Rose Problem

Roses do have pests and diseases that can attack them at different times. Please look at examples provided and then decide what looks closest to what you have. Click on the image to find out what the problem is and how to correct it.

There are other rarer problems which are not covered here. If none of the images show what you have please either email a photo to admin@rossroses.com.au or text image to 0432 202 943 and we will identify the problem for you.

Appropriately named due to the black spots which appear of the leaves. This rose problem is a fungal attack mostly occurring in spring and late autumn however it can occur at any time if the conditions are right. Warm sunny days with cool dewy nights and high humidity are ideal conditions for the spots to form.

Black spots show on the topside of the leaves, which turn yellow and drop off. If not treated the whole plant may be defoliated. When temperatures rise in midsummer the problem is reduced and can disappear. More likely to be seen on yellow and orange coloured varieties yet can occur on all but the healthiest varieties.

Once the spots are on the leaves it is not possible to remove them for the spots are dead parts of the leaf. To control the best solution is to spray with a systemic spray which will enter the leaves and kill the fungal problem.

Best controlled with a systemic spray with the active ingredient called ‘Mancozeb Plus’. This can be found in many forms with Rose Guns, Blackspot Control and Rose Fungal Spray all available. Eco Oil also recommended for control.

Blackspot is one of the only problems which can ruin the fun of growing roses. When planning a new garden ask about blackspot resistance roses from us. If a variety is highly susceptible to this problem maybe it should not be purchased.

A white powder on the leaves which can be rubbed off is most commonly called Mildew. Two forms of the fungus exist with Downy and Powdery Mildew their names. On roses most common is the powdery Mildew. It mostly appears on the top of the leaves, tips of the shoots or buds however it does not discriminate and can occur on any parts of the plant. Most commonly found when the weather is warm but moisture is present, usually spring and autumn. Most tropical regions with constantly high humidity will find mildew a problem in roses.

One of the best natural sprays is milk - 1 part milk to 10 parts water sprayed on the leaves which can transforms the white power to a grey/black appearance which shows it has killed the Mildew spores. Can be used once a week. If very humid and need more control use ‘Mancozeb Plus’ or ‘Eco-rose’ which are contact spray onto the leaves.

In severe cases plants can be defoliated by mildew and control must be taken. In tropical areas a selection of mildew resistant varieties should be considered.

Mildew is also closely linked with highly scented roses with the genetic susceptibility known. Newer varieties are much more resilient but some exceptions can still occur.

Rusty-red spots on the underside of the leaves are an indication of this fungal problem. The leaves can show small yellow spots on the tops of the leaves. On touching the rust spots will leave an orange powder on your fingers. Only in severe cases will plants affected with rust lose vigour, but it should be treated when it appears, mostly in late autumn.

Worth trying a milk spray - 1 part milk to 10 parts water sprayed up under the leaves to contact the rust area.

The best fungicides to use are ‘Mancozeb Plus’ or ‘Eco-rose’. These sprays will kill the spores. Best if sprayed under the leaves for direct contact with the pustules.

Rust is a problem mainly associated with a small number of rose varieties and only in certain weather conditions.

If you have a flower which will not open and looks similar to this the rose has the fungal problem of Botrytis. Botrytis is a fungus which forms on the rose petals and sticks them together stopping them from opening normally. Occurring mostly in wet climates and when the rose petals are particularly thin and soft.

There is little that can be done when a rose has been affected however prevention is the best solution. When selecting roses for a garden where constant moisture can be present ask the supplier if the rose may be prone to Botrytis or if the rose flower has soft petals and may be affected. Some suppliers may not know this information however rose experts should know immediately what petal strength any particular rose has.

Fungal sprays can help in limited ways however if conditions are right there is little that can be done. Best to cut off infected flowers and wait for the next flowering which is likely to be better.

On occasions a rose may have flowers with pink or red spots on them. The most common solution would be a bruising of the petals by rain or small hail. This is not a major problem with roses but can occur mostly on white or light coloured varieties and also mostly on those with soft petals.

