Australian growers of rambutan fruit are using a synthetic plant hormone to improve pollination rates.

Naphthalene acetic acid has recently approved for use in the Northern Territory and is sprayed on plants to change the sex of the rambutan flowers, from female to male.

Dry season temperatures have decreased production for local growers, with the majority of plants producing female or hermaphrodite flowers, the Australian Broadcasting Corporation reported on Monday.

Department of Primary Industry horticulturalist, Mark Hoult, said the acid is showing good results.

"It's been developed over the last 20 years and the use on rambutans is now registered," he said.

"It's principally (been used) to convert the sex ratio of the flowers of rambutan.

"Many of the commercial clones or varieties that have been selected and grown, have a predominance towards what they call functional female hermaphroditic flowers."

Hoult said there is usually a lack of stamens or male flowers which prevents pollination.