Blueberry growers need to watch out for an increasingly problematic bug that is impossible to eradicate once established, according to Farm Advisory Services Team consultant Rob Cook.

He said light-brown apple moth (Epiphyas postvittana) populations were spreading unchecked. Once present, the moth is impossible to wipe out, he added, so keeping on top of numbers was "imperative."

"Over the past three or four years they have spread rapidly, culminating in a widespread UK presence. They are very polyphagous - they'll eat anything," said Cook.

"Larvae roll together leaves, buds, shoots and fruit clusters to make a webbing. They eat immature fruits before 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 an option that was approved for the treatment of blueberries under a specific off-label approval.

Cook said growers should monitor populations. Pheromone traps were being used more often and treatments should start when counts rose to 10 moths a week.

"Close regular monitoring is critical. Populations can explode in a short time. Our control programmes use two applications of Dimilin. The first, after bloom has finished, depends on counts. The second, after harvest, attacks survivors."

Certis advises Dimilin Flo for a planned approach. But for established caterpillars, a quick knock down can be achieved using Spruzit (containing pyrethrins and oils).

Source: hortweek.com