文章
Dummer. ゛☀
2017年09月14日
A serious disease of apples and ornamental crabapples, apple scab (Venturia inaequalis) attacks both leaves and fruit. The fungal disease forms pale yellow or olive-green spots on the upper surface of leaves. Dark, velvety spots may appear on the lower surface. Severely infected leaves become twisted and puckered and may drop early in the summer.
Symptoms on fruit are similar to those found on leaves. Scabby spots are sunken and tan and may have velvety spores in the center. As these spots mature, they become larger and turn brown and corky. Infected fruit becomes distorted and may crack allowing entry of secondary organisms. Severely affected fruit may drop, especially when young.
Apple scab overwinters primarily in fallen leaves and in the soil. Disease development is favored by wet, cool weather that generally occurs in spring and early summer. Fungal spores are carried by wind, rain or splashing water from the ground to flowers, leaves or fruit. During damp or rainy periods, newly opening apple leaves are extremely susceptible to infection. The longer the leaves remain wet, the more severe the infection will be. Apple scab spreads rapidly between 55-75 degrees F.
Treatment
Choose resistant varieties when possible.
Rake under trees and destroy infected leaves to reduce the number of fungal spores available to start the disease cycle over again next spring.
Water in the evening or early morning hours (avoid overhead irrigation) to give the leaves time to dry out before infection can occur.
Spread a 3- to 6-inch layer of compost under trees, keeping it away from the trunk, to cover soil and prevent splash dispersal of the fungal spores.
For best control, spray liquid copper soap early, two weeks before symptoms normally appear. Alternatively, begin applications when disease first appears, and repeat at 7 to 10 day intervals up to blossom drop.
Bonide® Sulfur Plant Fungicide, a finely ground wettable powder, is used in pre-blossom applications and must go on before rainy or spore discharge periods. Apply from pre-pink through cover (2 Tbsp/ gallon of water), or use in cover sprays up to the day of harvest.
Organocide® Plant Doctor is an earth-friendly systemic fungicide that works its way through the entire plant to combat a large number of diseases on ornamentals, turf, fruit and more. Apply as a soil drench or foliar spray (3-4 tsp/ gallon of water) to prevent and attack fungal problems.
Containing sulfur and pyrethrins, Bonide® Orchard Spray is a safe, one-hit concentrate for insect attacks and fungal problems. For best results, apply as a protective spray (2.5 oz/ gallon) early in the season. If disease, insects or wet weather are present, mix 5 oz in one gallon of water. Thoroughly spray all parts of the plant, especially new shoots.
Symptoms on fruit are similar to those found on leaves. Scabby spots are sunken and tan and may have velvety spores in the center. As these spots mature, they become larger and turn brown and corky. Infected fruit becomes distorted and may crack allowing entry of secondary organisms. Severely affected fruit may drop, especially when young.
Apple scab overwinters primarily in fallen leaves and in the soil. Disease development is favored by wet, cool weather that generally occurs in spring and early summer. Fungal spores are carried by wind, rain or splashing water from the ground to flowers, leaves or fruit. During damp or rainy periods, newly opening apple leaves are extremely susceptible to infection. The longer the leaves remain wet, the more severe the infection will be. Apple scab spreads rapidly between 55-75 degrees F.
Treatment
Choose resistant varieties when possible.
Rake under trees and destroy infected leaves to reduce the number of fungal spores available to start the disease cycle over again next spring.
Water in the evening or early morning hours (avoid overhead irrigation) to give the leaves time to dry out before infection can occur.
Spread a 3- to 6-inch layer of compost under trees, keeping it away from the trunk, to cover soil and prevent splash dispersal of the fungal spores.
For best control, spray liquid copper soap early, two weeks before symptoms normally appear. Alternatively, begin applications when disease first appears, and repeat at 7 to 10 day intervals up to blossom drop.
Bonide® Sulfur Plant Fungicide, a finely ground wettable powder, is used in pre-blossom applications and must go on before rainy or spore discharge periods. Apply from pre-pink through cover (2 Tbsp/ gallon of water), or use in cover sprays up to the day of harvest.
Organocide® Plant Doctor is an earth-friendly systemic fungicide that works its way through the entire plant to combat a large number of diseases on ornamentals, turf, fruit and more. Apply as a soil drench or foliar spray (3-4 tsp/ gallon of water) to prevent and attack fungal problems.
Containing sulfur and pyrethrins, Bonide® Orchard Spray is a safe, one-hit concentrate for insect attacks and fungal problems. For best results, apply as a protective spray (2.5 oz/ gallon) early in the season. If disease, insects or wet weather are present, mix 5 oz in one gallon of water. Thoroughly spray all parts of the plant, especially new shoots.
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文章
Dummer. ゛☀
2017年09月14日
Botrytis blight is a cruel disease for flower gardeners, because it frequently strikes garden plants in their prime, destroying blossoms just as they are ready to open. Botrytis, also called grey mold, is a fungal disease, and gardeners can recognize it when they see these symptoms in plants:
Spotting or discoloration on leaves
Wilting or decaying leaves and shoots
Leaf drop
Fuzzy grayish brown growth on flowers and foliage
Flower buds that fail to open
Rotting flower buds
Damping off disease of seedlings
Botrytis thrives in high humidity and cool weather, so gardeners will see signs of grey mold most often on spring flowers.
Flowers Affected by Botrytis
In the outdoor flower garden, marigolds, impatiens, peonies and roses are the most likely plants to show signs of botrytis. In the greenhouse, several flowers are susceptible to this fungus, especially cyclamen, geraniums, and poinsettia. Seedlings that often succumb to damping off disease caused by botrytis fungi include pansies, petunias, and snapdragons.
Organic Sprays for Botrytis
Sulfur powders and sprays are effective at controlling fungal diseases like botrytis in the flower garden. Apply sprays early in the morning or evening to avoid harming bees or beneficial insects.
A less common, but very effective organic treatment against foliage diseases in the flower garden is the bacterium Bacillus subtilis, sold under the trade name Serenade.
Many gardeners report that the fragrance of this spray is less offensive compared to other organic or conventional fungicide sprays.
Cultural Control of Botrytis
When you notice the first signs of botrytis in the flower garden, get out the clippers. Remove all affected foliage and flowers, and destroy the plant matter.
Sanitize clippers with an alcohol wipe after pruning diseased plants to prevent spreading the fungi to healthy plants. It’s also important to keep the ground around plants free of decaying leaves, which act like a nursery for fungal spores.
