Identification
Potato leafminer fly’s Indonesian name is "lalat pengorok daun" and its scientific name is Liriomyza huidobrensis.
This fly is a major pest of potatoes in Indonesia but does not occur in Western Australia. Details on its identification and management are available in an article on the website of the Department of Primary Industries and Regional Development.
Various natural enemies attack potato leafminer fly in Indonesia. By farmers knowing more about these agents, management of potato leafminer fly without total reliance on insecticides can be possible.
Effective management of potato leafminer fly relies on farmers helping these natural enemies build up to attack adult flies and also the maggots which is the stage that damages leaves.
Being able to identify natural enemies of potato leafminer fly will enable farmers to see how successful they have been in encouraging these helpers.
One of these natural enemies is a predatory fly, similar in appearance and size to a house fly. This predatory fly feeds on adult potato leafminer flies and other small flying insects.
Other natural enemies are parasitic wasps that kill the maggot stage of potato leafminer fly.
At least 19 species of parasitic wasps occur in Indonesia to attack the maggot stage of potato leafminer fly that occurs within their feeding mines in potato leaves.
Assess the number of wasps in a crop by holding potato leaves infested with potato leafminer fly maggots in jars with gauze covers for three weeks. If parasites are present, adult wasps like the ones pictured here will emerge instead of adult potato leafminer fly.
The relative numbers of wasp parasites and potato leafminer flies shows how well the wasps are working to help protect the potato crop from this pest.
Promoting natural enemies
The predatory fly needs high organic matter soil for its soil-borne maggots to breed. Farmers can build organic matter in soil by using animal manure as a fertiliser source and applying compost.
Make sure that there are flowering plants near potato crops because parasitic wasps need nectar from flowers before they can mate and lay eggs.
Only spray for potato leafminer fly maggots if they are present above the spray threshold for this pest.
Acknowledgment
Funding for this work to support Indonesian potato farmers and WA seed potato exports was provided by ACIAR (the Australian Centre for International Agricultural Research) and the Department of Agriculture and Food, Western Australia.