The warning comes from FAST adviser Rob Cook, who said that once present the moth is impossible to eradicate and it is "imperative" growers keep on top of numbers.

Cook said: "Over the last three or four years, their spread has been rapid, culminating in a widespread UK presence. They are a very polyphagous species - they will eat anything.

"The larvae construct harbourages - rolling together leaves, buds, shoots and fruit clusters, producing a webbing, eating immature fruits before later burrowing and hollowing out the berries. Hidden away, they can be very difficult targets.

"There are so few approved insecticides available against the moth - even fewer approved for use on blueberries. Dimilin Flo (diflubenzuron) is one of the few options effective against the pest and approved for use on blueberries under a specific off-label approval."

Cook advises monitoring to assess the treatment threshold by using pheromone traps and that once counts increase at a rate of ten moths per week, then treatments should be introduced.

Cook added: "Our control programmes incorporate two applications of Dimilin, coinciding with each of the moths' two generations. The first treatment after bloom has finished, depending on counts, and a second after harvest to reduce any surviving populations able to over winter."

Certis advises that within a planned approach, Dimilin Flo is the preferred option but where caterpillars become established, a quick pest knockdown can be achieved using Spruzit.

FPJ News