Cow parsnip is not related to the root vegetable known as parsnips, but you can eat them, if you are careful.
Cow parsnip description
True to its Latin name, Heracleum maximum, these are very large herbaceous plants. Reaching over 9’ in height, all parts of cow parsnip are big. Lobed leaves can be 16” across and the typical umbel-shaped flowers of the carrot family are also large, averaging 8” across. These flowers are white and the outer flowers are often larger than the inner flowers. Stems are succulent and sturdy.
Uses for cow parsnip
Peeled flower stems have been used as food for a very long time. Tasting similar to celery, cow parsnip is also known as Indian celery or Indian rhubarb. The reason for peeling those stems is because the outer layers contain phototoxins that can irritate or burn your skin. Traditionally, infusions of the flowers were used to repel flies and mosquitoes. Before you start rubbing yourself with cow parsnip, be sure to take a closer look. If you see reddish or purplish spots on the stems, and serrated leaves, look out! You have discovered giant hogweed, a far more potent version.
Purple spots and serrated leaves may indicate giant hogweed (Heracleum mantegazzianum), rather than cow parsnip. The sap of giant hogweed contains phototoxins. These defensive oils cause severe burns and blisters when exposed to light.
Now, I am not talking about the discrete round blisters of sunburn fame. These are huge, swollen, ugly, painful burns that can leave black or purple scars for years to come. I won’t share photos here, but you can track them down yourself if you need convincing.
This dangerous sap is found on coarse white hairs (trichomes) on stems. It can cause third-degree burns serious enough to land you in the hospital or a burn unit. Giant hogweed has found its way to northern U.S. states. If you see it, report it to your local County Extension Office.
Another toxic plant commonly mistaken for cow parsnip is poison hemlock, also with purple marks on the stem. Bottom line: when in doubt, don’t.
Since cow parsnip, giant hogweed, and poison hemlock can all hurt you, to one degree or another, it is a good idea to be cautious and wear protective clothing whenever you might be around them.
Conifers produce seeds but not flowers. This makes them gymnosperms. Instead of flowers, conifers produce cones. Botanically known as strobili, cones are the reproductive organs of conifers.
There are male cones and female cones. Male cones, called microstrobilus or pollen cones, produce pollen and look very little like the cones we imagine. Male cones are more herbaceous than female cones and they look very similar to one another across species. Female cones are the familiar woody structures that produce and contain seeds. Female cones, also known as seed cones, ovulate cones, and megastrobili, are structurally unique to each species and helpful when it comes to identification.
Female cones are covered with plates called scales. Female cones start out as a central stem covered with bracts. Bracts are modified leaves or scales with a small flower or flower clusters in its axil. The bright red “petals” of poinsettia are not actually flowers. They are bracts. In some cases, the bracts harden and fuse to the woody seed scales.
Male cones appear in clusters and are much smaller than female cones. They contain pollen sacs and generally start growing on the end of the previous year’s branches, usually lower in the tree canopy, below female cones. This prevents self-pollination.
Cone and seed development
While male cones usually only last one year, it can take 3 or more years for a female cone to fully develop. Once a female cone is receptive and pollination has occurred, it can take up to a year for fertilization to be complete. As seeds develop, some cones will slowly begin to open, while other species need fire to trigger opening. Stone pine seeds, while delicious, require a lot of hard work to separate them from their cones.
Some conifer seeds have a wing that allows them to be carried on the wind, while other species rely on animals, such as squirrels, and birds help them disperse. Stone pine seeds, while delicious, require a lot of hard work to separate them from their cones.
Types of cones
The cones of holiday decoration fame are only one of many different types of cones. The scales can be arranged in one of two ways: imbricate or peltate. Imbricate scales overlap much like roof tiles and are attached along a common axis. Peltate scales do not overlap and are attached from a central point, more like an umbrella. Some cones look more like berries than cones.
Araucariaceae (monkey-puzzle tree, kauri, and the nearly extinct Wollemia tree) - fused scales create a spherical cone; imbricate
Cupressaceae (arborvitae, cypress, juniper, redwood, sequoia) - bracts and seed scales are fused; peltate
Pinaceae (cedar, fir, larch, pine, spruce) - archetypical cone; imbricate
Podocarpaceae (Prince Albert’s yew, Matai) - many of the scales are fused into a brightly colored, often edible aril; imbricate
Sciadopityaceae (Japanese umbrella pine) - imbricate
Taxaceae (yew) and Cephalotaxaceae (plum yews) - female cones have only one scale, with a single poisonous ovule; the surrounding fruit is sweet but the seed is deadly
While not conifers, cycads and welwitschia, or tree tumbo, also produce cones. Tree tumbo plants are considered living fossils and are unique in that female plants produce female cones and male plants produce male cones.
How many cone-producing plants do you have?
There are many claims about gypsum in the garden, but how many of them are true?
Used to make sidewalk chalk, plaster of Paris, and sheetrock, gypsum (CaSO4) is a soft mineral (along with silica and other minerals) that coats everything and everyone who attends Burning Man. Before we decide whether or not it is beneficial in the garden, let’s learn a little more about gypsum.