Although you can’t do anything about humid conditions in your area, you can help plants cope with excessive moisture. Use drip irrigation, which delivers water to the root zone where it's needed and keeps leaves dry. Avoid overhead watering, which can splash disease-carrying soil onto leaves. Water in the morning to allow the sun's rays to quickly evaporate any moisture on leaves. Follow proper plant spacing guidelines, to enhance air circulation. Prune the interior of dense plants to increase air movement that carries away disease spores.
Greenhouse Botrytis Management
The principles of botrytis management in the greenhouse are similar to those in the garden, but greenhouse gardeners can control the greenhouse environment more than the outdoors. Use fans of adequate size and number for the greenhouse size. You should aim for a relative humidity below 80%, and completely changing the air three one to three times an hour should help to achieve this.
Your greenhouse retailer can help you calculate fans needed according to the cubic feet of your greenhouse.
Raise the temperature of the greenhouse at sunset to dry condensation on leaves. This is especially important in the winter.
Isolate plants showing signs of botrytis from the greenhouse population. Destroy the plants on inexpensive specimens that you can easily replace; this prevents widespread, more costly outbreaks.
Conventional Control of Botrytis
Severe botrytis outbreaks may require fungicide applications to achieve control of the disease. Botrytis can become resistant to chemicals, so switching it up occasionally may achieve better control. Gardeners should look for fungicides that contain one of these active ingredients:
Chlorothalonil
Fenhexamid
Fludioxonil
Myclobutanil
Botrytis Resistant Flowers to Grow
Unfortunately, horticulturists haven’t developed any completely botrytis-resistant flower species.
'Fantasy Blue' petunias and 'Tidal Wave Pink' petunias are two varieties that are more resistant to flower blight than older petunia varieties. Peony lovers may have more luck with tree peonies and intersectional hybrids than with P. lactiflora garden peonies. Gardeners must continue to battle this tenacious fungal flower disease by practicing good garden and greenhouse hygiene and cultural practices.
Spotting or discoloration on leaves
Wilting or decaying leaves and shoots
Leaf drop
Fuzzy grayish brown growth on flowers and foliage
Flower buds that fail to open
Rotting flower buds
Damping off disease of seedlings
Botrytis thrives in high humidity and cool weather, so gardeners will see signs of grey mold most often on spring flowers.
Flowers Affected by Botrytis
In the outdoor flower garden, marigolds, impatiens, peonies and roses are the most likely plants to show signs of botrytis. In the greenhouse, several flowers are susceptible to this fungus, especially cyclamen, geraniums, and poinsettia. Seedlings that often succumb to damping off disease caused by botrytis fungi include pansies, petunias, and snapdragons.
Organic Sprays for Botrytis
Sulfur powders and sprays are effective at controlling fungal diseases like botrytis in the flower garden. Apply sprays early in the morning or evening to avoid harming bees or beneficial insects.
A less common, but very effective organic treatment against foliage diseases in the flower garden is the bacterium Bacillus subtilis, sold under the trade name Serenade.
Many gardeners report that the fragrance of this spray is less offensive compared to other organic or conventional fungicide sprays.
Cultural Control of Botrytis
When you notice the first signs of botrytis in the flower garden, get out the clippers. Remove all affected foliage and flowers, and destroy the plant matter.
Sanitize clippers with an alcohol wipe after pruning diseased plants to prevent spreading the fungi to healthy plants. It’s also important to keep the ground around plants free of decaying leaves, which act like a nursery for fungal spores.
Although you can’t do anything about humid conditions in your area, you can help plants cope with excessive moisture. Use drip irrigation, which delivers water to the root zone where it's needed and keeps leaves dry. Avoid overhead watering, which can splash disease-carrying soil onto leaves. Water in the morning to allow the sun's rays to quickly evaporate any moisture on leaves. Follow proper plant spacing guidelines, to enhance air circulation. Prune the interior of dense plants to increase air movement that carries away disease spores.
Greenhouse Botrytis Management
The principles of botrytis management in the greenhouse are similar to those in the garden, but greenhouse gardeners can control the greenhouse environment more than the outdoors. Use fans of adequate size and number for the greenhouse size. You should aim for a relative humidity below 80%, and completely changing the air three one to three times an hour should help to achieve this.
Your greenhouse retailer can help you calculate fans needed according to the cubic feet of your greenhouse.
Raise the temperature of the greenhouse at sunset to dry condensation on leaves. This is especially important in the winter.
Isolate plants showing signs of botrytis from the greenhouse population. Destroy the plants on inexpensive specimens that you can easily replace; this prevents widespread, more costly outbreaks.
Conventional Control of Botrytis
Severe botrytis outbreaks may require fungicide applications to achieve control of the disease. Botrytis can become resistant to chemicals, so switching it up occasionally may achieve better control. Gardeners should look for fungicides that contain one of these active ingredients:
Chlorothalonil
Fenhexamid
Fludioxonil
Myclobutanil
Botrytis Resistant Flowers to Grow
Unfortunately, horticulturists haven’t developed any completely botrytis-resistant flower species.
'Fantasy Blue' petunias and 'Tidal Wave Pink' petunias are two varieties that are more resistant to flower blight than older petunia varieties. Peony lovers may have more luck with tree peonies and intersectional hybrids than with P. lactiflora garden peonies. Gardeners must continue to battle this tenacious fungal flower disease by practicing good garden and greenhouse hygiene and cultural practices.
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文章
Dummer. ゛☀
2017年09月14日
Now that you have Basil Downy Mildew, what do you do next? It is a highly contagious disease, with little warning. Because it is transmitted through spores that are nearly invisible to the naked eye, it can be blown in on the wind, carried in on clothing, hands or tools. Here are some things you can do after you find Basil Downy Mildew in your garden.
Remove Infected Plants
Basil that has become infected with Downy Mildew may have a yellowish appearance, similar to a nutritional problem.
The leaves turn yellow and fall off, while the stems wither, and the plant eventually dies. The most common symptom is the dusty spots, actually spores, that are located on the bottoms of the leaves. If you want a definitive diagnosis, you can bring an affected leaf to your local County Extension office for identification. Carefully pinch off a leaf and place it in a ziploc baggie for transport.