Although it will give an unsightly flower it is not a concern for unless the conditions are ideal it is not likely to be a common occurrence.

On rare occasions a flower appears with what is best described as a malformed flower growing inside another flower. Known as Vegetative Centres they occur rarely but at some time in a rose grower’s life may cause a gardener concern.

Several varieties are known to produce this effect constantly and seen more commonly on roses which have been fertilised heavily.

If the variety is known for this effect there is nothing that can be done as it is in the genetics of the plant however if it only occurs on rare occasions cut off affected flowers and reduce how much fertiliser used.

Most leaves with irregular cuts or leaves totally removed are most likely been eaten by Caterpillars. There are several types which prefer roses and all are quite small.

As their life cycle is quite short unless a huge amount of damage is being caused it may be to just live with it. If you must control several specific bacterial caterpillar sprays exist which will be safe to other insects. ‘Success’ or ‘Dipel’ can be used to control as well as ‘Eco-neem’ as a more natural method.

Caterpillars can also ‘drill’ holes through forming flowers which appear as flowers with holes.

Leaves look speckled, pale colour; underside of leaf looks dusty with masses of tiny mites. Fine webbing found amongst leaves and stems. Breed in plague proportions in very hot dry dusty situations of midsummer.

Reduce the dryness of the area with water. Squirt water up into the foliage and wet the mulch and soil each morning for 3 or 4 days straight. This will stop their breeding as too damp. Keep moist.

No point in spraying with miticides as mites quickly become immune to each spray. No other insect sprays work either. ‘Eco-Pest Oil’ or ‘Pest-Oil’ will help if can be sprayed under leaves for contact with mites. Water is easiest and works best. Cause is very hot dry situations in the heat of summer – paving, gravel, stones, pots on verandah or patio, reflective heat off fence or walls are ideal situations when mites populate rapidly. Mulch the soil and keep wet in hot weather, no risk of fungal problems as still very hot and drying atmosphere. If blackspot did show up it is easier to control than mites.

Masses of small green or orange insects in masses found on the top new growth of a rose are called Aphids. Very common on the first new shoots in spring and less common in autumn.

They suck into the shoots, can distort the flowers and leaves, also leaving a sticky residue on the leaves. This attracts ants which ‘milk’ the aphids for the ‘honey dew’ residue. Ants move the insects to other parts of the bush spreading them wider.

Squirt the insects off with water jet from the garden hose, or throw soapy water over the insects. Rub off small colonies with fingers. Natural predators will help reduce these pests - Parasitic Wasp, Ladybirds and their nymphs, hoverflies, and birds all control these insects very well however natural predators will need time to build up their numbers.

Other options are ’Pest-Oil’ (not white oil) or ‘Eco-Pest Oil’ (a vegetable oil) which all coat the insect with oil and suffocate them. If in plague proportions use ‘Confidor’ which is of low toxicity.

Clusters of scale covered insects, found in bark of the bush or on old branches, usually at the base of the older roses. Branches slowly deteriorate. Spray heavily with soapy water, or ‘Pest-Oil’, or ‘Eco-Pest Oil’ to smother the insects. May need to do several times. Ants move the scale around the plant, so eliminate the ants that ‘milk’ the scale.

Usually found on very old bushes, can kill the rose if smothered in scale. Can use ‘Confidor’ but soap or oils usually work. Not one of the most damaging rose insects but control should be undertaken to avoid more severe problems in the future.

Appearing as brown bruising on the petal mainly on white and pale colours. A multitude of extremely small insects swarming on the petals. Blooms don’t open, petals stick together.

No easy to remedy. They blow in with hot north winds from paddocks and dry roadside grasses in country regions. Mostly effects the early spring flowers, but new growth will follow with clean petals. No cure, if spray one day fresh insects the next.

Very disappointing to see the damaged flowers, particularly if roses only flower in the spring.  This is one of the rose problems which although unsightly is best to just accept for it is no major problem and very short lived.

This insect infects twigs and branches and is about 5mm long. Although seen on occasions on roses it is not known as a pest and just using a rose bush to lay its eggs. It does produce copious amounts of honeydew which may cause sooty mould or attract ants.

