The Thrips Puzzle: Part 3

When thrips come to our variety trial

It was December before I started seeing thrips in the flowers in our variety trial in Lincoln.  Now I get to practice putting together all the control measures and scouting techniques that have been nice theories up until now.

I released hypoaspis mites way back in October.  I hope they have survived on fungus gnat larvae and are still in my strawberry troughs ready to mop up thrips pupae.  I could pop the plants out and look for the white mites crawling on the inside of the black plastic trough, but that’s a lot of effort and I haven’t done it yet.

I released 10,000 cucumeris just after Christmas.  The package was crawling with active mites, so that’s a good sign.  Recommendations out of the UK say to use 25 cucumeris per strawberry plant, which seems like a massive number, but they are cheap.  Just a couple days after release I sprayed Benevia for leaf roller caterpillars (they’re bad this year!), which is not ideal but the best option I could think of, given the fact that I have zero confidence that my sprayer could get Bt to the caterpillars rolled up in their protective leaves.  I can now see cucumeris under many of the developing strawberry calyx, where I can also see a few thrips larvae and cucumeris eggs.  All systems seem to be working.

To see cucumeris mite predators and juvenile thrips, peel back the calyx and use a hand lens. It will require good light and careful observation, as the thrips juveniles are light coloured and cucumeris are also a light honey-colour. Both move quickly, so quickly that I couldn’t get a photo.

I’m keeping track of the thrips number in flowers weekly.  At New Year, average was 2.8, the week after was 5.0, and the week after that it was 2.3.  So far we’re not really getting worse.  I’m not seeing any fruit damage at all.

So all in all, I’m in a holding pattern, monitoring thrips numbers, making sure that I still see the predator mites under the calyx.  We still have plenty of warm summer weather coming to see if the predator strategy will be enough.

‍