Roses Down Under

The scale which affects roses is a hard or armoured scale, and it can have serious consequences if left uncontrolled. Scales are white or greyish-white, and 1.5mm to 5mm long. The female scale has no distinguishable body parts - it appears to be a small round fungus, and is permanently attached to the stem. The male scale has wings and flies in the spring. It is said that bush and standard roses are more likely to be affected than climbing roses, and one source said that white roses are very susceptible.

Uncontrolled scale infestations will compete with the plant for nutrients, causing leaves to yellow and drop and eventually whole branches will die, the plant will become unthrifty and eventually expire. Scale is easily seen when the leaves have dropped, and if there is a severe infestation the bottom half of a branch may have little white spots all over it. These have been hidden all through the season, and are exposed when pruning starts.

How do you control scale? Firstly, prune out severely infested branches down to the bud union. Make sure you either burn these affected stems or wrap in them up and put into your rubbish bin - not your garden waste bin! You don’t want to spread the infection any further. Check around the plant - there may be stems or leaves which have dropped on the ground which are also infected, and these should be treated in the same way.

Some sources suggest spraying first with lime sulphur, but all sources say that a dormant oil spray is the best way to go. Oil smothers the scale insects and eventually kills them. If you do have a scale problem it is very important to apply a dormant spray liberally, making sure it gets into all the nooks and crannies of the rose, particularly around the bud union. I won’t quote application rates as brands can differ - just follow the application rates on the container. Insecticides will not get rid of scale because they cannot penetrate the hard shell.

Scale insects are persistent and you are unlikely to get rid of all of them in one season, but good garden hygiene and constant vigilance help to keep them at bay. Beneficial insects, such as lacewing and ladybirds, will devour scale as well as aphids and spider mite.

Many years ago oil as a spray was used far more in the rose garden both in the winter as a dormant spray and in the summer at summer strength, and in those days there were less aphids (greenfly), spider mites and scale. Perhaps we should consider using oil at summer strength through the flowering season instead of other costly chemicals?

Today i find it hard to believe that it's the first day of autumn. This morning when I walked around my garden it was calm and summy, and very quiet because the big machines working on the large subdivision next door don't work on Sundays. So I enjoyed the brief respite from the din, having my own quiet garden back again.

Although it seems hard to believe, the darker mornings and the earlier sunsets are signs that autumn is coming and the roses will soon be blooming their last, so enjoy them while you can. Now is the time to go around the garden with a more critical eye, deciding which roses are perhaps not living up to what you expect, and certainly in my case, there are some which are so covered in rust that i think it would be better to dig them out.

If you do have plants which are going to be discarded, it is a good idea to dig them out some time in the next few weeks while the weather is nice. The hole where the rose was should be forked over to make sure you have taken out all the dead root pieces which will still be in there.

There has been talk for years of 'rose sick' soil, which people said happens when a rose has been dug out. They said that another rose planted in the same spot would never thrive and that was because the soil was 'rose sick'. This always implied to me that somehow a rose plant could contaminate the soild. Certainly if you want to plant another rose where you have dug one out it is better to replace some of the soil, but my honest opinion is that it is more that roses are gross feeders and when a rose plant has been in the same position for some time it depletes the soil of all the goodness which has been in it. Because of that, a wheelbarrow load of soil should be taken out of the hole and replaced with other soil from your garden taken from places where neither tomatoes, potatoes nor roses have grown before. If you have some homemade compost, mix a lot of that into the hole too, as it adds humus and some welcome race elements. If this is done in the autumn it gives the new soil time to settle and it will be all read6y for the new plnts in early winter.

I have been looking carefully at the perennials and annulas which I've been growing among the roses this year. Most of them have been very successful and i will be leaving them in position for next season - hollyhocks, delphiniums, foxgloves and lupins added spiky height, and others like various daisies, geums, and pansies were colourful mounds. Some of the daisies, alas, grew too well and have overwhelmed some of the smaller roses, so i will dig them out in the late winter and plant them in other places in the garden where they can spread to their heart's content.

