Thrips have long been a major threat to crops, but worryingly, the number of species of thrips around the globe is on the increase, and they are spreading more easily. More worryingly though is the fact that there isn’t yet a biological solution to control every species in every crop. Koppert is, therefore, investing in more R&D in this area.
New species of thrips in soft fruit
In outdoor soft fruit crops, especially strawberries, there have been reports of increased thrips infestation. Infestation by the Western flower thrips is on the increase, and since this particular species is extremely resistant to pesticides, more and more growers are moving over to biological crop protection.
‘Alongside the species we’re used to seeing in strawberries, like Thrips tabaci, we’re starting to see new species appear in soft fruit like Frankliniella intonsa, Thrips fuscipennis, which attacks roses, and Thrips setosus,’ explains consultant Guido Roozemond. ‘Thrips setosus were clearly present in strawberries this year, but any damage and the extent of that damage is not yet clear.’ He points out that positive species of thrips do sometimes appear, such as Aeolothrips, which help to control other harmful species.
‘The problems may be more severe in other countries. In Germany for example, there are growers who can no longer cope with chemicals. It requires such enormous effort to control the thrips with biological means that they have been forced to change their cultivation system, switching from long ever-bearer cultivation to shorter June-bearer cultivation.’
Vegetable cultivation – thrips largely under control
In major greenhouse crops such as tomato, pepper, and cucumber, thrips are not a particularly significant problem. There are hardly any problems in tomato crops, and use of natural enemies has not been necessary. In cucumber crops, Amblyseius swirskii (Swirski Mite) is effective at keeping thrips under control.
In pepper crops, Swirskii is the designated natural enemy used for preventive treatment, while Orius laevigatus (Thripor-L) is used curatively. ‘At the moment, we’re seeing that Orius is slightly less effective in pepper crops,’ explains vegetable consultant Alex Taal. ‘As to why, we’re currently investigating. It’s clear that this reduced effectiveness will mean that higher numbers of Orius will be needed per square metre to keep the thrips under control.’
He emphasizes the importance of Horiver yellow and how its use can help growers to see whether or not a pest is there and how it is evolving.