Scientists Confirm Folk Remedy Repels Mosquitoes — ScienceDaily
Scientists Confirm Folk Remedy Repels Mosquitoes
- 1 Scientists Confirm Folk Remedy Repels Mosquitoes
- 2 Do ‘Natural’ Insect Repellents Work?
- 3 Not all products are created equal. Here’s what you need to know.
- 4 Oil of Lemon Eucalyptus (OLE)
- 5 How to Control Slugs in the Garden
- 6 How to Get Rid of Black Spot on Roses
- 7 Black Spot on Roses
- 8 What Causes Black Spots on Rose Leaves?
- 9 Symptoms of Black Spot Infection
- 10 Why Is Black Spot Bad for Roses?
- 11 Banish Black Spot From Your Garden in Four Steps
- 12 Step 1: Change Your Gardening Habits to Discourage Black Spot
- 13 Step 2: Know the Remedies
- 14 Step 3: Commercial Black Spot Sprays
- 15 Step 4: Choose Roses Resistant to Black Spot
- 16 Black Spot Blues? Don’t Despair
- 17 What Is Horticultural Soap: Information On Commercial and Homemade Soap Spray For Plants
- 18 What is Horticultural Soap?
- 19 Soap Spray for Plants
- 20 How to Make Insecticidal Soap
- 21 Alternate Horticultural Soap Recipe
Swatting mosquitoes and dodging other biting bugs is nearly a year-round chore in the Southeast, but such pests are swarming across the country with the advent of summer weather. And with warnings about West Nile virus and other insect-borne diseases out, keeping the pests away has taken on new urgency.
A traditional folk remedy, known among people in Mississippi’s hill country for at least a century, may provide some relief without all the worries of DEET and other harsh chemicals. Scientists at the United States Department of Agriculture-Agriculture Research Service housed at the National Center for Natural Products Research at the University of Mississippi have isolated compounds in the American beautyberry plant, Callicarpa americana, that may keep chomping insects away.
“My grandfather would cut branches with the leaves still on them and crush the leaves, then he and his brothers would stick the branches between the harness and the horse to keep deerflies, horseflies and mosquitoes away,” said Charles T. Bryson, an ARS botanist in Stoneville, Miss. “I was a small child, maybe 7 or 8 years old, when he told me about the plant the first time. For almost 40 years, I’ve grabbed a handful of leaves, crushed them and rubbed them on my skin with the same results.”
Bryson told his supervisor about the folklore repellent, and in 2004 the USDA-ARS at the UM natural products research center began investigating the beautyberry plant as a potential natural insect repellent.
Charles Cantrell, an ARS chemist in Oxford, and Jerry Klun, an ARS entomologist in Beltsville, Md., confirmed that the natural remedy wards off biting insects, such as ticks, ants and mosquitoes: “I’ve rubbed the leaves on my arms, and it works,” Cantrell said.
“Traditional folklore remedies many times are found to lead nowhere following scientific research,” he continued. “The beautyberry plant and its ability to repel mosquitoes is an exception. We actually identified naturally occurring chemicals in the plant responsible for this activity.»
Three repellent chemicals were extracted during the 12-month study: callicarpenal, intermedeol and spathulenol. The research concluded that all three chemicals repulse mosquitoes known to transmit yellow fever and malaria. Mosquitoes carrying the West Nile virus were not tested as part of the study, but the USDA-ARS has since filed a patent application to use callicarpenal as an anthropod repellent.
There are barriers, however, to producing the repellent for mass consumption. The product must be registered with the Environmental Protection Agency, which may cost millions of dollars, and a cost-effective manufacturing procedure must be determined.
“It’s difficult to bring a repellent onto the market,” Cantrell said. “We still have many unanswered questions: both the toxicity levels and evaporation rates are unknown. We’re still in the early stages.
Cantrell also said, “It’s quite unusual to find a plant producing this type of compound, but it’s synthesizing it for some reason. Perhaps, it’s naturally defending itself against insect attack.”
The National Center for Natural Products Research is the nation’s only university research center devoted to improving human health and agricultural productivity through the discovery, development and commercialization of pharmaceuticals and agrochemicals derived from plants, marine organisms and other natural products. University of Mississippi researchers at the center are studying hundreds of natural products that show promise to help treat a broad range of human illnesses, including cancer, AIDS, malaria, fungal infections, tuberculosis and emerging tropical diseases.
Other studies by both university and USDA scientists at the center may yield better products to control weeds, insects, fungal diseases in food crops and algae growth in commercial catfish ponds.