Once you are certain that it is Downy Mildew, cover the entire plant with a bag to prevent as much of the spores from being shaken off as possible. Pull up the entire plant and remove from garden area. Do not try to compost or try to remove only the visibly affected leaves. Both of these techniques can result in the spread of the spores. Do not save your basil seeds from any part of that year's crop. The spores can infect the seeds and affect the following year's plants.
Will It Stay In My Soil?
Yes.
The disease can stay viable for many years in the soil. Some experts say that the spores can stay viable for 8 years or more. If nothing else, rotate your crop of basil and plant in an entirely new location for the next season.
Is Basil Poisonous That Has Downy Mildew?
In a word, no. However, it is not advisable to eat leaves that are clearly affected.
When you first notice signs of BDM, it is best to remove the entire plant and make pesto out of all the healthy leaves. Because basil grows so fast, quick removal and starting new plants in a new location is the best way to prevent spreading spores.
Remove Infected Plants
Basil that has become infected with Downy Mildew may have a yellowish appearance, similar to a nutritional problem.
The leaves turn yellow and fall off, while the stems wither, and the plant eventually dies. The most common symptom is the dusty spots, actually spores, that are located on the bottoms of the leaves. If you want a definitive diagnosis, you can bring an affected leaf to your local County Extension office for identification. Carefully pinch off a leaf and place it in a ziploc baggie for transport.
Once you are certain that it is Downy Mildew, cover the entire plant with a bag to prevent as much of the spores from being shaken off as possible. Pull up the entire plant and remove from garden area. Do not try to compost or try to remove only the visibly affected leaves. Both of these techniques can result in the spread of the spores. Do not save your basil seeds from any part of that year's crop. The spores can infect the seeds and affect the following year's plants.
Will It Stay In My Soil?
Yes.
The disease can stay viable for many years in the soil. Some experts say that the spores can stay viable for 8 years or more. If nothing else, rotate your crop of basil and plant in an entirely new location for the next season.
Is Basil Poisonous That Has Downy Mildew?
In a word, no. However, it is not advisable to eat leaves that are clearly affected.
When you first notice signs of BDM, it is best to remove the entire plant and make pesto out of all the healthy leaves. Because basil grows so fast, quick removal and starting new plants in a new location is the best way to prevent spreading spores.
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文章
Dummer. ゛☀
2017年09月13日
What is Powdery Mildew?
Powdery mildew is one of the most commonly occurring plants problems. It is a fungal disease that affects plant leaves and stems, coating them in what looks like a white or gray powder-like substance. Although any plant can get powdery mildew, some are very susceptible, crab apples, cucumbers and all types of squash, lilacs, phlox and roses. In severe cases, powdery mildew can even spread to the buds, flowers, and fruits of plants.
The white coating greatly diminishes the appearance of the plant, but it is not fatal unless left uncontrolled. However, as it spreads, it stresses and weakens the plant and makes it hard for photosynthesis to occur. It's wise to treat it as soon as you see symptoms, or maybe even before.
Controlling Powdery Mildew with Baking Soda
Baking soda has long been used as an inexpensive control for powdery mildew on plants. Unfortunately baking soda fungicide is mostly effective as a preventative, offering only minimal benefits after your plants have become infected. If you know which plants are susceptible, spraying them weekly with the baking soda recipes, during humid or damp weather, can greatly reduce the incidence of powdery mildew in your garden.
To control powdery mildew on plants, mix together:
1 tablespoon of baking soda
½ teaspoon of liquid soap
1 gallon of water
Do not store unused mixture.
While this recipe has been known to be effective, it can burn the leaves of some plants. It is recommended that you water your infected plants well a couple of days before applying this mixture, and don’t apply it in full sun. Try on a small area first, to test the plant’s response before spraying the entire plant.
Some recipes also recommend applying 1 tablespoon of ultralight horticultural oil to the mixture. The oil coats and smothers the fungi. The soap is added to help the mix spread and cling to the leaf surface. Be sure to apply to lower leaf surfaces as well.
Control versus Cure
Unfortunately, this baking soda mixture works best as a preventative, applied before powdery mildew has a chance to spread on your plant. It is less effective as a cure, once the fungus has taken hold. If you know a plant is affected by powdery mildew year after year, as is the case with many monarda, pholx, and lilacs, they spraying early in the season may prevent any occurrence of powdery mildew that year. It is still worth trying after signs of powdery mildew appear, but it might not get rid of all the fungus.
Another Homemade Powdery Mildew Option
Spraying plants with a milk mixture, after they have been infected with powdery mildew, is showing a lot of promise for actually killing the fungus. Read more about how to use milk to control powdery mildew.
There May be More Uses for This Baking Soda Recipe
Researchers are still studying the effects of using a baking soda mixture on other fungal diseases such as: black spot, rust and anthracnose.
Powdery mildew is one of the most commonly occurring plants problems. It is a fungal disease that affects plant leaves and stems, coating them in what looks like a white or gray powder-like substance. Although any plant can get powdery mildew, some are very susceptible, crab apples, cucumbers and all types of squash, lilacs, phlox and roses. In severe cases, powdery mildew can even spread to the buds, flowers, and fruits of plants.
The white coating greatly diminishes the appearance of the plant, but it is not fatal unless left uncontrolled. However, as it spreads, it stresses and weakens the plant and makes it hard for photosynthesis to occur. It's wise to treat it as soon as you see symptoms, or maybe even before.
Controlling Powdery Mildew with Baking Soda
Baking soda has long been used as an inexpensive control for powdery mildew on plants. Unfortunately baking soda fungicide is mostly effective as a preventative, offering only minimal benefits after your plants have become infected. If you know which plants are susceptible, spraying them weekly with the baking soda recipes, during humid or damp weather, can greatly reduce the incidence of powdery mildew in your garden.
To control powdery mildew on plants, mix together:
1 tablespoon of baking soda
½ teaspoon of liquid soap
1 gallon of water
Do not store unused mixture.
While this recipe has been known to be effective, it can burn the leaves of some plants. It is recommended that you water your infected plants well a couple of days before applying this mixture, and don’t apply it in full sun. Try on a small area first, to test the plant’s response before spraying the entire plant.
Some recipes also recommend applying 1 tablespoon of ultralight horticultural oil to the mixture. The oil coats and smothers the fungi. The soap is added to help the mix spread and cling to the leaf surface. Be sure to apply to lower leaf surfaces as well.
