If you have a walnut tree, you should know about walnut scale. Even if you don’t, this is still an interesting read.
Walnut scale insects (Quadraspidiotus juglansregiae) have a unique behavior that makes them particularly fascinating. Like other armored scale insects, females protect themselves under round, dome-shaped covers. But walnut scale takes this concept to a whole new level.
Walnut scale lifecycle
Female walnut scale insects lay eggs in spring. These eggs hatch in only 2 or 3 days. Female crawlers move around a little bit, searching for a good spot to set up household. Once a spot is selected, they begin feeding and start building their protective cover.
Male crawlers wander around, looking for a female. When they find one, they huddle up next to her, tucking themselves under the edge of her ‘skirt’, where they excrete their own elongated scale coverings. This often creates a daisy-shaped cluster of scales.
After these groups mate, those females lay the year’s second batch of eggs. These eggs hatch, usually mid- to late summer, and stay in the crawler stage over winter. In spring, females claim real estate and males emerge with wings, which they use to find a female.
Walnut scale description
Walnut scale coverings start out white. This is called the white cap stage. Then they darken to grey or brown within a week or so. If you lift the covering off the central, round female walnut scale, you would see a yellowish body with indented margins. Other scale insects do not share those characteristics.
Damage caused by walnut scale
Like other scale insects, walnut scales use piercing mouthparts to suck plant juices from the cambium layer of twigs and branches. This weakens the tree, leading to branch dieback, cracked bark, and reduced harvest. Walnut scale feeding also increases the likelihood of canker development and fungal diseases caused by Botryosphaeria.
How to control walnut scale
You can’t control them if you don’t know they are present. Make a point of inspecting your trees regularly for signs of infestation and infection. You can apply sticky barriers near walnut scale adults to capture crawlers, as they emerge. There are many beneficial predators that feed on scale insects. Parasitic wasps, twicestabbed lady beetles, and a tiny black beetle that goes by the name Cybocephalus californicus, in particular, love to feed on walnut scales. Commercial growers apply insecticides during dormancy or when crawlers emerge in spring.
Narrow range oils can also be used, but walnut trees are very sensitive to horticultural oils. Do not use oils on walnut during dormancy, or between bud break and shoot elongation. Oil use at these times can harm your tree. Horticultural oil can be used with caution as buds begin to swell and the tree enters the delayed dormant period. If your walnut tree is water stressed or suffering other forms of stress, do not apply oil. Oils should also never be used when temperatures are above 90°F.
Scale infestations are on the rise. This is believed to be the result of several different factors, including reduced numbers of beneficial insects. Keeping your trees healthy makes them less likely to be harmed by pests such as walnut scale.
Now you know.
After investing time and garden space to asparagus, one of the last things you want to see is something attacking your spears. Originally from Europe, this tiny fly is now found everywhere asparagus grows. While asparagus miners do not cause serious damage, they can carry a disease that will
Asparagus miner description and lifecycle
You won’t see the early life stages of asparagus miners. Whitish eggs are only 1/1000” in diameter and laid under the epidermis, at the base of asparagus stalks. Slightly larger larvae (15/1000”) are also white and tapered at both ends, with black mouth hooks. After feeding, they will grow to 1/5” in length before pupating. Pupae are dark brown and flattened and can be up to 17/100” long. These pests overwinter in the pupal stage, either in the soil or in stalks.
Adult flies are small (1/10”), shiny black and somewhat humpbacked. They have clear, tapered wings. In California, they appear in May and again near the end of the summer.
Damage caused by asparagus miners
Damage is usually seen during the fern growth stage. As they feed, asparagus miners burrow a meandering pattern just below the surface. This feeding behavior can result in girdling, which causes chlorosis. More often, the damage is mostly cosmetic.
The real problem associated with asparagus miners is that they are vectors for Fusarium root and crown rot. If you see bright yellow discoloration or wilting in your asparagus plants, it may be that asparagus miners have brought Fusarium root and crown rot to your asparagus bed. In that case, both the affected plant and the surrounding soil should be removed and thrown in the trash.
Controlling asparagus miners
Generally, parasitic wasps keep asparagus miners in check. If a heavy infestation occurs, remove the fern growth at the end of its season and throw it in the trash. Insecticides are not effective.
Now you know.
Cardboard and newspaper have long been touted as excellent tools to block weeds, protect raised beds, and in sheet mulching.
We were wrong.
It is true that cardboard and newspaper block weeds. What we have found is that cardboard and newspaper do not always breakdown the way we expect. Without sufficient moisture, cardboard and newspaper can create durable barriers that attract a couple of serious pests.
Cardboard and vermin
It ends up that termites and voles love cardboard. By putting a layer of cardboard under your raised beds, you are putting out the vole and termite welcome mat. If you have voles, forget the cardboard and use sturdy hardware cloth instead.
Cardboard and sheet mulching
The use of cardboard and newspaper in sheet mulching restricts water and gas exchanges. This means nearby plants have a harder time getting the air and water they need. Depending on the soil structure and other conditions, the soil may become so dry that it is hydrophobic, leaving installed plants to die of thirst and weeds around the edges of the cardboard to enjoy the runoff it creates.