Gypsum, also known as calcium sulfate, is a salt that forms crystals. These crystals are particularly sharp. In Old English, it was known as “spear stone”.
Unlike other salts, gypsum becomes less water soluble as temperatures rise. Gypsum can take a variety of forms and, depending on the presence of other minerals, it can take on many different colors.
Gypsum in the garden
Gypsum is made of calcium and sulfur, two nutrients important to plant health. In the early 1800’s, gypsum was considered such a fertilizer miracle that smugglers battled local authorities in what became known as the Plaster War. At that time, gypsum was also known as sulfate of lime or lime sulfate.
Plants use calcium to maintain cell walls. Calcium in the soil helps build healthy soil structure by binding tiny clay particles into larger clumps called aggregates. Sulfur is an important component of proteins used by plants. As such, gypsum can be beneficial in the garden, but not always.
False claims about gypsum
Like most other quick fixes, many of the claims about gypsum are based in fact, but taken too far.
Applying gypsum unnecessarily can cause leaching of aluminum, iron, lead, manganese, potassium into local lakes, rivers, and underground water stores. It also interferes with the beneficial soil microorganisms responsible for helping plants absorb nutrients. Applying gypsum to sandy soils can slow the transport of copper, phosphorus, and zinc.
Benefits of gypsum
All that being said, there is one situation when gypsum can be helpful in the garden. This only occurs when clay soils contain high levels of salt or, more accurately, sodium. These sodic soils can benefit from gypsum applications, in moderation. High salt levels in clay compound poor drainage, often causing heavy crusts to form. Adding gypsum in this situation allows the calcium to bind to the clay, replacing the salt, which is then leached out of the soil over time through cation exchange. Ultimately, this improves soil structure and drainage and reduces salt levels. Adding gypsum to clay without high sodium levels is a bad idea, as it can make alkaline soils even more alkaline. In most cases, plants need a soil pH of 5.5 to 7.0 to thrive.
Rather than simply adding gypsum because you heard it was a good idea, get your soil tested, determine your soil structure, and mulch everything with coarse wood chips to improve your soil and help your plants grow.
If you happen to find a large, fine-grained seam of gypsum, you are in luck. Because that particular form of gypsum is more commonly known as alabaster.
Now you know.
You won’t see them, but fig mites can bring serious diseases to your figs.
Fig mites (Eriophyes ficus, also known as Aceria fici) are a type of eriophyid mite and they are found worldwide.
Fig mite description
Adult fig mites are pale yellow, wedge-shaped, and have two pairs of legs near the head, but they are extremely small. Even with a 20x hand lens, these mites are difficult to see. Larvae look something like a fat plant hair that moves. At only 1/250” long, the only way you will know they are present is by using a microscope or looking for signs of the damage they cause.
Damage caused by fig mites
Fig mites often infest young leaves and bud scales. Fig mite feeding causes russeting, most commonly seen on the underside of leaves and on the bottom of figs. Russetting transforms smooth, healthy tissue into rough, brown, dry tissue. Fig mite feeding also results in fruit and leaf drop and twig stunting. The real problem with fig mites is that they can carry and transmit fig mosaic. Trees infected with fig mosaic should be removed, so it is worth the effort.
Fig mite control
Monitor leaves for signs of mite feeding from late spring through summer. If fig mites are seen, apply sulfur or horticultural oils, depending on the time of year. [Oils can burn leaves in summer.]
I have also seen anecdotal recommendations for the use of spinosad against fig mites, but I do not know how effective it is.
Just before your cantaloupes, cucumbers, squashes, watermelons, and pumpkins are ready to harvest, suddenly they wilt and die, taking your crop with them.
Unlike slow wilts caused by lack of water (or too much water), or vascular diseases, such as Verticillium wilt and Fusarium wilt, sometimes the leaves of melon, cucumber, pumpkin, cantaloupes, and other cucurbits and cotton suddenly and completely droop. This sounds like sudden wilt.
Sudden wilt is a soil borne fungal disease that occurs after heavy irrigation on hot, sunny days. Contrary to what you might expect, moisture-saturated soil combined with hot sun can cause sudden wilt, also known as parawilt. This is a result of the imbalance between water uptake and water loss, combined with certain fungi.
Sudden wilt symptoms
Sudden wilt starts out as yellowing of the crown leaves, followed by total collapse of the entire plant. Death soon follows. If you dig up an affected plant, the roots will be straw-colored or darker than normal. There are three different fungi responsible for sudden wilt and each one has unique symptoms:
Sudden wilt treatments
There are no chemical controls against sudden wilt. Careful water management, proper plant spacing, and the removal of crop residue after harvest can help reduce the chance of sudden wilt occurring in your garden. Monitor your cucurbits for signs of sudden wilt near the end of the growing season. Good drainage and 2- to 3-year crop rotations can help prevent this disease from wiping out your cucurbit crops, and be sure to allow the soil to dry out completely between waterings.
Cucumber green mottle mosaic is a viral disease that can take a big bite out of cucumber, watermelon, and other melon crops.
