Rose troubleshooting: FAQs

My rose leaves and flowers are chewed. What does this?
Chewed looking leaves and flowers are a sign of the different beetles. You can pick them off by hand into a can of water or if the infestation is bad then an insecticide spray can be used.

What is causing my leaves to be half eaten?
Rose slugs (or cane borers) can devour leaves at a very fast rate so immediate attention to the problem is needed. A spray with an insecticide will stop the infestation.

Something is causing my rose leaves to roll up.
In the late spring budworms or caterpillars wrap themselves up in a leaf blanket and then eat their way out. Sprays don't affect them as the leaf protect the worms so hand picking off the leaves is the best method to get rid of them.

My rose leaves are dying and have webs underneath.
Spider mites are the smallest of the rose pest and sometimes can't be seen with the naked eye until you notice their webs. This pest arrives in the hot weather and stays on the underside of the leaf sucking it dry. Spray using an insecticide and make sure you get it mainly under the leaves.

What is a rose sucker? How do you recognize one?
Suckers are shoots that grow from the rootstock rather than from the named variety which has been grafted onto it. If nothing is done then the suckers will take over the plant completely and you will have a bush that has reverted. You can tell if it is a sucker if you see that it is coming from below the bud union and by the different leaf form and colour. Don't go by the number of leaflets as a guide. Try to pull the sucker off rather than cutting it as cutting stimulates growth again. Pulling if off causes the wound to make a callous and heal over.

How do I get rid of aphids?
Aphids are the most common of rose pests and are usually green, reddish or brown in colour. They feed on the sap of the tender new growth at the tips of the canes causing growth and flowers to be stunted. A hard spray of water from the hose will knock them off and often they will not be able to return to the plant. You can also remove them with your fingers by stroking the tips with your thumb and forefinger. Ladybugs love to dine on aphids and can devour hundreds in a short time. If the infestation is really bad then the plant can be weakened and an insecticide spray will be needed. Because they are soft-bodied, insecticidal soap is usually sufficient.

What is a rose gall?
Rose galls look like a large, brown growth with warts all over it. They are usually caused by bacteria that have entered because of damage to the stem and can simply be cut out. However if these type of growths are on the roots then it is more serious because they can weaken the plant.

What is causing the white foam on my rose canes?
There is a little greeny-yellow bug that hides inside a small blob of foam. It is called a spittle bug . It sucks the juices from the canes and may cause leaves to wilt. They can easily be removed with a jet spray of water from a hose.

Why have my rose leaves and stems all gone white?
When the weather is hot days and cold nights it becomes the idea condition for downy mildew. This is the worst kind as it will overwinter on the canes and show up again when next year. Spraying at the first sign with a fungicide weekly until all signs are gone will cure it. Some roses will get it if their roots are dry so a mulch is a good idea. Too close planting where air cannot circulate is another reason for this type of mildew.

Why did my rose bush just dropped all its leaves?
A rose drops off all its leaves for two reason. One is to conserve water for the roots when it is too dry and the other is because of stress such as newly planted. Roses have three leaf buds and can produce three sets of leaves. When they get enough water or get stabilised in their new home, they will then put out new leaves and start to grow again.

Why did some of my rose canes die back?
Die-back on roses is not a specific disease. It can be caused by frost damage, canker at the base of the stem, water-logging, mildew, and blackspot. Some colours are more susceptible to it such as yellow and orange varieties.

What is that mossy pincushion on my rose leaves?
These orange, moss-covered looking growths appear on rose leaves in June and July and are caused by the gall wasp. Each is a mass of cells which contain one gall wasp larvae which will hatch in the spring. Gall wasps like to eat aphids. They don't do any harm and can be cut off.

My rose leaves are suddenly twisted and deformed.
Leaf stalks that are twisted in a spiral, stems that are distorted and reddish are caused by a weed killer that was used on a windy day and has drifted on to the roses. Cut off all the infected stems and leaves then feed and water well. If the chemical hasn't reached the bud union or the roots then the rose will survive.

My rose bush has distorted bright red leaves and very thorny canes.
There is a virus type disease called rose rosette and it is caused my a microscopic mite. They usually don't attack hybrid teas mainly shrub type roses. The new growth has bright red distorted leaves and excessive thorniness on the canes. The bush usually dies within one year. This disease can be transmitted by cuttings.

Why is there only half a flower on my roses?
Beetles can get in and eat a hole in the side of the flower causing it to be one sided.

My rose blooms have flecks on them and are deformed. Why?
Deformed flowers are caused by very tiny four winged flies called thrips. This little pest can cause a lot of damage as it hides in the base of the infected flower bud sucking out the sap. Cut off all infected areas and burn then spray with an insecticide to get rid of them making sure you get the spray on the new growth as well as the base of all the flowers. A small hand spray bottle works well and insures more control.

My rose has black spots on the leaves. What can I do?
Blackspot is a plant disease caused by wind borne fungus spores in water drops. They land on the top of the leaves and when growing looks like circular black spots with irregular edges. The infected leaves will finally turn yellow and drop off. If the disease is severe all the leaves will drop off and the plant will have to grow a new set. The quality of the blooms will suffer and the plant will be weakened. Blackspot can not be cured but it can be controlled. In climates where there is a lot of rain in the summer or high humidity it becomes more prevalent. Blackspot can be controlled best by spraying with a dormant oil and sulphur spray in the early spring before the bush leafs out. Then again in the early summer using at half the strength. There are also other ways to keep it control. Clean up all dead and fallen leaves, water when the sun will dry the leaves off or use drip or soaker type hoses, remove first six inches of leaves from the ground up so splashed water won't jump the spores on the leaves, plus feed and water plants well as a weak or stressed plant will succumb more quickly . Finally choose varieties that are disease resistant.