Cardboard and newspaper can also slow evaporation and aeration, setting the stage for fungal disease and root rots. Newspaper, if kept moist, will break down. If it is not kept moist, it becomes a barrier. Sheet mulching only works successfully as a temporary weed control measure. Long term use of newspaper or cardboard actually creates more problems than it prevents.
What to do if the cardboard is already in place?
If you already have cardboard and newspaper in place, inspect it for signs of termites and voles. If signs of either are visible, remove it completely, bag it, and throw it in the trash. Then, inspect the soil underneath for signs of life. If the sublayer looks like hardpan or mud, you will need to treat it accordingly.
Hardpan layers need organic material. Mud needs to dry out. Unless roots have grown into the cardboard layer, it is better to remove it completely. If it cannot be removed, poke holes in it and water it until it decomposes.
Once you have corrected the problem, cover the area with a healthy layer of coarse wood chips and let it go fallow for a while. The wood chips will reduce weeds while feeding important soil microorganisms.
Adding manure to the garden provides a wealth of plant nutrients, right?
Yes, it does!
It can also make you very, very sick.
Improper management of manure in agriculture is what leads to those massive recalls of grocery store lettuce and salad mixes. Yes, it can kill you. But don’t panic, there are steps you can take to make it safe.
Chicken bedding, rabbit droppings, horse manure, and cow patties are filled with valuable plant nutrients. Rather than allowing those resources to go to waste [Sorry, I couldn’t resist], you can put them to good use in the garden by following some simple safety precautions.
Benefits of manure
Plants don’t care what you feed them. To them, an element is an element, wherever it came from. Instead of buying fertilizer, you can grow great soil by adding organic material such as manure. Animal manure provides far more than chemical nutrients. It is the slow-release vitamin plants need to grow and thrive - 700 million years of evolution can’t be wrong!
In addition to nutrients, manure contains undigested feed and bacteria that improve soil structure, increase water and nutrient retention and water holding capacity, reduce erosion, and supports important soil microorganisms. Incorporating manure into your garden soil improves its tilth, making it far easier to work.
Nutrient content of manure
Sadly, animal manure does not contain as much nitrogen as you might have hoped. Nitrogen occurs in two forms in manure: organic and inorganic. Organic nitrogen (N) is a slow release nutrient. Inorganic nitrogen occurs as ammonium (NH4+) and nitrate (NO3–) and is immediately available to plants. But you need to act quickly, when it comes to nitrogen.
Nitrogen is a highly volatile element. Left to sit on the surface, nearly 100% of the nitrogen is lost to the atmosphere in a process called volatilization. If manure is incorporated into the soil right away, only 20% is lost. If you are a fan of no-dig gardening, composting will be your only option.
Manure contains high levels of potassium and phosphorus, which your soil may or may not need. I’ve said it many times: get your soil tested by a reputable lab before adding anything. to avoid creating toxicities (and wasting money).
Manure also contains many important micronutrients. Varying levels of calcium, copper, magnesium, manganese, sulfur, and zinc may also be present in animal manure. But not all manures are created equally. Even within a species, nutrient values can vary. Still, there are ranges of nutrients found in most manures and beddings that make them a valuable asset to the home gardener.
Did you know that broiler chickens produce a different manure than roaster chickens? I didn’t either, but you can look at a chart from the Clemson University Extension if you want to learn more.
Raw manure should never be applied to the soil while plants are growing. If it is, be sure that the manure does not touch the plants. After manure is applied, plants that come into contact with the soil (lettuces, melons, squash) should not be harvested for 120 days. Crops that do not touch the soil (tomatoes, corn, pole beans) should not be harvested for 90 days. But you can’t wait that long, you say? What about composted manure? At what point does it become safe to use?
Simply allowing manure to sit in a pile until it looks done is not adequate to protect your family’s health against disease. Many pathogens can survive for years in a pile of poo.
Research has shown that manure must be composted for at least 45 days, 15 of which must be at temperatures between 131°F and 170°F, and turned at least 5 times to be safe to use. Assuming it hasn’t been recontaminated by air-dropped bird poop or other pathogens.
How certain are you that those temperatures have been reached? Seriously. If you are using manure in your garden, you need to be out there with a thermometer and a pencil, documenting those temperatures. You can get a soil/compost thermometer for around $10. Compared to trip to the emergency room, it’s worth it.
As many of you already know, I raise chickens for eggs and compost. Poultry manure has a high nitrogen content and, mixed with straw bedding, makes for an excellent soil amendment. I only feed my hens organic laying pellets, organic treats, and mostly organic kitchen waste, so I feel safe using it after it has been properly composted.
Before you accept a truck load of cow or horse manure from the local farm or stable, keep in mind that you have no control over medications being used on those animals. Also, horse and cow manure tends to be high in salt, which is fine once in a while, but it can build up to toxic levels if used too frequently.
Many people worry that using manure will make their garden smell bad. Properly aged manure smells more like rich earth. Mushroom compost, as my Gilroy neighbors know, has a much more pungent aroma.
Now you know.
You’ve heard of tannins, but what are they?
