Vampire moths may sound like something out of European folklore, but they exist and they suck blood.
The vampire moth family
Vampire moths have an entire genus of their own with 17 known species. Ten of them drink blood. Originally from Malaysia, the Urals, and southern Europe, Calyptra have expanded their range to include northern Europe, Sweden, and Finland. Due to international shipping and travel and climate change, it is expected that these moths will continue to expand their range. The Canadian owlet or meadow rue owlet moth (Calyptra canadensis) is the only New World member of this group.
Many adult moths do not eat. Some of them do not even have mouths. Those that do often have a surprisingly long, slender straw, called a proboscis. Moths keep their proboscis curled up in a flat, vertical spiral. The proboscis is generally used to drink nectar. The hawk moth has a proboscis that is over one foot long. In the case of the vampire moth, the end of that straw has a serrated edge that is sharp enough to cut through elephant skin. I don’t know how long it is.
Vampire moth diet
Male and female vampire moths eat the nectar of meadow rue and other members of the buttercup family (Thalictrum). They also suck the juices from fruits, such as strawberries. Vampire moth caterpillars feed on leaves.
Unlike mosquitoes, where it is the females who must drink blood to provide for their offspring (obligate), blood-sucking vampire moths are male and they drink blood because they like it (facultative). Some scientists suspect that male vampire moths drink blood for the salt, which they then pass on to the female in their sperm to provide for their offspring. No one knows for sure just yet.
Male vampire moths pierce the skin of vertebrates, including us, to drink blood. They do this by using a proboscis that is divided into two parts. They use a back-and-forth sawing motion to pierce the skin of their victims with these dual tubes.
Once attached, vampire moths are not easily removed and they may remain in place for up to 50 minutes. They do not technically “suck your blood”. Instead, they use their victims’ blood pressure to do that work for them. If you are the victim of a vampire moth, you will not turn into a vampire or a moth, but the site will be red and sore for several hours with an itchy rash. Vampire moths are not believed to carry or spread any diseases.
It is believed that vampire moths evolved from purely fruit-sucking species. I can’t help wondering what my tomato plants are planning…
Ghost ants may be scaring up problems in both your home and your greenhouse. Or, they may be helping you stay healthy.
Thought to have originated in Africa or the Orient, invasive ghost ants (Tapinoma melanocephalum), also known as tramp ants, are now found everywhere. Like other ants, ghost ant farm aphids and other sap-sucking garden pests for their honeydew, protecting them from their natural enemies.
Ghost ant identification
These ants are smaller than most ant species. Workers average only 0.051 to 0.079 inches long, which means you could line up more than a dozen of them across the face of an American dime. They have dark heads and milky white to translucent legs and bodies, hence the name. Ghost ants look similar to pharaoh ants.
If you were to look at ghost ants with a hand lens, you would see that their antennae have 12 segments. When disturbed, ghost ants tend to race around erratically. These ants do not sting, but they do cause problems.
Problems with ghost ants
Ghost ants have a sweet tooth. While they eat many household foods, including greasy foods, they have a strong preference for sweets. They will track down and devour your honey, syrup, cakes, and cookies while indoors and every sweet, juicy fruit and sap-filled stem outside.
Being a tropical species, ghost ants frequently invade and nest in homes, greenhouses, and potted plants. These ants are so small, they can create tiny satellite colonies inside plant stems and in between the books on your shelf. Most ghost ant colonies are significantly larger and are commonly found within the walls of homes and underground. Each colony may have several queens.
While cold weather generally limits the spread of this species, it is now found as far north as Minnesota, New York, and Canada. Apparently, all of our buildings are making life easier for ghost ants. Because ghost ants farm aphids, they also spread disease. These pests are so small that they are proving to be problematic in quarantine greenhouses. They sneak in, feed for a while, and then go elsewhere, taking whatever diseases were present in the greenhouse with them.
Ghost ants aren’t all bad
Ghost ants are scavengers in the garden, eating dead insects and speeding the decomposition process. They also eat the larvae of small beetles, moths, and butterflies. Ghost ants will also put a significant dent in the local two-spotted mite population. In Venezuela, ghost ants eat the eggs of kissing bugs (Rhodnius prolixus). Kissing bugs are vectors for Chagas’ disease, which damages the heart and nervous system.
