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Cow parsnips are not related to the root vegetable known as parsnips, but you can eat them, if you are careful.  Nine-foot tall cow parsnips in Alaska (Beeblebrox) CC BY-SA 4.0 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.
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. Did you know that pine cones are actually modified branches and leaves? It's true!
Cone anatomy 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.  Female cone anatomy (Nefronus) CC BY-SA 4.0
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  Monkey-puzzle tree with seed cones (MPF) CC BY-SA 3.0 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?  Gypsum from Poland (Elade53) Public Domain 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 crystals are plastic enough to bend under pressure of the hand (Rama) CC BY-SA 3.0 fr Gypsum description 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”.  Gypsum crystals in the Cave of the Crystals in Mexico. Note person for scale (Alexander Van Driessche) CC BY 3.0 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. Russeting 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, they suddenly 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 leaves of cucurbits droop suddenly, and the entire plant collapses. It is sudden wilt, also known as parawilt. Sudden wilt is a soil-borne fungal disease that appears after heavy irrigation on hot, sunny days. Contrary to what you might expect, lots of water combined with hot sun is not what melons and squashes need. Sudden wilt occurs when there is an imbalance between water uptake and water loss, combined with certain fungi. Sudden wilt symptoms Sudden wilt starts as yellowing of the crown leaves, followed by total collapse of the entire plant. Death soon follows. If you dig up an affected plant, you will see that the roots are straw-colored or dark. There are three different fungi responsible for sudden wilt, and each one has unique symptoms: • Pythium spp. - appears as brown root rot • Acremonium cucurbitacearum - corky bands on discolored roots • Rhizopycnis vagum - upper portions of the taproot turn reddish and corky Sudden wilt treatments There are no chemical controls against sudden wilt. Careful water management, proper plant spacing, and removal of crop residue after harvest can help reduce the chance of sudden wilt 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 let the soil dry out completely between waterings. Cucumber green mottle mosaic is a viral disease that can take a big bite out of your cucumber, watermelon, and other melon family crops.  Leaf symptoms of cucumber green mottle mosaic virus (Aviv Dombrovsky and Elisheva Smith) CC BY 3.0 This cucurbit disease comes in on infected seeds. And there is no known cure. Before 2013, it was only in Russia, China, Japan, Korea, India, Spain, and Israel. Scientists believe it came to the U.S. on infected seed. Cucumber green mottle mosaic enters plants through wounds and root-to-root contact.
Cucumber green mottle mosaic control
Since there is no cure for this contagious disease, remove infected plants and a few of their neighbors to prevent it from spreading. Using certified disease-free seeds and placing new plants in quarantine can help prevent this disease from infecting your soil. Since this virus can travel on tools, shoes, and clothing, good sanitation practices can help 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.  Heliotropism in sunflowers 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.  Thigmotropism of pumpkin 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?  German wasp (Fir0002/Flagstaffotos) GFDL 1.2 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. [This is one reason why using dish soap on plants is such a bad idea.]  Cross-section of non-woody eudicot root (Kate Russell) Cortex description 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. #/media/File:Stem-histology-cross-section-tag.svg) Flax stem cross-section: 1. Pith 2. Protoxylem; 3. Xylem; 4. Phloem 5. Bast fiber 6. Cortex 7. Epidermis 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.  Cavitation infographic by Kate Russell 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. Transpiration 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.  Male ten-lined June beetle (Amanda Townsend) CC BY-SA 3.0 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.  Male ten-lined June beetle (Junkyardsparkle) CC0 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 open (Amanda Townsend) CC BY-SA 3.0 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, monitor leaves early in the season for yellow rust.  Yellow rust pustules on raspberry leaf (James Lindsey) CC BY-SA 3.0 Like its cousin, the bright orange rust seen on the underside of rose leaves, yellow rust is a fungal disease. Unlike many other fungal infections, this rust only occurs on plant exteriors. When yellow rust occurs on wheat, rye, and barley, it is called stripe rust, a Puccinia striiformis infection.