The word tannin comes to us from Medieval Latin and it refers to oak bark. Oak, chestnut, and other tanbarks were used in tanning leather. Now, I do not mean some cow slathered itself with cocoa butter and lounged on the beach. Hardly. The process of tanning a raw animal skin and converting it into durable leather requires a lot of hard work and some powerful chemicals.
Tannins are large acidic molecules that bind to and alter proteins, which is why they were used in tanning leather. Tannins also bind to starches, minerals, and cellulose. This binding action slows decomposition. You may have seen ponds in forest environments with brownish water. That brown color is likely caused by tannins leaching out of nearby plants and into the water. In the plant world, tannins are used as pesticides, to protect against predators, and to regulate growth.
Plants produce tannins to make themselves less palatable and harder to digest. This discourages feeding by some herbivores. To counteract the presence of those tannins, some plant eaters have evolved to include a tannin-binding protein in their saliva. [Isn’t the world amazing?] The latex produced by dandelions contains tannins.
Tannins as growth regulators
Tannins also have antimicrobial and allelopathic actions. Allelopathy is a type of plant chemical warfare in which one plants releases chemicals that inhibit the growth of neighboring plants. This growth regulation can occur by reducing the available nitrogen or oxygen in the soil, killing nearby beneficial soil microorganisms that support plant life.
If you bite into an unripe fruit, it is the tannins that cause your mouth to pucker. As fruits approach maturity, the level of tannins decreases. Many popular garden plants contain tannins, to one degree or another, including:
In autumn, when leaves turn color, the golds and yellows you see are the result of tannins.
Now you know.
We’ve all heard about ladybugs, but what about twicestabbed lady beetles?
Common ladybugs, or lady beetles, have the classic red half-domed shape, stubby antennae, and multiple black spots. This particular lady beetle has a black domed shape with two distinct red spots, hence the name. If you turn one over, their undersides are red or yellow.
Twicestabbed lady beetle description
Twicestabbed lady beetles (Chilocorus orbus) are only one of four black lady beetles with red spots. The other three are Axion plagiatum, Chilocorus kuwanae, and ashy gray lady beetles. All four species are beneficial predators, so it isn’t critical to be able to tell them apart. [The ashy gray lady beetle has a unique ability to change its color from gray to red, but we will discuss that another day.]
Twicestabbed lady beetle larva have the same bristled, elongated, alligator shape of other lady beetle larvae, but are more grey than black. Adults are 1/10 to 15 of an inch long.
Twicestabbed lady beetle diet
Twicestabbed lady beetles feed predominantly on adults and larvae of scale insects. Their diet includes armored scale on avocados, brown soft scale on citrus, European fruit lecanium on cherry, San Jose scale on pear, and more. You will rarely see twicestabbed lady beetle larvae because they spend most of their time hidden under scale insect domes, feeding. Eggs are even less likely to be seen, at 1/32” in length. Eggs may be laid singly or in clusters.
Feeding is normally done by piercing the victim and sucking out their innards. Older lady beetles also bite and chew their food.
As with other lady beetle species, it does no real good to buy them. If they don’t like what’s on the menu in your garden, they will simply fly away. If you make your garden appealing to lady beetles, they will find you.
This means providing fresh, mosquito larvae-free water. [Use mosquito dunks in all standing water.] Lady bugs also eat pollen, so planting a variety of flower colors and shapes may attract them. Allowing dill, cilantro, and fennel to go to seed provides a ready food source for both you and lady beetles. Also, avoid the use of broad spectrum pesticides and insecticides.
How many different species of lady beetles are in your garden?
Many plant diseases are caused by viruses.
If you can get beyond their disease-carrying behavior, however, viruses are amazing things.
Most viruses are made up of half a DNA strand, called RNA, and are protected by a coat made out of protein. A small handful of plant viruses contain full DNA strands. There is another group, called viroids, which contain an RNA strand but do not have a protein coat. In a recent article, The Scientist reported that new research shows different segments of a virus’ genetic information are used to infect separate cells, creating a domino effect of plant disease. I swear, the more I learn, the more amazing the world gets! But I digress…
The science of viruses
Viruses enter a plant cell and use their RNA strand to reprogram the cell’s genetic instructions. This causes the cell to start producing more of the virus’ RNA. These new strands then infect neighboring cells, and so on.
There are several families of viruses that cause plant disease. We won’t go into that now. What’s important to know is that the common names of most viruses start with the plant most likely to be infected, followed by the most characteristic symptom. For example, bean yellow mosaic is commonly seen in beans and a yellow mosaic pattern is the most common symptom.
Symptoms of viral infection
While there are more viral diseases than I can count, many of them share similar symptoms. The most common symptoms of viral disease in plants include:
Bronzing and leaf rolling may also be seen.
Viruses are generally spread to plants through insect feeding. Common disease-carrying insects include:
Dagger nematodes and some fungi and single-celled organisms also carry viruses. Viruses can also be moved around the garden on pollen, clothing, tools, and plant debris. Many viruses overwinter in seeds, flowers, perennial weeds, and crop root systems, where they can lie dormant for years.
California’s viral diseases
There are dozens of viral plant diseases found in California. The most commonly seen include:
You can find lists of viral diseases common to other areas by contacting your local County Extension Office.
