There is no question!
Living in a humid, high rainfall climate has the advantage of providing an automatic watering system (it can be tricky finding the “off’ button though) so all the time you don’t have to spend watering or holding a sun lamp over your roses, you can use to spray roses.
The hard bare facts are, that if you want to grow good David Austin rose bushes in a humid environment, you will have to spray roses reasonably regularly. If you just have a few roses scattered amongst other plants the spraying program can be a lot more lenient, and of course you can choose to grow varieties known to be more resistant to disease in this particular climate, BUT to get the best out of them you will have to spray.
NEVER believe a label that says “totally disease resistant” and don’t underestimate the pest problem. They might be totally disease resistant in their climate of origin, but not in our (or your) subtropical clime. It is true, there are roses which get only the merest hint of blackspot. and none of the more spooky diseases, but you can pretty much guarantee these will be the ones most prone to spider mites. If you have a real problem with using environmentally unfriendly fungicides and pesticides there are alternatives, they’re just a lot more time consuming.
The first line of attack will always have to be selection of cultivars. If you don’t want to spray you will have to choose the most disease resistant varieties available.
Local knowledge is the most helpful tool, as books written for other environments won’t help much. Hopefully, this book could be your starting point. Once you have chosen the roses you want you just have to acquire them. Not necessarily that simple. We are lucky here in New Zealand to have a good selection of mail order nurseries that supply a big variety of the David Austin’s, new and old (but not all!). If you are intending to grow your roses without artificial aids, I would impress on you the necessity to buy your roses barerooted exclusively from these mailorder nurseries.
Buying bare-root roses
Any plant you buy potted and leafed up from a local garden centre, is likely to already be harbouring pests and/or diseases. Wherever roses are kept in crowded conditions like that, even if they spray them, the diseases will be around. If you buy them bare from a reputable nursery, at least you know they are as sterile as possible to start, with no spores or eggs hidden in the soil. You will have the added advantage of getting your roses off to the best possible start, without the added stress of a second move.
The price is often similar or cheaper than buying them from a garden centre, but you will need to be better organized and get your order in early, while there’s plenty still available. If you are into instant gratification, like us, the mail order thing can be very agonizing, especially until you receive confirmation of your order and know you’re getting what you want, but the excitement of a box on the doorstep eventually makes up for it.
If you have chosen well and give the plants all the organic treats of which you can think, they should be vigorous enough to shrug off disease and do well. But disease will inevitably arrive, airborne, or on a person or plant from another garden.
Stressed roses get disease
If your rose bushes are under any stress (that you may or may not know about) they will succumb to the disease, to some extent, resistant or not. Therefore, if you’re not spraying your roses, you must make very sure they are never thirsty or hungry or crowded or competing with other plants. If you want or need to move them, always cut them back hard, as there is a lot more stress on a plant moved with lots of foliage and buds to feed, than one cut right back to short canes.
There are remedies available you can easily make yourself, and some now available in shops, that will help combat pests and diseases, without harming you or the environment. Help, being the operative word, as they are nowhere near as effective, and much more time consuming than the inorganic alternatives.
If disease/pests are still a problem on certain roses, and you still don’t want to or can’t be bothered to spray roses, your only alternative left now, is to dig up the offending bushes and give them to someone who will. (Usually in books, they ruthlessly suggest you throw unwanted rose bushes away, but this always seems like murder to us, and we pot them up till we find someone who appreciates the offender. To date, we have never had an unwanted rose that someone didn’t want.)