A healthy rose field depends on more than proper planting, irrigation and fertilization. Plants must also be inspected regularly so that signs of diseases and pests can be detected at an early stage.

Not every yellow leaf, spot or instance of leaf drop in an oil-bearing Damask rose (Rosa damascena) field has the same cause. A fungal disease, a small pest, excessive irrigation, nutrient deficiency or an unsuitable cultivation practice may produce similar symptoms. Correctly identifying the underlying cause is therefore essential before any control measures are taken.

In his work on oil-bearing rose cultivation in Isparta, Prof. Dr. Hasan Baydar identifies rose rust, powdery mildew, rose aphids and two-spotted spider mites among the important diseases and pests affecting production (Baydar, n.d.).

Rose Academy Note:
A symptom is a visible change in the plant. The cause is the disease, pest or environmental condition responsible for that change. Effective management begins by identifying the cause, not merely reacting to the symptom.

What Is the Difference Between a Disease and a Pest?

Plant diseases may be caused by fungi, bacteria, viruses or unsuitable environmental conditions. Rose rust and powdery mildew are fungal diseases.

Pests are living organisms that feed on a plant’s leaves, shoots, buds, flowers or roots. Aphids and spider mites are included in this category. However, the organism commonly called a spider mite is not an insect. It is a very small arthropod belonging to the mite group.

Quick Identification Table

This table is intended only as an initial assessment tool. When a definitive diagnosis is required, consult a qualified agricultural professional or an authorized plant health laboratory.

1. Rose Rust

What is rose rust?

Rose rust is a group of fungal diseases caused by species belonging to the genus Phragmidium. Baydar identifies Phragmidium mucronatum as a rust pathogen affecting oil-bearing roses. Current sources also show that other species, including Phragmidium tuberculatum, can cause rust disease in roses (Baydar, n.d.; EPPO, n.d.; Wilson & Aime, 2014).

It is therefore not always possible to determine the exact species of the pathogen from visible symptoms alone. Microscopic examination or laboratory analysis may be required.

What are the symptoms?

Common symptoms of rose rust include:

• Yellowish spots on the upper surfaces of leaves.
• Orange or yellow-orange pustules on the undersides of leaves.
• Powder-like spores released from these pustules.
• Dark brown or nearly black structures later in the season.
• Distorted leaves and premature leaf drop.
• Orange growths or pustules on young shoots.

Severe leaf loss reduces the surface area available for photosynthesis and may weaken the plant’s overall growth.

How can it be prevented?

• Avoid excessive plant density that restricts air circulation.
• Do not leave pruning waste or infected plant material in the field.
• Avoid irrigation practices that keep foliage unnecessarily wet.
• Keep pruning tools clean to reduce the risk of transferring pathogens between plants.
• Inspect the field regularly and record whether early symptoms are spreading.
• Use healthy and, where available, resistant planting material.

2. Powdery Mildew

What is powdery mildew?

The currently accepted scientific name for the fungus commonly associated with rose powdery mildew is Podosphaera pannosa. Older publications may use names such as Sphaerotheca pannosa or Sphaerotheca pannosa var. rosae.

These different names do not indicate that the disease itself has changed. They reflect revisions to the scientific classification of the pathogen over time (EPPO, n.d.).

What are the symptoms?

Powdery mildew is particularly noticeable on young plant tissues:

• A white coating resembling flour or powder develops on the leaves.
• Young leaves may curl and lose their normal shape.
• Shoots and flower buds may become covered with white fungal growth.
• Reddish discolouration may appear around the leaf margins.
• Bud development and flower opening may be adversely affected.
• Shoot growth may slow when infections are severe.

Not every white substance found on a rose is powdery mildew. Spray or fertilizer residues, dust and certain pests may create a similar appearance. Close inspection is therefore important.

Under which conditions does it develop?

Powdery mildew does not require leaves to remain continuously covered with water. Suitable temperatures, favourable relative humidity, dense foliage and poor air circulation may encourage its development.

Excessive nitrogen fertilization can also produce tender, rapidly growing shoots that may be more susceptible to infection.

How can it be prevented?

• Plan planting and pruning to maintain adequate air circulation.
• At the appropriate time, prune weak, overcrowded or rubbing branches.
• Avoid excessive nitrogen fertilization.
• Do not leave infected leaves and shoots in the field.
• Inspect new shoots and flower buds regularly.
• Base irrigation and fertilization decisions on the plant’s actual needs.

3. Rose Aphids

What are rose aphids?

One of the aphid species most commonly found on roses is Macrosiphum rosae. However, several aphid species may occur on the same plant.

Aphids are small, soft-bodied insects that feed on plant sap. They are usually found in colonies around young shoots, leaf stalks and flower buds.

What are the symptoms?

