Rose diseases and pests

Sporotrichosis or Rose gardener’s disease: Symptoms, Treatment and Prevention

Definition

Sporotrichosis is an infection caused by a fungus called Sporothrix schenckii. The fungus lives throughout the world in soil, plants, and decaying vegetation. Cutaneous (skin) infection is the most common form of infection, although pulmonary infection can occur if a person inhales the microscopic, airborne fungal spores. Most cases of sporotrichosis are sporadic and are associated with minor skin trauma like cuts and scrapes; however, outbreaks have been linked to activities that involve handling contaminated vegetation such as moss, hay, or wood.

Epidemiology

Sporotrichosis occurs worldwide, with focal areas of hyperendemicity. The global incidence is unknown. In the highlands of Peru, the incidence of sporotrichosis is approximately 1 case per 1000 people. China is a serious endemic region. Epidemics have been described in western Australia, Brazil, and South Africa.

Types

Cutaneous (skin) sporotrichosis is the most common form of the infection. It usually occurs on a person’s hand or the arm after they have been handling contaminated plant matter.

Pulmonary (lung) sporotrichosis is very rare but can happen after someone breathes in fungal spores from the environment.

Disseminated sporotrichosis occurs when the infection spreads to another part of the body, such as the bones, joints, or the central nervous system. This form of sporotrichosis usually affects people who have weakened immune systems, such as people with HIV infection (see Risk & Prevention).

Risk factors

  • Wound contaminated with soil and organic debris.
  • Immunosuppression (eg, corticosteroids administration) is likely to increase the risk of disease development, progression, and/or recurrence.

Contagion and Zoonosis

Although zoonotic potential exists, there are no reports of transmission from an infected horse, presumably because tissues from infected horses have fewer numbers of organisms compared with tissues from infected cats.

Associated Conditions and Disorders

  • Sporadic infection affecting a number of susceptible hosts, including horses, mules, cattle, dogs, cats, rats, mice, domestic fowl, and humans.
  • Similar to horses, the most common form of sporotrichosis in humans is cutaneolymphatic.
  • In dogs, the most common forms are cutaneous and cutaneolymphatic; in cats, the disseminated form occurs in addition to the other two.

Causes

Sporotrichosis is caused by a fungus called Sporothrix schenckii. Sporotrichosis usually begins when mold spores are forced under the skin by a rose thorn or sharp stick, although the infection can begin in apparently unbroken skin after contact with hay or moss carrying the mold. More rarely, cats or armadillos can transmit the disease. In rare cases, the fungus can be inhaled or ingested, causing infection in parts of the body other than the skin.

Microscopic view of Sporothrix schenckii

Who Gets Sporotrichosis?

People who handle thorny plants, sphagnum moss, or bales of hay are at increased risk of getting sporotrichosis. The infection is more common among people with weakened immune systems, but it can also occur in otherwise healthy people. Outbreaks have occurred among florists, plant nursery workers who have handled sphagnum moss, rose gardeners, children who have played on bales of hay, and greenhouse workers who have handled thorns contaminated by the fungus.

Symptoms

  1. Once the fungal conidia (spores) are moved into the skin via thorns, scrapes, or other mechanisms, the disease takes days to months to develop.
  2. The first symptom is a firm bump (nodule) on the skin that can range in color from pink to nearly purple. The nodule is usually painless or only mildly tender.
  3. Over time, the nodule may develop an open sore (ulcer) that may drain clear fluid; in other instances, mycetomas may be formed. Mycetomas are areas where sinus tracts are formed from the lymph to the skin surface and discharge granules containing masses of organisms that cause the infection.
  4. Untreated, the nodule and the ulcer become chronic and may remain unchanged for years.
  5. In about 60% of cases, the fungus spreads along the lymph nodes. Over time, new nodules and ulcers spread in a line up the infected arm or leg. These can also last for years.
  6. In very rare cases, the infection can spread to other parts of the body.
  • The disease can infect the bones, joints, lungs, and tissues surrounding the brain (fungal meningitis).
  • Such spreading usually occurs only in people with a weakened immune system.
  • The widespread infections can be life threatening and are difficult to treat.

Complications

Most cases of sporotrichosis aren’t deadly. However, if you don’t treat the infection, you could have the bumps and sores for many years. Some cases can become permanent.

Left untreated, this type of infection can develop into disseminated sporotrichosis. With this condition, the fungal infection spreads to other body parts. Examples include your bones or your central nervous system. You might experience:

  • Joint pain
  • Severe headaches
  • Confusion
  • Seizures

A weakened immune system can put you at risk for this type of sporotrichosis, especially if you have HIV.

If you’re pregnant, antifungal medications can harm your baby. Be sure to discuss any possibility of pregnancy with your doctor before taking any antifungals.

Diagnosis and test

Sporotrichosis is typically diagnosed when your healthcare provider takes a small tissue sample (biopsy) of the infected area of the body. The sample is sent to laboratory for tests (usually a fungal culture) to find out what is causing the infection. Blood tests can help diagnose severe sporotrichosis, but they often can’t diagnose a cutaneous (skin) infection.