Ghost ant control
Ants are one of Earth’s most successful species. Controlling them is difficult, and it all starts with cleanliness. If ghost ants are haunting your home, put all foods into airtight containers and wipe up spills right away. Caulk cracks and other points of entry. These pests enjoy a little moisture, too, so eliminate leaks and condensation.
If you can control aphids, whiteflies, and other insects that produce honeydew, ghost ants will find your garden less attractive.
Ant baits are effective against ghost ants. The closer they are placed to the nest, the most effective they will be. Just follow the ant trail. Also, make sure outdoor plants are not touching your house. Those stems make excellent insect highways to your home.
Apparently, if you crush a ghost ant, they smell like rotten coconuts.
Another name for your household ficus tree or weeping fig (Ficus benjamina) is strangler fig.
Strangler figs get their name because their seeds germinate on the branches and trunks of other trees, as well as boulders, buildings, and soil. As roots emerge, they wrap around their host, strangling them.
Strangler figs are not always the bad guys. In many cases, the host tree ends up gaining strength against storms from this exterior structure. I don’t know that the relationship is so benign when they start battling for sunlight.
Most of these trees produce both male and female flowers. Their fruits are inverted inflorescences, called syconia, that have mutualistic relationships with specific wasp species. Leaves are broad and waxy. Strangler fig trees, in particular, are hemiepiphytes.
Unlike most plants, strangler fig roots start out by growing aboveground. This makes them something called hemiepiphytes [hemi-EP-ifits]. Epiphytes are plants that grow on other plants without being parasites. Air plants, many ferns, and orchids are epiphytes.
Strangler fig fruit
Your garden variety fig tree (F. carica) is not a strangler, though they are cousins. Some strangler fig tree fruits are delicious. Some of them are pretty bland. Banyan tree figs taste awful, but they won’t hurt you. Wherever they grow, strangler fig trees are important food sources for native fruit-eating birds who, in turn, spread the seeds near and far.
These trees make very nice house plants. Unless they are native to your region, they do not belong outside because they can easily become invasive and disrupt the local ecosystem.
Note: If your ficus tree keeps dropping its leaves, give it more water and be sure it’s near a sunny window.
Now you know.
Rhizopus head rot is the most common fungal disease of sunflowers, and it can result in losses of up to 100%.
It starts with a tiny wound and ends with the loss of the entire head.
Rhizopus head rot is caused by three different fungi: Rhizopus stolonifer, R. oryzae (syn. R. arrhizus), and R. microsporus. These fungi are everywhere. They are found in the soil and are easily disturbed and spread on the wind. These are the same fungi that cause bread molds, and soft rots in carrots, melons, raspberries, sweet potatoes, and many other crops.
Rhizopus head rot symptoms
The fungal spores that cause Rhizopus head rot first make their way into your lovely sunflowers through wounds caused by birds, hail, rubbing, and head moth and other insect feeding. At first, these wounds look like small holes or dark spots on the back of ripening heads. Those spots start to rot, eventually drying to a dark brown. As the disease progresses, heads dry prematurely, and the interiors take on a shredded appearance.
You can differentiate this disease from others, such as bacterial head rot or Sclerotinia head rot, by the presence of grey threads (mycelium) and tiny black reproductive structures (sporangia) within the shredded tissue.
Rhizopus head rot management
High temperatures and high humidity set the stage for this disease. There isn’t much you can do about those besides avoiding overhead watering. There are no chemical treatments for this condition.
Wound prevention is the best way to prevent this disease from robbing you of all those delicious seeds. That means monitoring for bird and insect damage and possibly staking plants to prevent rubbing. If you live in areas with hail, there isn’t much you can do short of providing your sunflowers with umbrellas.
You can reduce the likelihood of Rhizopus head rot in your sunflowers by removing rouge plants that may harbor the pathogen and insects most likely to feed on sunflowers. While there are no resistant cultivars, sunflower varieties with more upright heads seem to be more susceptible.
Pickleworms! With a name like that, I had to learn more.
Pickleworms (Diaphania nitidalis) are serious pests of squash, cucumbers, melons, and other cucurbits. Mostly found in the southern United States, these pests are poised to expand their range. It can’t hurt to know what to watch for, right?
