Answer: It's vital to follow the instructions on the label. If the spray is intended for use only on ornamentals, then don't use it on food plants. If it is labeled for use on food, it should state specifically the number of days you must wait to harvest and eat the food. I'm surprised it does not give this information.
Do NOT use this product unless you've checked its appropriateness. I suggest you contact the NPTN -- National Pesticide Telecommunications Network, at 1-800-858-7378. This is a non-profit organization based at Oregon State University, and has detailed information about pesticides.
One way to improve the "stickiness" of sprays is to add a few drops of liquid dish detergent to the mix.
Good luck. I'm glad you're checking into this.
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