Do ‘Natural’ Insect Repellents Work?
Not all products are created equal. Here’s what you need to know.
It’s a simple question, one that CR readers frequently ask us: Do natural insect repellents work?
The answer, however, is a bit complicated. Two of the three active ingredients that have regularly earned recommended status in our insect repellent ratings—picaridin and oil of lemon eucalyptus, or OLE—are derived from plants. But several other plant-based chemicals, including lemon grass and soybean oil, typically end up at the very bottom of our ratings.
The Natural Products Association, a trade group, has defended those low-scoring insect repellents by pointing out that there’s variation in the effectiveness of all repellents, natural and synthetic.
But the discrepancy between what works and what doesn’t is less random than that statement suggests. All of the top-rated repellents in CR’s ratings are registered with the Environmental Protection Agency, while none of our bottom-rated ones are. An EPA registration means that the product has been evaluated by federal regulators to ensure safety and effectiveness. The agency requires this verification for some chemicals, such as deet, picaridin, and oil of lemon eucalyptus, but not for others.
Here’s a quick breakdown of which compounds are EPA-registered, which aren’t, and what our testing has found.
Oil of Lemon Eucalyptus (OLE)
What is it? It’s important not to confuse this product with lemon eucalyptus oil. The names are very similar, but the two chemicals are quite different. OLE is an oil extracted from the gum eucalyptus tree (native to Australia); the actual extracted chemical is called PMD and has demonstrated efficacy as an insect repellent.
Lemon eucalyptus oil, by contrast, is distilled from the leaves and twigs of the lemon eucalyptus tree. The distilled product contains several botanical substances, including citronella and a very low and variable amount of PMD.
Does it work? In our insect repellent testing, we found that one product, Repel Lemon Eucalyptus, 30%, warded off mosquitoes for more than 6.5 hours. Other OLE products in our ratings gave mixed performances. Two products, also with 30 percent OLE, provided between 3.5 and 5 hours of protection against mosquitoes. And two other OLE repellents performed a little worse than that. (Digital and all-access members can see our ratings for full details.)
Is it safe? The EPA classifies PMD as a biopesticide, which means it’s subject to more safety testing than botanicals (see below), including lemon eucalyptus oil, but less testing than synthetic chemicals like deet and picaridin. Both federal regulators and our experts agree that OLE is relatively safe.
But it’s important to use OLE repellents carefully and as directed, because when misapplied they can cause temporary eye injury. The product hasn’t been well-tested on children, and the Centers for Disease Control and Prevention and Consumer Reports advise against using OLE-based repellents on children younger than 3.
How to Control Slugs in the Garden
John A. Rizzo/Getty Images
- Total Time: 60 mins
- Skill Level: Intermediate
- Estimated Cost: $15
Slugs can be a gardener’s nightmare. They hide under leaves in the moist pockets of your garden and will eat almost anything they come in contact with. Garden slugs are especially damaging to vegetable and berry crops because they eat both the leaves and the fruit. Plus, damage can happen before you even know there’s an infestation, though chewed leaves and slimy trails are telltale signs. To rid a garden of these pesky critters, some gardeners turn to homemade solutions while others use commercial treatments for more serious infestations.
How to Get Rid of Black Spot on Roses
It starts gradually — a few yellowed leaves dropped to the ground, a few dark brown or black spots on the leaves you can easily attribute to just natural aging. Then suddenly, your rose bush looks terrible! Leaves are falling off at a rapid clip. Before tumbling to the ground, the leaves are dotted with black spots or splotches that fade into the leaf itself. As the days progress, nearly all the leaves yellow and fall from your prized roses, leaving a thorny skeleton behind. What happened? Was it an insect that attacked overnight or something else?
Black Spot on Roses
If this scenario sounds familiar, welcome to the bane of the rose gardener’s existence: black spot on roses. Black spot (Marssonina rosae or Diplocarpans rosae) is a fungal disease considered to be the most serious rose disease in the world. The parasitical fungus spreads rapidly through direct contact among roses — usually at an infected grower’s site or in the home garden — or through wind-borne spores. Once black spot takes hold on a rose bush, it can quickly decimate the plant or weaken it to the extent that the plant dies.
What Causes Black Spots on Rose Leaves?
Before addressing horticultural practices to help prevent black spot disease, it’s important to understand what causes black spot on rose leaves.