No control is needed as it is not an insect we need to worry about.

Sometime can be confused with damage caused by caterpillars except main difference is the location of the damage. Caterpillars work higher up in the plant however Garden Weevil damage occurs mainly on the lower leaves as this is where they collect under the dry mulch or dry soil.

Best way to control is by flooding the ground by either forming a moat around the plant or continued deep soaking of the area with drippers or a hose. This also helps the plant to form new leaves and establish quicker so the problem also seems less obvious.

Can spray with ’Confidor’.

If flower buds and young shoots are being chewed but no insects visible it may be earwigs. These insects come out at night and can be found in leaf matter under the plant, under bark or under rocks if available. In some cases the insect can be found amongst the petals of the rose flower.

Best control is to trap them – crumple newspaper into an empty flowerpot, dribble vegetable oil or linseed oil onto paper, lay pot on its side amongst the plants. They will hide in the paper during the day. Dispose of next day, do over and over again, will reduce their population. More likely if garden is very dry, so mulch well to retain moisture.  Most common in spring and autumn.

Can spray with ‘Confidor’.

This is another interesting insect which can confused gardeners. It is a good insect being the larvae form of a Ladybird. It enjoys chomping on Aphids in larger numbers than the adult bug so care must be taken to avoid using insecticides if these are seen.

Although not a rose problem this goldish stationary aphid can confuse gardeners with what to do with it. What are they? These are aphids which have been mummified by a Parasitic Wasp. The Wasp will lay its eggs in a live aphid and the developing new wasp will form a cocoon inside the Aphid killing it.

When it emerges the female wasp can lay up to 800 eggs a day and in very little time will control your aphid infestation.

Care must be taken not to spray aphids with insecticides for this will kill the wasp and deny them ‘hosts’ for their next generation. It takes around a week for the wasp to build up numbers great enough to control a mass of aphids so ‘soft’ options are recommended.

Another of the good insects in the rose garden. This is the adult stage of the Ladybird beetle and one which we enjoy seeing. A vital control of the rose pest Aphids these insects feed on them and in time reduce the population of the Aphids significantly.

This is another good bug which can be seen on rose bushes. These too are insects which are predators of Aphids. Although quite small, insects in larger numbers can make an effect on Aphid when combined with other insects.

Always avoid using insecticides on your Aphids for given enough time nature can attend to your Aphid problems.

There may be times in a gardener’s life when this is found. It is caused by Glyphosate spray. Roses are as susceptible as grasses and other plants to this spray, but can overcome the damage if it is not too severe.

If accidently sprayed it takes time for the plant to recover. Cut back very severely to eliminate as much sprayed material as possible and keep moist. Can take 12 months to begin to recover. Most gardeners will remove the plant which is sometimes safer as there is no guarantee the plant will recover.

Another similar look is called Spring Dwarfing where the first shoots after spring appears with this wispy, ferny look. Unknown what causes this problem which only occurs in spring but plants do grow out of it. May be linked with ingredients in chemical sprays which may have translocated into your property from other locations over winter.

A ‘new’ disease identified in Australia by Dr Thomas in the early 1900’s. Not commonly found however an infected plant rarely survives. This example was photographed over 40 years ago.

Thought to be a complex of viruses it is said to be spread by insects such as Aphids. Other thoughts relate to chemical use. Unfortunately few cases are ever seen so hard to have tested to find out more.

Symptoms vary from stunted growth through to curling of the leaves. Affected leaves seem brittle and will fall from the plant with slightest touch. Occurs mostly on the new growth which appears in spring.

This form of deficiency would have to be the most common in the rose gardens of Australia. Caused by the inability of the plant to access the element Iron from the soil. Most common cause would be soil with a very high pH level of 9 or 10.

Commonly seen in South Australia or soils where limestone is present. Can also be found in new housing properties and mostly identified where the mortar was being mixed.

Most common and quickest remedy is the use of iron chelates however this is not a long term solution. Changing the pH of the soil to a more neutral level is the best solution. Adding plain Sulphur reduces the pH level and allows the plant to access the Iron existing in the soil. It is not a quick fix and many applications of Sulphur are needed over several years.

