help prevent and treat olive knot infections, but there is no sure cure. Luckily, this bacterial disease is not a serious threat to your olive tree’s health. It is spreading, however, and becoming more of a problem. This is due, in part, to the popularity of a particularly susceptible cultivar, the Manzanillo olive
You’ve heard of raised beds and garden beds, but what about nursery beds?
Nursery beds are the perfect place for that “just couldn’t pass it up” seedling, the gift plant with no permanent location, sale priced plants that you haven’t had time to work into your regular garden or landscape, or it can be used as a quarantine station. These are all plants that may need a little extra care or attention, as they settle in.
Maintaining a nursery bed takes up very little time or space, but it can save you a lot of money on plants.
What is a nursery bed?
A nursery bed may simply be a plot of ground, tucked away in a corner of the yard. It may be a slightly raised area, walled in with cinderblocks or scrap lumber. Nursery beds do not have to be pretty. They simply need soil, water, and sunlight. If you want to get fancy, you can add corner posts to support protective netting or shade cloth. Again, looks are not important.
Start seeds in a nursery bed
Vegetable seeds can be started in a nursery bed, and grown there until they are big enough for transplanting. This is an excellent tool for succession planting. As you wait for the current crop to wind down, your next season’s crop is already on its way! Nursery beds are also a great place to start plants that can be used to fill empty spots as they occur. As a tomato plant gives up the ghost, simply cut it off at ground level and install a cheery chrysanthemum in its place! Viola!
Transplant recovery in a nursery bed
Most gardeners feel frustrated by thinning young seedlings. A nursery bed offers the perfect place to put the removed seedlings, allowing them a chance to recover from the ordeal and, possibly, grow to a large enough size to be moved elsewhere, or gifted to a friend or neighbor.
Propagating with a nursery bed
If you want to try you hand at vegetative propagation, nursery beds provide an easy starting point for cuttings and divisions, allowing them time to recover and to develop new roots before being moved to more permanent locations. Nursery beds also provide a good location to start parent plants that will ultimately be divided into many smaller plants (for a tiny fraction of the cost of buying all mature plants).
Nursery beds for hardening off
Delicate seedlings may need a transitionary period before they can handle being planted in the garden. With the addition of shade cloth or old glass windows, cold frame style, you can give these babies a taste of the great outdoors without exposing them to more than they can handle.
How to make a nursery bed
While you want your nursery bed to be convenient to the rest of the garden (and a hose bib), it can easily be tucked away behind a shed or some shrubs, as long as it gets at least 6 to 8 hours of sunlight each day, and is relatively level. Being sheltered is actually a bonus for a nursery bed, as it helps block strong winds.
Use these steps to create your own nursery bed:
Nursery beds are different from raised beds in that they are designated as an unplanned, layover location, rather than a permanent home.
Finally, if you have a nursery bed set up and know that you won’t be using it for a while, it makes a great place to age compost. The nutrients left behind will be exactly what all those baby plants need to thrive!
Hesperidium is the name given to certain types of fruits.
Hesperidia are berries with a tough, leathery skin that tends to be bitter.
If you cut a hesperidium open, you will see separate compartments, called carpels. Within these carpels, you will see hundreds of tiny, fluid-filled vessels that are made out of specialized hair cells. These vessels are called vesicles.
If you haven’t already guessed, all citrus fruits are that special type of berry, known as hesperidia.
Bud scar may sound like a great punk band name, but knowing how to recognize this tiny bit of plant anatomy can come in handy.
At the tip of most twigs is an area of meristem tissue. This plant tissue can turn into several different types of plant cells. When the tissue grows upward, to continue the trunk of a tree, or a branch stem, it is called apical meristem, or a terminal bud. In this sense, terminal does not mean lying on its death bed. Rather, it refers to the bud at the end of the branch.
As these terminal buds burst forth with new growth, the protective scale normally falls away, leaving a bud scar. Bud scars look like rings around stems and branches of trees and other woody plants. Bud scars are from the terminal bud on a stem. These marks are different from leaf scars. Leaf scars occur at the point of attachment for a leaf, after the leaf has fallen off. Just above a leaf scar, there is usually a lateral bud that can grow into a twig or flower.