This cucurbit disease is found on infected seeds and there is no known cure. It was first seen in the U.S. in 2013. Prior to that, it was only seen in Russia, China, Japan, Korea, India, Spain, and Israel. It is believed to have been brought to the U.S. on infected seed.
Cucumber green mottle mosaic symptoms
Cucumber green mottle mosaic enters plants through wounds and root-to-root contact. Symptoms of cucumber green mottle mosaic (CGMMV) are subtle. At first, infected plants may look fine. Then you may see light yellow spots on young leaves, vein clearing, or chlorotic mottling. Leaves may also become deformed. Stunting and leaf death are more commonly seen in older plants. As leaves mature, the symptoms seem to disappear, providing a false sense of security.
By the time the disease is full-blown, it still doesn’t look terrible. The problem is, this disease causes fruit drop and reduced fruit size. Crops can be reduced by 25 to 80%. Fruit that makes it to harvestable size can also have a mottled appearance and the interior is often damaged and inedible.
Cucumber green mottle mosaic control
Since there is no cure for this contagious disease, infected plants must be removed completely, along with a few of their neighbors, to prevent it from spreading. Using certified disease-free seed and placing new plants in quarantine can help prevent this disease from infecting your soil. Since this virus can also be transported on tools, shoes, and clothing, good sanitation practices can also protect your plants.
Plants grow in response to their environment. When the direction they grow is determined by the location of the stimulus, it is called tropism.
Types of tropism
Tropisms can be positive or negative. Positive tropisms attract the plant toward the trigger, while negative tropisms push the plant away. Sunlight is generally a positive tropism, causing plants to lean, turn, and pivot to follow its rays. In some cases, particularly darkened jungle floors, sunlight is a negative tropism, initially, driving vines to seek trees which they will later climb.
Tropisms are generally named for the stimuli:
Plants also respond to chemicals (chemotropism), electric fields (electrotropism), magnetic fields (magnetotropism), oxygen levels (aerotropism), and temperatures (thermotropism)
The opposite of tropism
When a plant responds in a direction that is not determined by the position of the stimulus, it is called a nastic movement. Common nastic movement triggers include being touched or the way a flower opens and closes each day (nyctinasty). When being touched causes flowers or leaves to suddenly close themselves up in a specific and regular pattern, rather than the thigmotropism seen in climbing tendrils, it is a nastic movement. The location of the finger has nothing to do with the way the flower closes. In the latter case, the sun going down may trigger the flower to close, but the direction of that closing is not related to the sun’s position.
Plants may not be able to get up and walk around, but they have a unique arsenal of movement-related responses they can use to help themselves grow and thrive.
Which tropisms do you see in your garden?
Swatting at a yellow jacket is never a good idea.
Rather than chasing them off, you can easily cause them to give an alarm, triggering the attack of several hundred yellow jackets. So, who invited them to the picnic?
Yellow jackets (or yellowjackets) are omnivorous social wasps and they can be a royal pain at outdoor summer events. Not only can yellow jackets be annoying, as they feed on your burgers and cupcakes, they can sting and bite at the same time!
Unlike honey bees, which lose their stingers (and die) after a single sting, yellow jacket stingers do not have barbs and can be used repeatedly and with great prejudice. The more you know about yellow jackets, the better you can protect yourself and your family from painful stings.
Yellow jacket identification
Yellow jackets are frequently confused with bees and other wasps. Unlike stubby, brown honey bees, which are covered with short hairs, yellow jackets appear more smooth-bodied and shiny. Beneficial mud daubers have a very narrow waist and build their nests out of mud and paper wasps build small, umbrella-shaped nests with exposed cells. Mud daubers and paper wasps generally do not eat human food and are rarely aggressive unless provoked.
Aside from being unique in their high level of aggression, yellow jackets are generally medium-sized black wasps with jagged bands of yellow or white on the abdomen. While yellow jackets have the classic wasp-waist, it is often not clearly visible.
There are several different species of yellow jackets found in North America:
You may be able to identify a yellow jacket from a distance by its tendency to fly side-to-side as it prepares to land. And if you ever see white grubs coming out of a wasp nest, it means that the adults have been unable to provide for their larvae, who are now in search for food on their own. Often, it is easier to identify a yellow jacket by its nest.
Yellow jacket nests
Yellow jackets make their nests by scraping up wood fibers and mixing them with saliva. These nests look like fat, paper footballs when you can see them, but sometimes you can’t.
Yellow jackets can be divided into ground-nesting and aerial nesting varieties. Aerial-nesting yellow jackets build the familiar rounded, hanging nests with a single entry hole at the base. While aerial-nesting wasps are generally not aggressive, they will attack if you get too close to their nest.
Ground-nesting yellow jackets, on the other hand, are extremely aggressive and you might not see them until it’s too late. Ground-nesting yellow jackets frequently build their nests in rodent burrows, rotted tree cavities, and houses. Apparently, to a yellow jacket, the space between the interior and exterior walls of your house make the perfect site for a nest that can contain up to 15,000 wasps.
If you see a yellow jacket, it is safe to assume that there is a yellow jacket nest no more than 1/4 mile away.
Seasonal wasp aggression
Yellow jackets are particularly aggressive when it comes to protecting their nest. Yellow jackets are also likely to sting while out foraging for food. The aggressiveness of yellow jackets changes with the seasons.