Control versus Cure
Unfortunately, this baking soda mixture works best as a preventative, applied before powdery mildew has a chance to spread on your plant. It is less effective as a cure, once the fungus has taken hold. If you know a plant is affected by powdery mildew year after year, as is the case with many monarda, pholx, and lilacs, they spraying early in the season may prevent any occurrence of powdery mildew that year. It is still worth trying after signs of powdery mildew appear, but it might not get rid of all the fungus.
Another Homemade Powdery Mildew Option
Spraying plants with a milk mixture, after they have been infected with powdery mildew, is showing a lot of promise for actually killing the fungus. Read more about how to use milk to control powdery mildew.
There May be More Uses for This Baking Soda Recipe
Researchers are still studying the effects of using a baking soda mixture on other fungal diseases such as: black spot, rust and anthracnose.
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文章
Dummer. ゛☀
2017年09月13日
Powdery mildew is a fungal disease that results in a powdery gray or white coating on the leaves and stems of infected plants. Several different species of fungi in the order Erysiphales can cause the disease, though the symptoms are always similar. A powdery mildew infection generally starts out as a few spores on the leaves but quickly spreads. The white powdery surface is a thick coating of the fungi spores.
The fungi easily overwinters in garden debris, and thus is very hard to eradicate entirely. It can eventually cause yellowing the leaves and premature leaf drop.
As virtually all gardeners know, powdery mildew thrives in humid conditions with moderate temperatures. In any region with humid summers, powdery mildew virtually always makes its appearance. While it can affect any plants, there are certain species much more susceptible to heavy infection:
Some Plants Susceptible to Powdery Mildew:
Apples
Begonia
California poppy
Dahlia
Delphinium
Hollyhock
Hydrangea
Lilacs
Monarda
Oak
Strawberries
Phlox
Roses
Strawberries
Zinnia
Damage to Plants
In many cases, powdery mildew does little damage to plants but is merely unattractive. And some plants seem so susceptible to powdery mildew that it is virtually unavoidable--an expected cost if you choose to grow these species. Many gardeners simply resign themselves to the fact that powdery mildew will make an appearance nearly every year and don't bother to fight it aggressively.
But besides being unattractive, powdery mildew can in extreme cases result in leaf yellowing and dropping, stunted plant growth, distortion of buds, blooms, and fruit, and eventual overall weakening of the plant.
Disease Life Cycle
Spores overwinter on diseased plant parts and begin asexual production of new spores once the weather warms.
New spores are carried on the wind to other parts of the plant or to other nearby plants. Spores never stop producing more spores, so if infected leaves are not destroyed, the problem can never be eradicated and will only get worse.
Treatment and Prevention
Powdery mildew thrives in temperatures between 60° and 80°F. Dry, shady conditions are ideal, as are areas with poor air circulation. Few chemical fungicides offer much cure for powdery mildew; the best strategies are more mechanical in nature, such as simply removing and destroying diseased plants and plant parts.
Planting disease-resistant cultivars and making sure you allow for good air flow are two ways to guard against powdery mildew. Beyond this, possible control methods to keep powdery mildew in check include the following:
Plant species that are most susceptible in a location where they can receive early morning sun. This will allow condensation to dry out quickly and reduce the humid conditions that foster the fungus.
Enhance air circulation by spacing plants well apart. Better ventilation will reduce the disease. Dense plants can be thinned out to improve air flow.
Inspect plants regularly during warm, dry conditions, and remove any leaves that show signs of infection. Destroy (do not compost!) infected plant parts.
A spray made with baking soda, if applied weekly at the first signs of infection, can protect plants against further damage.
Plants that are badly infected should be ripped out and destroyed to prevent the disease from spreading further.
A commercially available organic option is Neem oil, which both treats existing powdery mildew and protects the plant against further infection.
Interestingly enough, an effective measure in preventing and treating powdery mildew is to spray the foliage of your plants daily with plain water from the hose. Powdery mildew hates water! The only caveat with this method is to be sure you do it early in the day so that the foliage completely dries before cooler evening temperatures arrive, otherwise you may invite other fungal diseases such as black spotinto your garden.
The fungi easily overwinters in garden debris, and thus is very hard to eradicate entirely. It can eventually cause yellowing the leaves and premature leaf drop.
As virtually all gardeners know, powdery mildew thrives in humid conditions with moderate temperatures. In any region with humid summers, powdery mildew virtually always makes its appearance. While it can affect any plants, there are certain species much more susceptible to heavy infection:
Some Plants Susceptible to Powdery Mildew:
Apples
Begonia
California poppy
Dahlia
Delphinium
Hollyhock
Hydrangea
Lilacs
Monarda
Oak
Strawberries
Phlox
Roses
Strawberries
Zinnia
Damage to Plants
In many cases, powdery mildew does little damage to plants but is merely unattractive. And some plants seem so susceptible to powdery mildew that it is virtually unavoidable--an expected cost if you choose to grow these species. Many gardeners simply resign themselves to the fact that powdery mildew will make an appearance nearly every year and don't bother to fight it aggressively.
But besides being unattractive, powdery mildew can in extreme cases result in leaf yellowing and dropping, stunted plant growth, distortion of buds, blooms, and fruit, and eventual overall weakening of the plant.
Disease Life Cycle
Spores overwinter on diseased plant parts and begin asexual production of new spores once the weather warms.
New spores are carried on the wind to other parts of the plant or to other nearby plants. Spores never stop producing more spores, so if infected leaves are not destroyed, the problem can never be eradicated and will only get worse.
Treatment and Prevention
Powdery mildew thrives in temperatures between 60° and 80°F. Dry, shady conditions are ideal, as are areas with poor air circulation. Few chemical fungicides offer much cure for powdery mildew; the best strategies are more mechanical in nature, such as simply removing and destroying diseased plants and plant parts.
Planting disease-resistant cultivars and making sure you allow for good air flow are two ways to guard against powdery mildew. Beyond this, possible control methods to keep powdery mildew in check include the following:
Plant species that are most susceptible in a location where they can receive early morning sun. This will allow condensation to dry out quickly and reduce the humid conditions that foster the fungus.
Enhance air circulation by spacing plants well apart. Better ventilation will reduce the disease. Dense plants can be thinned out to improve air flow.
Inspect plants regularly during warm, dry conditions, and remove any leaves that show signs of infection. Destroy (do not compost!) infected plant parts.
A spray made with baking soda, if applied weekly at the first signs of infection, can protect plants against further damage.
Plants that are badly infected should be ripped out and destroyed to prevent the disease from spreading further.