Ultimately, the growth of the tree or branch will grow over these scars, but that can take a long time. Until then, you can use the number of bud scars to determine the age of a branch, since each terminal bud indicates one year’s growth.
There are no aboveground symptoms, but a carrot root fly infestation can ruin your carrot crop, along with several other umbellifers. Carrot root fly (Psila rosae), also known as the carrot rust fly, is a pest found in most temperate regions.
Carrot root fly description and lifecycle
These tiny, fast flying pests are slender, greenish-black metallic flies. Their legs and head are yellow. Carrot rust flies tend to hang out in weeds and undergrowth near carrot fields. After mating, females head for the carrots, where they will lay their tiny, white eggs on the soil surface. Larvae are creamy white, approximately 1/3 of an inch long, and rather stiff, as far as maggots go. Orangish-brown pupal cases can be found in the soil.
In addition to feeding on carrots, carrot root flies also feed on caraway, celery, dill, fennel, parsley, and parsnips. Other plants, such as lettuce, endive, and chicory can serve as host plants in areas where the maggots are already in the soil.
Damage caused by carrot root flies
Like other root maggots, carrot root maggots feed on tiny root hairs and then tunnel along the surface and burrow into the root. These tunnels and burrows are then filled with mushy frass. The initial feeding causes stunting, and tunneling makes it easy for other pathogens to enter, which leads to several different types of rot and other problems.
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.
A dibble is a gardening tool.
Back in Roman times, farmers needed a tool that would help them poke holes in the ground so that they could plant seeds, seedlings, and bulbs. These gardeners came up with an ingenious tool that has remained relatively unchanged and is still just as useful as it was 2,000 years ago.
The dibble, also known as a dibber, or a dibbler, was first carved from wood. The first dibble was probably nothing more than a pointed stick. To make it easier to use, the digging end was made pointier, and the handle end was rounded.
During the Renaissance, dibbles were made from iron. Today, they are made from lightweight metals and plastics. I’m not a fan of plastics, but some of the hand-carved wooden dibbles are nothing less than works of art. You can also find high end stainless steel dibblers, if you like to spend your money that way. Many dibbles feature depth markings, to make it easier to plant seeds and bulbs at the proper depth.
Types of dibbles
Dibbles come in several different varieties: straight, T-handled, L-shaped, and trowel:
Dibbles can also be transformed into a board that creates the perfect spacing for seeds. These are easy to make from scrap wood and a dowel. Simply take a flat board, or a piece of plywood, and drill several, evenly-spaced holes in the wood. These holes should be just shy of the dowel’s diameter. Then, cut the dowel into pegs. These pegs will be the width of the board plus whatever planting depth you prefer, usually 1 inch. The pegs are tapped into the holes. You can glue them in place, or leave them somewhat moveable, to adjust the depth. If you're feeling crafty, you can add points to the digging end of end peg, but it isn't necessary
When starting seeds, simply press the dibble board against the soil for perfectly spaced seedlings. This reduces the amount of thinning you need to do later on. If you need to space plants out more, simply skip holes.
The down-side to using dibblers, especially in heavy clay soil, is that the surrounding soil is somewhat compressed by the pressure applied to make the hole. If the soil lacks organic material, this can make it difficult for young roots to take hold. As long as you aren’t pressing really hard, and your soil is relatively loose to begin with, this shouldn’t cause any problems. Dibblers are best used in planting trays filled with potting soil.
If you live in the Bay Area, growing lemons is a no-brainer. Lemons love this area.
Native to Asia (we think), lemons evolved out of a cross between bitter orange and citron during the times of Ancient Rome. Lemons did not become popular until they were introduced to Persia and Egypt around 700 AD. Christopher Columbus brought lemon seeds to Hispaniola (modern day Haiti and Dominican Republic), but lemon trees were seen as medicinal and ornamental plants at that time. Though they didn’t know about Vitamin C at the time, James Lind discovered that adding lemon juice to the diet prevented scurvy in 1747.
Lemons are a type of fruit called hesperidium. Hesperidium are berries with a leathery skin and fruit that forms in sections, called carpels. Within each carpel are hundreds of juice-filled sacs, called vesicles. Lemons contain citric acid, which is what makes them taste sour. Lemons are only a little more sour than limes, but they can be almost twice as sour as grapefruits, with five times the bite found in orange juice.