• Small green, pink, reddish or brownish insects appear on young shoots.
• Leaves may curl or become distorted.
• The development of shoots and flower buds may slow.
• A sticky secretion known as honeydew may accumulate on plant surfaces.
• Black sooty mould fungi may grow on honeydew-covered surfaces.
• Increased ant activity on shoots may indicate the presence of aphid colonies.

Why are natural enemies important?

Ladybirds, lacewing larvae, hoverfly larvae and certain parasitoids feed on aphids or limit their reproduction. Unnecessary use of broad-spectrum plant protection products may also harm these beneficial organisms.

The presence of a few aphids does not always justify immediate treatment. Colony size, damage to new growth and the presence of natural enemies should be evaluated together.

Preventive practices

• Avoid excessive nitrogen fertilization.
• Inspect new shoots and flower buds regularly.
• Protect biodiversity that provides habitat for beneficial insects.
• Observe ant activity throughout the field.
• Plan any physical removal of heavily infested shoots in consultation with a qualified professional.

4. Two-Spotted Spider Mites

What is a two-spotted spider mite?

Tetranychus urticae, commonly known as the two-spotted spider mite, is a small mite species capable of feeding on many different plants.

Despite the word “spider” in its common name, it is not a true spider, nor is it an insect. Because it can be difficult to see with the naked eye, the undersides of leaves should be examined with a hand lens.

What are the symptoms?

• Numerous small, pale feeding spots develop on the leaves.
• The natural green colour of the foliage becomes dull.
• Heavily damaged leaves may develop a bronze or brownish appearance.
• Leaves may dry out and fall prematurely.
• Fine webbing may appear between leaves and shoots when populations are high.
• Small moving mites, eggs or shed skins may be visible on the undersides of leaves.

These symptoms may be confused with drought stress, nutrient deficiencies or certain leaf diseases. Examining the undersides of affected leaves is essential for a more reliable assessment.

Under which conditions do populations increase?

Two-spotted spider mite populations may increase rapidly during hot, dry periods. Water-stressed plants and plants covered in dust may become more vulnerable.

Some broad-spectrum treatments may also reduce populations of beneficial mites, allowing pest mite populations to increase.

Preventive practices

• Prevent water stress while also avoiding excessive irrigation.
• Inspect the undersides of leaves regularly during hot weather.
• Reduce conditions that cause excessive dust in the field whenever possible.
• Protect beneficial mites and other natural enemies.
• Avoid unnecessary broad-spectrum treatments.

How Is Integrated Pest Management Applied?

Integrated pest management, or IPM, does not depend on a single product or control method. Its purpose is to manage diseases and pests through regular monitoring, cultural practices, biological balance and, when necessary, legally authorized and carefully selected treatments.

1. Use healthy planting material

When establishing a field, choose plants that show no signs of disease and whose cultivar and source are known.

2. Monitor the entire field regularly

Inspections should not be limited to plants already showing symptoms. Both the edges and interior sections of the field should be examined, following a zigzag or W-shaped sampling route where appropriate.

3. Inspect different parts of the plant

• Compare young and mature leaves.
• Examine both the upper and lower surfaces of leaves.
• Inspect shoot tips and flower buds.
• Record whether symptoms occur on a single plant or across a wider area.

4. Use a hand lens

A hand lens is particularly useful when looking for spider mites, mite eggs and small aphids.

5. Keep records

Record the date, location in the field, weather conditions, stage of plant development and observed symptoms. Re-examining the same locations several days later can show whether the problem is progressing.

6. Apply cultural preventive measures

Appropriate pruning, balanced fertilization, suitable irrigation, field sanitation and adequate air circulation can reduce the risk of many diseases and pest problems.

7. Protect beneficial organisms

Ladybirds, lacewings, hoverflies and beneficial mites are important components of natural pest management.

8. Confirm the diagnosis

If different problems produce similar symptoms, consult a qualified agricultural professional or plant health laboratory before applying any treatment.

9. Monitor the results

Evaluate the effectiveness of any action taken. If the problem continues, reassess the diagnosis, environmental conditions and management method.

What Does Organic Pest and Disease Management Mean?

Organic management does not mean applying homemade “natural” substances to a field without careful evaluation. Preventive agricultural practices, biodiversity, the protection of natural enemies, mechanical methods and inputs authorized for organic production must be considered together.

A naturally derived substance can still cause leaf burn, harm beneficial organisms or contribute to environmental contamination when used at an inappropriate concentration.

Household detergents, bleach, vinegar, alcohol, cooking oils, salt, highly concentrated essential oils and uncontrolled baking soda mixtures should not be regarded as professional plant protection treatments.

Even in organic production, only products currently authorized for the relevant crop and target organism should be used. All applications must follow the approved product label, organic certification requirements, applicable regulations and the recommendations of a qualified agricultural professional.

Prof. Dr. Hasan Baydar’s work includes examples of certain products and practices that were in use when the source was prepared. However, product registrations, authorized uses and approved application rates may change. Recommendations in older publications should therefore not be treated as current treatment instructions.

