Answer: It is difficult to comment on the frequency of the spray schedule without knowing what disease(s) and insect(s) you are trying to control. More than likely, after a couple of applications the sprays are either no longer necessary or proving to be ineffective.
I almost never recommend indiscriminate spraying on a regular schedule. A much better approach is to spray only when a particular pest or disease warrants a spray control. Regular applications of pesticides wastes time and money and can be a threat to the environment. Plus, such an approach tends to be harder on the beneficial organisms that keep plant pests in check. When you destroy them, you inherit their job.
A final thought is that no one insecticide or fungicide will control all pests and fungal diseases you may encounter on your many garden plants. It is much more effective to identify the specific problem and determine whether or not a spray control is warranted. If so, choose the best, safest and most effective product for the particular problem.
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