In spring, yellow jackets are busy building their nest and providing larvae with protein, usually in the form of insects. As summer progresses and the colony population increases, their need for protein decreases and sugary foods, needed by the queen and her workers, are in greater demand. This is also when many resources start becoming more scarce and wasp aggressiveness becomes more of a problem.
By late summer and autumn, yellow jackets are best described as angry scavengers. This is when they end up at your picnics and cookouts. They are also seen around pet food, trash cans, and around fruit trees, where overripe fruit provides easy access to sugar.
Preventing yellow jacket stings
If you are eating outside, the best way to prevent stings is to keep food and sugary drinks in sealed containers. This is especially true for canned soft drinks that contain sugar, as a wasp may go in the can and then sting your mouth when you take a drink. Once yellow jackets have found a food source, they will pester the area long after the food is gone. One popular method at reducing yellow jacket stings is to toss a piece of raw meat and a sugary food away from the area before unpacking the rest of the food. If yellow jackets discover this food source first, they may be less likely to become a problem at your picnic. I don’t know if it actually works, but it sounds good.
Working in the yard, one of the best ways to prevent stings is to be alert. Before digging, always look for ground-nesting wasps. I once was chased into my house by a swarm of very angry stinging insects when I tried to plant an apricot tree in my front yard. It is far better to be on the lookout before a confrontation occurs. If you do get stung, read my post on wasps for treatment tips.
Yellow jacket control
Lure traps placed around your property line are effective control measures against yellow jackets. You can buy yellow jacket lures at garden centers and many home improvement stores, as well as online. Most of these lures use a chemical called heptyl butyrate. This attractant works well on western yellow jackets, but not so well on other yellow jacket species. You can improve the effectiveness of yellow jacket lure traps by adding a small piece of raw meat to the trap. This will be especially effective on German yellow jackets. Just be sure to replace the meat frequently, as wasps are not attracted to rotting meat. Newer bait traps, those using esfenvalerate, have not been shown to be effective.
If you know the location of a yellow jacket nest, there are nest sprays that can kill the colony. Before you start spraying, you need to know that wasps will attack when they sense the poison being sprayed. While these poisons are effective, you should be sure to wear protective clothing and keep your distance while using the spray. Nighttime applications are significantly safer, but there is no guarantee. Plus, it may take a day or so for all the wasps to die and the remaining wasps are going to be very angry.
Consider yourself warned.
Plants are particularly thin-skinned. Did you know that a plant’s epidermis is only one cell thick? Just under that skimpy outer layer is a plant’s cortex.
The cortex is made up of thin-walled cells called parenchyma. Some of those cells are purposefully torn or separated to create air spaces. This porous tissue is called the aerenchyma [a-REN-ky-ma], from the Greek word for ‘infusion’. This word makes sense when you learn that the phloem is not the only part of a plant that transports nutrients. The cortex does, too!
The cortex is responsible for transporting nutrients and carbohydrates into the central core of a plant’s roots through diffusion. But there is even more to the cortex than just nutrient transportation.
Functions of the cortex
Depending on the plant, cortical cells may also store carbohydrates, essential oils, latex, resins, and tannins. in many cases, the cortex also contains chloroplasts that are able to perform photosynthesis, converting carbon dioxide and water into simple carbohydrates. Taking things one step further, the cortex can then convert those simple carbohydrates into the complex carbohydrates found in bulbs, tubers, and root vegetables, such as beets, carrots, and turnips. The cortex also manufactures the bark seen on the outside of woody plants and the underlying cork.
Cortex and water flow
In herbaceous plants, the innermost layer of the cortex is called the endodermis and the outermost layer is called the exodermis. The endodermis and exodermis are unique in that all of the cell walls have a woody band, called the casparian strip, except those facing the center or the outside of the plant. These casparian cells help regulate the flow of water between the vascular bundles, found just inside the cortex, and the outer cells of the cortex and epidermis.
Flax stem cross-section: 1. Pith 2. Protoxylem; 3. Xylem; 4. Phloem 5. Bast fiber 6. Cortex 7. Epidermis (Public Domain)
Pests and diseases of the cortex
Several bacterial diseases invade the root cortex through injury sites and natural openings. These diseases include bacterial wilt of beans (Curtobacterium), ring rot of potatoes (Clavibacter), cucurbit bacterial wilt (Erwinia), black rot of cucurbits (Xanthomonas), and Pierce’s disease of grapes (Xyella). The Pythium oomycete, which causes blackleg, also moves through the cortex. Dry, brown lesions seen in the main or taproot cortex can indicate Fusarium crown and root rot.
The next time you cut a plant stem or root, use a magnifying glass or hand lens to see what’s really going on in there. There are some amazing things going on in there!
Cavitation is the sound of water breaking.
While we don’t normally think of water being able to “break”, the columns of water that move upward through a tree’s veins can be broken, allowing air bubbles to form or simply severing a pathway for life-giving water.