Pickleworm moths have triangular, iridescent brown wings with white edges and a yellow stripe. When light shines on these wings, they look metallic blue. Their legs and tail segment are white and the tail ends with a tuft of bristles called hairpencils. The wingspan is just a little more than one inch wide.
Caterpillars start out thin and white with black spots. As they grow and feed, they lose those spots and turn more of an opaque green. Spherical to flattened eggs are extremely small. They start out white but turn yellow in a day or so.
These moths are only active at night. Each adult female lays 300 to 400 tiny pickleworm eggs in small clusters on new buds, and flowers, and shoots. These tender plant tissues make the perfect meal for pickleworm caterpillars, who eat voraciously for two weeks, going through five instars. Then they curl themselves up in dead leaves where they pupate for 8 to 10 days and turn copper-colored. There can be up to four generations each year.
Pickleworms cannot handle extreme cold (yet), so winter weather often takes care of the problem for some regions. Pickleworms have several natural predators, such as soldier beetles and ground beetles, but these predators cannot eliminate the problem. Bacillus thuringiensis (Bt) can be used but is only marginally effective because of where these pests feed and hide. Pickleworm moths are not attracted to light and there are no pheromone traps available, so what’s a gardener to do?
Commercial growers facing pickleworm damage must resort to preventative sprays of insecticides. These sprays can also kill the honey bees needed to pollinate cucurbit crops. It’s a dilemma.
If pickleworms are a problem in your garden, you can buy Steinernema carpocapsae. These are parasitic nematodes that love to eat pickleworm larvae. Also, because these moths only fly at night and honeybees generally pollinate during the day, you can cover your cucurbits each evening with row covers and uncover them each morning.
I know it means more work, but those delicious cantaloupes and chocolate zucchini cake are worth protecting. And nobody wants wormy pickles.
[Email me if you'd like the chocolate zucchini cake recipe.]
Dusky stink bugs (Euschistus tristimus) are native to North and Central America and they feed on plant juices. Cousin to leaf-footed bugs, these pests have piercing and sucking mouthparts.
Dusky stink bug damage
Dusky stink bugs can damage several crops, but they seem to prefer fruit trees. Their favorites include apples, cherries, peaches, pears, and plums. As they feed, they create catfacing and dimpling in fruit. Those dimples allow other pests and diseases access to the fruit and rot quickly sets in. Early feeding can cause trees to abort fruit altogether. Your citrus, grapes, peppers, and tomatoes are also vulnerable to dusky stink bug feeding.
Dusky stink bug identification
All stink bugs have shield-shaped bodies. From above, dusky stink bugs look identical to brown stink bugs (Euschistus servus). They also look a lot like dreaded invasive brown marmorated stink bugs (Halyomorpha halys) and one-spotted stink bugs (E. variolarius). You can tell them apart, however. Dusky stink bugs are significantly smaller than brown marmorated stink bugs, and they have pointed shoulders (pronotum). Brown stink bugs have orange shoulder points and ‘duskies’ do not. Dusky stink bugs are smaller than most other stink bug species, ranging from ⅜” to ½” long and ¼” to ⅜ ” wide. They have long, slender antennae.
Dusky stink bugs tend to be dark brown to dark gray, depending on where they live and what they’ve been eating. And they have stripes on their sides. They get the tristimus part of their name from the three (sometimes four) spots found on their bellies, though they will struggle if you flip them over.
Eggs are cream-colored and barrel-shaped. Nymphs look somewhat like rust-colored, steampunked ladybugs with a dark head and a black stripe down the back.
Dusky stink bug lifecycle
Adult dusky stink bugs overwinter in leaf litter and plant debris. Eggs are laid in tight rows on the underside of leaves, netting, and elsewhere in spring and again in late summer. A single female stink bug can lay 500 eggs. In 40-60 days, those offspring are creating youngsters of their own.
Dusky stink bug management
If you squish or frighten a stink bug, you will learn how they got their name. They stink. And they are tough. Insecticides are only slightly effective against stink bugs and the timing must be perfect for them to work against immigrating adults. Handpicking is your best stink bug control. Drop them in a container of soapy water, or you can try feeding them to your chickens. Mine turned up their beaks most of the time. I guess stinkbugs taste as bad as they smell.
