A new diagnostic to help growers combat spraing could further help the reduction of nematicide use, says SCRI’s Finlay Dale.

The new test takes advantage of the fact that weeds are the main hosts of the tobacco mosaic virus within fields, which offers the potential as a diagnostic that could be applied when weeds are apparent, says Dr Dale.

The advantage of using weeds such as fat hen and chickweed is that they are in situ for a number of months acting as bait plants compared with soil testing, which relies on the nematodes being in the soil profile at the time of sampling.

Weed samples

Growers can collect the weed samples themselves and send off for testing.

The sap from the roots is extracted and tested for the presence of the virus.

“This test can be turned around in a week compared to five to six weeks for current glasshouse bait tests, and it is also cheaper,” says Dr Dale.

Having detected the virus, and mapped it within the field, growers would be better informed and can plan a management strategy that may involve treating or avoiding areas or whole fields, or a switch to different cultivars, he says.

“Given that nematodes don’t migrate very far horizontally, mapped areas should be good for a number of years.”