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.

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.

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. 

Raw manure

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?


Composted manure

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.


Manure sources

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.

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 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?

​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.

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 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.

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!


Snakefly lifecycle

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!

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?

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:

• Asian citrus psyllid (Diaphorina citri)
• Eugenia psyllid (Trioza eugeniae)
• olive psyllid (Euphyllura olivina)
• pear psyllid (Psylla pyricola)
• potato/tomato psyllid (Bactericera cockerelli)

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. ​

When disturbed, leafroller caterpillars tend to wriggle wildly and then rappel to the ground on a single silken thread.

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.
​

How many different stigmata shapes are there in your garden?

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!

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.

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.

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:

• Space plants to allow for good air circulation.
• Avoid overhead watering.
• Plant resistant varieties.
• Monitor plants frequently.
• Apply sulfur to make leaves and pods less hospitable to bean rust.
• Remove infected leaves and dispose of them in the trash.
• Avoid excessive use of nitrogen and overfertilizing. 
• Cut spent (uninfected) plants off at soil level and add them to the compost pile.
• Use a 2-year crop rotation with bean plants.
• Infected leaves should be removed and thrown in the trash.

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.