Controlling viral diseases in the garden
Healthy plants are better able to ward of viral infections. This means proper feeding, irrigation, and pruning. It also means selecting resistant plants that are suitable to your microclimate, buying only certified disease-free plants and seeds, planting at the proper depth, and avoiding mechanical injuries from rubbing branches and weed wackers, among other things.
Use an integrated pest management (IPM) program to control viral diseases. This means encouraging natural predators and parasites of viral diseases, sanitizing garden tools regularly, and using cover crops and crop rotation to interrupt disease triangles. Yellow sticky sheets can be used to trap many disease-carrying pests. Pesticides and insecticides used to kill disease carriers are not effective. Reflective mulches have been used successfully to confuse some disease-carrying pests. Diseased plants should be removed and thrown in the trash to prevent healthy plants from becoming infected.
Viral diseases of plants are on the rise, largely due to monoculture, mass production, climate change, global shipping and other human activities. You can reduce the likelihood of viral diseases affecting your plants by placing new plants in quarantine and knowing what to look for.
Now you know.
Odds are pretty high that you are walking around your garden each spring, removing spent stems and frost damaged twigs and leaves, shaping shrubs, deadheading spent blossoms, and curbing rampant growth. All of those snips, trims, and cuts are then taken to the compost pile, where they are watered and flipped repeatedly, until the mixture is ready to be spread out as plant food and soil amendment. That’s fine, but, in many cases, you can simply chop and drop, right where you found the plant in the first place.
Stop fighting natural cycles
Moving materials around is often unnecessary. Instead, copy the natural cycles that have evolved over millions of years. Simply chop plant material where you find it and drop it on the ground. This saves a lot of time and energy, while still putting all that organic matter to work for you in the garden. Insects, animals, microbes, rain, and foot traffic will move that chopped plant matter into the soil, improving soil structure and adding important nutrients, just as it has since plants arrived on the planet’s surface. No wheelbarrow required.
Benefits of mulch
Mulch, of practically any sort, creates a buffer against erosion and temperature extremes. It also makes weeding a lot easier. While I am a huge proponent of coarse wood chip mulch, you can use the same idea to simplify your spring garden work: trim off bits of plant, chop it where you stand, and let it fall. Using a plant’s own material to create instant mulch puts the nutrients that plant needs to grow and thrive within easy reach. Of course, you should still get your soil tested every 3 to 5 years, to make sure there are no deficiencies or toxicities.
Levels of effort
In one school of thought, the chopped material is simply dropped to the ground after the first snip. This green manure will, over time, break down. Obviously, woody stems will take far longer than green leaves and new growth, but they will break down eventually. Personally, I take a slightly more active role and chop the removed plant parts into smaller pieces, just as I do at the compost pile.
Recycling plant material
Chopping plant material speeds the decomposition process. Dropping it where you found it puts nutrients back where the plant can reuse them. This is the same idea behind grasscycling, which is when you mow the lawn without the bag attachment, allowing the clippings to fall right back on the lawn. Yes, you will be more likely to track snipped blades of grass around on your shoes for a day or two, but the nutrients and soil structure improvements are worth it.
Come autumn, when leaves start falling, leave them where they fall, unless they fall on your lawn. In that case, mow them where they fall, or blown them into flower beds and around shrubs and trees, where they will create a winter blanket of protection that is transformed into food in spring.
Some claims are made about plants containing especially high levels of nutrients, making them excellent green manure crops, perfect for chop and drop mulching. These ‘dynamic accumulators’ are mostly hype. The truth is, plants contain a wide variety of elements used to help them grow. Some produce more volume, or biomass, than others. That’s all.
A word of warning
While chopping and dropping is an excellent way to save time while improving soil health, you don’t want to drop heavily diseased or infested plant material where reinfection or re-infestation can occur. By throwing diseased plant material in the trash, you are breaking the disease triangle for that pathogen on your property. In most cases, infestations by insects can be added to your compost pile. In both cases, you can also go ahead and drop everything, allowing natural predators to kill off most of the pests. Most disease pathogens do not last long in green manure, with the exception of fungal diseases, such as peach leaf curl and rust. When those diseases are present, I toss leaves in the trash.
Chop and drop weeding
Unless they have gone to seed or are spread by runners, weeds can be pulled, chopped, and dropped where they are. Weed plants with seeds and those that spread using runners are fed to my chickens, or you can add them to your compost pile. [Compost piles are still great to have for kitchen waste and to process chicken or other animal bedding.
As you move through your garden, pruners at the ready, snip off unwanted stems, spent blooms, and the like, chop them where you stand and let them fall to the ground. If you think it looks messy, you can chop while standing behind the plant instead of in front. In a surprisingly short period of time, you will forget they were even there as natural cycles take hold and transform yard waste into valuable plant food and soil amendments. For free.
Brown soft scale (Coccus hesperidum) may be found on pomegranate and citrus trees, as well as bay laurel.
These pests can suck the life out of your lemon, orange, kumquat, lime, and pomegranate trees, killing twigs, and reducing your harvest. Like other sap-sucking insects, brown soft scales excrete sugary honeydew, which creates habitat for sooty mold, and attracts disease-carrying ants.
