Hundreds have been stolen in bulk from orchards, with thieves using rakes to drag fruit straight from the tree before selling them on.
The fruits themselves are immature this time of year so consumers buying them will have a “very bad eating experience”, an industry body said.
In New Zealand avocado sell for between NZ$4-6 (US$2.8-$4.2; £2-£3) each.
The CEO of New Zealand Avocado, Jen Scoular, described the thefts as small-scale and opportunistic.
“In New Zealand we don’t import avocados, and we’ve had a moderate supply of avocados in the last season and a big increase in demand,” she told the BBC’s Newshour programme.
“People want them, people know they need them in recipes, so the thieves are thinking maybe we’ll be able to get a good price for these avocados.”
The thefts have been happening at night, and local police said although they were happening over a wide area they had just one suspect in mind.
“Anything that is going to make them money, they are going to hook on to,” Sergeant Aaron Fraser told Stuff.co.nz.