Black spot is caused by a fungus, Marssonina rosae or Diplocarpans rosae. Scientists give this fungus two names to signify its normal state — Marsonnina — and its reproductive state — Diplocarpans. Most rose gardening sites simply refer to it as Diplocarpans rosae since it causes the most trouble when it’s reproducing and spreading throughout your garden, leaving behind noticeable yellow leaves with black spots on rose bushes.
Infected plants produce spores, and the spores are carried along by the wind until they land on the ground or on a plant. The spores must be moist for several hours in order to develop into full-fledged black spot, which is why the disease is more prevalent in areas with high humidity. Rainfall, mist, fog or even lawn sprinklers can provide sufficient moisture for black spot to thrive.
About two weeks after the spores infect a plant, the telltale black spots develop on the leaves. These black spots are what biologists call “fruiting structures.” The fruiting structures or spots produce spores, which continue to infect other areas of the same plant, new canes or other roses in the garden.
Black spot is a tenacious fungus — it thrives in warmth and moisture, but it tolerates a wide range of conditions including extreme heat and cold. Even a harsh winter won’t kill the spores lying dormant in your garden. To get rid of black spot disease on roses, you’ll need to try one or more of the four steps listed later in this article.
Some gardeners with severe infections may need all four steps to stop black spot in its tracks. This may seem extreme, but like many fungal diseases, black spot is tough to eradicate completely from the garden.
Symptoms of Black Spot Infection
At first, roses show no signs of infection. After the spores alight on a rose bush, it takes about two weeks for them to germinate and develop into mature fungus that can reproduce. Signs of black spot infection start small but rapidly increase, especially if the weather is particularly hot and humid.
Symptoms of black spot infection include:
- The telltale black spots or dots on the rose bush’s green leaves. These spots may start as a dark, chocolate brown and turn darker over time. They can be anywhere on the upper surface of the leaf. The edges are irregular, almost feathery, and extend out from the darker center.
- As the spots grow larger, the leaves turn yellow. The yellow leaves with black dots on roses form clusters of infected leaves. Soon, the whole plant looks sick. Eventually, leaves fall off the plant as their ability to make food (photosynthesis) is compromised by the infection.
- Both old and new canes can also be infected with black spot. Black spot on canes looks like a purple dot or blotch. If the cane dies, the pathogen remains in the cane, so new canes are immediately infected. Black spot can live inside a rose’s canes over the winter, too.
Why Is Black Spot Bad for Roses?
Black spot looks ugly, of course. Yellowed leaves on roses aren’t attractive, and when they fall off, they leave a bare, skeletal plant. More importantly, black spot weakens the entire plant so that it may eventually die.
Plants produce energy within special cells of their leaves called chloroplasts. These cells are like little food factories, using the sun’s rays to transform water and carbon dioxide into energy for growth, maintenance and reproduction. This process is called photosynthesis.
Because black spot defoliates roses, there are fewer leaves to produce energy for the plant. The plant cannot produce enough new leaves fast enough to make up for the shortfall. As new leaves emerge, they’re also infected, and soon the plant doesn’t have any way left to make its energy supply. Although some plants can survive a year of this, two or more years in a row weakens them to the point at which they die, or a harsh winter kills an already weakened plant. That’s why black spot is such a dreadful disease.
Some tough garden roses can, in fact, survive a black spot infection. Roses are an ancient plant. Fossilized specimens indicate they have been around for 35 million years. Individual specimens and some rose species do indeed have a natural resistance to black spot, but many hybrids, particularly hybrid tea roses, are extremely susceptible to black spot disease.
Banish Black Spot From Your Garden in Four Steps
Armed with a good description of black spot disease, you’ve determined the problem in your rose garden is most likely caused by this pest. Now it’s time to take action.
There are four steps you can take to combat black spot disease on roses:
Step 1: Change Your Gardening Habits to Discourage Black Spot
Several gardening habits provide the ideal conditions necessary for the black spot spores to develop into full-blown disease. Here are five easy ways to help prevent black spot on roses.
Clean up your garden in the fall. Snip dead branches on perennials and shrubs and prune your roses. Don’t compost these garden scraps. Instead, bag them and set them out for the trash, hence, if any black spot spores are on the canes, they’ll go to the landfill and not back into your compost pile where they may eventually infect yours or someone else’s roses.
Water at the base. Many automated watering methods, like sprinklers, tend to wet the leaves without delivering water beyond the drip line — boundary created by the foliage extending over the plant’s central stem. It’s within that drip line that the plant’s roots can take up water, and that’s where to direct your spray of water to be the most effective. Water the ground near the roots instead of soaking the bush with a spray from above.
