Roses have earned a reputation as the temperamental divas of the plant world. While it is true that the romantic rascals attract their share of illnesses, they are easier to conquer than you might think. Fungi cause the vast majority of rose diseases. Regardless of which nasty fungus is attacking your roses, the treatment is pretty much the same. Cut off the affected parts of the plant and destroy them.
Be aware of the symptoms that can arise in an unhealthy rose. Sometimes buds only partially open or not at all. Outer petals can turn pale brown, dry and papery in wet weather or as the result of too much overhead watering. Buds can often develop a gray mold before rotting and dropping off. Purple black spots can form on leaves, and later, a yellow halo develops. Other times, the symptoms are in the cane of the rose, where it might appear discolored. Most of these are caused by fungi.
Know your fungus. Balling, botrytis blight, blackspot, canker and dieback and crown gall, are the most common fungi and bacteria found in roses. Destroy virus-infected flowers and request additional buds for free from the store where they were purchased. Viruses like rose mosaic, rose rosette, rose leaf curl and rose ring pattern can cause broom-like clusters and knots and are extremely nocuous. Stores should refund you because viruses are nearly always spread by using infected material when grafting buds.
To avoid spreading the disease, dip your shears in rubbing alcohol or peroxide after every cut. Then, to get the plants back on their feet, follow this simple routine:
Water the soil, not the plant. Moisture that clings to leaves, stems and flowers is an open invitation to fungi.
Keep your beds clean. Pick up and destroy plant litter as soon as you see it, especially at the base of the plant, where fungal spores thrive.
Cut off odd-looking leaves or canes the minute you see them. Then burn them as soon as you can or toss them out with the weekly trash. Don’t add them to the compost pile, or you’ll be asking for more trouble.
Prune with a vengeance. Each year, cut out all diseased or damaged canes, and any canes more than three years old. Vigorous, new wood is far less vulnerable to diseases and pests. Aim for a structure that lets air circulate to all parts of the plant, especially to the bud union, where new canes develop.
Be careful when you’re working or playing around rose bushes. Nicked or broken canes are an open invitation to fungi.
Spray once a week with this fungicide developed at the Cornell University Horticulture Department: In one gallon of water, mix three teaspoons of baking soda and one teaspoon of non-detergent dishwashing liquid OR one teaspoon of canola oil – BUT NOT BOTH!!
Reduce fungal woes by planting disease-resistant varieties. You’ll find them identified as such in garden catalogs, especially those that specialize in roses. Bear in mind, though, that no rose – or any other plant for that matter – is guaranteed to be completely trouble-free.
Keep in mind that fungi thrive in damp, humid weather. Roses growing in Seattle or Atlanta will always be more prone to problems than those in Tucson or Palm Springs.
You say you’ve got bugs chewing on your prize roses? Well, here’s something the folks at the nursery probably didn’t tell you: Rose pests rarely cause permanent damage. Furthermore, most of them have natural predators that usually keep bad-guy populations in check if you don’t use pesticides.
Understand the symptoms of rose pests. They aren’t clearly visible, but the sick plant is. Distorted, curled and stick foliage can result. Holes in flowers or buds and skeleton leave can appear. Your shoots and flower buds turn black and die, or fail to open at all. When they do, the petals can often be marked with brown spots.
Know your enemy. The most common rose pests are aphids, the rose midge, cane borers, Japanese beetles, the bristly rose slug and thrips. Leaf cutter bees cause slight cosmetic damage (small holes, skeleton foliage), but are great pollinators of other plants, so think twice before killing those.
Dislodge the pests with a strong stream of water. Do this early in the day, so the plant has time to dry out and not harbor tendencies to invite fungi to take root. Spray the plant with insecticidal soap. Encourage predators of rose pests to nearby plants by planting sunflowers or geraniums nearby. Plant garlic or chives in the plant soil. Cut loose any clinging pests and get rid of canes that have holes in them. Cover any holes or external wounds in the plant that you yourself have made, saving the plant with white glue or petroleum jelly. Spray with a steady stream of water again. The excess insecticide will wash off while sufficient levels are absorbed.
