Wettable sulfur for spraying is available at any good garden center, but whether it is a part of an organic control method, Integrated Pest Management, depends on many things. Is this the first means of control or have other means been tried and failed?
IPM is a 5 step precess starting with
1) Identifying the problem.
2) Indentifying whether some control is necessary
3) Identifying the least toxic means of control
4) Applying that least toxic control
5) Evaluating the results

Not every problem will need some control, by spraying broad spectrum poisons around you not only kill the pests but beneficial insects as well so due care is necessary in any control method. Will just water work? Will soapy water work? Do I really need to do something? Will the beneficial insects control this problem for me? What is the root cause of this problem and can I fix it by making the soil healthier, or growing a different plant here, or growing this plant someplace else?