Water in the morning. Evening watering schedules promote mold and fungus, including black spot. That’s because moisture and darkness make ideal conditions for these microorganisms to grow on plants. Morning watering gives the sun’s rays a chance to dry splashes of water on the leaves. Switch your watering schedule to the morning instead evening.
Clean and sterilize your tools. It’s a good idea to clean your pruners every time you use them. Keep a bottle of rubbing alcohol near your pruners and a clean rag — just wipe the blades with alcohol before putting them away. Dip or rub the blades in alcohol before using them on another plant, too. When you prune your roses, you create an open wound through which infection can enter the canes. Alcohol kills bacteria, mold and fungi.
Plant roses in full sun. Roses don’t do particularly well in shade. Partial shade, especially morning shade, keeps dew on the leaves just long enough to provide the conditions that black spot loves. Grow roses in full sunlight only.
Changing your gardening practices may not entirely prevent black spot, and they do not treat black spot if it’s already rampaging through your garden. What if you’re doing everything right, yet your roses still have black spot? It’s time to move on to step two in our list of steps to tackle black spot: Try natural remedies.
Step 2: Know the Remedies
Botanists have long searched for an effective, natural remedy for black spot on roses. Milk, a popular folk remedy, has been deemed ineffective by researchers at Washington State University. Although milk can be useful to help various foliar sprays stick to leaves, it may actually cause other diseases that can harm your roses.
So which natural cures do work for black spots on roses? A paper published in the Journal of Medicinally Active Plants lists the essential oils of English thyme and “Scotch” spearmint, two common plants, as potentially effective in the treatment of black spot disease.
The essential oils of these two garden herbs were tested against a control of fungicide and a second of water, and the results indicate that English thyme and “Scotch” spearmint both provided antifungal properties that lessened the severity of black spot lesions. Other herbal essential oil extracts were also tested, including that of sweet basil and holy basil, two other plants with alleged antifungal properties. Neither species of basil produced notable results.
Neem oil, produced by the Asian Neem tree, offers some relief of black spot. Neem has notable antifungal properties that seem to work well on roses. Neem oil is also useful against powdery mildew, which is another fungus roses tend to get.
Step 3: Commercial Black Spot Sprays
By far the most popular method of treating black spot on roses is through the use of conventional sprays. Sulfur compounds are effective at treating black spot. Safer® Brand Garden Fungicide uses sulfur as the active ingredient and is available in a convenient spray bottle or concentrate that can be mixed according to package directions for a foliar spray.
When using commercial fungicides in your garden, be sure to use only the recommended amount according to the label directions. More may not necessarily be better. Be sure to wash your hands and clothing after application, and dispose of the container according to the label on the package.
Step 4: Choose Roses Resistant to Black Spot
Rose growers should keep their eyes open for plants that aren’t susceptible to black spot. Disease-resistant roses should be grafted into hardy root stock to produce new plants with strong growth and resistance to common diseases. They may also breed new varieties of roses by crossing two kinds that are naturally disease resistant.
Thanks to the test of time and long-standing exposure to black spot, older rose varieties tend to have natural disease resistance. While many of these older roses have a different flower shape and petal configuration than what you may imagine when you hear the word “rose”, they often have a stronger fragrance, and they tend to be vigorous, healthy plants. It’s worth a try if you love roses but have trouble growing them due to black spot disease.
Keep in mind that roses may be resistant in one location, but not when planted in another. That’s because there are numerous strains of the black spot fungus. For example, a rose may be resistant in Oregon to one strain but susceptible to the strain living in Pennsylvania. Always try to purchase plants grown locally for your best chance at roses resistant to black spot.
Roses naturally resistant to black spot disease include:
- The Carpet Rose®: Flower Carpet roses are easy to care for and low-water tolerant. They have won numerous awards for their disease resistance, including Germany’s strict ADR awards where no chemicals are allowed to be used in the trials.
- Drift Roses: These ground cover roses only grow a little over a foot high and don’t require pruning. The Coral Drift and Sweet Drift varieties are fragrant.
- Floribunda Roses: Floribunda roses are a shrubby type of rose bush that produces copious sprays of small, rose-shaped flowers. Most shrub roses or Floribunda roses are hardy and disease resistant. Some are also resistant to rust and other fungal diseases in addition to being resistant to black spot.
- Meilland Hybrids: Originally grown in the south of France, Meilland hybrids are now available worldwide and are cultivated for disease resistance.
- Knock Out Roses®: These are a new rose hybrid produced by Star Roses and Plants. Available at nursery and garden centers nationwide, they are said to offer better disease resistance than similar plants.
