Western Australian plant pathologists are having difficult diagnosing grey and white spots found on wheat crops.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 2 minutes 50 seconds 2 m 50 s Plant pathologist Ciara Beard says they are yet to diagnose what is causing spots to appear on wheat crops ( Lucinda Jose ) Download 1.3 MB

The mysterious spots have appeared on crops throughout the northern half of WA's agriculture region.

According to the WA Department of Agriculture and Food (DAFWA) the spots have not been caused by disease.

The department has received reports of grey or white oval spots found on plants in a widespread area from Geraldton to Narrogin.

While not being sure what is causing the spots, the department is encouraging growers to be cautious about treating suspected disease before they know what they are dealing with.

DAFWA plant pathologist Ciara Beard said there were several theories about the cause of the abiotic spots.

"Because it is quite widespread we are thinking it must be some environmental cause," Ms Beard said.

"Despite testing by Curtin University, who tested the DNA of the leaves that we received and we have looked at the under the microscope and tried a few different tests, we haven't been able to identify any disease."

She advised growers to hold-off applying fungicide or fertiliser unless farmers had confirmed the presence of a disease or a nutrient deficiency.

"This is to save wasting money and also in the case of fungicide to prevent fungicide resistance problems later," she said.