Treatment and medications

Treatment of sporotrichosis depends on the severity and location of the disease. The following are treatment options for this condition:

Saturated potassium iodide solution

Although its mechanism is unknown, application of potassium iodide in droplet form can cure cutaneous sporotrichosis. This usually requires 3 to 6 months of treatment.

Itraconazole (Sporanox) and fluconazole

These are antifungal drugs. Itraconazole is currently the drug of choice and is significantly more effective than fluconazole. Fluconazole should be reserved for patients who cannot tolerate itraconazole.

Amphotericin B

  • This antifungal medication is delivered intravenously. Many patients, however, cannot tolerate Amphotericin B due to its potential side effects of fever, nausea, and vomiting.
  • Lipid formulations of amphotericin B are usually recommended instead of amphotericin B deoxycholate because of a better adverse-effect profile. Amphotericin B can be used for severe infection during pregnancy. For children with disseminated or severe disease, amphotericin B deoxycholate can be used initially, followed by itraconazole.
  • In case of sporotrichosis meningitis, the patient may be given a combination of Amphotericin B and 5-fluorocytosine/Flucytosine.

Terbinafine

500mg and 1000mg daily dosages of terbinafine for twelve to 24 weeks has been used to treat cutaneous sporotrichosis.

Newer triazoles

Several studies have shown that posaconazole has in vitro activity similar to that of amphotericin B and itraconazole; therefore, it shows promise as an alternative therapy. However, voriconazole susceptibility varies. Because the correlation between in vitro data and clinical response has not been demonstrated, there is insufficient evidence to recommend either posaconazole or voriconazole for treatment of sporotrichosis at this time.

Surgery

In cases of bone infection and cavitatory nodules in the lungs, surgery may be necessary.

Prevention

  • The most important step in preventing sporotrichosis is preventing mold spores from entering the skin.
  • People who work with roses, hay, or sphagnum moss should cover any scratches or breaks in their skin.
  • They should wear heavy boots and gloves to prevent puncture wounds.
  • People with a suppressed immune system should be exceptionally careful to avoid any contact with rose thorns or soil and moss used for gardening or farm use.

Why does my rose bush have holes and white spots on the leaves? How can I help it?

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As symptoms continue to develop, much of the leaf surface becomes covered by the grayish-white mildew and the leaves may become twisted or distorted. The powdery mildew pathogen can infect any green tissue including flower buds. Severe infections of flower buds cause poor quality flower formation. Powdery mildew symptoms typically begin as discrete circular, powdery white spots that often join to produce a large matt of powdery mildew.

A. Powdery mildew on roses is one of the most widespread and destructive diseases of garden and greenhouse roses. Its name reflects the distinctive grayish-white powdery mats or patches that form on plant tissue.

Powdery mildew is caused by a fungal pathogen (Sphaerotheca pannosa var. rosae) which infects the epidermal or outer surface cells of the host plant cells. The pathogen has a high demand for the nutrients necessary for growth and spore production. It obtains its nutrition from host plant cells by means of small, root-like organs (known as haustoria) that feed within the epidermal layer of the host plant.

The fungal pathogen can infect any green tissue; thus, powdery mildew may be found on leaves, green stems, and flower parts. Young, tender growth is most susceptible. Leaves become distorted and eventually fall prematurely. Powdery mildew spores are easily spread by wind to nearby healthy plants.

Newly unfolded leaves are the most susceptible to infection. Mature leaves are more resistant to infection and usually show no symptom development or, at most, only small local lesions.

Leaves of garden roses often are attacked first on the lower surface and then later on the upper surface. First symptoms are small, raised, blister-like distortions on the leaf that may or may not be accompanied by a slight purpling and curling.

As symptoms continue to develop, much of the leaf surface becomes covered by the grayish-white mildew and the leaves are twisted or distorted. The coating of the leaf by the mildew reduces the leaf surface area available for photosynthesis.

Unopened flower buds sometimes become partially covered with mildew before the leaves show extensive symptoms. The petals are usually not affected, but the sepals can be covered with mildew. Infection of flower buds causes poor quality flower formation.

Environment plays a major role in powdery mildew development. Disease incidence is most severe under cloudy, humid conditions when days are warm and nights are cool. Day temperatures in the 80s and high night humidity provide a very favorable environment for this disease. In our Texas Upper Gulf Coast growing area, powdery mildew tend to be more of a problem during our mid-spring growing season. Once hot weather conditions prevail, powdery mildew on roses usually disappears.

Powdery mildew symptoms typically begin as discrete circular, powdery white spots. However, as these spots expand, they will coalesce or join, producing a large matt of powdery mildew. Although powdery mildew rarely kills a plant, infection reduces host vigor and lowers aesthetic value.

Although powdery mildew rarely kills a plant, infection reduces host vigor and lowers aesthetic value. Some rose varieties are more susceptible to powdery mildew than others.

Powdery mildew is best managed by using an integrated approach or combination of cultural practices including the following:

  • Select rose varieties that are resistant to powdery mildew.

  • Plant roses in full sunlight

  • Allow adequate spacing between plants to provide ample air circulation.

  • Provide roses adequate fertilization to maintain plant vigor, but avoid excessive fertilization.

  • Avoid wetting leaves when irrigating.

  • When possible, use a drip irrigation system to avoid wetting of foliage.