Brown soft scale description
These pests live under yellowish, mottled shells. They may look like nothing more than little bumps on leaves and twigs, Brown soft scale look similar to citricola scale insects.
Brown soft scale lifecycle
Brown soft scale females give live birth, or lay eggs which hatch almost immediately. These young crawlers move around freely on leaves and twigs, feeding as they go. They continue moving around until they are about half grown, molting twice.
Controlling brown soft scale
Sticky barriers around the trunks of susceptible trees can cut off protection to brown soft scale pests by ants. Also, avoiding the use of broad spectrum pesticides allows natural predators to feed on these pests. If you see scale shells with holes in the top of them, you will know they have been parasitized by beneficial insects. Heavy infestations can be treated with dormant oil in winter, but this is rarely necessary.
No, it's not a flying snake.
Introducing another beneficial insect on the California garden scene: the snakefly.
I don’t know why they call it a snakefly. It doesn’t look like a fly or a snake. Apparently, snakeflies are native to the western half of North America, as well as Europe and Asia. Until yesterday, I had never heard of snakeflies. Let’s see what we can find out!
The first thing I learned about snakeflies is that they are considered living fossils, having remained relatively unchanged for over 140 million years.
Snakeflies (Agulla adnixa) have long, thin bodies with lifted torsos (prothorax), large eyes, extended mouthparts (mandibles), relatively long antennae, and a long, thin backend. Adults are reddish brown and can be 1/2 to 1” long. All four wings are transparent, and longer than the body, similar to lacewings (except that snakefly wings are covered with black veins). The long backend is not a stinger. Instead, it is an ovipositor, or egg-laying tube.
Larvae have squishy bodies, and the head and first segment are hardened (sclerotised), but they look like a cross between an earwig and a ladybug larvae. [Sorry, but I couldn't find any free-to-use photos.] Snakefly larvae have 3 pairs of true legs, and, you won’t believe this: Snakeflies have an adhesive strip on their abdomens that allows them to move up walls and trees!
Eggs are deposited in the soil, where they are able to absorb soil nutrients to help them grow and develop. When they hatch, larvae stay in the soil or move to the bark of nearby trees. There, they feed on soft-bodied pests, such as grubs and caterpillars, as well as the eggs and larvae of many garden pests. Snakefly larvae go through as many as 10 moltings before reaching adulthood. This process can take 2 to 6 years. Next, after temperatures reach 32°F, the larvae enter a pupal stage. Unlike other insects, the snakefly pupa is mobile, leaving its pupal cell for day trips or to relocate. The pupal stage is temperature dependent, lasts a few days to 3 weeks, upwards of 10 months. [This is one long lived insect!]
Adults snakeflies are very territorial as they feed on insects, such as mites and aphids. [Yay!] It is also believed that they occasionally nibble on pollen.
Snakeflies court one another with cleaning rituals. You may see them practicing their flirting skills by cleaning their legs and antennae when alone.
Have you seen any snakeflies in your garden? Let us know in the Comments!
Calendula officinalis is an edible flower that can add color and attract honey bees to your garden.
Believed to be native to Europe, Calendula officinalis has been grown by people for so long and in so many locations, it is hard to tell for sure.
Sunny yellow and orange calendula create lovely borders that bloom throughout most of the year. Blossoms look similar to daisies because both are members of the sunflower family, or Asteraceae.
Many faces of marigold
Most marigolds sold in retail outlets are members of the Tagetes genus. Tagetes, or simply ‘marigolds’, are native to the Americas. Tagetes are known for their pungent aroma that may (or may not) deter deer, rabbits, voles, and other pests from grazing on your garden plants. Tagetes marigolds also attract and then kill nematodes.
Today’s topic, Calendula officinalis, will not protect your plants from herbivores or nematodes, but they have their place, having been used as food and medicine for centuries.
Pot marigold description
Unlike the Tagetes genus of marigold, which have leaves that appear alternately along a stem, pot marigolds have slightly hairy leaves that are arranged in a spiral around the stem. They are short-lived perennials, typically grown as annuals, that grow 18 to 30” tall, with 2” flowers. Flowers are bright yellow or orangish-yellow, with ray florets and disk florets, common to sunflowers. Pot marigold’s curved seeds are actually dried fruits, called achenes.
Pot marigold as an attractant
In addition to looking lovely as a border plant, or in a parterre, Calendula officinalis will attract important pollinators, such as honey bees to the garden. Unfortunately, they will also attract cabbageworm butterflies, large yellow underwings, an invasive moth of the cutworm variety, and setaceous Hebrew character moths, whose larvae feed on a number of popular garden plants.
Pot marigolds as food
Pot marigold flower petals have a tangy, peppery flavor. Traditionally added to German soups an stews, pot marigold is also added to herb butters and cheeses, or chopped and used to garnish deviled or scrambled eggs, fish dishes, or steamed vegetables.
Pot marigold flower petals add color and tang to salads. If you add marigold flower petals to rice, while cooking, the rice will turn yellow. For this reason, it is also known as Poor Man’s Saffron. Farmers have fed marigolds to chickens for years to make the yolks a deeper yellow.
