Blueberry growers need to keep an eye out for light-brown apple moth (Epiphyas postvittana) as populations continue to spread unchecked. The warning comes from FAST adviser Rob Cook, who explains that once present the moth is impossible to eradicate. "For soft and tree fruit growers they are very problematic, so keeping on top of numbers is imperative," he advises."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’ll eat anything," explains Rob.
"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," explains Rob. "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. He advises monitoring to assess the treatment threshold. "Pheromone traps are increasingly being used to monitor populations. Once counts increase at a rate of ten moths per week then treatments should be introduced," he recommends. Close regular monitoring is critical, urges Rob. "Populations can explode in a short period of time, with counts one week going from one or two per week to over 60 per trap the next," he warns. "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 advise that within a planned approach Dimilin Flo is the preferred option but where caterpillars become established a quick pest knock down can be achieved using Spruzit (containing pyrethrins and oils).