Decades-old DNA match aids battle against pasture pests

AgResearch research associate Nicky Richards and her colleagues, recently confronted with a Porina (Wiseana) caterpillar found in Southland, were challenged with identifying which species of the pasture-munching Porina pest they were looking at.

Some species of Porina pose a much greater threat to pasture on New Zealand farms than others. Although seven Porina species are recognised, and the species can be identified by sight at the adult moth stage, it is impossible to do the same with the caterpillars because they look identical.

The research team suspected the caterpillar found in Southland was from an elusive Porina species known as Wiseana (W.) fuliginea.

To confirm this they needed to analyse an adult moth of the same species.

Mrs Richards explains:

“Unfortunately, no adult W. fuliginea had been found by us in our previous 20 years of field collections. So we had to find another way. Our connections led us to museum specimens held in the New Zealand Arthropod Collection hosted by Landcare Research. There we found dried adult W. fuligineaspecimens that had been identified and preserved after their deaths 33 years ago.”

“We took legs from these long-dead moths to generate genetic sequences – which takes more work when the DNA has broken down over time. It’s basically like putting together pieces of overlapping Lego to build what you need.”

Information gleaned from the 33-year-old specimens proved identical to the sequence from the caterpillar found in Southland. In other words, the researchers had a DNA match.

The work has helped in the development of a new DNA-based method to identify Porina caterpillars. By building a better understanding of this pest, scientists can learn how best to help farmers prevent the hundreds of millions of dollars of damage it can do to pasture on New Zealand’s farms each year.

Environmentally friendly treatments for Porina outbreaks can be explored and species that are the key pasture annihilators targeted, Richards said.

More can be learned about Porina and other pests at