Selenium (Se) is a plant nutrient that easily falls into the “too much of a good thing can be a bad thing” category.
If you grow a lot of your own food and your soil lacks selenium, you might, too. In fact, selenium deficiencies are a global dietary problem. On the flip side, if your soil has too much selenium, it can make you very, very sick.
People and animals must have a little selenium to be healthy. The same is true of some plants. Let’s see what selenium does, which plants use it, and how to tell when there’s too much selenium in the soil.
How plants use selenium
Selenium isn’t considered an essential plant nutrient. For some plants, such as poplar trees, selenium is useful. Selenium is believed to stimulate plant growth and to counteract stress, pests, and disease. [In the human body, selenium makes antioxidant enzymes that prevent cell damage.]
Plants grown on selenium-depleted soils end up being less nutritious for us. The Pacific NW, New England, the Great Lakes, and certain areas around the New Mexico and Arizona state line are traditionally low in selenium. But, as we all know, each yard has its own characteristics.
You won’t see selenium listed in a soil test report unless you specifically ask for it. The presence of certain weeds and other plants may. In some cases, high selenium levels are needed for growth. These plants will accumulate toxic levels of selenium in their tissues. These plants are referred to as obligate and include:
Facultative selenium accumulators do not need selenium to grow, but will accumulate it anyway:
Most other plants are referred to as passive selenium accumulators. These plants can absorb too much selenium and suffer toxicosis. This is especially true for grasses and cereals, such as barley.
Toxic soil can be corrected with something called phytoremediation. Phytoremediation takes advantage of the fact that some plants absorb toxins through their roots. Before plants can cough those toxins into the atmosphere through their stems and leaves (transpiration), the plants are harvested and disposed of safely.
Signs of selenium toxicity
Selenium toxicity appears as stunting, early leaf death, and chlorosis. Leaves of affected plants may wither and dry up. High selenium levels in the soil can also cause copper, iron, and zinc deficiencies. Of course, these symptoms can mean several other things, as well. You will have to consider symptoms, location, and the presence of the aforementioned plants in your analysis.
Too much selenium in the soil can make your edible plants toxic. This can be the result of native bedrock. It can also be caused by industrial runoff. If you suspect high selenium levels in your soil, contact your local County Extension Office or Department of Agriculture.
Mites and spider mites are garden pests. They suck the life from your plants and spread disease. Unless they are predatory mites. Predatory mites are our allies, though you may never see them without a hand lens.
Predatory mite description
Generally speaking, predatory mites are pear-shaped and translucent. They may also be white or the color of their prey, usually reddish or brown. Nymphs look like tiny adults with the same coloration. Wedge-shaped eggs are clear or white.
Some predatory mites are smaller than others. The Western predatory mite (Galendromus occidentalis) weighs in at only 1/70th of an inch in length (0.36mm). This means you could line up almost 50 of them, end-to-end, across an American dime. But don’t let their size fool you.
Predatory mite species
Predatory mites may be incredibly small, but they can take a serious bite out of your mite (Eriophyidae) and spider mite (Tetranychidae) problems. There are hundreds, perhaps thousands, of different types of predatory mites. They are grouped into one of four categories:
Different species have different favorite meals, so you can customize your protection with just a little research.
Predatory mite lifecycle
The life of a predatory mite is short. Once the eggs hatch, they quickly go through a 6-legged larval stage and two 8-legged nymph stages before reaching adulthood. In her 30-day life, an adult female predatory mite will lay up to 21 eggs on the underside of leaves, in flowers, and within the crevices of buds. Depending on the weather, those eggs will hatch in 1 to 4 days. There can be up to 10 generations each year.
It is difficult to know if predatory mites are present because of their size, but you can buy them. They will help protect your avocado, citrus, grape, plum, strawberry, and many other crops. Before you release your predatory mites, be sure to reduce dust in the area by giving everything a quick rinse with the hose. You’ll want to avoid broad-spectrum pesticides and miticides, as well.
Miticides kill mites and protect rhinos. I’ll get to the rhinos in a moment.
When temperatures are high and humidity is low, mite populations can quickly get out of hand. They suck the life from your garden plants, reducing crop sizes, and making plants more susceptible to other problems.