One variety of pot marigold, ‘Mexican Mint’, has the flavor of tarragon. It is also known as Texas tarragon. Pot marigold petals also make a delightful tea.
Pot marigolds as medicine
Pot marigolds also have medical merit. Research has shown that tinctures of pot marigold are used today to treat skin irritations and burns, to speed healing, and to control bleeding. [I wonder how they would look growing next to some aloe vera - just to keep the medicinals together.] This is not my area of expertise, and I won’t make any personal claims, but it is interesting to see how, every once in a while, those old treatments hold true. That being said, some people are allergic to pot marigolds.
How to grow pot marigolds
Pot marigolds are easy to grow from seed and they tend to be drought tolerant. Start seeds in small pots, only lightly covered with soil. Keep the soil moist, but not soggy, until germination occurs. Then, move plants to a sunny location with good drainage. Calendula may need protection from scorching summer afternoon sun, and they can be grown in containers, or on windowsills. Marigolds readily self-seed.
Calendula pests and diseases
While these plants are relatively trouble-free, they may become infected with powdery mildew, root rot, and smut. They are also susceptible to Alternaria leaf spot, aster yellows, charcoal root rot, cottony rot, cucumber mosaic, gray mold, Pythium root rot, root knot nematodes, rust, southern blight, spotted wilt (from the tomato spotted wilt virus), stem rot, and Verticillium wilt. I couldn't find any pests that significantly bother pot marigolds.
Many of these diseases can be prevented by providing good drainage and air flow, so top dress soil regularly with organic matter, space plants with mature sizes in mind, and avoid overhead watering.
So, do you know if your marigolds are edible or not now?
Psyllids are jumping plant lice that suck plant juices. There are over 160 psyllid species in California, 140 of which are native to the area.
Most native psyllid species do not pose a serious threat to your garden. Local predators tend to keep those populations in check most of the time. Invasive psyllid species are something else altogether.
Psyllids look like tiny cicadas or winged aphids, with tubular mouthparts. They have very strong legs and short antennae. Psyllids can be 1/12 to 1/5” long. Adults hold their wings in a roofline position. Nymphs are flattened and look a lot like soft scale insects. Psyllid nymphs commonly produce waxy filaments or covers, called lerps. Lerps are made from wax and honeydew.
Regardless of the species, psyllids start out as tiny eggs that hatch and go through five developmental stages, or instars, before reaching adulthood. Adult psyllids can fly, but most prefer to jump. If you see what you think is a psyllid run or fly away, it is probably a psocid [SO-sid]. Psocids are beneficial insects that feed on fungi. They differ from psyllids in that they have a narrow “neck” and chewing mouthparts.
Psyllid host plants
As a species, psyllids have strong preferences for particular host plants. While some psyllids will prefer your sweet peppers and chili peppers, other varieties will go after your peaches and nectarines, while others will only feed on olive or pear trees, and yet other psyllid species will only feed on potato and tomato plants.
The invasive Asian citrus psyllid carries huanglongbing, a deadly citrus disease. Orange, lemon, lime, kumquat, and grapefruit trees infected with huanglongbing must be destroyed by a professional. Sad, and expensive. These pests, when present, are most active April through June in the San Francisco Bay Area.
Psyllid species most likely to threaten your garden include:
There are dozens of psyllid species that infest ornamental trees and shrubs, as well. These include the recent invasions of Ficus leaf-rolling psyllids and spotted gum psyllids. On the other hand, some psyllid species are being used to our advantage. The Australian melaleuca psyllid, for example, has been purposefully introduced to Florida to help control paperbark trees, an invasive weed tree.
Damage caused by psyllids
One of the biggest problems associated with psyllids is their poop. After they have robbed your plants of valuable nutrients, weakening the plant, they add insult to injury by excreting a large portion of the sap they stole and depositing on leaves. Known as honeydew, the excrement of sap-suckers is filled with sugar and other nutrients. Honeydew ends up being food for fungal sooty mold and disease-carrying ants.
Psyllid feeding can also spread viral diseases, such as calico, bacterial diseases, such as zebra chip, galls, leaf and bud discoloration and deformation, and premature leaf drop. Leaf distortions often look similar to peach leaf curl. Pear psyllids inject fruit with toxins that blacken leaves and fruit skins. Psyllid feeding also creates points of entry for other pests and diseases.
How to control psyllids in the garden
Once psyllids appear in your garden, insecticidal soaps and yellow sticky sheets can be used to help control them. Parasitic wasps and pirate bugs can put a serious dent in psyllid populations, so avoid using broad spectrum insecticides. Severely infested plants should be removed and destroyed or thrown in the trash. Usually, simply monitoring plants regularly can make controlling these and other pests much easier.
To prevent invasive psyllids from finding your garden, only buy pest-free plants from reputable nurseries, place new plants in quarantine, and do not bring plant products that may be infested into your state, community, or yard.
Because of the risks posed by invasive psyllids, any unrecognized psyllids should be taken to your agricultural commissioner or local County Extension Office for identification.
You walk past a tree and notice leaves rolled up into neat tubes. What causes this and is it a problem?
