"We've had a good reception from the business owners we've visited. There are some issues around communication because of the nationalities of some business owners but we work around that."
Cigarettes tend to be the most targeted item, especially in service station robberies, Mr Wainhouse said.
"Cash is also a target but not a lot of premises hold a large amount of cash," he said.
"Where you have offending like this, and particularly where cigarettes have been taken and they are being disposed of cheaply in the community, people will know about it. We encourage people to pass any information on to us."
Mr Wainhouse said while there was no set pattern to recent robberies in the Whanganui area, there were some similarities between a number of robberies where people have subsequently been arrested.
"With a recent robbery in Hawera, the suspects arrested for that were from the Manawatu area so there is some travel involved. It's not just people committing robberies in their immediate area.
"There's a range of ages, from some in their teens to others in their 20s or 30s, committing robberies.
"It's not necessarily spur-of-the-moment offending. Usually they look at the premises first and work out a plan so we're interested in hearing if people see that sort of activity. If you're travelling around and see something that doesn't quite look right, we want to hear about it when it's happening rather than putting two and two together after the fact. If someone looks like they're up to no good, there's a pretty good chance they are."
While robberies were a problem throughout New Zealand, Mr Wainhouse said Whanganui had the advantage of a smaller population where people knew what was going on and were usually happy to help if they had information to assist the police.
"They may not think there's any relevance but any bit of information we get is helpful. Most people find that sort of offending abhorrent, particularly the brutality of the robbery of the Rangitikei St dairy."
People who have information to report to the police should dial 111 if the matter is urgent, or phone Whanganui Police on 349 0600 or Crimestoppers on 0800 555 111.