Miticides are also known as acaricides. These pesticides specifically target members of the arachnid subclass Acari. If your garden plants are suffering from infestations of mites or spider mites, you may want to consider using miticides. Or you may not.
Researching various miticides for this post, I ran across some very hard to pronounce words and some scary warnings. I started to list the most commonly used miticides, their targets and toxicities and realized it made for tedious reading (and writing). Bottom line: not all miticides are safe to use on edible plants. Many of these chemicals are dangerous to beneficial insects, honey bees, and us. Whenever using chemical treatments, be sure to read the label completely and follow the instructions.
Organic mite control
Diatomaceous earth (DE) can also be used against mites and spider mites. It desiccates them and kills them without leaving any chemical residue. Other food-grade dusts that also kill these pests without chemicals. These other dusts have an advantage over DE in that they do not contain silica. Breathing in silica dust is bad for us, too.
There are also predatory mites that prey on mites and spider mites.
Whichever treatment you decide to use, don’t apply it on a windy day. It and your money will simply fly away on the breeze. To be effective, sprays and dusts must coat the underside of all the leaves affected by mites or spider mites.
Now, about those rhinos
Rhino poaching is being deterred by drilling holes in the horns of sedated rhinos and packing those holes with miticides. It doesn’t hurt the rhinos, but it brings on nausea, diarrhea, and convulsions in anyone who eats the horn, thinking it will provide them with some magical powers. And it won’t kill them. I think it’s the least punishment they should have to suffer for needlessly killing an endangered animal, don’t you?
This word may not help you grow better tomatoes, but it is relevant. I found it interesting and I hope you do, too.
No one knows where the word strig came from. In England, strig refers to the thread that holds a button to your shirt. It also refers to the tang of a sword blade. In the plant world, strig refers to the footstalk or pedicel of flowering or fruit-bearing plants, such as currants. A type of peduncle, these tiny stems occur within flower clusters or inflorescences. They provide support for the individual florets. The flowers that grow from a strig are called a sessility.
Female hops flowers are cone-shaped blooms called strobiles. If you sliced one of those flowers in half, you would see a central stem. That central stem is known as a rachis or strig. This strig is what attaches the flower to the bine or pedicel.
If you open up a fresh fig, you will see lots of hair-like structures. Those are male and female flowers held up with strigs.
While adult pea leaf weevils (Sitona lineatus) are chowing down on the leaves and growing tips of your legumes, their miscreant offspring are underground, gnawing away at the nitrogen fixing nodules found in and around the root system. Originally from Europe, pea leaf weevils are now found around the world.
How can you tell if pea leaf weevils are attacking your plants, and what can you do about it?
Pea leaf weevil damage
Scalloped leaf edges and gnawed-off stumps where growing tips used to be are the first signs that these invasive pests have reached your garden. Leaf scalloping tells you that adult pea leaf weevils are feeding. What you can’t see without digging up the plant is all the damage being done to the root nodules. Larval feeding can completely halt nitrogen fixation, resulting in stunting, chlorosis, and plant death. All legumes are susceptible to pea leaf weevil feeding, though lentils are less likely to be affected. I have no idea why. Larvae may also burrow into young pea pods and start feeding on young peas.
Pea leaf weevil identification
Pea leaf weevil adults are one-fifth of an inch long, grayish-brown, and rather slender in physique. If you look closely, you may be able to see three pale lengthwise stripes down the thorax. Larvae are milky white with a dark head. Like other grubs, they tend to hold themselves in a C-shape. These larvae have no legs and are about the same size as adults. Eggs are white at first but turn nearly black just before hatching.
Pea leaf weevil lifecycle
These pests tend to have one generation each year. After overwintering in protected feeding grounds, adults fly and walk to new territories where female pea leaf weevils will lay 1,000 to 1,500 eggs on or near young legume plants. When those eggs hatch, the larvae enter the soil where they go through five developmental stages or instars. They feed heavily on the nodules that allow legumes to convert atmospheric nitrogen into a form they and neighboring plants can use for food. While these pests feed on all legumes, they only reproduce on peas and fava beans.