There are several leafroller species found in California:
A quarantine is in place for the light brown apple moth. See if you live in an affected area by clicking on the CA Dept. of Food & Agriculture’s Boundary Index Map. If you live outside of California, you can contact your local Cooperative Extension Office for more information
Leafrollers start out as clusters of flat, irregularly shaped eggs often found on twigs and leaves. These egg masses are coated with a dark gray or brown glue that later bleaches to white, giving them an appearance similar to fish scales. If you look closely at an egg mass in spring, you can see tiny pinholes where larvae have hatched.
After hatching, larvae pull leaves into a cylinder for protection as they feed. Most larvae feed through summer and then overwinter as pupae, though some species continue feeding throughout the year, causing considerable damage.
When disturbed, leafroller caterpillars tend to wriggle wildly and then rappel to the ground on a single silken thread.
Botanical stigmata are part of the female reproductive system.
Tiny stigmata may not grab your attention at first glance, but maybe they should.
Before we learn why, let’s do a quick review of flower anatomy.
Stigmas and pollination
Carried by insects, bats, or wind, pollen is received at the stigma by sticky, specialized cells (stigmatic papillae). Once the pollen has been captured, the stigma, which is often quite moist, helps to rehydrate the pollen after its lengthy travels. Once hydrated, the pollen grain germinates, sending a pollen tube down the style to the ovary. To ensure that the proper pollen is collected, stigmas have evolved some very fancy attraction and capture methods.
You may be surprised to learn, as I was, that high temperatures, usually above 104°F, for 2 or more days prior to pollination, can exhaust the stigma of tomato plants to the point they cannot capture pollen. This may explain why, during particularly hot summers, we see lots of tomato blossoms, but no fruit. High temperatures (above 100°F) also reduces pollen germination.
Besides being sticky, stigmas use various shapes, flaps, and hair arrangements to help ensure that the correct pollen is captured and all others are rejected. These shapes can be simple tubes, truncated tubes, threadlike, bulbous, conical, lobed, feathery, hairy, beaked, fan-shaped, brush-like, leaflike, or disc-shaped. The familiar threads found on ears of corn, called silk, are stigmata.
How many different stigmata shapes are there in your garden?
The word rachis comes to us from the Greek word for backbone.
But, plants don’t have backbones!
That’s true. But they often have a main axis or shaft, similar to those seen in feathers. In fact, the shaft of a feather is also called its rachis [ray-KIS].
Botanically, the rachis can be the central stem seen in ferns, in compound leaves, or in the portion of an inflorescence found above the peduncle. Rachis is a type of stipe. Stipes are stalks that support other structures.
Now, when someone mentions a rachis or a stipe, you will know what they are talking about!
When you cut flowers for a bouquet, you are generally cutting the peduncle. Peduncles are simply flowering stems, but they may surprise you.
Peduncles can occur in plants without stems, they may continue to grow indefinitely, and some peduncles grow underground.
The peduncle of a simple flower is easy to recognize. It is the classic stem you hold, cut, or put into a vase to admire. Its job is to support the flower. An artichoke stem is a peduncle, and for the same reason.
Now you know.
A flower is a flower, unless it is a bunch of flowers growing on the same stem, then it’s an inflorescence.
Anatomy of an inflorescence
A singular flower appears at the end of a stem, called a peduncle, nestled in a (normally) green cup, called the receptacle, and surrounded by modified leaves, called sepals. When there are multiple stems or branching stems (rachis), or flowers that occur on a disk, it is an inflorescence. The stalks of individual flowers within an inflorescence are called pedicels. These flowers are called florets, and their leaves are called bracts.
Types of inflorescences
Inflorescences can be determinate or indeterminate. The oldest flowers of a determinate (cymose) inflorescence are found at the end of the stem, as other flowers bloom in succession, down the stem, with the youngest flowers at the base. Indeterminate inflorescences are just the opposite, with older flowers at the base and younger flowers occurring closer to the tip.
There are also catkins (mulberry), spadix (cobra plant), and many subdivisions of each category, but this is a good start.
When an inflorescence produces fruit, such as sunflower seeds, it is called an infructescence.
Now you know.
April is the time to start checking apple, apricot, avocado, cherry, peach, pear, plum and prune trees, and blueberries, for signs of the dreaded Pacific flathead borer.
Like other borers, these pests chew tunnels in wood, weakening a tree’s structure, and robbing it of important nutrients found in the inner cambium layer. Newly planted trees and trees weakened by drought, water-stress, scale insects, carpenterworms, or diseases, such as Phytophthora or Armillaria, are particularly susceptible. These weakened areas are then more likely to be attacked by other pests, such as shot hole borers.
Pacific flathead borer feeding can also girdle a young tree, killing it. The only symptom you may see is a dark colored depression in the bark, or tiny cracks where you might see frass (bug poop), usually on the side receiving the most sunlight.
Pacific flathead borer identification
Pacific flathead borers (Chrysobothris mali) are flattened, wedge-shaped, dark bronze beetles that can be 0.5 to 0.75” long. You may see copper-colored spots on the wing covers.
Eggs are very tiny, only 0.04” in diameter, flattened, oval, and white. Larvae grow to 0.75” in length and are white, with an amber colored head. Larvae are flattened, with a widened area just behind the head, tapering towards the rear end. Pupae are also whitish and flattened, getting darker as they mature.
