Tackling Japanese flower thrips in protected ornamental and herb crops

A new thrips species has been confirmed on protected crops in the UK. Primarily on ornamentals, including primrose and cyclamen, the pest has also been noted on pot herb crops, including basil and rosemary. However, the pest has a wide host range including cucumber, lettuce, pepper, strawberry and tomato.

Identified as Japanese flower thrips (Thrips setosus), the thrips species is not native to the UK but is not currently classified as a notifiable quarantine species. Originally from South-East Asia, it has also been recorded in a number of Northern European countries. It was first detected in the Netherlands in 2014 on hydrangea, and in 2016 in the UK on poinsettia.

How do I identify Japanese flower thrips?

Like some other thrips species, the pest feeds on the underside of leaves causing scarring and also on flowers, damaging petals. In addition to causing direct plant damage, like western flower thrips (WFT), it can transmit Tomato spotted wilt virus.

The adult has a much darker body than WFT, with a pale patch on the base of each wing.

How can I control Japanese flower thrips?

At the moment, control of the pest is proving problematic using the usual range of biological control agents commercially applied for thrips control. UK growers are finding that the predatory mite Neoseiulus cucumeris, commonly used for control of WFT, does not seem to give control of T. setosus.

To understand more about the biology of Thrips setosus and ultimately improve control measures, we commissioned a review of current problems and potential IPM-compatible control measures. The review also looked at other new thrips species (for example, Dichromothrips corbetti – ‘vanda thrips’) on phalaenopsis orchids in the UK.

As part of this review, Jude Bennison, ADAS Horticulture, contacted entomologists at both Koppert Biological Systems and Wageningen University and Research in the Netherlands to find out how Dutch growers are dealing with T. setosus.

Promising control is being achieved in the Netherlands, for example, on hydrangea using another species of predatory mite, Transeius montdorensis, on the advice of Koppert.

Research also indicates that the Orius species predatory bugs are also showing promise.

Source: AHDB