A commercially available organic option is Neem oil, which both treats existing powdery mildew and protects the plant against further infection.
Interestingly enough, an effective measure in preventing and treating powdery mildew is to spray the foliage of your plants daily with plain water from the hose. Powdery mildew hates water! The only caveat with this method is to be sure you do it early in the day so that the foliage completely dries before cooler evening temperatures arrive, otherwise you may invite other fungal diseases such as black spotinto your garden.
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文章
Dummer. ゛☀
2017年09月13日
What is Black Spot?
Black spot is a fungal disease (Diplocarpon rosae), that affects roses. It causes black spots on leaves, eventually causing the leaves to turn yellow and drop off. Besides looking unsightly, it can seriously weaken the rose plant. Ideal conditions include hot, humid or rainy summers and hot days with cool, damp nights.
Symptoms:
Somewhat circular black spots on leaves. They usually occur on the upper sides of leaves, but can also develop on the undersides.
The outer margins of the black circles are ragged or feathery and they are usually surrounded by a ring of yellow.
Spots begin on the lower foliage and move upward. They can appear as early as when the leaves first unfurl. These spots can enlarge and merge. Severally affected leaves often fall off the plants and left unchecked, the entire plant can defoliate.
The fungus can also infect young canes, causing dark purple or black blisters, and even the flowers may show some red spotting. Infected plants will set fewer flower buds and without leaves, the plant becomes stressed and is susceptible to even more problems.
Cultural Controls
Growing Conditions - Make the growing conditions less hospitable for black spot. Black spot is easier to prevent than to cure. The spores can remain in the soil and overwinter on leaves and stems, waiting for favorable conditions. They make contact with the rose by splashing up in drops of water.
Give the plant what it wants. This is true for avoiding any plant disease. A healthy, vigorous plant is less susceptible to problems. Roses prefer a sunny location with well-draining soil and regular weekly watering.
Air Flow - Provide good air circulation around and through your rose plants. Don't plant your roses too close to other plants. Prune to open the spaces between canes, if the plant gets too dense and air can not get through.
Proper Watering - Avoid getting the leaves wet, while watering. There's not much you can do about rain, but at least limit the time the leaves remain wet.
Plant resistant cultivars - Roses are often labeled for resistance, from highly resistant on down. While you are looking for black spot resistance, you might as well look for a rose that is also resistant to rust and powdery mildew. Rugosas, the newer shrub and ground cover roses and many of the Canadian Explorer Series, like John Cabot and William Baffin, show good resistance.
Sanitation - Remove any infected leaves and always do a thorough cleanup each fall. Remove and dispose of any remaining leaves, when you do your dormant pruning in late winter/early spring. Spores can remain on leaves and stems throughout and will reinfect whenever conditions are favorable. Within 10 days of the first symptoms, the disease has already started spreading. Spores can spread by water and wind.
Prune out any canes showing signs of infection. Prune 6 – 8 inches below the infection and only prune in dry weather. Disinfect your pruners with a 10% bleach solution or alcohol, between cuts.
Mulch - Apply a thick layer of mulch around the plants. Mulch will prevent water from splashing up on the plant and spreading spores.
Sprays for Treatment and Prevention
It is easier to prevent black spot than to cure it, but it is time-consuming.
If black spot is a reoccurring problem in your area, you may need to spray your plants weekly, starting in early spring.
Baking soda spray - Dissolve 1 teaspoon baking soda in 1-quart warm water. Add up to 1 teaspoon liquid soap. Spray leaves thoroughly. This mixture works better as a preventive than as a cure. Also offers some protection from powdery mildew.
Bordeaux Mix - This is a fungicide that contains copper sulfate and hydrated lime. It can be used as a powder or mixed with water and sprayed. Bordeaux mix also repels some insect pests, but it can burn plant leaves. It is generally used as a preventative in the spring, before plants leaf out.
Insecticidal soaps with added fungicide - These are basically some type of organic fungicide, often sulfur, added to regular insecticidal soap. The soap helps the fungicide adhere to the plant leaves and spread to coat them.
Neem Oil - Neem is an organic fungicide and pesticide, derived from the seeds of the neem tree. It gets inside the plant's system, so you don't need to worry about coating everything or reapplying after a rain. However, it can burn plant leaves in hot sun. You should not apply need oil within 2 weeks of using a product containing sulfur.
Sulfur - Sulfur both prevents and gets rid of fungus diseases. It is also used to control several insect pests. However it can be mildly toxic to humans and other animals. You should wear protective clothing when you spray it. It can also corrode metal, so use a plastic sprayer . And it can burn plants leaves in hot weather.
Sulfur comes as a finely ground powder. If you prefer to spray it on, look for one labeled as wettable, so that it will mix with water.
Black spot is a fungal disease (Diplocarpon rosae), that affects roses. It causes black spots on leaves, eventually causing the leaves to turn yellow and drop off. Besides looking unsightly, it can seriously weaken the rose plant. Ideal conditions include hot, humid or rainy summers and hot days with cool, damp nights.
Symptoms:
Somewhat circular black spots on leaves. They usually occur on the upper sides of leaves, but can also develop on the undersides.
The outer margins of the black circles are ragged or feathery and they are usually surrounded by a ring of yellow.
Spots begin on the lower foliage and move upward. They can appear as early as when the leaves first unfurl. These spots can enlarge and merge. Severally affected leaves often fall off the plants and left unchecked, the entire plant can defoliate.
The fungus can also infect young canes, causing dark purple or black blisters, and even the flowers may show some red spotting. Infected plants will set fewer flower buds and without leaves, the plant becomes stressed and is susceptible to even more problems.
Cultural Controls
Growing Conditions - Make the growing conditions less hospitable for black spot. Black spot is easier to prevent than to cure. The spores can remain in the soil and overwinter on leaves and stems, waiting for favorable conditions. They make contact with the rose by splashing up in drops of water.
Give the plant what it wants. This is true for avoiding any plant disease. A healthy, vigorous plant is less susceptible to problems. Roses prefer a sunny location with well-draining soil and regular weekly watering.
Air Flow - Provide good air circulation around and through your rose plants. Don't plant your roses too close to other plants. Prune to open the spaces between canes, if the plant gets too dense and air can not get through.
Proper Watering - Avoid getting the leaves wet, while watering. There's not much you can do about rain, but at least limit the time the leaves remain wet.
