Answer:
Step-by-step explanation:
In order for the sentence to not have parallelism errors it needs to have all three of the options the same. They all need to be nouns, gerunds, phrases, etc. The main thing is that they all share this similarity. Therefore with the sentence in the question the best way to get rid of these errors would be rewriting it to the following sentence.
"For best effects, spray pesticide around the garden bed, plant leaves, and flowers."