Your trusted source for independent, high-quality, science-based advice
© 2025 Berryworld, All Rights Reserved
During the winter we grow strawberries in one of our greenhouse units in Lincoln. It’s not an official trial, but we like strawberries on our breakfast. And because we’re paying rent for the space anyway, we might as well get some fruit!
We also enjoy seeing the performance of the varieties during the winter months, and tweaking our system to hopefully get better every year.
This year the thrips started becoming a menace in July. We had a few lingering from the summer and they happily reproduce in the heated space, even with low winter light levels. Given that we don’t have any high-health motherstock in there during winter, we decided to make the unit a “petri dish” for biological thrips control. We “threw the kitchen sink” at the thrips problem, and introduced 4 predators. Incidentally these are some of the same predators we’ll be testing on strawberries against intonsa thrips during the coming summer.
Predators were released on 7th August, with extra lacewings on 22nd August.
The lacewings came from Bioforce as beautiful green eggs on hair-like stalks, lain on frost cloth. The tiny insects that hatch spend their life crawling around looking for prey to eat –they have no wings until they become adults. I failed to cut up the cloth and distribute the first batch evenly throughout the greenhouse, so they all hatched in one spot. Turns out that they’re highly cannibalistic. Oops. There’s my learning curve…. We got a new batch on 22nd August and distributed them better.
On 22nd August I discovered that I had little pockets of spider mites. While I had failed to notice the mites when I released the cucumeris, the cucumeris did not fail to find the mites. By the time I saw them, there were more cucumeris than spider mites. Success! I don’t know if the cucumeris were eating thrips, but they were certainly eating spider mites.
I did some soil pH testing and in the process was able to see a Stratiolaelaps mite or two. I can’t quantify what impact the mites were making, but at least I could observe their presence.
I only once saw the minute pirate bug, a week after we released it. I haven’t seen one since, and I’m told this is not unusual. Perhaps I have to become a nocturnal observer. Or perhaps they don’t survive in the greenhouse. I don’t know.
Today, I was delighted to spot some small lacewing larvae. They were comically adorned with bits of detritus, including vermiculite, and looked like little dust bunnies wobbling across the leaf surface. I was gratified to find them because I hadn’t seen any of them post-hatching, and they apparently hunt best at night.
I’ve struggled to objectively quantify the progress the predators are making on the thrips. In our trial, we have four day neutrals (Moxie, Royal Royce, Valiant and Monterey), and one short day (Fortuna). Fortuna seems to be a lot more attractive to thrips, and there seem to be as many on the leaf surfaces as in the flowers. Therefore the standard thrips-counting method of tapping flowers over a white paper has been unsatisfactory. While I’ve not employed an objective count to thrips numbers, the newer leaves are showing less damage, and the fruit is in better shape. I can still find thrips easily on leaf surfaces, but not as many.
We have about six more weeks before I need to clean out the space and make way for the high health mothers, so we’ll see where the journey takes us by October.