Thresholds for plague thrips in the Victorian strawberry industry (BS12003)

What was it all about?

This project, which ran from 2012 to 2014, investigated if plague thrips, either alone or in combination with onion thrips, cause damage to strawberry flowers and berries. Findings would assist growers to decide whether to use chemical controls for the pest.

Over two seasons, thrips were caged around flowers of potted strawberry plants to assess subsequent levels of damage. The variety of strawberry grown was Albion, commonly grown in Victoria. Fifty plus adult thrips were placed on each flower then more thrips added to the same flower over three days, to replicate a flight of thrips.

The cages were removed at petal drop and each flower was tagged and continued to grow until the berry was fully formed and ripe. It was photographed and scored for damage.

The results of the study showed that even at a density of 150 thrips per flower, the pest caused no damage to subsequent fruit.

The research suggests that it is not worth applying insecticides for plague or onion thrips in flowers, at least on the variety Albion. In fact, chemical use could prevent beneficials from controlling insects and mites that do cause damage to strawberries.