The lemon tree
Lemon trees (Citrus limon) are evergreen, which means the leaves stay green all year. They do not, however, handle cold temperatures very well. Mature trees can handle occasional light frosts, but young trees need protection in temperatures below 45°F. Lemon leaves and fruit both have waxy coatings that reduce moisture loss. You can grow a lemon tree in a sunny spot in your yard, in a container, or even on a balcony. The blossoms smell heavenly!
Most grocery store lemons are ‘Eureka’ lemons. This variety is also known as ‘Four Seasons’ because of its continuous production. This is also the most commonly available variety as bare root stock. There is also a pink-skinned variety of ‘Eureka’ that features green and yellow variegated skin. Thinner skinned and seedless “Bonnie Brae’ is grown in San Diego County, CA. If you want to make your own limoncello (lemon liquor), you will want to plant a ‘ ‘Femminello St. Teresa’, also known as ‘Sorrento’ lemons.
Contrary to popular opinion, ‘Meyer’ lemons are actually a cross between citron and a mandarin/pomelo hybrid. Other lemons-that-are-not-lemons include:
Caring for a lemon tree
Lemon trees are relatively trouble free, when grown in an appropriate location. Lemon pruning is normally limited to the standards of removing dead, diseased, and crossing branches. You will also want to remove vertical water shoots. Lemon tree trunks and the upper surface of exposed branches benefit from whitewashing, to prevent sun scald. Regular feeding will help your lemon tree stay healthy and productive. Each of the doasges listed below should be divided into 2 or 3 separate feedings:
1st year - 3 tablespoons of nitrogen per tree
2nd year - 1/4 pound of nitrogen per tree
3rd year - 1/2 pound nitrogen per tree
4th year - 3/4 pound nitrogen per tree
5th year and on - 1 pound nitrogen per tree
Understand that 1/4 pound of nitrogen is not the same thing as 1/4 pound of packaged fertilizer. Assume, for example, that your 5 pound bag of fertilizer has an NPK of 10-5-2. This means that out of the 5 pounds, 10% of the bag is nitrogen, 5% is phosphorus, and 2% is potassium. [The rest is filler.] This works out to 1/2 a pound of nitrogen, a 1/4 pound of phosphorus, and 1/10 of a pound of potassium. In all likelihood, your lemon tree will not need those other nutrients, so they are best left out of the equation (especially until after you get a soil test). An easier way to feed your lemon and other citrus trees is to use blood meal or ammonium sulfate.
Blood meal contains 13.25% nitrogen, 1% phosphorus, and 0.6% potassium. To equal one pound of nitrogen, you would need to apply 7-1/2 pounds of blood meal. Five pounds of ammonium sulfate will give you the same amount of nitrogen. Just remember that these feedings are totals for the year and that they should be spread out over three different feedings, ideally in April, June, and August. Lemon trees also benefit from a top dressing of aged compost.
Lemon pests and diseases
The biggest insect threat to your lemon tree (and lemon trees across the country) is the Asian citrus psyllid, which can infect your tree with a fatal disease called huanglongbing, or HLB, for short. Leaf miners will burrow tunnels in citrus leaves, but the damage is mostly cosmetic, unless it becomes extensive. Other lemon pests include aphids, katydids, citrus cutworms, several varieties of mites, mealybugs, glassy-winged sharpshooters, Fuller rose beetles, hoopla beetles, leafrollers, snails, thrips, whiteflies, and nematodes. Several varieties of scale insects are attracted to lemon trees, including, black scale, brown soft scale, California red scale, citricola scale, cottony cushion scale, and purple scale. Lemon tree diseases include alternaria rot, armillaria root rot, anthracnose, brown rot, citrus blast, exocortis, phytophthora-related diseases, and the Tristeza disease complex.
Like other citrus trees, many lemon trees will follow an abundant year with a year of reduced production. This does not mean that anything is wrong.
Lemons are very easy to grow and they can produce an astounding amount of fruit. Get yours today!
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.