Trees use a lot of water
The general rule of thumb for how much water a tree needs each week of summer is 10 gallons of water for every inch of trunk diameter, as measured at knee height. This means a large, mature tree, with a trunk diameter of 18”, will need 180 gallons of water every week at the peak of summer, on average. The flow of that water is critical to a tree’s health.
In healthy trees, water is absorbed through the roots and pulled upward through tubes called xylem. There are thousands of xylem in a mature tree. Picture the xylem as straws that run the vertical length of a tree. Water moves through xylem in a process called transpiration.
Transpiration refers to the way negative pressure is created within xylem as water evaporates from the surface of the leaves. This occurs because of surface tension, or the tendency of water molecules to stick together. When one water molecule leaves the plant through evaporation, lower water molecules are pulled upward.
Bubbles can be bad
Bubbles might be fun to play with, but bubbles in veins are bad. Just as air bubbles in an IV tube can kill you, so, too, can bubbles block the flow of life-giving water for a tree. Rapid transpiration can cause air bubbles to form in xylem. If too many air bubbles remain in place, it can kill a tree. Cavitation is much like an embolism for trees. Small, infrequent bubbles are not a serious problem. Large, fixed bubbles are deadly.
During periods of drought, the rate of evaporation on the surface of the leaves is so great that xylem can collapse and break, like a rope pulled too tautly. These breaks halt the flow of water completely, also killing a tree. Cavitation also occurs in response to thawing after water within a tree has frozen.
The sound of silence
If you could hear higher frequencies, it would sound similar to popcorn popping. In most cases, the frequency of this sound is too high for us to hear, but it can, occasionally, be heard. [It might be fun to try using a stethoscope on a tree…] I can only imagine that our peaceful summer walks in the woods sound more like a riot of trees screaming for water to our dogs…
Bottom line: make sure you irrigate your trees properly to keep them healthy, especially during summer.
Has a largish beetle with stripes ever hissed at you? It was probably a ten-lined June beetle. Ten-lined June beetles (Polyphylla decemlineata), also known as watermelon beetles, can kill mature trees outright.
Ten-lined June beetle description
The stripes are a giveaway for this relatively large beetle. Averaging 1.5 inches or longer, male ten-lined June beetles have distinctive antennae made up of overlapping scales, called lamellate plates. When these pests feel threatened, those plates are closed up and air is forced between the back and wings to create a hissing sound. Adult females do not fly. Eggs are 1/16" long, oval and cream-colored. Larvae have a white body and a brown head. They can grow to 2” in length with 3 pairs of legs.
Damage caused by ten-lined June beetles
Almond, apple, cherry, and plum trees are susceptible to damage caused by larval feeding of ten-lined June beetles. Trees may simply not thrive, at first. By the time the damage is significant, it is usually too late to save the tree. Adult ten-lined beetles feed on leaves, but that damage is insignificant.
Ten-lined June beetle lifecycle
Ten-lined June beetles are relatively long-lived insects. It takes 2 years to complete one generation of ten-lined June beetles. They can exist in the larval stage for up to 4 years. Larvae are found in the top 14” of soil where they feed on roots. Each summer and early autumn, adult females emerge from the soil and release pheromones to attracts males. Males fly from dusk until midnight or so. After mating, the females return to the soil where they lay eggs.
Ten-lined June beetle controls
Heavily infested trees must be removed and the surrounding soil fumigated to prevent infestation of nearby trees. Luckily, that is rarely necessary in a home garden. Because female ten-lined beetles do not fly, populations spread slowly. Commercial growers use soil insecticides to kill beetles in the larval stage. Aboveground insecticides are not effective.
Tachinid flies parasitize these pests, but not significantly. Because male ten-lined June beetles are attracted to light, you can capture them on your porch with a butterfly net and feed them to your chickens, or simply squish them whenever you see them.
Bulb mites, also known as spinach crown mites, refer to a small collection of very tiny pests that can damage your onions, garlic, saffron crocus, and spinach plants.
Bulb mite description
Bulb mites are a collection of pests from the Rhizoglyphus and Tyrophagus genus and they look like miniature ticks with spiky hairs. These pests may be tiny, but they can cause significant damage. Ranging in size from 1/2 to 1 mm long, you could 15 to 30 or more of them nose-to-tail across a dime. If you were to look at one with a magnifying glass, you would see that they are a shiny, creamy white, with four pairs of brown legs.
Bulb mite host plants
As the name implies, bulb mites infest bulbs, such as tulips, daffodils, and saffron crocus. They can also be found under the root plate of garlic and onion, or in the crown of spinach plants.
Damage caused by bud mites
Bud mite feeding is not particularly destructive by itself. The problem lies in the wounds created by that feeding. These damaged areas allow organisms responsible for decomposition to get inside your plants, causing them to rot. Overall stunting, leaf distortion, and softened stems are common responses to bud mite feeding.
How to manage bulb mites
Protect your bulbs against bulb mites by inspecting them before planting. Infested bulbs should be destroyed. Crop rotation and the removal of post-harvest plant debris can interrupt this pest’s lifecycle.
If you grow red raspberries, you need to monitor leaves early in the season for yellow rust.