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. Black spots 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 more severe orange rust (Arthuriomyces peckianus). Either way, infected leaves wither and die, reducing the plant’s ability to perform photosynthesis, which cuts crop size significantly. Yellow rust control Pruning for good airflow helps leaves and stems dry out, making life more difficult for these 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. Canes of summer-bearing raspberries won’t produce any more fruit, so you might as well. Just dispose of these canes in the trash and not the compost pile. If unproductive canes stay in place, any spores they contain will spread the infection to the next season’s primocanes or vegetative growth. Keep the ground around cane fruit 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. Their root systems will quickly put out new stems. That first growth is the most likely to have become infected. Fixed copper sprays and lime sulfur can treat severe outbreaks. Otherwise, remove infected leaves by hand and improve the airflow 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, watch for pea seed-borne mosaic. The same is true for fava beans and chickpeas.  Purple-podded peas Sadly, I was unable to find any freely available photos of pea seed-borne mosaic, so you will have to 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. Vein clearing describes how leaf veins appear translucent. Seeds shrivel and become discolored. Pea seed-borne mosaic infection is easily mistaken for chemical overspray, nutrient toxicities, and water stress. Laboratory tests are needed to verify this infection. You can often take ziplock 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 by aphids. Do the best that you can control them. Remove any plants infected with pea seed-borne mosaic and dispose of them in the trash. 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. The only way to prevent pea seed-borne mosaic from occurring in your garden is to buy certified pest- and disease-free seeds. This disease can overwinter in nearby weeds, such as shepherd’s purse, vetches, and black medic. 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 of this publication, unidentified viral diseases that all infect the Ficus subspecies.  Fig mosaic virus symptoms (Scot Nelson) CC 2.0 generic How fig mosaic spreads All eriophyid mites,, especially fig mites, can bring fig mosaic to your trees. As they feed, their saliva transfers the virus to plant tissues. Grafting and cuttings can also spread the fig mosaic virus.  Symptoms of fig mosaic on fig leaves (Plantpathfinder) CC BY-SA 3.0 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. 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. Look for signs of mite feeding if you suspect fig mosaic. Look around bud scales and young leaves for signs of mite feeding. You may also see faint russeting. Twig stunting and leaf drop may also occur.  Fig mosaic virus symptoms (Scot Nelson) CC 2.0 generic Fig mosaic management
Trees infected with fig mosaic must be removed and destroyed by a professional. Tree removal is expensive. You can help prevent fig mosaic with these tips:
Sulfur treatments and horticultural oils can control fig mites. And those delicious figs are worth the effort. Beetles among your squashes and melons are never good, 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 both cases, your crop will be lumpy, discolored, and significantly reduced, though still edible.  Yellow squash infected with squash mosaic virus (Alton N. Sparks, Jr., UGA, Bugwood.org) CC BY 3.0 Crops vulnerable to squash mosaic All cucurbits are susceptible to squash mosaic, including cucumbers, melons, pumpkins, and zucchini. Except for watermelons, they do not get 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, blistering, yellowing (chlorosis), leaf hardening and distortion, and vein clearing. Vein clearing is a common symptom of viral disease. It refers to how leaf veins become almost translucent while the leaf blades remain green.  Effect of squash mosaic virus on squash leaves (OllieMartin) CC BY-SA 3.0 Squash mosaic carriers
Unlike other mosaic diseases, aphids are not responsible for squash mosaic. Instead, striped cucumber beetles, leaf beetles, spotted cucumber 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, so remove any infected plants. Squash mosaic controls In addition to removing infected plants, beetle control helps prevent 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. Handpicking is one way to control beetles, but only if you are quick enough. You can also use neem oil to kill beetle eggs. Encourage beneficial predators, such as ladybugs, mantids, and soldier bugs, in the garden with fresh water, insectary plants, and little or no chemical use. Supporting beneficial insects is the easiest method of keeping beetle populations within reasonable limits. Squash mosaic can infect seeds, so get clean, disease-resistant seeds and seedlings from a reputable supplier (not that melon from the grocery store). Certain chenopod weeds, including lambsquarters, goosefoot, and Russian thistle, 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 leaves are wet. Warty zucchinis with skinny leaves may mean the zucchini yellow mosaic virus has infected your plants.  Fruit distorted by zucchini yellow mosaic (Rasbak) CC BY-SA 3.0 No garden would be complete without the versatile, fast-growing zucchini. A favorite in stir-fry, bread, and the ever-popular chocolate zucchini cake, zucchini can be a very productive plant, but only 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. These two viral diseases often occur in tandem with zucchini yellow mosaic. Watermelon mosaic infections exhibit blistered leaves, while zucchini yellow mosaic has long, narrow leaf lobes, creating a shoestring or ferny appearance.  Zucchini yellow mosaic on squash leaf (Public Domain) Zucchini yellow mosaic host plants