  • Prune infected canes and periodically rake up infected leaves that fall from infected plants (do not place in the compost pile; dispose of through curbside garbage pick-up)

  • Use fungicide sprays with care. Control is mainly achieved by protective sprays.

Fungicides such as triforine (Funginex) and myclobutanil (Immunox) can be used to control powdery mildew. Alternating between fungicides is recommended to reduce the development of fungicide resistance in the natural population of powdery mildew. Through coverage of the foliage (including the upper- and lower-leaf surfaces) and canes is needed.

Always read and follow all directions provided on the label of a pesticide before using. Information given above is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Texas Cooperative Extension is implied.

Learn More About Common Rose Bush Diseases

By Stan V. Griep
American Rose Society Consulting Master Rosarian – Rocky Mountain District

There are some frustrating diseases that will attempt to attack our rose bushes when the circumstances are right for them to get going. It is important to recognize them early, as the quicker the treatment is started the quicker control is gained limiting the stress on the rose bush as well as the gardener!

Here is a listing of the most common diseases to know about with our rose bushes in my Rocky Mountain Area as well as other areas across the Country. Following this common listing are a few other diseases that may need to be dealt with from time to time in some areas. Remember, a disease resistant rose bush is not a disease free rose bush; it is merely more resistant to disease.

A List of Common Rose Diseases

Black Spot Fungus (Diplocarpon rosae) – Black spot on roses can go by other names as well, such as leaf spot, leaf blotch and star sooty mold to name a few. This disease first shows itself on the upper leaf surfaces and some newly forming canes with small black spots upon the foliage and newer canes. As it gains strength, the black spots increase in size and will start to form yellow margins around the larger black spots. The entire leaf can turn yellow and then fall off. The black spot fungus, if left untreated, can totally defoliate a rose bush, causing a weakening of the overall rose bush, thus high stress on the plant.

This particular disease is a worldwide problem for Rosarians and gardeners that grow roses. Even after treatment and control has been achieved, the black spots will not disappear from the foliage. The new foliage should be free of the black spots unless there is still a problem with it being active.

Powdery Mildew (Sphaerotheca pannosa (Wallroth ex Fr.) Lév. var. rosae Woronichine) – Powdery mildew, or PM for short, is one of the most prevalent and serious diseases of roses. This fungal disease produces a white powder along the tops and bottoms of the leaves and along the stems. Left untreated, the rose bush will fail to perform well, the leaves will have a wrinkled appearance and eventually die and fall off.

The first hints that powdery mildew may be getting started are small minutely raised blister looking areas on the leaf surfaces. Once this disease has taken hold enough to wrinkle the leaves, the wrinkled appearance will not go away even after treatment and the powdery mildew is dead and no longer active.

Downy Mildew (Peronospora sparsa) – Downy mildew is a rapid and destructive fungal disease that appears on the leaves, stems and blooms of roses as dark purple, purplish-red, or brown irregular blotches. Yellow areas and dead tissue spots appear on the leaves as the disease gains control.

Downy mildew is a very tough disease that can kill the rose bush if left untreated. Some treatments by themselves may be ineffective, thus using two or three fungicidal treatments 7 to 10 days apart may be required to gain control and stop this disease.

Rose Canker or Cankers (Coniothyrium spp.) – Canker usually appears as brown, black or gray areas on a cane or stem of the rose bush. These areas can be caused by damage from the deep cold of winter or some other damage to the rose bush.

This disease is easily spread to healthy canes on the same and other rose bushes by pruners not being cleaned after having pruned out the damage on infected canes. It is highly recommended that the pruners be wiped down with a disinfectant wipe or dipped into a jar of Clorox water and let air dry, prior to using the pruners for any further pruning after having pruned out a diseased area.

Rust (Phragmidium spp.) – Rust first shows itself as small rust-colored spots on the undersides of leaves and eventually becoming visible on the upper sides as well as this fungal disease gains control.

Rose Mosaic Virus – Actually a virus and not a fungal attack, it causes reduced vigor, distorted leaves, and reduced flowering. Roses with rose mosaic virus are best discarded from the garden or rose bed, and the only sure way to tell if a rose bush has this is to have it tested.

Rose Rosette – This too is a virus that is transmitted by microscopic mites. This virus is contagious and is usually fatal to the rose bush. Symptoms of infection are peculiar or disproportionate growth, extreme thorniness on the new growth and canes, and witches brooms (a weedy splayed looking growth pattern of the foliage resembling a witch’s broom). Use of a miticide can help slow the spread of this virus in the garden or rose bed.

Anthracnose (Sphaceloma rosarum) – This is a fungal infection with symptoms being dark red, brown, or purple spots on the upper sides of the leaves. The spots formed are usually small (about 1/8 inch) and circle shaped. The spots may develop a gray or white dry center that can fall out of the leaf, leaving a hole which can make a person think this was done by an insect of some kind.

Tips for Preventing Rose Diseases

I highly recommend a preventative fungicide spraying program to avoid having problems with these fungal infections. There is not much that can be done about the viruses other than removing the infected rose bush(es) as soon as it has been verified that they are infected with the virus. To my way of thinking, there is no need to chance infecting other rose bushes trying to save the one or two with a viral infection.