Melon fly host plants
It would probably be easier to list the plants that are not seen as food by melon flies, but it is important to know where to look, and to know what to watch for, so here’s the fruit fly menu of favorites from your garden:
Melon fly description
The size of a house fly, melon flies are mostly orange or yellow and brown with a pale black T-shape on the abdomen and distinct wing patterns. Wings are clear with a large brown spot at the tip and a brown stripe along the back edge and along the base. Melon fly antennae also have an especially long third segment. Melon fly larvae (maggots) are creamy white, without legs, somewhat flattened at the back end. Maggots are less than 1/2 an inch long. Pupae are somewhat smaller than the maggots, held in a protective case that can be dull white or red, or brownish yellow. Eggs are very tiny, white, and somewhat elliptical.
Melon fly lifecycle
A single female melon fly can lay 1,000 eggs. Eggs are laid on young fruit and tender new stems, which will provide food for newly hatched maggots. Eggs that have been laid under the skin of fruits, or in host plant stems, flowers, and exposed roots, will hatch and the feeding damage begins. There are three larval stages, or instars. After feeding continuously, mature maggots drop to the ground, where they burrow into the top inch of soil and enter a pupal stage. There can be 8 to 10 generations a year.
Melon fly damage
During the heat of the day, adult melon flies rest on the shady undersides of leaves. When temperatures are more comfortable, they feed on nectar, decaying fruit, sap, and bird poop. [Keep in mind, as these pests fly from one food source to another, they can be carrying pathogens from the bird poop to your fruit crop.] Tunneling and feeding create points of entry that allow bacterial, fungal, and viral diseases to enter. Generally, the fruit ends up rotten and inedible.
Melon fly control
Unfortunately, there are not any effective controls available to the home gardener. You can certainly rake up the soil under and around potential host plants, to spot, remove, and report any pupal cases you find, and be sure to quarantine new plants. Currently available insecticides have not been found to work against melon flies.
If you think you see a melon fly, please make every effort to capture or kill it. Then call the CA Pest Hotline at 1-800-491-1899, or your local Department of Agriculture, to report it. Only by working together can we protect commercial agriculture and our own gardens from the melon fruit fly. And don’t smuggle fresh fruit or produce across state lines. There’s a lot more at stake than you might think.
Lovage tastes like a cross between parsley and celery, but it can grow to over 8 feet tall!
Lovage is a perennial herbaceous plant that requires very little care. Stronger tasting than either celery or parsley, a little goes a long way, but all parts of the lovage plant make an excellent addition to soups, salads, casseroles, and stews, and the minced leaves take pasta and potatoes to new heights. Lovage seeds and stems are also used in candy-making.
The lovage plant
Even though lovage looks and smells more like celery, it is actually a member of the carrot, or umbellifer family. While lovage plants can grow more than 8 feet tall, more often, they grow 3 to 6 feet tall and 2 or 3 feet wide. Small yellow flowers grow in umbrella-shaped umbels. Seeds are one-half an inch long. Lovage is native to eastern Europe
How to grow lovage
You can start lovage seeds indoors, 4 to 6 weeks before the last frost date, or outside any time the soil has warmed to at least 60°F. Plant seeds 1/4 inch deep and keep the soil moist until seedlings are several inches tall.
Lovage grows best in full sun to partial shade and it needs soil with plenty of organic matter. You can help your lovage plant thrive by top dressing the planting area ahead of time with aged compost. As the growing season nears the end, you can allow flowers to produce seeds for future crops. In cold regions, the root is dug up and stored where it will be protected from freezing until the next spring.
Lovage has very few pest or disease problems. Leaf miners can cause cosmetic damage, but that’s about it. Because of its rugged demeanor and its celery-like flavor, lovage is an excellent addition to any California foodscape.
White mold, also known as lettuce drop, is a disease that affects far more than just lettuce in your garden.
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.
Symptoms of white mold
White mold is seen on outer leaves, lower stems, and pods, in the case of beans. Starting at the base, the mold spreads, causing outer leaves to wilt and fall away from the plant, while remaining attached. Garbanzo beans are particularly likely to become infected in the crown area. Affected plant tissue develops watery lesions as cottony white mycelium form on the surface. Mycelium are the vegetative part of a fungus, made up of threadlike hypha.
Stems may become girdled by the decay. As damaged tissue dies and dries up, it will turn white and looked bleached. Tiny (0.25–0.5 inch), irregularly shaped black flecks, called sclerotia, can be seen on the surface and inside of dead stems. Sclerotia are the resting body of the fungi, made of of a cluster of hyphal threads, and able to remain dormant for a surprisingly long time.