Pea leaf weevil management
Commercial growers apply insecticidal seed treatments before planting, but that’s probably not an option for the home grower. The good news is that black clock beetles, ground beetles, and rain beetles all love to eat pea leaf weevils. By mulching and applying aged manure and compost around your legumes, you can encourage these beneficial insects. This will also provide your legumes with any nitrogen they may need.
As always, avoid using broad-spectrum pesticides. Those chemicals end up killing off all your helpers. Bacillus thuringiensis (Bt) can also be used against these pests, but it only works on the weevils it touches. Eggs and larvae will be unaffected. These other tips can help protect your peas and other legumes from pea leaf weevil damage:
I hope that pea leaf weevils never find your garden.
I thought I saw a whitefly on my apartment windowsill, but I was wrong. It was a dustywing.
Unlike whiteflies, which can carry diseases and suck the sap from your garden plants, dustywings are beneficial predators. They prey on slow-moving invertebrates, such as aphids, mites, and scale insects. They also eat arthropod eggs, including corn earworms, mealybugs, and tomato hornworms.
These net-winged hunters are very tiny. Their wingspan can range from one-twentieth of an inch up to one-fifth of an inch wide. They are covered with a whitish or grayish powdery wax. They secrete that wax from glands on the abdomen, head, and thorax. [Imagine being able to create your wardrobe that way!] They have tan-colored translucent wings and short antennae. Eggs are oval, yellowish-pink to orangish, and somewhat flattened. Larvae are red and white.
Dustywings are commonly found around woody plants. They are mostly active at dusk (crepuscular) and attracted to lights. Each female can lay up to 200 eggs. These eggs are laid singly on nearby leaves and on the bark. There are two generations each year. Each larva goes through four instars. And all that growing requires a lot of food. A single dustywing larva was recorded as eating 226 red mites. That’s what I call helpful!
You can encourage dustywings to stay in your landscape by providing woody shrubs for them to live in and avoid using broad-spectrum pesticides. Have you seen dustywings in your garden? I released mine into the Seattle wilderness.
Do your cucumbers, melons, squash, and watermelons have spots? Do your pumpkins have warts? It may be papaya ringspot.
Papaya ringspot wiped out 94% of the papaya crops grown on Oahu back in the early 1960s. As a result, papaya production was moved, under quarantine, to the Big Island of Hawaii. As is often the case in these situations, the virus found its way there, again devastating the papaya industry and homegrown papaya trees. More moves and more quarantines occurred, but it wasn’t until resistant varieties were developed that papayas could be grown successfully. That might be the end of the story, but it’s not
The papaya ringspot virus (PRSV) mutated, traveled, and expanded its diet to include several common garden plants. These include members of the squash family, tree spinach (Chenopodium amaranticolor, aka C. giganteum), peas, castor beans, and quinoa (C. quinoa). Currently found in the U.S., Europe, India, the Middle East, and South America, it is safe to say that papaya ringspot falls under the plant pandemic category.
Papaya ringspot symptoms
Like many other viral plant diseases, papaya ringspot looks like infected cucumbers and melons have developed measles. A mosaic of scattered dark green or intense yellow spots appears all over the fruit surface. Blisters may also be seen. Leaves of infected plants are chlorotic and distorted and may develop shoestringing. Stems and petioles may have oily streaks. This disease looks a lot like watermelon mosaic. In both cases, infected plants should be removed and tossed in the trash.
Papaya ringspot lifecycle
This virus congregates around the mouths of aphids, never actually entering the pest. As the carrier aphid feeds on sap, the virus moves from the aphid’s face to the plant’s veins. Wouldn’t that make an interesting video?
The papaya ringspot virus can also travel on seeds and seedlings.
Papaya ringspot prevention
There is no cure for papaya ringspot, and it can spread to neighboring healthy plants. Quarantining new plants and investing in certified pest- and disease-free seeds and seedlings are the best ways to prevent the papaya ringspot virus from attacking your garden.
Your lawn may be harboring a plant pandemic that’s killing your corn. That disease is called barley yellow dwarf (BYDV). More than 20 different aphid species spread this viral disease, and it is found around the world.
Barley yellow dwarf host plants
Barley, corn, and the ryegrass and fescue in your lawn are not the only plants that can become infected with this disease. All members of the grass family (Poaceae) are susceptible.This means that your millet, oats, rice, rye, ryegrass, sorghum, sugarcane, and wheat can also become infected with barley yellow dwarf. It is the costliest disease worldwide of all cereal crops.