For preventative fungicides, I have used the following with success:

  • Green Cure – an earth friendly fungicide (very good)
  • Banner Maxx
  • Honor Guard (generic of Banner Maxx)
  • Mancozeb (simply the best against Black Spot once it has gotten going.)
  • Immunox

My program consists of spraying all the rose bushes as soon as the first leaf buds of spring start to appear. Spray all the rose bushes again in 10 days with the same fungicide. After those initial applications, follow the directions on the label of the fungicide being used for further prevention use. The labels on some of the fungicides will have special instructions for using the product at a Cure Rate, which is used for battling the fungus once it has gotten a good hold on the rose bush concerned.

Introduction

Powdery mildew is one of the most common foliar diseases of roses. It is caused by the fungus Podosphaera pannosa. The conspicuous white growth can affect all aerial parts of the plant, but mainly new soft growth – producing microscopic spores that spread the disease. High humidity is favourable for infection, as well as plants growing in areas where air movement is poor or on plants that are grown in too much shade.

Description

A white, powdery fungal growth on the leaves and shoots. Both leaf surfaces can be affected.

There may be discolouration (yellow, reddish or purple) of the affected parts of the leaf, and heavily infected young leaves can be curled and distorted.

Mildew growth may also be found on the stems, flower stalks, calyces and petals.

Damage

Powdery mildew not only causes the foliage to curl and distort making it unsightly but the fungus also lowers photosynthetic efficiency that results in reduced plant growth and vigour.

The growing tips and flower buds may be malformed but the death of an entire plant is rare. Plants can be severely stunted if they are heavily infected early in the growing season. Rose tissue becomes more resistant to infection as it ages.

Severely infected foliage can prematurely fall off.

Environmental conditions

High relative humidity is favourable for infection. Temperatures bewteen 16-27 degrees Celsius make conditions favourable for the development and spread of the Fungus.

Plants growing in shaded areas or where air movement is poor or the soil is dry can be prone to Powdery Mildew.

Unlike many other fungal diseases, extended periods of leaf wetness are not required in order for the spores to germinate. This means that powdery mildew is often a problem during dry summers.

Life Cycle, Survival and Dispersal

All powdery mildew fungi require living plant tissue to grow. On perennial hosts such as roses, powdery mildew survives from one season to the next as vegetative strands in buds or as spherical fruiting bodies, called chasmothecia, on the bark of branches and stems.

The powdery mildew fungus overwinters as dormant mycelium in bud scales and rudimentary leaves within the dormant buds. (That is why we recommend that all the leaves are removed after winter pruning so that the leave axil does not harbor the dormant spores.)

Infected buds break open in the spring and develop into systemically infected shoots. The fungus sporulates on these shoots, producing large numbers of microscopic spores (conidia) in chains that are carried by the wind or other means to healthy rose tissue where they infect the upper and lower leaf surfaces, thus initiating a new disease cycle.

Rose powdery mildew spreads during the growing season by means of microscopic, air-borne spores produced on the powdery growth.

Treatment and Prevention

Plant roses in full sun. They should receive a full six to eight hours of sun daily.

Plants will grow more robustly and be able to resist powdery mildew better. Shade causes slower moisture evaporation thus creating a breeding zone for powdery mildew and other fungal diseases.

Plant roses in an area with good air circulation and space them well. Moisture evaporates faster. In addition the breeze will dry off the foliage.

Aerate the soil in winter. The roots of roses need an aerated soil; plants are stressed if water logging occurs and stunt new growth, thus being more susceptible to powdery mildew.

Water correctly. Plants that do not receive enough are more prone to fungal infection. Deep soakings, 3 times a week in the hot summer months will suffice.

Choose resistant varieties. Roses vary in their resistance to this disease. Use resistant varieties for low maintenance plantings.

The method of picking off diseased leaves to prevent spreading has become an old fashioned method due to the availability of new, disease tolerant roses and effective pesticides that should be used for major infestations.

Pesticides

Spot checks and preventative spraying are essential. Effective fungicides should be on the shelf in regions where this disease is prevalent. Protecting the leaves by spraying is effective.

During ideal “powdery mildew” weather conditions, spraying on a fortnightly basis is essential. The following fungicides are effective to a degree in preventing the spores to enter the leaves as well as killing spores on the leaves. The most common group contains the active ingredient Mancozeb. Of these are many fungicides registered under various trade names. Several fungicides are registered for control of powdery mildew. Because of the waxy nature of rose leaves, a spreader added to the spray will give better coverage.

We strongly recommend ‘CHRONOS’, a suspension concentrate fungicide with the active ingredient: Prochloraz zinc complex (imidazole) & Prochloraz equivalent.

The old remedy of treating powdery mildew with a baking soda spray has been shown to be ineffective.

The most common

Funginex Triforine

Rose Protector/Rosecare Propiconazole

Dithane mancozeb

Fungicides absorbed by the leaves

(These have a partial curative action as they clear the blocked capillaries)

Proplant proparmocarb

Proparmocarb proparmocarb

Chronos imidazole prochloraz zinc complex

When Using Pesticides always follow the instructions.

Resources

http://web.aces.uiuc.edu/vista/pdf_pubs/611.pdf http://apps.rhs.org.uk/advicesearch/profile.aspx?PID=748

<http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7493.h

Rose Clinic

Symptoms, diagnosis and treatment for all your rose problems

Symptoms: tiny green 1mm long insects gathering in numbers on new foliage and buds.