White mold host plants
Along with lettuce and escarole, several members of the nightshade family and the cabbage family are susceptible to white mold. This means that your tomatoes, potatoes, and eggplants, along with Brussels sprouts, mustard greens, broccoli, cauliflower, turnips, radishes, rutabagas, and kale can all become infected. Dried bean plants, alfalfa, other broad-leafed plants, and many weeds can also become infected.
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:
As prevalent as white mold is, it’s a good idea to know what to look for ahead of time.
Johnson spot is a fungal disease of rice, wheat, barley, rye, and millet. It also attacks your lawn.
Other names for this disease include rice blast fungus, pitting disease, and ryegrass blast. As a threat to your lawn, Johnson spot can infect kikuyugrass, fescues, rye grasses, and St. Augustine grass.
The fungal pathogen
The fungi that causes Johnson spot is called Magnaporthe grisea (previously known as Pyriculria grisea). Magnaporthe grisea is a highly effective fungus. Spores attach themselves to plant surfaces. They can reproduce both sexually and asexually, and they are prolific. A single spore can complete its reproductive cycle in one week, though it can live for 20 days. Thousands of new spores are generated each night. I don’t know how to calculate the math on all that, but I am certain that those numbers would be overwhelming to a plant. As the fungi perform all that precreation, seed production is reduced and entire leaves are killed.
Johnson spot symptoms
Early signs of fungal infection include white to grayish green spots with dark borders. As they age, the lesions take on a more elliptical shape. These symptoms can be seen on many parts of the plant, including the leaf collar, stems (culms), and flowers (panicles).
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.
Don’t let the green skin fool you. Greengages are sugary sweet dessert plums.
While most plums tend to be purple to black, and sometimes yellow, with an edge of tang to their flavor, greengage plums are green, and as sweet as candy!
Greengages were first brought to Europe from Iran in the 1700s. George Washington and Thomas Jefferson both grew greengages on their farms, but greengages seem to have fallen out of favor since the 1800s. I do not know why, but I like to think that they are on their way back.
Botanically, all plums (Prunus domestica) are members of the rose family. If you want a cultivar that is descended from the original green Iranian plum, you will need to look for a label that reads Prunus domestica subsp. italica var. claudiana.
Greengages are round or oval pale green to yellowish fruits with smooth-textured, pale green flesh. Greengages are freestone fruits. You may see some varieties with a pale blue blush. Greengages are smaller than mirabelle prune, or cherry plums, but larger than most other palm varieties. There are also some crossbred greengages that may be reddish-purple.
How to grow greengages
Unlike most modern fruits, greengages grow true from seed. This means, if you can find one, you can plant a tree of your own. The original cultivar, now called Reine Claude Verte, remains nearly unchanged from its ancestor. Not all greengages are self-fertile, so you may need to plant two trees to get fruit, spending on the variety. You can grow greengages outside in USDA Hardiness Zones 5-9. Like other plums, greengages love our hot, California summers, and cool, moist winters. You can start a seed indoors any time of year, but bare root trees should be planted January through March. If you don’t have a lot of room, greengages can also be espaliered along a fence.
Caring for greengages
Greengages should be given nitrogen in spring and fall. Amounts vary, depending on tree age, health, and soil. Trees should be pruned while they are dormant, in winter, and again just after fruit is harvested. Thin fruits to 4 to 6 inches apart, for the best quality and to reduce the chances of pest damage or disease.
Greengage pests and disease
Aphids and scale insects are the most common plum pests. Brown rot and shot hole fungus are the most common diseases.
Fruit is ready for harvest June through October, depending on the variety. It in not uncommon to have a bumper crop year followed by a more sparse crop, similar to many citrus trees. They simply do not have the energy or resources to crank out huge crops every year.
See if you can make room for these delicious fruits in your foodscape!
Did you know that there are good grubs and bad grubs?
Before we get started on grubs, let’s clarify the difference between grubs and caterpillars.
Grub or caterpillar?
Grubs and caterpillars are both the larval form of certain insects. They both feed like crazy before transforming into their adult versions. They both have longish, squishy bodies. So, what’s the difference? The difference is in family lines. Caterpillars are the offspring of butterflies and moths, while grubs are baby beetles. There are other differences, as well. Caterpillars have thick, meaty legs, and several of them, while grubs have stubby, ineffective legs (if they have any at all). Also, caterpillars tend to be brightly colored, whereas grubs tend to be white or tan. Grubs are generally one inch long, can feature a dark head, and may or may not have bristles, and they tend to rest curled up in a C-shape.