In addition to infecting zucchini, zucchini yellow mosaic also infects other cucurbits, including cantaloupe, cucumbers, melons, pumpkins, squash, watermelon, and some gourds. Aphids bring this disease to your garden. Zucchini yellow mosaic management 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 effective at managing zucchini yellow mosaic because the disease has often been transmitted before you even know the aphids are there. Reflective mulches can discourage aphids. Remove or cover the reflective material before it gets too hot, or your plants will cook where they stand. Row covers can reduce access to susceptible plants. This disease can also travel on infected garden tools and seeds, so sanitize your garden tools regularly and get your seeds from a reputable source (and not that zucchini from the grocery store). Remove infected plants and replace them 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.  Cucumber mosaic (Public Domain) Mosaic diseases are a collection of viral infections that can infect most of your garden plants. Since these diseases are difficult or impossible to treat, recognizing and removing infected plants as soon as possible can help prevent the disease from spreading. Symptoms of mosaic diseases The classic mottled appearance of infected leaves is only one symptom of a mosaic disease. Leaf cupping, blistering, stunting, crinkling, and other distortions are other common symptoms of mosaic diseases. Stems may also be shorter, creating a bushy appearance to vines. Fruit may also show the same mottling and other distortions seen on leaves. Warty bumps are also commonly seen. 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. Distortions only occur in post-infection leaves and fruit.  Turnip yellow mosaic virus on cabbage (Michal Maňas) CC BY 2.5 Plants that host mosaic diseases It would be easier to list plants that are not affected by mosaics. But the plants most commonly infected with mosaic diseases include the following:  French bean infected with bean common mosaic (ShoutWiki) CC BY-SA 3.0 Common mosaic diseases While there are dozens (hundreds?) of mosaic diseases, some of the more common varieties include this list: Mosaic disease management
Generally speaking, mosaic diseases are not curable. Remove infected plants and toss them in the garbage. Prevention is a far better course of action. Depending on the specific virus, it may catch a ride into your garden on seeds, tools, aphids, dryberry mites, and other sap-sucking pests. These tips can help reduce the chance of a mosaic disease robbing you of your harvest:
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 corn makes a dramatic statement in the garden. Reaching ten feet or more, modern corn plants can be grown alongside other garden giants, such as sunflowers and hollyhocks. Unless they become infected with corn stunt, that is.  Corn growing in schoolyard (Michael Zimmer) CC BY-SA 2.0 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 practically eliminating kernel production. Corn stunt disease complex Some people see corn stunt as a single disease. Other people see it as part of a complex along with maize bushy stunt mycoplasma and maize rayado fino virus (MRFV). Other people include maize chlorotic dwarf virus in the corn stunt complex. Any combination of these diseases can be devastating to your corn crop. [And you don't need to remember all the names to be able to see there is a problem.] Corn stunt symptoms Healthy corn plants produce one or two ears of corn, depending on whether they are early or late-maturing varieties. Plants infected with corn stunt are significantly shorter, 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 in completely. You end up with a lot of empty spaces. The kernels that 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.  Corn plant infected with corn stunt (Clemson University Extension, CC BY-SA 3.0) How corn stunt spreads
Corn stunt is carried by leafhoppers. Corn leafhoppers (Dalbulus maidis), in particular, host the bacteria (Spiroplasma kunkelii), 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. The first generations of emerging bacteria are less effective at spreading the disease than 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 maggot flies (Martin Cooper) CC BY 2.0 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 gray flies with gray 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. Juicy, sweet kernels of corn transform, overnight, into hideous, purple-gray, tumors. And these tumorous galls are delicious! Introducing, corn smut.  Corn smut (Kembangraps) Public Domain Now, corn has many pests and diseases: corn earworms, European corn borers, seed-corn maggots, soft rot, seed rot, fusarium root and ear rot, maize dwarf mosaic, pythium stalk rot, and damping off disease, just to name a few. If you are an American corn farmer, corn smut is not what you want to see in your field. A lot of money and effort have gone into eradicating corn smut in North America.