Plant resistant cultivars - Roses are often labeled for resistance, from highly resistant on down. While you are looking for black spot resistance, you might as well look for a rose that is also resistant to rust and powdery mildew. Rugosas, the newer shrub and ground cover roses and many of the Canadian Explorer Series, like John Cabot and William Baffin, show good resistance.
Sanitation - Remove any infected leaves and always do a thorough cleanup each fall. Remove and dispose of any remaining leaves, when you do your dormant pruning in late winter/early spring. Spores can remain on leaves and stems throughout and will reinfect whenever conditions are favorable. Within 10 days of the first symptoms, the disease has already started spreading. Spores can spread by water and wind.
Prune out any canes showing signs of infection. Prune 6 – 8 inches below the infection and only prune in dry weather. Disinfect your pruners with a 10% bleach solution or alcohol, between cuts.
Mulch - Apply a thick layer of mulch around the plants. Mulch will prevent water from splashing up on the plant and spreading spores.
Sprays for Treatment and Prevention
It is easier to prevent black spot than to cure it, but it is time-consuming.
If black spot is a reoccurring problem in your area, you may need to spray your plants weekly, starting in early spring.
Baking soda spray - Dissolve 1 teaspoon baking soda in 1-quart warm water. Add up to 1 teaspoon liquid soap. Spray leaves thoroughly. This mixture works better as a preventive than as a cure. Also offers some protection from powdery mildew.
Bordeaux Mix - This is a fungicide that contains copper sulfate and hydrated lime. It can be used as a powder or mixed with water and sprayed. Bordeaux mix also repels some insect pests, but it can burn plant leaves. It is generally used as a preventative in the spring, before plants leaf out.
Insecticidal soaps with added fungicide - These are basically some type of organic fungicide, often sulfur, added to regular insecticidal soap. The soap helps the fungicide adhere to the plant leaves and spread to coat them.
Neem Oil - Neem is an organic fungicide and pesticide, derived from the seeds of the neem tree. It gets inside the plant's system, so you don't need to worry about coating everything or reapplying after a rain. However, it can burn plant leaves in hot sun. You should not apply need oil within 2 weeks of using a product containing sulfur.
Sulfur - Sulfur both prevents and gets rid of fungus diseases. It is also used to control several insect pests. However it can be mildly toxic to humans and other animals. You should wear protective clothing when you spray it. It can also corrode metal, so use a plastic sprayer . And it can burn plants leaves in hot weather.
Sulfur comes as a finely ground powder. If you prefer to spray it on, look for one labeled as wettable, so that it will mix with water.
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文章
Dummer. ゛☀
2017年09月13日
When this bacterial disease infects young cabbage-family plants, the leaves turn yellow and plants become stunted and die. In older plants, first signs of infection are usually on the lower leaves, which develop yellow, V-shaped lesions at their edges. The infection gradually spreads toward the center of the leaf, and the veins within this dead tissue turn black. As the disease progresses, the heads of cabbage and cauliflower may rot.
The bacterium is spread by insects and splashing water and on contaminated tools. Warm, humid weather encourages the disease, which occurs in most of North America, but is most common in the East.
Prevention and Control
Plant certified disease-free seed and transplants.
When possible, choose varieties that are resistant to black rot.
If space in your garden allows, follow a three- to four-year crop rotation to avoid planting susceptible crops in the same area.
Use drip irrigation or soaker hoses rather than overhead watering to keep foliage dry.
Destroy or deeply bury infected plants.
The bacterium is spread by insects and splashing water and on contaminated tools. Warm, humid weather encourages the disease, which occurs in most of North America, but is most common in the East.
Prevention and Control
Plant certified disease-free seed and transplants.
When possible, choose varieties that are resistant to black rot.
If space in your garden allows, follow a three- to four-year crop rotation to avoid planting susceptible crops in the same area.
Use drip irrigation or soaker hoses rather than overhead watering to keep foliage dry.
Destroy or deeply bury infected plants.
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文章
Dummer. ゛☀
2017年09月13日
Symptoms of this fungal disease vary with the crop. Beans develop round, black, sunken spots on the pods and stems; on leaf undersides, veins turn black. When the fungus infects cucumbers and melons, the leaves develop yellow spots that dry up and flake away; spots on watermelon leaves are black. Infected fruits develop sunken areas with dark borders. On tomato plants, ripe fruit develops sunken spots with dark centers.
Anthracnose can also develop in other vegetable crops and in strawberries. Wind and wet weather fosters the spread of infection. Anthracnose overwinters in plant residues in the soil. It is an especially troublesome disease in hot, humid regions.
Prevention and Control
Plant resistant varieties such as Calypso cucumber and Charleston Gray watermelon.
Different species of fungi cause anthracnose in different crops. Thus, if you had anthracnose on your tomatoes last year, there’s no harm in planting beans in that bed this year. It can be helpful to wait two years before replanting tomatoes in that bed, though.
Use drip irrigation or soaker hoses rather than overhead watering. Avoid disturbing plant foliage when it’s wet.
Harvest tomato and pepper fruits promptly and wash and dry them immediately to remove any fungal spores on the fruit surface.
Clean up crop debris in fall.
Anthracnose can also develop in other vegetable crops and in strawberries. Wind and wet weather fosters the spread of infection. Anthracnose overwinters in plant residues in the soil. It is an especially troublesome disease in hot, humid regions.
Prevention and Control
Plant resistant varieties such as Calypso cucumber and Charleston Gray watermelon.
Different species of fungi cause anthracnose in different crops. Thus, if you had anthracnose on your tomatoes last year, there’s no harm in planting beans in that bed this year. It can be helpful to wait two years before replanting tomatoes in that bed, though.
Use drip irrigation or soaker hoses rather than overhead watering. Avoid disturbing plant foliage when it’s wet.
Harvest tomato and pepper fruits promptly and wash and dry them immediately to remove any fungal spores on the fruit surface.
Clean up crop debris in fall.
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文章
Dummer. ゛☀
2017年09月13日
Water-soaked spots on blossoms or leaves are an early symptom of this fungal disease. A cottony white growth may develop on the spots. White mold attacks many types of edible plants, including beans, peas, potatoes, soybeans, carrots and cabbage. White mold gradually spreads to all above-ground plant parts. Infected tissues wilt, yellow and die. Cool, wet weather favors the development of the disease. The fungus overwinters in the soil.
Prevention and Control
Choose disease-resistant varieties when possible.