Bad grubs, such as masked chafers, cutworms, Japanese beetles, armyworms, June beetles, and some weevils, can create brown patches in your lawn and wilting of fruit and vegetable crops. They do this by feeding on roots.
Not so bad grubs
While adult dried fruit beetles can cause problems, feeding on your figs, peaches, and plums, their larvae actually feed on organic material in the soil, helping in the decomposition process, making more nutrients available to your plants.
A while back, I discovered a huge grub population in a raised bed that I use for potatoes. I dug them up (below) and fed them to my chickens. Then I learned that they were green fruit beetle larvae and that they had been making better use of the aged compost I had added to the bed. Ah, well. Live and learn. The chickens were happy.
Since most grubs are root feeders, getting rid of them can help your edibles, ornamentals, and your lawn stay healthy. Hand picking is the most effective method. This means breaking up the soil and picking them up. Breaking up the soil also makes it easier for birds to get their share of those high protein snacks. As much as we would all love easy fixes, products such as diatomaceous earth and white milky spore are not your best choices against grubs. Diatomaceous earth, while it can kill grubs, will also kill off beneficial insects. White milky spore, frequently advertised as a great grub killer, is generally only effective against Japanese beetle larvae, which are not (yet) a real problem here, in California.
Beneficial nematodes can be used against grubs, but the timing must be exactly right for them to do their job. Soil temperatures must be above 60°F, making it the method of choice in summer and early fall, but completely ineffective in spring.
How do you know if you have a grub problem?
Brown patches and wilting can be caused by several factors. The easiest way to see if you have a grub problem is to conduct a drench test. To do this, fill a large watering can or bucket with 2 gallons of water and gently stir in 1/4 to 1/2 cup liquid dish detergent. Then, mark off an area, 3 feet square, with some string. Pour the soapy water evenly over this area. Within 10 minutes, you will see whatever insects are living in that particular piece of soil. If you have a problem, it will be obvious.
As a child, I would eat around the center core of my carrots, leaving the darker, sweeter core for last. I didn’t know it then, but that inner core is called the stele.
Vascular plants have both root and stem steles, but they didn't start out that way. Primitive steles were nothing more than a strand of xylem, surrounded by phloem. [Remember, water and minerals ‘rise up the xylem’ from the roots, and manufactures sugars ‘flow down the phloem’ from the leaves. In case you forgot.]
More modern steles may consist of vascular tissue, pith, and pericycle. Pith is the spongy material seen in the center of stems, and the pericycle is a thin layer of tissue between the xylem and the endodermis. There are two major types of stele: protostele and siphonostele.
Protostele describes the more primitive stele, which consists of a strand of xylem, surrounded by phloem. Protosteles may or may not have an endodermis that controls the flow of water. There are three different types of protostele:
Siphonosteles are a little more complex than protosteles. Siphonosteles may have gaps in their vascular tissue in places where leaves are born. These spaces are called leaf gaps. You can think of these leaf gaps as sections cut from a hula hoop and pulled a little apart, making room for leaf tissue to grow through. Siphonosteles also contain pith. If the xylem is found only outside of the pith, it is called ectophloic. If the xylem can be found both within and outside of the pith, it is called amphiphloic. Members of the nightshade family, such as tomatoes and peppers, are amphiphloic. There are three types of amphiphloic steles:
Diseases of the stele include phytophthora root rot, verticillium wilt, black root rot, and crown rot. In each case, prolonged exposure to wet soil creates the conditions needed for pathogens to infect your plants. Maintaining good drainage and soil structure can help prevent these diseases.
So, why would you care what sort of stele your plants have? Besides sounding really smart, being able to look up information about what’s inside a plant stem can help you identify unknown plants.
What's inside your stems?
With a name like tarantula hawk, you might expect to see some B-movie horror monster soaring out of the sky with eight legs, but the tarantula hawk is actually a spider wasp that hunts tarantulas. It is also one of the most poisonous insects in North America.