Diagnosis: aphids are sap-suckers that love the new growth and tender young buds of roses. They cause stems to wilt and can also cause problems by transmitting diseases from one plant to another.

Treatment: remove them with a gloved hand, or if you are squeamish, use a pyrethrum-based spray. Persistent infestations may require the use of stronger sprays such as Confidor or Mavrik. Use strictly in accordance with directions and follow safety precautions.

Symptoms: a white mottled appearance on leaves, browning of petals and flower drop

Diagnosis: pale-coloured roses can be affected by thrips. These tiny threadlike insects suck the sap from the flowers, and can also spread plant viruses. If left unchecked the leaves, new shoots and flowers will become deformed.

Treatment: thrips lay eggs in unopened buds making them difficult to control. They blow in on westerly winds and infest certain light-coloured roses, then pass on to other areas. New flushes of roses will be fine.

Scale

Symptoms: white-crusted stems

Diagnosis: scales are small, sap-sucking insects with a hard cap which is hard to remove. Scales found on roses include cottony cushion scale, red scale and rose scale.

Treatment: Oil sprays such as Eco-oil or Pest Oil kill all stages of scale insects by suffocation and have low impact on beneficial insects.Yates Lime Sulphur is also a useful tool in reducing the population of scale; spray on to onto bare stems after winter pruning. Best treatment is prevention – scale is only found on weak roses.

Two-spotted mite

Symptoms: tiny insects invisible to the naked eye, but seen as webbing and silvering of new growth.

Diagnosis: this insect was formerly called red spider mite, and is hard to control. It loves hot dry weather.

Treatment: insecticidal potassium soap sprays such as Natrasoap work by blocking the breathing pores and dissolving the scale’s outer covering, causing dehydration. These treatments will not harm beneficial insects and have a very low toxicity to people and pets. The use of Mavrik should control this pest but in the case of severe infestation the use of predatory mites is helpful. Contact Integrated Pest Management. P.O. Box 436 Richmond NSW 2753. Yates Lime Sulphur is also a useful tool in reducing the population of two-spotted mite, spray onto bare stems after winter pruning.

Grasshoppers

Symptoms: flowers chewed

Diagnosis: in dry times grasshoppers will eat flowers.

Treatment: because grasshoppers move so quickly, they are impossible to control.

Fungal disease

Symptoms: black spots with yellowing leaves; white or grey powdery coating on leaf

Diagnosis: fungal disease, the scourge of roses grown in humid climates, can cause major decline in the health and vigour of your roses.

Treatment: apply a fungicide once a fortnight. Spray applications should begin when the first leaves appear in spring, and continue through summer and autumn. Recommended chemical products are Rose Shield and eco Rose. These are good, used alternatively. Spray till the plant is dripping with the mixture.

Planting for health

Avoid planting beneath trees as roses do not like competition from tree roots or shade

Avoid planting in saturated or boggy soils or after heavy rainfall

Avoid adding manures or fertilisers in the planting hole – new feeding roots will be damaged if they make contact with these materials at planting time.

Avoid planting too closely, as roses that get tangled into each other are harder to prune and more susceptible to fungal disease.

Avoid tying climber and standard roses too tightly. Figure of 8 loose ties are best

Avoid overhead watering and watering during the hottest part of the day as this will promote leaf fungal diseases.

Avoid using chemical fertilisers until the plants are in full leaf as this will burn young roots. We like organic fertilisers which can we used anytime, enrich the soils, and feed our plants.

Rose care calendar

We’re keen advocates of the ‘prevention is better than a cure’ regime for roses. Here is our annual program for optimal rose health.

Spring

Water: once a week give a full watering can and seaweed solution to the root systems of every rose.

Spray: every second week spray with Yates Rose Shield plus seaweed solution (Plant Health Spray), alternate every second week with eco oil plus eco rose

Feed: every six weeks with organic pelleted rose food

Summer

Water: twice a week give a full watering can and seaweed solution to the root systems of every rose.

Spray: every week with Yates Rose Shield plus seaweed solution (Plant Health Spray), alternate every week with eco oil plus eco rose

Feed: every six weeks with organic pelleted rose food

Pruning: trim by one-third to encourage a better autumn flush

Autumn

Water: once a week give a full watering can and seaweed solution to the root systems of every rose.

Spray: every week with Yates Rose Shield plus seaweed solution (Plant Health Spray), alternate every week with eco oil plus eco rose

Feed: every six weeks with organic pelleted rose food

Winter

Water: no watering

Spray: lime sulphur is spray useful in reducing the population of insects, disease, fungal spores and insect eggs, disinfecting the rose giving it a fresh start for the coming spring season. This must be done onto bare stems, not on leaves, so is a job for just after the winter prune

Pruning: winter prune in late July-August, depending on where you live. Tidy up climbing roses.

Feed: fertiliser is unnecessary, but you can condition the soil around your rose with seaweed (actual seaweed, seaweed granules or pellets such as Seamungus)

Other jobs: Check ties on standard roses and climbers so they aren’t ring barking the stems.

