Hi Sharon, unfortunately, as Gail suggested, Rugosa's won't tolerate
being sprayed with anything bar water. Blasting them with water, as you
are doing, should help remove them. Are you holding the hose up really
close? Just keep going over them until they're all off , usually they
can't hang on. I also squash them (we have water restrictions here, so
can't use the hose at the moment) Put some rubber gloves on and just
run your fingers firmly along the bud stalk and bud, squishing down as
you go - not the nicest thing to have to do, but it does work, though
blasting them with the hose is quicker. Also, as higgledy suggests,
ladybugs are a natural predator, so you could always try that
alternative. Aphids will produce another colony quickly so you will
have to water blast/squash them every day or so for several days - take
15 mins a day to do this on a daily basis - you'll eventually win!
Also the honeydew that aphids produce attracts ants, which discourages
natural predators like ladybirds, hoverflies etc.so ant control is also
needed. Banding the trunk at ground level if you can with grease or a
cardboard band with something sticky applied to it, or even foil will
stop them from walking up the trunk. Regards Elsie