Among the hybrid tea roses, several older varieties offer black spot resistance. These include Mr. Lincoln — a classic red tea rose — Tropicana — an orange variety — and Miss All American Beauty — a pink rose.
You can find black spot-resistant rose varieties from among all types of roses including climbing roses, miniature roses and more. With over 50 strains of black spot fungi identified, not all roses are resistant to each strain. Strains are found locally, so roses known to be black spot-resistant in local gardens are likely the best ones to plant in your garden for disease resistance.
Black Spot Blues? Don’t Despair
Many roses naturally survive an outbreak of black spot. The earlier you begin treating your roses for black spot the better chances it has at recovering.
One rose, the Hildesheim climbing rose, has been verified by scientists to be over 1,000 years old. If a rose can survive 1,000 years of exposure to black spot and other diseases, maybe your rose can survive, too.
What Is Horticultural Soap: Information On Commercial and Homemade Soap Spray For Plants
Taking care of pests in the garden doesn’t need to be expensive or toxic. Horticultural sprays are a great way to combat many issue in the garden without harming the environment or your pocketbook. Learning how to make insecticidal soap spray for plants is easy to do and the benefits are worth the extra effort.
What is Horticultural Soap?
What is horticultural soap? Horticultural soap is not a cleaning product for foliage–it is an environmentally friendly application used to eliminate small soft bodied insects such as aphids, whiteflies, spider mites and mealybugs.
Horticultural soaps may be used either on indoor houseplants or on outdoor plants, including vegetables. Insecticidal soaps have several advantages over pesticides in that they leave no nasty residue, are non-toxic to animals and birds, and do not harm beneficial insects. They are often also less expensive solutions to pest problems.
Horticultural soaps are derived from petroleum or plant oils. When horticultural soap is sprayed onto the plants’ foliage, it comes into contact with the pest and kills it. Horticultural soaps disrupt the cell membranes of the insect, resulting in suffocation. To be most effective, horticultural soaps must be applied vigilantly and thoroughly and may need to be reapplied weekly until you attain the desired result.
Insecticidal soaps also have a beneficial effect in the removal of sooty mold, honeydew and other leaf fungi.
Soap Spray for Plants
Insecticidal soap may be made at home using ingredients which are commonly used and found around the house. That said, most garden professionals recommend using a commercial soap spray that is specifically formulated for this purpose and is safer to use with more predictable results. Commercially formulated horticultural soaps are readily available at most garden supply stores and are sold as either a concentrate or ready-to-use (RTU).
How to Make Insecticidal Soap
There are several ways to make an insecticidal soap. The choice depends on the ingredients on hand and the extent to which one wants to use natural ingredients, i.e. those without perfumes or dyes.
To make insecticidal soap, simply mix the following horticultural soap recipe ingredients thoroughly:
- Combine one cup of oil, any variety, such as vegetable, peanut, corn, soybean, etc. with one tablespoon of dishwashing liquid or other “pure” soap. Be sure to avoid any dish washing liquids which contain degreaser, bleach, or those that are for an automatic dishwasher.
- Mix two teaspoons of this “soap” mixture to every cup of warm water and put into a spray bottle. Mix only what is needed for a one-day application.
Alternate Horticultural Soap Recipe
Homemade horticultural sprays can also be made using a natural soap product without synthetic additives or perfumes, which can be found in local natural food stores.
Combine one heavy tablespoon of liquid soap to one quart of warm water. Tap water is okay to use, but if you have hard water you may want to substitute bottled water to avoid any soap scum buildup on foliage.
To either of these soapy concoctions, a teaspoon of ground red pepper or garlic may be added to further repel chewing insects. Also, a teaspoon of cider vinegar may be added to assist in the removal of powdery mildew. Bar soap may also be used in a pinch by placing into a gallon of water and leaving to sit over night. Remove the bar and shake well before use.
There are few limitations to horticultural soaps. Just be sure to thoroughly wet the insects, and be aware that effectiveness may be limited if the soap solution dries or washes away. Phytotoxicity may occur if applied during hot days, so avoid spraying if temperatures are over 90 F. (32 C.).
BEFORE USING ANY HOMEMADE MIX: It should be noted that anytime you use a home mix, you should always test it out on a small portion of the plant first to make sure that it will not harm the plant. Also, avoid using any bleach-based soaps or detergents on plants since this can be harmful to them. In addition, it is important that a home mixture never be applied to any plant on a hot or brightly sunny day, as this will quickly lead to burning of the plant and its ultimate demise.