Many questions from radio callers to Garden Clinic on 2GB on the weekends involve roses.
We feel your pain! These are our go-to fixes for six common rose problems.
Words: Linda Ross
Photo - Robin Powell
1. Tiny green insects encrusting new budsare aphids and can be washed off with a strong jet of water. Nature’s Way Natrasoap or Betta
Bug are safe organic sprays for aphids. Ladybird larvae are natural predators; encourage them with plants such as fennel and yarrow (Achillea).
Aphids and other tiny green insects. Photo - Still For Style / Shutterstock
2. Browning of petal edges, withering flowers and black droppings on leaves can be due to thrips. Thrips are a seasonal nuisance especially
prevalent in hot, dry weather. They are sapsuckers, which also pass viruses from one plant to another. Numbers are reduced by heavy rain, spraying
is not very effective. The best defence is to keep your roses in peak condition.
Rose thrip damage. Photo - TRIG / Shutterstock
3. Black-spotted, yellow leaves is caused by the fungal disease black spot. It reduces vigour and spreads to other roses quickly. Encourage
overall rose health by ensuring plants get at least five hours of sunshine a day, no root competition from nearby trees, regular food and water and
good circulation underneath. It’s good to know that warm, humid conditions (no fault of the gardener!) will be most to blame.
Reduce the risk of black spot by alternating Yates Rose Shield with Eco-rose, spraying regularly with seaweed and boosting vigour with liquid fertilisers
such as Harvest or Eco-aminogrow. Spraying rose stems with lime sulphur in winter will clear up fungal spores.
Black spot on roses.
4. White crusty stems and trunks are a sign of rose scale. Keep a watch as once scale gets a serious hold it’s hard to get rid of. Spray
regularly with Eco-oil, or scrub off the insects with an old toothbrush. Stubborn infestations may be solved with Yates Scale Gun.
Rose scale on trunks.
5. Semi-circles cut out of rose leaves are the work of a charming and harmless native bee called the leaf cutter bee. Be pleased they’re
sharing your garden, and don’t worry about the leaf damage.
Leaf cutting bee damage.
6. Yellow mosaic-looking discolouration and distorted leaved can be due to an accidental spray of glyphosate, which is the active ingredient
in the herbicides Roundup and Zero. It can be fixed by watering with seaweed solution as soon as you realise what’s happened. If left untreated the
rose finds it difficult to recover. Roses are very susceptible to glyphosate so weeding around them is best done by hand.
Rose glyphosate damage