Like its cousin, the bright orange rust seen on the underside of rose leaves, yellow rust is a fungal disease. Unlike many other fungal diseases, this rust only occurs on the outside of plants. This is not the same yellow rust seen on wheat, rye, and barley, which is called stripe rust. Stripe rust is caused by Puccinia striiformis.
Symptoms of yellow rust
Plants infected with yellow rust (Phragmidium rubi-idaei) will initially have yellow pustules, called aecia, on the tops of the lower leaves. These symptoms are usually only seen in spring and early summer. In early to mid-summer, yellow to orange pustules, called uredinia, are found on the underside of leaves. As summer progresses, these growths darken and a black spot can be seen in the middle, if you look closely. You may also see orange spots on the fruit. Similar infections that occur later in the season may be late leaf rust (Pucciniastrum americanum), or the more severe orange rust (Arthuriomyces peckianus). In any case, infected leaves wither and die, reducing the plant's ability to perform photosynthesis. This can reduce crop size significantly.
Yellow rust control
Pruning for good air flow helps leaves and stems dry out, making life more difficult for this fungi. Since yellow rust spores (teliospores) overwinter in fruiting canes, or floricanes, pruning those canes out at the end of the growing season can break this disease triangle. The canes of summer-bearing raspberries won’t produce any more fruit anyway, so you might as well. Just be sure to dispose of the trimmed canes in the trash, and not the compost pile.
Left in place, these spores then spread the infection to the next season’s primocanes, or vegetative growth. Also, keep the area around the plants clear of dead leaves and other plant debris. If your raspberries are especially prone to yellow rust, you may want to cut the first spring growth of new canes back to ground level. Don’t worry, the root system will put out new canes pretty quickly. That first growth is the most likely to have become infected.
Fixed copper sprays and lime sulfur are recommended for severe outbreaks. Otherwise, you can simply remove infected leaves by hand and improve the air flow between plants to keep this disease in check and protect your delicious raspberries.
Resistant varieties are available, so check with your local Department of Agriculture or Master Gardeners for recommendations for your area.
If you grow peas or lentils, you should know about pea seed-borne mosaic. The same is true for fava beans and chickpeas.
[Sadly, I was unable to find any freely available photos of pea seed-borne mosaic, so you will have to go by the description or search for your own images. The purple-podded peas pictured above are perfectly healthy.]
Symptoms of pea seed-borne mosaic
Stunting, deformation, and rosette-type growths at the ends of stems are all signs of pea seed-borne mosaic. Chlorosis, downward cupping, vein clearing and swelling, and the classic mosaic or mottling of mosaic diseases may all be present in infected plants. Vein clearing is a common symptom of viral infections and it refers to the way leaf veins appear translucent. Seeds tend to be shriveled and discolored. Infected plants are slow to reach maturity, but don’t leave them in the ground long enough to notice. Pea seed-borne mosaic infection is easily mistaken for chemical overspray, nutrient toxicities, and water-stress. Laboratory tests are needed to be sure of infection. You can often take zip-lock bagged samples to your local Department of Agriculture for analysis.
How to control pea seed-borne mosaic
The pea seed-borne mosaic virus (PSbMV) is carried to your garden on aphids. I would tell you to control the aphids, but that is an ongoing battle in the garden. Do the best that you can. Plants infected with pea seed-borne mosaic should be removed immediately. Unfortunately, some infected plants will never show symptoms. As aphids feed on these asymptomatic plants, they then carry the disease to nearby plants, spreading infection. For the most part, as the name implies, this viral disease is carried by infected seeds. Plant infected seeds and the aphids do the rest. To prevent pea seed-borne mosaic from occurring in your garden, only buy clean, disease-free seeds.
This disease can overwinter in nearby weeds, such as shepherd’s purse, vetches, and black medic. It can also be carried on alfalfa and sugar beets without causing the host plants any problems. If you notice outbreaks of pea seed-borne mosaic, and you know your seeds were clean, look at what is growing nearby.
You can prevent pea seed-borne mosaic by planting resistant varieties.
Fig trees can be stately and highly productive, but fig mosaic can take a toll on your fig tree. Fig mosaic is a complex of several, as yet unidentified, viral diseases that all infect Ficus subspecies.
Fig mosaic symptoms
Yellow leaf mosaic patterns are a common symptom of fig mosaic. These patterns are brighter yellow toward the center of each spot, fading to light yellow before reaching the healthy green leaf tissue. As the condition progresses, a rust-colored band appears around the edge of each mosaic spot. Leaves may also be deformed. Infected fruit shows mild mosaic patterning but may be smaller and less abundant than on healthy trees. Most often, fig mosaic causes early fruit drop, all but eliminating your crop.
How fig mosaic is spread
Fig mosaic is spread by eriophyid mites, particularly fig mites. As the mites feed, the virus is transmitted through their saliva. Fig mosaic can also be spread by grafting and cuttings.
Fig mosaic management
Tree infected with fig mosaic should be removed. Trees take time to grow, so having to remove an infected tree is best avoided. Begin by only installing disease-free tree and planting them at the proper depth, giving them the irrigation and food they need to stay healthy. Monitor your fig trees for sign of mite feeding. You will need a 20x hand lens to see these tiny sap-suckers. Fig mite feeding is usually seen around bud scales and young leaves and it often causes a faint russetting. Twig stunting and leaf drop may also occur.
