SAN DIEGO -- Termites are a big problem in California, costing homeowners about $1 billion a year to repair the damage they cause.

Entomologist Gail Getty has studied termites for 15 years and said regular pest control inspections can protect your home. However, she also said homeowners should watch out.

"There is an element of human error in the industry in detecting every singe infestation," said Getty.

It was an error that Getty experienced when she had her own home inspected.

"I found damage later that wasn't found," said Getty.

The Structural Pest Control Board said this is the biggest complaint they receive; they call it under-calling. It's when an inspector misses or overlooks something in an inspection, and 10News discovered this happens mostly during escrow inspections.

That is what happened to homeowner Nick Massalas in his new home in Carlsbad.

"I was shocked because I just moved in the house about 3 months previous and the house was cleared," said Massalas.

A company called North County Exterminators inspected the home for escrow. Their report reads, "No evidence of active infestation or infection was found."

But when Lloyd Pest Control was called, their report said, "Evidence of drywood termites found in attic."

Massalas called North County Exterminators back to his home to give them a second chance. But the company came back with the same answer, "No evidence of termites."

"Somebody is obviously, you know, not being straight up with me," said Massalas.

10News was curious, too.

The I-Team scheduled two more pest control companies to inspect Massalas' home -- Truly Nolen and Dewey Pest Control.

When the inspectors arrive, they were unaware 10News was watching.

They check the inside and outside of the house.

When they're done, both companies told Massalas the same thing.

"They told me I do have termites," said Massalas.

Lloyd, Truly Nolen and Dewey all find termites in the attic, an infestation that North County Exterminators missed.

While 10News can't tell you why North County Exterminators missed the termites in two trips to Massalas' home, experts in the industry said there is an incentive to "undercall" during escrow inspections.

A thorough inspection takes time.

"When I do inspections of homes for research, I can't do it under an hour," said Getty.

Infestations left untreated are a serious problem, Getty added.

"At some point in time there will be structural issues," said Getty.

The cost to the homeowner could range from $300 to $30,000.

Massalas showed 10News where the termites were found in his attic. The area has been marked by one of the inspectors.

"It was sectioned in one section of the attic, in one of the beams. Thank God, so it was a relatively small area," said Massalas.

Professionals told 10News homeowners should have three or four companies look at their property. They also advised homeowners to watch the inspector during the inspection, making sure he inspects the locations claimed, like an attic or crawl space.

If inspectors find termites, experts said to ask the inspector to show where the infestation is and what they found. Experts advised not to accept a single inspection from a realtor.

North County Exterminators came back and treated the termite problem at Massalas' home on their third visit.

If a termite company misses the problem, they do have to come back and treat it at no cost to the homeowner.

If you have termite problems, you have probably heard about orange oil. There are a lot of claims floating around about this product.

Learn more about it Monday on 10News at 6 a.m.