Text: Sandra Ross

#1 Rose Spray
Available Here

“A thorn defends the rose, harming only those who would steal the blossom” – Chinese Proverb

You’re not the only one who loves roses. Pests and disease adore them as well. I don’t have the space (or the time!) to devote to each and every garden pest that may attack, but here I have listed several of the more common rose problems, as well as what to do about them. If you’re having difficulty diagnosing what the problem is, enlist the aid of your local agricultural extension agent or a friendly rosarian. You can also visit our Pest Problem Solver for pictures, descriptions and a complete list of earth-friendly remedies.

At Planet Natural we offer a large selection of organic pest control solutions that are guaranteed SAFE and effective. Got bugs? Visit our Pest Problem Solver for pest pictures, descriptions and a complete list of earth-friendly remedies.

Always start with the least harmful method of control and only “escalate” if you’re not getting results. Also, weigh the damage of the infestation against how much time and money you want to spend. Strive for a balance that will create the healthiest rose bushes at the lowest cost to you and the environment.

Finally, remember to keep a garden journal about your pest control adventures. Documenting what you’ve done, will help you monitor results and can help you learn what works and what doesn’t – given your plants, your garden and your local climate.

Insects

Spider Mites

Common throughout the United States, many species of spider mites attack roses. Found in colonies, mostly on the undersides of leaves, they feed by piercing leaf tissue and sucking out the juices. Signs of mite infestation include yellowed, dry looking leaves with white feeding marks (small dots). Sometimes you’ll notice silvery webbing on the leaves and stems. Mites are tiny (1/50 inch) so you probably won’t see them — just the damage that they are causing. In extreme cases, your rose bushes will lose their leaves. Use neem oil or insecticidal soap to eradicate the mites.

Rose Bud Borers
There are actually two types of borers. Rose curculios are about 1/4 inch in size, bright red with black beaks. Rose leaf beetles are much smaller — about 1/8 inch — and are shiny blue or green. They both damage roses the same way: by boring into the flower buds and preventing the buds from blooming. The least invasive way to get rid of borers is to pick them by hand, as well as by removing and destroying infected buds. To reduce their numbers and prevent them from spreading to other plants, spray insecticidal soap mixed with pyrethrin.

Rose Chafers

Commonly found east of the Rocky Mountains, these insects chew large, irregular holes in rose blossoms. Like the borers, the least-toxic solution is to hand pick rose chafers off your roses, but you can also try using a botanical insecticide to knock down their numbers. Just remember to add a little horticultural oil to the insecticide. That way it will stick to the leaves and not get washed away by rain or watering. The organic insecticides pyrethrum (made from chrysanthemum flowers) and rotenone are good choices.

Leafcutter Bees
As their name suggests, leafcutter bees (smaller and darker than a common honey bee) cut precise round or oval holes from the sides of plant leaves, which are used to form nest cells. In rose plants, more serious problems can occur when they bore into recently pruned stems and canes, causing wilt. To reduce damage caused by leafcutter bees, prune out the injured tips several inches below the damaged area and seal the cut with grating compound or some sort of sealing putty.

Japanese Beetles

Found in most states east of the Mississippi River (and some isolated spots in California, Oregon, and Wisconsin), Japanese beetles (1/2 inch) are metallic green with copper-colored wing covers. Adults are very destructive and chew small holes in both the leaves and flowers of rose bushes. Often feeding in groups, the beetles will start on the upper part of a plant and work downward. If detected, apply milky spore to lawns to attack grubs (larvae) and spray organic insecticides as needed. Also, in the early morning or evening, when beetles are less active, shake them from plants onto tarps and drop them into a bucket of soapy water.

Disease

Most of the common rose diseases are fungal in nature. You can nip that problem in the bud by ensuring good air flow for your plants. That means providing plenty of room between roses, ideally five feet apart from each other. Overcrowding means excessive moisture and gives fungal spores the opportunity they’ve been waiting for.

Botrytis
This fungal disease attacks rose leaves and canes, and may also prevent blooms from opening. Buds and flowers infected with botrytis will appear grayish-brown and shriveled. Surrounding areas may become covered with a fuzzy coating of fungal spores. Prune and destroy diseased plant parts. Apply micronized sulfur to prevent further damage, and provide plenty of air circulation. Also, be sure to keep the area under the plant clean to prevent reoccurrence. Roses under stress are highly susceptible to this fungal disease that can spread very quickly.

Powdery Mildew

If the leaves of your rose plants look like they’ve been treated to an after-bath dousing of talcum powder, chances are they’ve fallen prey to powdery mildew. Severe infection will cause leaves to yellow or brown and can disfigured shoots and flowers. To reduce the chances of powdery mildew, be sure to keep the ground under rose bushes clean and try to increase air circulation. Water only in the morning hours to avoid moisture build up. To treat powdery mildew, try this home made remedy: 1 teaspoon baking soda, 1/2 teaspoon oil and one quart of warm water. Mix and then apply by spray bottle. Green Cure will also get rid of powdery mildew.