Many roses across Australia may have the appearance of these examples or other variations. Two versions exist with Prunus Necrotic Ringspot and Apple Necrotic Ringspot the official names.

Caused by either infected propagation material or rootstock there is nothing that can be done if your plant shows this. Another name for this problem is Heat Induced Chlorosis for the effect is more prevalent in the heat of summer or in hot weather.

Although the plant will always have this look it is in the cellular level of the plant and can only affect other plants in the propagation process. Cutting flowers, Pruning or Insects will not move it to other plants.

Most good nurseries now use a Virus Tested Understock for their rootstock and new varieties are unlikely to have the virus however old favourites and many Heritage Roses do not have ‘clean’ plants so it is just something that must be endured if wanting these varieties.

Research has identified ways to lessen the effect however the large cost eliminates rarer varieties from being cleaned up.

Commonly found on roses during summer. Caused mostly by watering where salt in the water is deposited on the leaves along the edges and the sun evaporates the water leaving the salt which then burns these areas.

Solution is to avoid getting too much water on the leaves with watering. Using drip irrigation is both more efficient and also eliminates this problem.

Properties close to the sea can also see this problem occur. In these cases it is best to wash plants with a hose after it is suspected salty winds may have deposited salt on the plants.

Have seen this occur with foliage sprays where the same action takes place.

Not a problem widely seen however some sprays do cause a burn on the leaves as per this example. More likely due to spraying products such as insecticides or fungicides on hot days where the water evaporates and the sun burns the residue remaining.

Always best to consider spraying when the weather is not expected to be coming into hot weather or if rain is forecast.

If your roses are constantly being eaten overnight you may have an herbivorous animal attacking the plants. This is most common in outer suburbs or heavily tree areas.

Most common animals would be kangaroos and possums and also rabbits have been known to eat roses. Low growing bushes are more likely to be eaten by rabbits and kangaroos, taller bushes by kangaroos and climbers or shrubs can be eaten by possums. There have been cases of roses being eaten by sheep, goats and horses.

Control is one of the hardest in a rose garden. Fencing can control ground feeding animals however those attacking from above simply climb over a fence or gain entry via overhanging branches.

On the market are ultra-sonic animal scarers and barriers. Some success has been achieved by Quasier chips and Chilli sprays but many say this is short lived.

On several occasions I have been confronted by a sample as above. This damage was caused by Galahs. The birds open the stems of the rose bush to obtain moisture from the sappy new growth of the rose bush.

In most cases this damage occurs in late spring through summer and appears worse when in drought years. Properties where Galahs and Parrots are in large numbers will see this problem more regularly than most city dwellers.

Little can be done except the use of chilli or bitter sprays and these are effective only occasionally. Best control I have seen is to string through the garden numerous lines of fishing line. The birds try to land on the roses and their wings touch the lines which they cannot see and cause them to retreat.

Only other option I am aware of is bird scarers which may annoy the neighbours more than the birds.

Sometimes confused with Crown Gaul however this problem exists in the open air and not in the ground.

Caused by roses which want to send out roots from nodes. A callus forms at the nodes and turns into woody material when in the air.

Not a common problem but have seen on several varieties which are very easy to grow as cuttings. Their ability to form own roots makes them more susceptible to this problem. Seen widely on weepers Dorothy Perkins, Sea Foam and Bloomfield Abundance as well as the bush forms of these varieties and Alba Meidiland.

Nothing can really be done to correct this problem however a strong prune will give new growth and the problem will have been removed for a time period.

Not a typical looking specimen but a mass of woody growth at or just under the soil. Not commonly found and can be easily confused with Aerial Canker.

Caused by a soil bacteria entering a wound in the rose. A proliferation of growth occurs as the bacterium grows and the rose tries to health the wound.

Not much can be done once a rose infected except taking out the plant. The bacteria in the soil affect future roses growing in the same region. Soil can be removed or fumigate the area. As only enters the plants through a wound it may be best to grow in a pot until plant established.