Tarantula hawk stings
Tarantula stings are ranked right up their with honey bee stings. Painful, but not debilitating. Tarantula hawk stings, however, are ranked as the second most painful in the world, with the African bullet ant being first. Tarantula hawk stings only last for 3 to 5 minutes, but all you can do during that time is scream bloody murder. Luckily, tarantula hawks do not sting unless provoked. [Apparently, we would be more reasonable to fear the tarantula hawk, than those big, furry spiders.] Unless you are allergic, tarantula hawk stings are not dangerous, just extremely painful.
Tarantula hawk description
There are actually 250 different species of tarantula hawk, worldwide, with 21 species in North America. The most common tarantula hawk found in California is Pepsis grossa, formerly Pepsis formosa. These parasitic wasps are 2 inches long, making them the largest wasps in North America. From above, they look black, with orange wings.
From below, you can see a metallic blue-black abdomen. These bright colors are a warning to potential predators that they might not be worth the effort (aposematism). They have no known predators. Tarantula hawk legs are long, with hooked claws, for grasping prey. Females have stingers that can be more than 1/4 of an inch long.
Tarantula hawk lifecycle
Adult tarantula hawk females hunt tarantulas as food for her offspring. If tarantulas are in short supply, they will also use grasshoppers and other large insects. She captures and stings her prey, injecting them with a paralyzing venom. Then, she brings it to a nest where she lays a single egg on the victim’s body. If this egg was fertilized, it will hatch as a female; if it was not fertilized, it will hatch as a male. Whatever the gender, when the egg hatches, the larva enters the prey and begins feeding. Interestingly, the larva know to leave vital organs of the still living edible for last, to keep everything fresh and delicious. In a few weeks, the larva pupates and emerges from its childhood meal as an adult, and the cycle begins again.
Tarantula hawk diet
Adult tarantula hawks are nectarivorous, which means they feed on nectar and ripe fruit. They feed primarily on the flowers of milkweed plants, and mesquite and western soapberry trees. In some cases, that fruit has become fermented and tarantula hawks can find flying difficult.
Imagine, if you will, a drunk tarantula hawk riding a terrified tarantula, buckaroo style. There may be a movie in there after all…
Did you know that tarantulas migrate each fall? Now you know.
Vedalia beetles are a breed of Australian ladybug that devours their weight in cottony cushion scale pests found on citrus, olives, roses, magnolia, and acacia. The vedalia beetle claim to fame is that it was California’s first attempt at biological pest control
Back in the late 1800s, cottony cushion scale was decimating California’s citrus trees. In 1888, vedalia beetles (Rodolia cardinalis) were imported from Australia to counteract that pest, and it saved the California citrus industry
Vedalia beetle description
Like other lady beetles, vedalia beetles are easy to recognize because of their domed body shape and stubby antennae. The difference being coloration. While bright red lady bugs feature dark spots, vedalia beetles feature a much darker red dome with splotchy black markings. Adults are approximately 1/16 to 1/8 of an inch long and covered with fine hairs that can make them look more grayish than red and black. Larvae are elongate, grayish, and can look like tiny alligators.
Vedalia beetle diet
While the bright red variety most of us think of as ladybugs feeds heavily on aphids, vedalia beetles prefer cottony cushion scale insects. Adult vedalia beetles simply chew up their prey, while younger larvae pierce their victims and suck out their juices.
Vedalia beetles start out as tiny red eggs. These eggs hatch out into tiny red larva. Vedalia larva start feeding right away and they go through several instars, or developmental stages, as they grow. They continue to feed until just before pupating. Then they attach themselves to a leaf as they prepare for their final transformation. [Unlike other insects that pupate, if you touch a healthy vedalia pupa, it should move.] One week later, an adult vedalia beetle emerges, ready to lay 100 to 200 eggs in its 1 to 3 month lifespan.
Combined with a parasitic wasp (Cryptochaetum iceryae), cottony cushion scale is now well under control in California, without the use of any chemicals. Since vedalia beetles are extremely sensitive to pesticides, it is a good idea to inspect an area for these beneficial insects before spraying chemicals.
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.
Beans are easy to grow, they help improve soil structure, and they add nitrogen to the soil. They can also become infected with bean yellow mosaic.
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:
Finally, if you see an infected plant, trash it.
You can grow a surprising amount of food in your own yard. Ask me how!