"The one in Lynmore was found in a rubbish bin. The owner fished it out and brought it to me and I'm almost 100 per sure it's a redback, but it hasn't been confirmed by anyone else.
"I've looked at about five or six other spiders since, and they are definitely not redbacks."
Mr Brunel said he hoped the spiders had not found a new home in the city and was happy to identify any spiders people thought were redbacks at no cost.
"Some people could say I was scaremongering, but I'm not. If these spiders are here in Rotorua people need to know about it because they can be very dangerous, especially for kids or older people."
Rotorua Pest Control owner Neil Olive said Mr Brunel was not one to exaggerate and probably had a better idea of what he was looking for.
"I've never seen one, but that doesn't mean they are not here in Rotorua.
"It's been a typically busy year for us with white tails [spiders] but there's been nothing unusual for us."
Redback spiders have been established in parts of New Zealand since the 1980s.
The adult female - the dangerous one - is easily recognised by her spherical black body with a prominent red stripe on the upper side of her abdomen and an hourglass-shaped red or orange streak on the underside.
Females have a body length of about 1cm, while the male is much smaller, being only 3 to 4mm long.
If people believe they have found redbacks, they can call MPI's pests and diseases hotline on (0800) 80 99 66.