Be aware of the symptoms that can arise in an unhealthy rose. Sometimes buds only partially open or not at all. Outer petals can turn pale brown, dry and papery in wet weather or as the result of too much overhead watering. Buds can often develop a gray mold before rotting and dropping off. Purple black spots can form on leaves, and later, a yellow halo develops. Other times, the symptoms are in the cane of the rose, where it might appear discolored. Most of these are caused by fungi.
Know your fungus. Balling, botrytis blight, blackspot, canker and dieback and crown gall, are the most common fungi and bacteria found in roses. Destroy virus-infected flowers and request additional buds for free from the store where they were purchased. Viruses like rose mosaic, rose rosette, rose leaf curl and rose ring pattern can cause broom-like clusters and knots and are extremely nocuous. Stores should refund you because viruses are nearly always spread by using infected material when grafting buds.
To avoid spreading the disease, dip your shears in rubbing alcohol or peroxide after every cut. Then, to get the plants back on their feet, follow this simple routine:
Water the soil, not the plant. Moisture that clings to leaves, stems and flowers is an open invitation to fungi.
Keep your beds clean. Pick up and destroy plant litter as soon as you see it, especially at the base of the plant, where fungal spores thrive.
Cut off odd-looking leaves or canes the minute you see them. Then burn them as soon as you can or toss them out with the weekly trash. Don’t add them to the compost pile, or you’ll be asking for more trouble.
Prune with a vengeance. Each year, cut out all diseased or damaged canes, and any canes more than three years old. Vigorous, new wood is far less vulnerable to diseases and pests. Aim for a structure that lets air circulate to all parts of the plant, especially to the bud union, where new canes develop.
Be careful when you’re working or playing around rose bushes. Nicked or broken canes are an open invitation to fungi.
Spray once a week with this fungicide developed at the Cornell University Horticulture Department: In one gallon of water, mix three teaspoons of baking soda and one teaspoon of non-detergent dishwashing liquid OR one teaspoon of canola oil – BUT NOT BOTH!!
Reduce fungal woes by planting disease-resistant varieties. You’ll find them identified as such in garden catalogs, especially those that specialize in roses. Bear in mind, though, that no rose – or any other plant for that matter – is guaranteed to be completely trouble-free.
Keep in mind that fungi thrive in damp, humid weather. Roses growing in Seattle or Atlanta will always be more prone to problems than those in Tucson or Palm Springs.
You say you’ve got bugs chewing on your prize roses? Well, here’s something the folks at the nursery probably didn’t tell you: Rose pests rarely cause permanent damage. Furthermore, most of them have natural predators that usually keep bad-guy populations in check if you don’t use pesticides.
Understand the symptoms of rose pests. They aren’t clearly visible, but the sick plant is. Distorted, curled and stick foliage can result. Holes in flowers or buds and skeleton leave can appear. Your shoots and flower buds turn black and die, or fail to open at all. When they do, the petals can often be marked with brown spots.
Know your enemy. The most common rose pests are aphids, the rose midge, cane borers, Japanese beetles, the bristly rose slug and thrips. Leaf cutter bees cause slight cosmetic damage (small holes, skeleton foliage), but are great pollinators of other plants, so think twice before killing those.
Dislodge the pests with a strong stream of water. Do this early in the day, so the plant has time to dry out and not harbor tendencies to invite fungi to take root. Spray the plant with insecticidal soap. Encourage predators of rose pests to nearby plants by planting sunflowers or geraniums nearby. Plant garlic or chives in the plant soil. Cut loose any clinging pests and get rid of canes that have holes in them. Cover any holes or external wounds in the plant that you yourself have made, saving the plant with white glue or petroleum jelly. Spray with a steady stream of water again. The excess insecticide will wash off while sufficient levels are absorbed.
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