Pacific flathead borer lifecycle
These pests overwinter in a prepupal stage. As temperatures begin to rise, they pupate. From April through July, adult beetles emerge, usually beginning around the same time apple trees are blooming. Then females mate and begin laying eggs in the bark, favoring areas weakened by sunburn or mechanical injury from tree supports, weedwackers, and out of control lawn mowers. When the eggs hatch, larvae burrow directly into the bark and begin feeding on the nutrient-rich cambium layer, robbing your trees of the nutrients they need to grow and produce fruit. As the larvae mature, they will either create a pupal chamber in the xylem, or burrow under the bark, where they will stay until the following spring.
Pacific flathead borer controls
Healthy trees are better able to resist and recover from Pacific flathead borer attack. This means selecting trees suitable to your microclimate, planting them at the proper depth, and feeding, irrigating, training, and pruning them properly.
Since eggs are laid in weakened bark, protect trees from mechanical injury, and be sure to whitewash exposed bark before sun damage can occur.
Birds, especially woodpeckers, will find and remove Pacific flathead borers, and carpenter ants eat both larvae and pupae. Insecticides are commonly used in commercial orchards to kill new larvae, but once the larvae are inside the tree, there is nothing you can do besides pruning out infested wood and burning it.
Now you know.
Ashy stem blight, also known as charcoal rot, is a fungal disease of cucurbits. This means that your melons, squash, and cucumbers are susceptible. It can also affect common beans, blackeyed peas, lima beans, chickpeas, corn, fenugreek, soybeans, sorghum, and sunflowers.
Ashy stem blight is a soil borne fungus (Macrophomina phaseoli) that loves hot days (> 85°F) and cool nights. This pathogen can stick around for up to 12 years. It is common in California and often infects plants within 2 weeks after being planted, but symptoms generally do not appear until much later in the growing season, as temperatures begin to rise - after you’ve invested weeks of irrigation, feeding, and weeding. So, learning how to recognize and prevent this disease can help ensure a better harvest.
Symptoms of ashy stem blight
The first sign of ashy stem blight are black, water-soaked lesions or cankers along the stem at the soil line, stunting, and chlorosis (yellowing) of the upper, or crown leaves. If you look closely at the lesions, you may be able to see concentric rings. Infected pods may ripen prematurely. As the fungi population grows within the plant, you may see an amber gum oozing from the infected plant. Eventually, the stem turns dry and brown. If lesions girdle the plant, it will die. If you dig up an infected plant, you will see blackened roots and a lack of feeder roots.
Preventing ashy stem blight
Ashy stem blight is known as a “stress pathogen”. This means it preys on stressed plants. Stresses, such as a heavy fruit load, high temperatures, drought, and water-stress can make plants more susceptible to infection. Keeping your plants healthy can help them protect themselves.
While furrow-irrigated plants rarely have severe cases of ashy stem blight, you may be surprised to learn that the disease is common with drip-irrigated systems. It is believed that this particular set-up increases salt levels near the soil surface, creating salt stress.
Monitor plants regularly for signs of infection. Once infection occurs, affected plants should be removed and thrown in the trash, and a 3-year crop rotation with non-susceptible crops should be put into place. There are no effective chemical treatments for this disease.
Now you know.
We’ve all heard that beans cause gas, but did you know beans rust? Well, not rust like the undercarriage of a New England truck, but rust just the same.
Bean rust, like other plant rusts, is a fungal disease. Rust is found worldwide and it can wipe out your bean crop if it takes hold early enough in the growing season.
California’s cool, wet springs are just the conditions needed for rust to thrive. Add overhead watering or a decent breeze and the stage is set for an epidemic. Fungi are so efficient that, under ideal conditions, the disease cycle can be repeated every 10 to 14 days!
There are several strains of bean rust. Two of the most common are Uromyces appendiculatus and Uromyces phaseoli typica, but you don't need to know the Latin to recognize bean rust in the garden.
Bean rust symptoms
Similar to other rusts, bean rust prefers moist places and moderate temperatures (65 to 85°F). While it can occur on any aboveground portion of a plant, bean rust is most commonly found on the underside of leaves. Pods can also be affected. At first, it just looks like tiny white or yellow bumps. Then those bumps break open and turn into bright orange, reddish, or yellowish flecks. Those flecks are pustules that are made up of more fungal spores than any of us cares to count. [Okay, some scientists love counting things like that.] A yellow outer ring is sometimes visible. Leaves may begin to curl downward and plants may develop a scorched appearance. These symptoms are easy to see and make identifying the condition simple. Getting rid of it is something else all together.
Bean rust control
The fungi that cause bean rust can be spread by ants, aphids, and gardeners. It can stick to tools, fingers, and clothing. As with many other plant diseases, prevention is far easier than eradication. Use these tips to prevent and control bean rust in your garden:
Keep in mind that rust pustules are easily dislodged and can land somewhere else, or on the soil, where they can be bounced back up into your plants by rain, wind, and overly exuberant irrigation. And be sure to disinfect your tools after removing rust-infected leaves, to avoid spreading the fungus to healthy plants.
You can grow a surprising amount of food in your own yard. Ask me how!
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