Black Spot
A fungal disease that will cover your rose plants in…well, black spots! One of the most common plant diseases affecting roses, black spot can be difficult to control and may also increase the likelihood of winter injury. Spores lay dormant under rose plants throughout the winter and are spread to healthy leaves by splashing water. Infection most often occurs in areas of high humidity and rainfall. Like most fungal diseases, the key to getting rid of black spot is to keep the area under your roses as clean as possible. Remove and destroy any fallen debris or foliage and mulch often. Make sure your roses have proper air circulation and water from below, if at all possible. Apply organic fungicides, like sulfur on a weekly basis.

Canker

Appearing as dead or discolored areas on rose canes, this fungal disease can enter healthy plants through pruning wounds and is spread by splashing water, insects and even dirty tools! If you suspect that your plants are infected with rose canker, do not fertilize or prune as this will stimulate new growth, which is most susceptible to this disease. As with other fungal diseases, keep your plants and the area around them clean and raked up. Get rid of infected plant parts as soon as possible. If necessary, apply copper-based fungicides to establish control.

Gardening Advice: Rose Problems and Solutions

By Teri Dunn Chace | May 22, 2012

1 / 2 Even if you choose a spray that is clearly labeled for the culprit or disease, if you don’t follow the label directions regarding timing and amount (not to mention safe application), it won’t be as effective as you want it to be. Courtesy Timber Press, Inc. 2 / 2 “The Anxious Gardener’s Book of Answers” by Teri Dunn Chace identifies the 100 most common gardening mistakes and gives you the information you need so that you’ll never make them. Or, if you’ve already goofed, it tells you how to fix the mistake. Courtesy Timber Press, Inc. ❮ Photo Credit

Your garden is supposed to be fun — a place to relax in and recharge your batteries, a source of beauty and pleasure. But all too often, things go wrong. Those expensive tulip bulbs you planted last fall never came up. Your lilac doesn’t bloom. The lawn looks terrible. And worst of all, you don’t know what to do about it. The Anxious Gardener’s Book of Answers (Timber Press, 2012) contains great gardening advice to help you solve virtually any gardening challenge. In this excerpt from the chapter “Roses,” author Terri Dunn Chace provides solutions to your most pressing rose problems.

Desperately spraying roses

Roses, particularly the older yet still popular hybrid teas, do get pests and diseases. When you find your bush infested with aphids or Japanese beetles, or mildewed, or marred by blackspot, it’s only natural to be upset. You may storm down to the garden center, scoop up a can of a product whose label mentions treating rose problems, and blanket the bush with spray. But unless you have the right product, it won’t help–and could even be harmful. Even if you choose a spray that is clearly labeled for the culprit or disease, if you don’t follow the label directions regarding timing and amount (not to mention safe application), it won’t be as effective as you want it to be.

The right way to do it: Take a more methodical approach. First, examine the plant carefully, including under the leaves, to accurately diagnose the problem and assess its scope. Next, pick off all afflicted plant parts, as well as any on the ground at its base, and throw them in the trash.

Then research remedies. Japanese beetles can be handpicked and drowned in a bucket of soapy water (do this in the evening, when they congregate). You can blast off aphids with a spray from the hose. Common rose diseases respond to correctly applied sprays, but also to careful sanitation and proper care (including watering on the ground so the leaves don’t get splashed). If you decide to spray, try less-toxic treatments first and always read and heed the label. If the material is at all dangerous–this sort of caution will be noted on the label–protect yourself with eyewear, gloves, long pants, and long sleeves.

If I goofed, can I fix it? With renewed attention and prudent care, a rose will often recover from a common pest or malady; if it doesn’t, it’s time to replace it, possibly with a tougher, more resistant variety. Let this be a reminder to take good care of your rose plants so they are less vulnerable to problems. Desperate spraying is not only foolish and wasteful, it doesn’t remedy the actual problem.

Choosing a disease-prone rose variety

Let’s be honest: we love, and grow, roses primarily for their gorgeous flowers. It’s all too easy to choose one based on the beauty of its blossoms. Once in the ground and growing for a while, the plant indeed produces the blooms you were dreaming of. But soon you begin to see its flaws, mostly in the growth or the leaves, but possibly in buds and blooms, too. Your plant has blackspot (worst in hot, humid weather) or suffers from mildew (which thrives in dry conditions). Or it may even have an incurable rose virus, such as Rose Mosaic Virus (RMV; deformed new growth, yellow mottling on leaves) or Rose Rosette Disease (RRD; distorted, crinkled leaves, dark reddish-purple color all year, rapid aberrant growth and elongation). If caught early, you may be able to fight the common diseases. There is no remedy for the viruses except ripping out and disposing of the afflicted plants.

The right way to do it: Check with a local rose expert before you buy or plant a rose, and tell her you want one resistant to rose diseases prevalent in your area. Or get assistance at your nursery from someone who knows roses (reputable nurseries will sell only virus-free stock). For all the susceptible roses, there are plenty of worthy and gorgeous tough ones whose foliage creates a handsome foil for those beautiful blooms.

If I goofed, can I fix it? Legions of rose lovers have put up with common rose diseases by picking off and getting rid of affected leaves and plant parts or spraying–they love the flowers too much to forgo them. If you are among the smitten, undertake prevention and control wisely. Diagnose the disease correctly, then research the remedies, which can vary from spraying with baking-soda solution to using a fungicide or other chemical control. Get good advice on what to do, and when, from your local consulting rosarian (see the American Rose Society) or rose club.