Barley yellow dwarf symptoms
This disease is tricky to identify. It looks similar to root and crown diseases, nutrient deficiencies, environmental stresses, and wheat streak mosaic. Closer inspection of unhealthy-looking patches in your lawn or grass family crops may reveal purple, red, orange, or yellow discolorations. These discolorations are seen from the tip downward and from the edges to the midrib. Infected leaves are often shorter, stiffer, and more upright than healthy leaves. Stunting is common due to shortened internodes. You may also see serrations along leaf edges and some infected plants start growing into a corkscrew shape.
Barley yellow dwarf prevention
Fungicides are ineffective against barley yellow dwarf. Instead, good cultural practices are your best plan of attack. Since aphids are the vectors for barley yellow dwarf, planning your planting schedule around aphid migrations can help reduce the likelihood of disease occurring. I know that aphid migrations aren’t usually mentioned on the evening news. But regularly monitoring your plants for aphids will make it very clear when they arrive and start reproducing. Planting seeds at times when aphids and seedlings are less likely to occur at the same time will help reduce disease. These other tips will also help keep your garden plants healthy:
Black citrus aphids (Toxoptera citricida) are vectors for citrus sadness, a potentially fatal disease of grapefruit, lime, lemon, and orange trees. They spread this disease as they feed on the sap found in new leaves and tender buds. And that feeding causes damage of its own, weakening trees, stunting growth, and generating honeydew. That honeydew provides the perfect growth medium for sooty mold and other fungal diseases, which block photosynthesis. Black citrus aphids are considered one of the world’s most serious citrus pests.
Originally from southeast Asia, this pest is now found in Africa, Australia, India, and Central and South America. In 1995, black citrus aphids appeared in Florida, where they are now well established. It is estimated that these pests will devastate the California citrus industry if they find their way across the Rockies. This is one reason why you have to wait in line at the agricultural inspection stations when driving across some state lines.
Black citrus aphid identification
Also known as oriental citrus aphids and brown citrus aphids, they get the different color names because they change color as they develop. Adult black citrus aphids are black and shiny. Like other aphids, they can be winged or wingless. Nymphs are reddish-brown. And there are no eggs unless they live in Japan.
Black citrus aphid lifecycle
All black citrus aphids are female, and all of those females give birth to live young unless they live in Japan. For some bizarre reason, black citrus aphids occurring in Japan do lay eggs. In either case, those populations can explode in record time. It is estimated that a single black citrus aphid can produce more than 4,400 offspring in three weeks. Those offspring can start reproducing on their own when only one week old. You can see how things could quickly get out of hand. The network effect of all that reproduction can result in 600 billion aphids in a single season, all starting with one aphid.
Managing black citrus aphids
One way to reduce aphid problems is to only feed nitrogen to plants at the appropriate times and avoid shearing citrus trees. Shearing and nitrogen both stimulate vulnerable new tip growth. Also, ants protect aphids. You can eliminate that protection by wrapping the trunks of citrus trees with sticky barriers. You can also use sticky sheets hung in your citrus trees to monitor for winged aphids and other pests.
Natural predators, such as ladybugs, and parasitic wasps will help reduce aphid populations. You can attract these beneficial insects to your garden by installing insectary plants, providing water, and avoiding the use of broad-spectrum pesticides.
A powerful stream of water from your hose can dispatch large clusters of aphids which are then unable to return to the tree, but this treatment won’t get them all, and it only takes one. Insecticidal soap can also be used, but that treatment is only effective on the aphids it touches.
Monitor your trees regularly for signs of black citrus aphids and report any potential sightings to your local County Extension Office right away.
Citrus sadness is not a case of lemon tree depression. But citrus growers around the world are pretty sad about this plant pandemic.
Citrus sadness, more scientifically known as citrus tristeza virus (CTV), is the costliest citrus virus. It has killed more than 80 million citrus trees and made an added 40 million more citrus trees useless for growing edible fruit. And it spreads quickly.
First seen in South America in the 1930s, this disease was called “tristeza” which means sadness in Spanish and Portuguese. Citrus sadness attacks several citrus species and passion flowers (Passiflora gracilis).