Sulfur treatments and horticultural oils have been shown to control fig mites.
Go take a look at your fig tree to see if mites might be present. If they are, get rid of them so that you can enjoy many years of sweet, delicious figs.
Beetles among your squashes and melons is never a good thing, especially when they carry the squash mosaic virus.
Squash mosaic is second only to cucumber mosaic in damage to cucurbits caused by disease. There are two strains of squash mosaic, strain 1 affects melons most often, while strain 2 prefers squash. In either case, your crop will be lumpy, discolored, and significantly reduced, but still edible.
Crops vulnerable to squash mosaic
All cucurbits are susceptible to squash mosaic. This includes your zucchini and other summer squashes, melons, gourds, cucumbers, and pumpkins. Watermelons, however, are not susceptible to squash mosaic. Some legumes and umbellifers can also become infected with squash mosaic.
Squash mosaic symptoms
Squash mosaic causes a dark green mottling or mosaic pattern on leaves, as well as blistering, yellowing (chlorosis), leaf hardening and distortion, and vein clearing. Vein clearing is a common symptom of viral disease and it refers to the way leaf veins become almost translucent while the rest of the leaf remains green.
Squash mosaic carriers
Unlike other mosaic diseases, squash mosaic is not spread by aphids. Instead, striped and spotted cucumber beetles, leaf beetles, and 28-spotted ladybird beetles are the most common vectors of squash mosaic. Many other beetles are also capable of hosting the virus. As these insects feed, their saliva transfers the virus to the plant. This is why it is so important to remove infected plants right away.
Squash mosaic controls
In addition to removing infected plants, beetle control is important in the prevention of squash mosaic. And beetles can be tough to control. The virus can stay viable inside a beetle for up to 20 days, so it is worth the effort. A single beetle can infect dozens of plants in that time frame. To control beetles, handpicking is always an option, if you are quick enough. You can also use neem oil to kill beetle eggs. Encouraging beneficial predators, such as ladybugs, mantids, and solider bugs, in the garden with fresh water, insectary plants, and little or no chemical use is probably the easiest method of keeping beetle populations within reasonable limits.
Squash mosaic can also be carried on melon seeds, so be sure to get clean, disease-resistant seeds from a reputable supplier (and not that melon from the grocery store).
Certain chenopod weeds, including lambsquarters, goosefoot, Russian thistle, and kochia, provide overwintering sites, so keep these weeds away from your cucurbits.
As with many other viruses, tools, clothing, and other surfaces can also become carriers. To prevent the spread of this disease, sanitize tools regularly and avoid working around plants while they are wet.
Warty zucchinis with skinny leaves may mean the zucchini yellow mosaic virus has infected your plants.
No garden would be complete without the versatile, fast-growing zucchini. A favorite in stir-fry, breads, and the ever popular chocolate zucchini cake, zucchini can be very productive plant, as long as it stays healthy.
Zucchini yellow mosaic symptoms
Whitened leaf veins, mottled, abnormally small leaves with alternating light and dark areas, and deformed, warty fruit are all signs of zucchini yellow mosaic. These are also symptoms of watermelon mosaic and papaya ringspot virus, two viral diseases that often occur at the same time as zucchini yellow mosaic. Watermelon mosaic infections tend to include blistered leaves, while zucchini yellow mosaic has the added symptom of leaf lobes becoming long and narrow, creating a ‘shoestring’ or ferny appearance.
Zucchini yellow mosaic host plants
In addition to infecting zucchini, zucchini yellow mosaic also infects other members of the cucurbit family, including melons, squash, pumpkins, some gourds, cucumbers, cantaloupe, and watermelon. The disease is transmitted by aphids.
Zucchini yellow mosaic management
As anyone who gardens knows, controlling aphids is difficult. These pests seem to appear overnight, in huge numbers. And all it takes is one aphid to get the whole process started. Unfortunately, insecticides are rarely useful in managing zucchini yellow mosaic, because the disease has often been transmitted before you even know the aphids are there. Reflective mulches can be used to discourage aphids, just be sure to remove the reflective material before it gets too hot. Row covers can also be used to reduce access to susceptible plants.
This disease can also be spread on infected garden tools and seeds, so be sure to sanitize your tools regularly and get your seeds from a reputable source (and not that zucchini from the grocery store).
Infected plants should be destroyed and replaced with resistant cultivars.
Since this virus is only viable for a few hours within their aphid carriers, creating a physical barrier of tall, non-host plants around your cucurbits can be enough to prevent the aphids from getting to the plants while the virus is still active.
Speckled, mottled, or otherwise deformed leaves and fruit usually indicate a mosaic disease.
Mosaic diseases are caused by a variety of viruses that can infect the majority of your garden plants. Since these diseases are difficult or impossible to treat, recognizing and removing infected plants right away can help prevent the disease from spreading.
Symptoms of mosaic diseases
The classic mottled appearance of infected leaves is only one symptom of mosaic disease. Leaf cupping, blistering, stunting, crinkling, and other distortions are also common symptoms of mosaic disease. Stems may be shortened, creating a bushy appearance to vines.
