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Tracking potato tuber moth trends through crop monitoring

A potato tuber moth larva on a potato leaf

Tracking potato tuber moth trends through crop monitoring

Fruitfed Supplies Crop Monitoring Scouts are providing the boots on the ground as part of a Potatoes New Zealand Potato Tuber Moth (PTM) trapping project.

The PTM monitoring project is running for the third year across the wider South Auckland growing area with pheromone traps placed into potato crops to attract adult PTM moths. 

This season ten growers from Putamahoe, Pukekohe, Tuakua, Onewhero and Pukekawa are involved, each making a 10 ha block available for the traps to be placed in. The idea is to build a regional summary of PTM pest numbers across the season to help growers make better informed decisions, alongside in-field crop monitoring, about the degree of pest risk in their own crops and any crop protection applications that may be required. 

Carmen Pieterse, Crop Monitoring Coordinator, explains Fruitfed Supplies’ involvement: “We co-ordinate contact with the participating growers and place traps in their blocks. Then our Scouts collect moth counts from each trap every seven days, with the first counts for the 2023-24 season collected in the last week of October. In the field, we also replace the pheromones in each trap every four weeks. Growers have the option of utilising our Scouts for in-field monitoring and regular replacement of yellow sticky traps.”

Fruitfed Supplies personnel also collate the trap data each week, supplying this in graphs and tables for Potatoes New Zealand to share with growers.
Daniel Sutton, Research, Development and Extension Manager for Vegetables New Zealand, says that more than 170 trap counts were collected in the region last season. “Adding this season’s data helps us all build a valuable understanding of PTM population variation across the season.”

Up to the end of November, Pukekawa had the highest catch numbers with eight moths per day and Pukekohe the second highest catch with six moths per day. The average catch, until that point, was five moths per day, keeping the whole area in the moderate risk bracket. (Moth catch risk range: zero to four is lower risk, five to nine is moderate risk, 10 plus is a higher risk).

With PTM larvae being found in potato canopies in early December, Daniel’s advice was for growers to continue regular monitoring of their crops throughout the season and being aware of soil cracks developing during drier periods as these give moths and larvae a direct route to tubers.