Symptoms of citrus sadness
Symptoms of citrus sadness vary depending on the infected plant species. They are generally grouped into one of three categories: decline, seedling yellows, and stem-pitting. In each case, viruses populate the phloem, causing chlorosis, vein clearing, leaf speckling, fruit dwarfing, and stem dieback.
Decline can be fast or slow. It presents as chlorotic leaves and stem dieback. Citrus sadness decline may take only days to kill a mature tree (fast), or it may take years (slow). In the case of slow decline, infected trees often exhibit a bulge just above the graft. Decline is most commonly seen in grapefruit, mandarin, and sweet orange trees.
Seedling yellows most commonly affects lemon, pomelo, and sour orange. This type of citrus sadness causes overall yellowing and dieback.
Stem-pitting is the most virulent form of citrus sadness. It most often infects sour orange, a variety commonly used as rootstock for several other citrus species. [Which rootstock is your orange tree grafted onto?] Symptoms of stem-pitting match its name: pits form along the trunk and branches. This damage reduces crop yield and weakens the tree, making it susceptible to other diseases and pest damage.
Citrus sadness prevention
Citrus sadness is spread by aphids, especially brown citrus aphids and oriental citrus aphids. As you probably already know, controlling aphids is an ongoing battle. Aphids can have wings, and they reproduce at mind-boggling rates. As much as possible, monitor and treat for aphids. And be sure to buy certified disease-free and disease-resistant rootstock. And if you wrap tree trunks with sticky barriers, ants will be unable to protect aphids from their natural predators.
If you suspect citrus sadness has found its way to your tree, contact your local County Extension Office right away.
Nobody wants scabby cucumbers, squashes, or melons, but sometimes it happens.
Cucurbit scab goes by several other names, some of them quite colorful: cucumber gummosis, cucumber leaf blight, cucumber spotting, cucurbit fruit blight, gray anthracnose of cucurbits (even though it’s not a type of anthracnose), and, my favorite, cucurbit pox.
I can hear it now, as Renaissance Faire washerwomen throw insults and dirty undergarments at the crowd: “A pox upon thy cukes!” Of course, I would never wish a pox upon anything in your garden, so let’s see what we’re up against with this one.
The what and when of cucurbit pox
This disease affects nearly all members of the cucurbit family. This means cantaloupe, gourds, honeydew, summer and winter squash, and pumpkins are all susceptible. For some reason, watermelon is rarely affected. I don’t know why.
Cucurbit scab is a fungal disease of the squash family caused by Cladosporium cucumerinum. This disease thrives in areas with cool, moist weather and becomes a serious problem when temperatures are between 57°F and 77°F. Moisture can be from heavy dew, frequent fog, or light rain.
Cucurbit scab symptoms
Cucurbit scab is found around the world. Symptoms can vary quite a bit, depending on where it occurs. Generally speaking, this disease presents as dark, olive-colored, velvety lesions on the surface of cucurbit fruits. Those lesions may also be brown or black. They are usually sunken and one-eighth of an inch in diameter. These lesions occur because of the pathogen’s ability to break down pectin and cellulose. A gummy substance may ooze from these lesions. As they mature, these spots get darker and sink into the fruit, creating holes loved by fruit flies and other pests. These pits can merge into rotted areas up to two inches across. In more resistant varieties, these lesions evolve into hard, warty structures.
Infected leaves have pale green, water-soaked areas that fade to gray. These areas may have a yellow halo. From a distance, it may look like powdery mildew. Closer inspection shows that these areas are distinctly triangular, hence the anthracnose assumption. These dead areas dry and fall out, leaving plants looking quite ragged. Cucurbit scab can also shorten the internodes, making plants look stunted.
Cucurbit scab management
Prevention is your first line of defense with any disease. Buying certified disease-free seeds, seedlings, and mature plants can help keep spores out of your landscape. Spores are spread by insects, tools, clothing, splashing rain, and the wind, so you’ll still have to be on the lookout.
You can prevent cucurbit scab from occurring with some simple cultural practices:
I hope this information helps you keep your cucurbits healthy and productive.
You can grow a surprising amount of food in your own yard. Ask me how!
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