Potentially damaging populations of the weevil have been found from Greymouth through to Karamea.
The crown institute was asking southern West Coast farmers who suspect they may have weevils to get in touch.
The weevil, whose impact can be identified by the distinctive U-shaped notches on clover leaves made by the adults, can be killed by the Irish wasp.
If a weevil outbreak was identified there AgResearch would release the wasp.
The wasp, which laid parasitic eggs in the weevil, normally spread at the same rate.
“However, we’re concerned that the weevil may be getting a jump start on the wasp further south on the West Coast,” AgResearch entomologist Dr Scott Hardwick said.
“We’re now considering carrying out releases of the Irish wasp south of Greymouth when new populations of the weevil are found, rather than relying on it making its own way.”
The wasp had brought clover root weevil under control in AgResearch trials in Waikato, Hawke’s Bay and Manawatu.
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