Space plants and rows widely so that plants remain dry as much as possible.
Avoid handling plants when wet.
Water early in the day so plants dry before nightfall. Use drip irrigation or soaker hoses rather than overhead watering.
Minimize the use of nitrogen fertilizers.
Uproot and destroy diseased plants as soon as you notice them.
Prevention and Control
Choose disease-resistant varieties when possible.
Space plants and rows widely so that plants remain dry as much as possible.
Avoid handling plants when wet.
Water early in the day so plants dry before nightfall. Use drip irrigation or soaker hoses rather than overhead watering.
Minimize the use of nitrogen fertilizers.
Uproot and destroy diseased plants as soon as you notice them.
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文章
Dummer. ゛☀
2017年09月13日
Leaves with gray-brown areas surrounded by a dark or yellowish margin are one of the early symptoms of this fungal disease. These discolored areas lack the concentric rings characteristic of early blight, but they may be filled with many small, black spores. Symptoms generally appear on lower leaves first. The fungus can infect a wide variety of plants. In a severe outbreak, septoria leaf spot fungi may also attack seedlings.
The disease is most problematic in cool, wet weather. The fungus overwinters on plant debris in the soil and on weeds such as jimsonweed, horsenettle and nightshade.
Prevention and Control
Plant disease-free seed.
Rotate crops to avoid growing susceptible plants in the same area year after year.
Pick off and destroy any infected leaves.
Mulch around the plants to reduce soil splashing, which can spread the disease.
Use drip irrigation or soaker hoses rather than overhead watering.
In the fall, remove any diseased plant material and destroy it.
The disease is most problematic in cool, wet weather. The fungus overwinters on plant debris in the soil and on weeds such as jimsonweed, horsenettle and nightshade.
Prevention and Control
Plant disease-free seed.
Rotate crops to avoid growing susceptible plants in the same area year after year.
Pick off and destroy any infected leaves.
Mulch around the plants to reduce soil splashing, which can spread the disease.
Use drip irrigation or soaker hoses rather than overhead watering.
In the fall, remove any diseased plant material and destroy it.
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文章
Dummer. ゛☀
2017年09月13日
A powdery white growth on leaves is the first evidence of this fungal disease, which affects beans, cucumbers, squash, pumpkins, lettuce, peas and many other kinds of plants. The fungus can spread to flowers and fruit. New growth and succulent plant tissues are particularly vulnerable to infection. Infected areas eventually turn yellow and dry up; severe infection can weaken or even kill entire plants.
Unlike other fungal diseases, powdery mildew does not require wet foliage for infection to occur, although it does require high humidity. It can spread quickly in warm, dry climates. The fungus overwinters on plant debris.
Prevention and Control
Plant powdery mildew-resistant varieties, such as Super Sugar Snap pea.
Water plants as needed to prevent moisture stress.
Keep plants well spaced and weeded to optimize air flow around the leaves.
Avoid excess nitrogen fertilizer, especially late in the growing season.
Unlike other fungal diseases, powdery mildew does not require wet foliage for infection to occur, although it does require high humidity. It can spread quickly in warm, dry climates. The fungus overwinters on plant debris.
Prevention and Control
Plant powdery mildew-resistant varieties, such as Super Sugar Snap pea.
Water plants as needed to prevent moisture stress.
Keep plants well spaced and weeded to optimize air flow around the leaves.
Avoid excess nitrogen fertilizer, especially late in the growing season.
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文章
Dummer. ゛☀
2017年09月13日
Early symptoms of late blight infection include irregular olive or gray water-soaked lesions on the leaves and stems of tomatoes and potatoes. Both crops are vulnerable to this fungal disease at every stage of their growth cycle. A mildew-like white mold may also develop on or near these lesions. The disease spreads rapidly and can kill crops within a week of infection. (Late blight fungus, Phytophthora infestans, was the cause of the potato famine in Ireland in the 1850s.)
Unlike early blight, late blight does not cause the plant’s leaves to drop off; leaves usually remain attached even after they’ve turned brown and dried up. On tomato plants, infected fruits develop large sunken areas. These may not appear until after harvest. On potato plants, infection of leaves doesn't necessarily mean that tubers will be diseased. Tubers become infected by late blight when fungal spores wash down through the soil or tubers come in contact with foliage at harvest.
To prevent this from happening, remove and destroy all potato foliage and wait a week before harvesting to allow the tuber skins to cure. Monitor potatoes in storage for dry brownish rotted areas; disease symptoms may not appear until after harvest.
Wet weather with cool nights and warm days favors the spread of late blight. In warm parts of the United States, the pathogen can overwinter in soil and plant debris. In cold-winter areas, it survives only in potato tubers left in the soil, though the fungal spores move easily and quickly on the wind, spreading northward each growing season.
Prevention and Control
As a preventive measure, use Actinovate®, an organic fungicide. Add a copper-based product, such as our ready-to-spray Copper Fungicide, when late blight is present.
Buy certified disease-free seed and transplants. Seek out late blight-resistant varieties of tomatoes and potatoes.
Keep plant foliage as dry as possible; use drip irrigation or soaker hoses rather than overhead watering. Space plants generously to ensure good air circulation.
Uproot and destroy any volunteer tomato or potato plants that sprout in your garden.
Plants that become infected with late blight can rarely be saved. As the disease advances, the number of fungal spores produced multiplies rapidly. Remove infected plants from your garden as soon as possible. Bury deeply in the soil or put them in a plastic bag for disposal.
Be thorough when harvesting potatoes. Destroy any infected tubers that you find.
Unlike early blight, late blight does not cause the plant’s leaves to drop off; leaves usually remain attached even after they’ve turned brown and dried up. On tomato plants, infected fruits develop large sunken areas. These may not appear until after harvest. On potato plants, infection of leaves doesn't necessarily mean that tubers will be diseased. Tubers become infected by late blight when fungal spores wash down through the soil or tubers come in contact with foliage at harvest.
To prevent this from happening, remove and destroy all potato foliage and wait a week before harvesting to allow the tuber skins to cure. Monitor potatoes in storage for dry brownish rotted areas; disease symptoms may not appear until after harvest.
Wet weather with cool nights and warm days favors the spread of late blight. In warm parts of the United States, the pathogen can overwinter in soil and plant debris. In cold-winter areas, it survives only in potato tubers left in the soil, though the fungal spores move easily and quickly on the wind, spreading northward each growing season.