Remember, too, that practicing good sanitation (get rid of afflicted plant parts), judicious pruning (to improve air circulation in and near the plant), and watering on the ground (rather than splashing the leaves) can help.

Pruning roses the wrong way

When a rose outgrows its space, sending its thorny canes taller or wider than you want them to go, you’ll want to prune. Or perhaps you wish to shape an unruly rose to achieve a tidy, formal look. Either way, it’s important to prune at the right time and in the right way. While it’s often tempting to clip and shape a rosebush in the fall as the leaves drop and the profile of the plant is more obvious, this is the worst time in colder climates. Cold and freezing air can damage the fresh cuts (causing blackening and dieback) and stunt or kill the fresh flush of new growth that cutting often inspires.

Improperly executed cuts can also mar the look of a rose plant. Cuts made too close to a bud cause it to shrivel up and die. Cuts made over an inward-facing bud encourage growth in the wrong direction, contributing to a crowded, tangled bush. Overzealously cutting long-stemmed bouquets of blooming roses in the summer can scalp a plant.

The right way to do it: Generally speaking, the best time to prune most roses is in early spring, just as the buds are beginning to swell and after all chance of hard frost is past. (In warmer climates, where freezing is not an issue, you may safely prune in fall or winter.) Start by taking out winter-damaged and very old canes at the ground. If the plant is grafted, closely cut off unwelcome suckers emanating from below the graft. Next, remove branches that are rubbing, crossed, or too close together. Shorten trailing stems. Aim for a half-dozen or so healthy canes, shortening them to about a foot high. As spring arrives, the revitalized plant will surge into fresh new growth.

A proper cut is made with a sharp, clean pair of pruners or loppers, on a slant, about 1/4 inch above an outward-facing bud. If a branch has leafed out, cut just above a five-leaflet side stem.

If I goofed, can I fix it? Give an improperly pruned rose a year off, during which time it will hopefully generate some new growth and recover, even if it doesn’t look great. Then prune early the following spring as described.

Planting roses the wrong way

A rose planted in poor-quality or poorly drained soil, or in a spot with not enough sunshine, sulks. It may not die, but it will never produce lush, healthy foliage or lots of pretty blossoms, and its growth may be stunted or look lanky. A rose planted too deeply struggles because its root system is not getting sufficient water and oxygen, and it can suffocate. One planted too shallowly, however, has a root system that is too exposed.

The situation is further complicated if you are planting a grafted rose. Set the plant in too shallowly, and it may produce unwanted canes off the rootstock rather than the desirable grafted plant.

The right way to do it: Whether you are planting a bareroot rose or a potted one, set it in the ground at the same depth at which it was growing–there will be a line evident on the main stem. Fine-tune this directive if it is a grafted plant. In mild areas, position the graft union slightly above the soil surface; in colder climates, bury it slightly below the soil surface.

Plant a rose in a sunny, prepared site in good, organically rich soil that drains well. For a bareroot one, create a cone of soil in the hole and gently array the roots over it. For a potted rose, take time to gently tease the roots loose so they can grow into the surrounding soil. To avoid air pockets, backfill the hole about halfway, then water well and let it soak in before continuing. Make adjustments as needed at the end of the job, adding or removing soil until the plant is at the desired depth.

If I goofed, can I fix it? Assuming the rose is not on its last legs after you realize you planted it incorrectly, dig it out. Temporarily move the plant into a large pot or protect the root system from drying out by laying a damp cloth over it while you prepare a new hole, in a better spot if necessary. Replant as described.

Letting a rose produce suckers

Something is obviously wrong when, one or two seasons into life in your yard, a rose you chose for its beauty starts putting out wayward stems with thin, small, or unattractive leaves, shooting up suckers from the base, and producing flowers that are not what you expected. You’re so disappointed and disgusted, you’re ready to tear it out.

Were you sold a mislabeled plant? Maybe. But more likely you didn’t protect the graft, and winter’s cold, or something else–a wayward string trimmer?–knocked off or killed the grafted or top plant. What you are seeing is growth produced by the rootstock. Rose rootstocks are not chosen for their beauty, but for the cold-hardiness, uniformity, and even disease-resistance they can confer to the more attractive plant grafted on top.

The right way to do it: Gardeners who grow roses in colder climates have two choices. If you want to enjoy a rose that is grafted atop a rootstock (if you are not sure if the one you are contemplating is grafted, ask or look for the telltale bulge in the stem just above the roots), plant it correctly. Set it so the graft, or bulge, is slightly below the soil level, and mulch several inches deep over the plant to help it through the winter months.

Alternatively, shop for an own-root rose. Many shrub roses are in this category, including lovely heirloom varieties. Make sure it is rated hardy in your climate zone. If winter kills or harms the top, when the roots send up new growth, it will be the same plant you expected and wanted.

If I goofed, can I fix it? If you planted a grafted rose too shallowly and winter (or a mishap) killed the top, there is no recourse. Tear out the remains, including all of the unwanted rootstock, and start over. Invest in a cold-hardy own-root rose, or plant a grafted rose properly and be sure to mulch it well come winter.

This excerpt has been reprinted with permission from The Anxious Gardener’s Book of Answers, published by Timber Press, 2012.

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