Plants infected early in the growing season rarely produce fruit. Interestingly, plants infected later in the season retain their healthy, earlier growth and fruit production, while future growth is distorted. Fruit may also show the same mottling and other distortions seen on leaves. Warty bumps are common.
Plants that host mosaic diseases
It would be easier to list plants that are not affected by mosaic disease. Plants commonly infected with mosaic diseases include:
Common mosaic diseases
While there are dozens (hundreds?) of mosaic diseases, some of the more common varieties include:
Mosaic disease management
Generally speaking, mosaic diseases are not curable. Infected plants should be removed. This means that prevention is a far better course of action.
Depending on the specific virus, it may be carried in to your garden on seeds or tools, or by aphids, dryberry mites, and any number of other sap-sucking pests. Removing weeds that could provide overwintering sites, creating physical barriers with row covers and walls of non-host plants, and regularly sanitizing your tools goes a long way toward preventing mosaic disease from taking hold in your garden, as does buying clean, disease-resistant seeds and plants from reputable suppliers.
While mosaic diseases make plants look funny, the fruit of infected plants is still safe to eat. The viruses responsible for mosaic diseases are not harmful to people.
Growing your own corn makes a dramatic statement in the garden. Reaching 10 to 12 feet in height, modern corn plants grow in tandem with other giants, such as sunflowers and hollyhocks. Unless they become infected with corn stunt.
Corn stunt does not mean ears of corn will suddenly start doing gymnastics over the fence into your neighbor’s yard. Instead, this bacterial disease will infect the phloem of corn plants, reducing them in size and all but eliminating kernel production.
Corn stunt disease complex
Some people see corn stunt as a single disease, while others see it as one part of a complex of three disease, the other two being maize bushy stunt mycoplasma and maize rayado fino virus (MRFV). Yet others include maize chlorotic dwarf virus in the corn stunt complex. Any combination of these diseases can be devastating to your corn crop.
Corn stunt symptoms
Healthy corn plants produce one or two ears of corn, depending on whether they are early or late maturing varieties, respectively. Plants infected with corn stunt are significantly shorter than normal, often only 5 feet tall, and may produce 6 or 7 ears. That may sound great, but it’s not. These ears are small and they do not fill properly, meaning there ends up being a lot of empty spaces. The kernels that do develop are not well attached, in a condition known as “loose tooth ears”. Infected plants will also exhibit pale yellow new leaves at the top. As these leaves mature, they tend to turn reddish.
How corn stunt spreads
Corn stunt is caused by Spiroplasma kunkeliiI, which is carried by leafhoppers. Corn leafhoppers (Dalbulus maidis), in particular, carry this disease with them, spreading it as they feed.
Corn stunt management
You can prevent corn stunt by using reflective mulches that deter leafhoppers. Planting your corn as early as possible in the growing season has been shown to reduce the impact of corn stunt infections. Apparently, the first generation of emerging bacterium are not as effective at spreading the disease as those that occur later in the season. Insecticides are generally not effective.
You don't have to grow corn to have a reason to worry about seed corn maggots.
Seed corn maggots mostly feed on decaying organic material, but sometimes they feed on the roots and seeds of over 50 different garden plants. Also known as the bean seed fly, seed corn maggots may be tiny, but they can ruin several of your crops.
Seed corn maggot description
Seed corn maggots (Delia platura) are small, dark grey flies with grey wings, black legs, three stripes on the back, and scattered bristles. Less than 1/4” long, seed corn maggot adults looks nearly identical to onion maggot flies. White or off-white larvae are legless and have rounded tails and pointed heads. Pupal cases are brown and hard and look like skinny footballs.
Seed corn maggot damage
Seed corn maggots often feed on the seeds of corn, peas, beans, and soybeans but they do not always kill the embryos within the seeds. When those seeds germinate, they are spindly and rarely make it to maturity, wasting valuable resources. Other crops commonly attacked by seed corn maggots include cucumbers, melons, onions, peppers, and potatoes.
Seed corn maggots may tunnel into the stems and roots of many different garden plants and feed on spinach leaves, often providing points of entry for other pests and diseases.
Seed corn maggot lifecycle
Adult flies emerge in spring and begin feeding on nectar and honeydew. After mating, females lay an average of 270 eggs in the soil, near the surface. One week later, larvae emerge and begin feeding. One to three weeks later, larvae move back into the soil where they pupate for one to three weeks, or over the winter.
How to control corn seed maggots
The key to controlling corn seed maggots is in the soil. While I am a proponent of no-dig gardening, repeated appearances of corn seed maggots warrants disturbing the top 2 or 3 inches of soil on a regular basis during the spring and summer months. Research is being conducted on the possibility of beneficial fungi being used to control these pests, but it is not currently an option.
As is nearly always the case, prevention is far easier. You can reduce the odds of seed corn maggots attacking your crops by waiting for the weather to warm up before planting, and spacing plants properly. Anything that slows germination or initial seedling growth makes it easier for seed corn maggots.
You can grow a surprising amount of food in your own yard. Ask me how!
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