Prevention and Control
As a preventive measure, use Actinovate®, an organic fungicide. Add a copper-based product, such as our ready-to-spray Copper Fungicide, when late blight is present.
Buy certified disease-free seed and transplants. Seek out late blight-resistant varieties of tomatoes and potatoes.
Keep plant foliage as dry as possible; use drip irrigation or soaker hoses rather than overhead watering. Space plants generously to ensure good air circulation.
Uproot and destroy any volunteer tomato or potato plants that sprout in your garden.
Plants that become infected with late blight can rarely be saved. As the disease advances, the number of fungal spores produced multiplies rapidly. Remove infected plants from your garden as soon as possible. Bury deeply in the soil or put them in a plastic bag for disposal.
Be thorough when harvesting potatoes. Destroy any infected tubers that you find.
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文章
Dummer. ゛☀
2017年09月13日
This common fungal disease of tomatoes and potatoes first appears as dark brown spots on leaves. On close examination, the spots show a pattern of concentric brown rings. Spots may enlarge and merge, and the leaves will turn yellow and die. Infected plants slowly lose leaves from the bottom up as the disease progresses. Tomato plant stems may also be infected, and eventually tomato fruit will display leathery black lesions. If the disease progresses relatively slowly, gardeners can usually expect to harvest usable fruit, but the quality and yield will be reduced. When potatoes suffer from early blight, their leaves display similar black spots and the tubers become covered with brown, corky spots.
The early blight fungus overwinters in plant residues in the soil; the disease spreads rapidly in warm, humid conditions.
Prevention and Control
Grow blight-tolerant tomato varieties and purchase disease-free seeds and plants.
If space allows, rotate susceptible crops.
Destroy any volunteer potato or tomato plants that sprout in your garden, as they may already be infected.
Keep foliage as dry as possible. Use drip irrigation or soaker hoses rather than overhead watering.
Keep tomato plants staked to encourage good air circulation and minimize contact between plants and soil.
Mulch tomato plants early in the season to slow the disease spread.
Pick off and destroy infected leaves. If the disease continues to spread, uproot and destroy or deeply bury the diseased plants.
After harvest, remove all potentially infected plant debris from the garden and destroy it. Compost the material only if you maintain a “hot” compost pile that will reach 150 degrees F for several days.
The early blight fungus overwinters in plant residues in the soil; the disease spreads rapidly in warm, humid conditions.
Prevention and Control
Grow blight-tolerant tomato varieties and purchase disease-free seeds and plants.
If space allows, rotate susceptible crops.
Destroy any volunteer potato or tomato plants that sprout in your garden, as they may already be infected.
Keep foliage as dry as possible. Use drip irrigation or soaker hoses rather than overhead watering.
Keep tomato plants staked to encourage good air circulation and minimize contact between plants and soil.
Mulch tomato plants early in the season to slow the disease spread.
Pick off and destroy infected leaves. If the disease continues to spread, uproot and destroy or deeply bury the diseased plants.
After harvest, remove all potentially infected plant debris from the garden and destroy it. Compost the material only if you maintain a “hot” compost pile that will reach 150 degrees F for several days.
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文章
Dummer. ゛☀
2017年09月13日
Irregular brown or yellow spots on leaves are an early symptom of this fungal disease, which can infect many vegetable crops. Check the undersides of affected leaves; presence of a hairy white or purple mold confirms the diagnosis. Severely infected leaves may die, and the disease can eventually spread to stems, flowers, and fruit.
The fungus overwinters on plant debris. Downy mildew is a host-specific disease. Thus, if your cucumber plants become infected, that doesn’t necessarily mean your onions will succumb.
Prevention and Control
Grow mildew-resistant varieties such as Fanfare cucumber and Allstar melon. Late-season crops tend to be more vulnerable to downy mildew.
Plant disease-free seeds and plants.
Space plants widely to promote good air circulation. This will help leaf surfaces stay dry, which inhibits infection.
Keep foliage as dry as possible by using drip irrigation or soaker hoses rather than overhead watering.
Control weeds, such as wild mustard, that can harbor the disease.
The fungus overwinters on plant debris. Downy mildew is a host-specific disease. Thus, if your cucumber plants become infected, that doesn’t necessarily mean your onions will succumb.
Prevention and Control
Grow mildew-resistant varieties such as Fanfare cucumber and Allstar melon. Late-season crops tend to be more vulnerable to downy mildew.
Plant disease-free seeds and plants.
Space plants widely to promote good air circulation. This will help leaf surfaces stay dry, which inhibits infection.
Keep foliage as dry as possible by using drip irrigation or soaker hoses rather than overhead watering.
Control weeds, such as wild mustard, that can harbor the disease.
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文章
Dummer. ゛☀
2017年09月13日
This disease produces small, dark irregular spots on tomato and pepper leaves; leaves eventually turn yellow and drop off. This defoliation weakens plants and exposes developing fruits to sunscald. Small, dark, wartlike raised spots with slightly sunken centers may appear on green fruits. Rot organisms are able to enter the fruit at these spots and cause decay. Bacterial spot symptoms are similar to, and often indistinguishable from, bacterial speck.
Very warm, wet weather encourages the development of the disease. The bacteria overwinter in plant residues. This disease is a problem mainly in the East and Midwest.
Prevention and Control
Purchase certified disease-free seeds.
Remove volunteer tomato and pepper plants, which may harbor the bacteria.
Use a three- to four-year crop rotation for susceptible crops.
Space plants well apart and support vines to ensure good air circulation.
Use drip irrigation or soaker hoses instead of overhead watering to keep foliage as dry as possible.
Keep the soil surface covered with mulch to prevent spores from splashing up from the soil surface.
Remove infected plant parts from the garden and destroy them or add them to a hot compost pile.
Very warm, wet weather encourages the development of the disease. The bacteria overwinter in plant residues. This disease is a problem mainly in the East and Midwest.
Prevention and Control
Purchase certified disease-free seeds.
Remove volunteer tomato and pepper plants, which may harbor the bacteria.
Use a three- to four-year crop rotation for susceptible crops.
Space plants well apart and support vines to ensure good air circulation.
Use drip irrigation or soaker hoses instead of overhead watering to keep foliage as dry as possible.
Keep the soil surface covered with mulch to prevent spores from splashing up from the soil surface.
Remove infected plant parts from the garden and destroy them or add them to a hot compost pile.
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