Corn smut in your garden is something else entirely. While this distant cousin of mushrooms reduces crop size and makes ears of corn unmarketable for July picnics and canning purposes, it is edible and delicious. Unlike other corn problems, corn smut is said to taste like truffles, with a sweet, earthy, inky flavor. If it appears in your garden and you don’t want it, your local chef would love to hear from you! To my way of thinking, if life gives you lemons, make lemonade. Or, if you are given corn smut, make quesadillas! Corn smut can be eaten raw, or added to many dishes, such as omelets, soups, sauces, meat dishes, or even desserts! As an extra bonus, corn smut is high in lysine. This means eating it with corn, or any other seed, provides a complete dietary protein. Corn smut description Also known as devil’s corn, common smut, boil smut, Mexican truffles, or huitlacoche [pronounced weet-la-COH-cheh], corn smut is a parasitic fungus that can occur on any aboveground portion of a corn plant as purplish blobs covered with papery greenish-white tissue. These fungi prefer meristem tissue and the galls are mostly seen on the ears of corn. Ear galls are significantly larger than those which form elsewhere on the corn plant. Corn smut gets its purple color from pigments called anthocyanins. These are the same pigments found in blueberries, raspberries, and purple cauliflower. When you cook with corn smut, don’t be surprised to see the purple color change to black, because it will. Purple pigments generally don’t hold up well to heat. Corn smut lifecycle The corn smut fungus (Ustilago maydis) infects plant ovaries, causing kernels to swell up into large purple galls that are filled with fungal threads, called hyphae, and spores. Corn smut spores are already in the soil and can be carried on the slightest breeze or splashed water from rain or irrigation. Dry conditions and temperatures between 78°F and 93°F are all that corn smut needs to get started. Adding nitrogen or applying manure increases the chance of corn smut developing on your corn plants. Plant injuries also increase infection rates. Corn plants try to defend themselves against corn smut by blasting the invaders with reactive oxygen (hydrogen peroxide). Sadly, from the corn plant’s perspective, this bubbling action simply spreads the smut spores. If smut appears on your corn, fear not! Instead, harvest the galls while they are young and have the texture of a foamy popcorn, kind of firm and spongy. These moist galls are ready for harvesting 2 or 3 weeks after infection appears. As the galls mature, they turn dry and are mostly filled with unappetizing dry, black fungal spores. Love it or hate it, corn smut is here to stay, so you may as well learn to cook with it (or sell it). Do you see spirals on your watermelons? Watermelon mosaic (WMV) is a viral disease that can infect cantaloupes, squash, and other cucurbits, along with some legumes, such as peas and alfalfa, and many chenopods. Infected watermelons look like they have ringworm. There are two different watermelon mosaic viruses: WMV1 and WMV2. While these are two distinctly different viruses, they are similar enough.  Watermelon mosaic leaf symptoms (Scot Nelson) Public Domain Symptoms of watermelon mosaic
Symptoms of watermelon mosaic virus vary by host, but the first sign of infection is light discolorations in the leaves. This irregular chlorosis occurs along leaf edges (margins) and veins. Leaves may also be small, deformed, blistered, or wrinkled. That wrinkling is called rugosity. Finally, infected fruit develops a mottled appearance. The mottling looks like light-colored rings just under the skin. Warty growths may also appear, and fruit production is minimal. How to prevent watermelon mosaic Spread predominantly by aphids and occasionally leaf miners, watermelon mosaic virus can also travel on garden tools and clothing, so sanitize your tools regularly. The virus survives inside aphids for only a few hours, so physical barriers between potential carriers can also reduce infection. Crop rotation and removing infected plants can break this disease triangle. Horticultural oil spray can also interrupt transmission of this virus but may cause problems of its own. Weeds, such as lambsquarters, cheeseweed, goosefoot, and Russian thistle, can act as vectors , can act as vectors for this disease, so keep them away from your watermelon and other susceptible plants. Insecticides are ineffective against watermelon mosaic because the disease is transmitted before the chemicals kill the carrier. You can use reflective mulches under susceptible plants to repel aphids. If you use reflective mulch, remove it before the summer sun uses it to cook your plants. |
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