"There is simply no room for complacency," she said.
"It is every employee's right to return home safe and well to their loved ones at the end of the working day."
Avo-Plus was charged with breaching Section 6 of the Health and Safety in Employment Act 1992, which stated that every employer should take all practicable steps to ensure the safety of employees while at work.
The company should have identified an exclusion zone of trees under and near to the power lines, de Rooy said.
It also should have made sure its employees wore harnesses while operating the HEWPs and were supervised by a trained spotter to ensure they did not move within a four-metre limit of the power lines.
She said Avo-Plus needed to ensure employees received adequate instruction and information about how to safely undertake such tasks.
"Using the correct equipment for the job, and following to the letter the correct safety procedures could have prevented this unnecessary accident," said de Rooy.