With the problems I have been having I decided to do some research onthe rust which is found on roses. The species Phragmidium (rst) has a number of different types, each of which is restricted to one or a few host species. For example P. rubi-idea is only found on raspberries, P. violaceium on cultivated blackberries and loganberries, and P. tuberaculatum is the particular type of rust which infects roses. The rust on hollyhocks is different again, Puccinia malvacearum, and fromwhat i read everywhere rust does not jump from species to species, so I don't have to worry that the rust on my hollyhocks is infecting the roses.

Rose rust is a fungus which first appears as small orange or rust coloured spots on the leaves and will become more prominent as the infection advances. At this stage there will also be rust spots on some of the stems too. Some publications say that rust will be more likely to be foundwhen the humidity levels are high and the temperatures are warm to very warm. Certainly when conditions are favourable rust can appear quite early in spring, first showing as small orange spots on the top of the leaves. The infection then spreads quite quickly and there will be many small raised orange spots on the underside of the leaves. If this is left and the weather is giving the best incubation conditions some roses will have all the lower leaves infected.

As the season and the disease prgress the orange spores change to small black pustules or raised areas which contain overwintering teliospores. Leaves which are badly infected will fall off the bush. Some rose bushes affected by rose rust will completely defoliate, and this can threaten the life of the bush.

When looking this up on various websites there are many differing view as to how bad a rust infection can be, from 'most infections are light enough not to require control' to 'if left untreated rust spots on roses will eventuially kill the plant'.

How do you treat it? Spraying with a fungicide of some sort is the recommended treatment. Sprays containing sulphur or copper are the ones mentioned most often. But just as important as spraying is good garden hygiene, picking up all infected leaves as they fall and in bad cases pruning out infected stems and destroying them.

Some cultivars are definitely more pront to getting rust than others. I have a few in my garden which are my indicator plants, and some of them are so badly infected this season they will probably be given a ride to the bonfire heap in the late autumn! But for some reason this year plants which have never had rust before are quite badly infected. It must be the weather conditions which are causing it.

I normally don't spray my roses at all, but this summer I think I will have to get out my sprayer and douse the worst affected roses with a copper spray. I know that will mean most of the affrected foliage will drop, but it may stop the infection from spreading even more. And one day when I feel so inclined, I will go out with a large plastic bag, pick up all the dropped leaves, and put them in the rubbish bin.

When the weather is hot and dry it can be difficult to keep the rose garden looking good.

Did you go away over the Christmas holidays, and perhaps forget to arrange for a neighbour to water your garden? I went away for a few days in January and although the roses were watered they were showing signs of dehydration when I arrived back home. Some of the leaves were brown and brittle around the edges, a sure sign that the rose was under stress.

Perhaps worse than that, though, was the amount of rust which I found on many of the plants. Rust is a fungus disease, and I don't spray the roses much so they hadn't had any type of preventative spray applied and it showed. The roses needed deadheading when I got back into my garden, so I cut the worst affected roses back harder, taking off as much of the affected stems as I could.

Rust shows as little orange spots on the underside of the leaves. The markings show on the top of the leaves quite quickly, and eventually the orange spots turn black, and at that stage the leaves will drop off the plant. It is important to either take the leaves off before this happens, or at least pick them up off the ground, as if they are left the spores of the rust fungus will overwinter in the soil and infect the plant again next spring. Rust is a very specifric disease, so the rust that appears on say, hollyhocks or chicweed, won't spread to roses, and vice versa. Do NOT put any leaves infected with ruse in the compost bin - throw them out with the rubbish or burn them.

It is too early to take rose cuttings. At this stage there is too much risk of hot dry weather for another month or so, and unless you have a greenhouse it is almost impossible to keep enough moisture up to the cuttings to enable them to survive.

The most important this to do in the garden midsummer is to make sure you water your roses well and deeply. Roses flower on new growth, and if the plants don't get enough water the growth will stop and there won't be many flowers in the autumn.

My rose garden mid-summer

leaves showing rust

If you have any rose gardening questions, send me a question and if I can't answer it I'll refer you to someone who can.