For production in Türkiye, current information should be verified through the Ministry of Agriculture and Forestry’s Plant Protection Products Database. It is not sufficient for a product to be generally authorized “for roses.” Its current authorization must specifically cover the relevant rose crop, target disease or pest, and intended method of application.

Producers outside Türkiye must consult the current legislation, approved product labels and relevant regulatory authorities in their own country or region.

Seasonal Field Inspection Guide

Ten Common Mistakes

1. Assuming that every yellow leaf is caused by a disease.
2. Examining only the upper surfaces of leaves.
3. Beginning a treatment without identifying the pest.
4. Applying excessive amounts of nitrogen fertilizer.
5. Confusing irrigation problems with disease symptoms.
6. Leaving pruning waste in the field.
7. Using pruning tools on different plants without cleaning them.
8. Mistaking beneficial insects for pests.
9. Assuming that homemade mixtures are completely safe because they are “natural.”
10. Using a product named in an older source without checking its current registration and approved uses.

When Should Professional Assistance Be Sought?

Consult a qualified agricultural professional or plant health laboratory when:

• Symptoms are spreading rapidly.
• More than one problem appears on the same plant.
• A disease cannot be distinguished from a nutritional disorder.
• Cultural preventive measures have not produced results.
• Product quality or yield is at risk in commercial production.
• The use of any plant protection product is being considered.

Frequently Asked Questions

Is a white coating on rose leaves always powdery mildew?

No. Dust, treatment residues and certain pests may produce a similar appearance. Powdery mildew is generally recognized by a spreading white fungal coating that develops on young leaves, shoots and flower buds.

Do orange spots always indicate rose rust?

Orange spore pustules are an important sign of rose rust. However, the exact species of the rust pathogen may not be identifiable from appearance alone.

Can aphids kill a rose plant?

Small aphid colonies do not always cause serious damage. High populations, however, may disrupt the development of young shoots and flower buds. The presence of natural enemies should also be considered when assessing the situation.

Why are two-spotted spider mites difficult to detect?

They are extremely small and usually live on the undersides of leaves. Pale stippling and bronzing of the foliage are often noticed before the mites themselves.

Are plant protection products completely prohibited in organic production?

Organic production permits only those inputs authorized under applicable organic production regulations and certification requirements. Not every substance described as “natural” is suitable or approved for organic production.

Is removing infected leaves sufficient?

Removing infected leaves may help reduce disease pressure, but it is not always sufficient on its own. Field conditions, irrigation, air circulation, fertilization and the extent of infection must be considered together.

What Have We Learned in This Chapter?

• Rose rust and powdery mildew are fungal diseases.
• Aphids are insects, whereas spider mites are mites.
• Similar symptoms may have different causes.
• The undersides of leaves, young shoots and flower buds should be inspected regularly.
• Balanced fertilization, appropriate irrigation, field sanitation and adequate air circulation are the foundations of preventive management.
• Protecting beneficial organisms is an important part of integrated pest management.
• No plant protection product should be used before the diagnosis has been confirmed.
• Product names and application rates found in older publications should not be treated as current recommendations.

Akita Rose Academy Note

Growing healthy Isparta roses requires careful observation throughout the year—not only after plants become diseased. Akita Rose Academy aims to preserve Isparta’s rose-growing knowledge and pass it on to future generations together with current scientific information.

In the next chapter, we will examine flowering in oil-bearing Damask roses, the correct harvest time and the traditional practice of collecting roses during the early morning hours.

References

Baydar, H. (n.d.). Oil-bearing rose cultivation and industry [Yağ gülü tarımı ve endüstrisi]. Süleyman Demirel University. The source provided does not specify a publication date; therefore, “n.d.” is used in accordance with APA style.

European and Mediterranean Plant Protection Organization. (n.d.). Phragmidium mucronatum. EPPO Global Database. View the database entry.

European and Mediterranean Plant Protection Organization. (n.d.). Podosphaera pannosa. EPPO Global Database. View the database entry.

Isparta Provincial Directorate of Agriculture and Forestry. (n.d.). Diseases and pests of oil-bearing roses [Yağ gülü hastalık ve zararlıları]. View the source.

Royal Horticultural Society. (n.d.). Rose rust. View the RHS guidance.

Republic of Türkiye Ministry of Agriculture and Forestry. (n.d.). Plant Protection Products Database. Check current registration information.

University of Minnesota Extension. (n.d.). Roses: Discoloured leaves. View the diagnostic guide.

Wilson, A. W., & Aime, M. C. (2014). The rose rust fungus, Phragmidium tuberculatum, is widespread in the Americas: First reports from California, Oregon, Massachusetts, and Honduras. Plant Disease, 98(11), 1581. https://doi.org/10.1094/PDIS-03-14-0248-PDN.