More than one subspecies of Bacillus thuringiensis has been isolated. Kurstaki is the type used in Dipel, Solabiol and Bayer which are all available from mainland Europe. I have been told the kurstaki strain was isolated in the UK but it’s not easily available there. Aizawai is the strain in Xentari, which is more easily available in the UK.
Which strain of bacillus is best for protecting fruit and vegetables, kurstaki or aizawai?
It’s odd really. Xentari’s marketed for box caterpillar and some say they use it on fruit and veg but I haven’t seen the results to know if subsp. aizawai works. Thank you very much for replying so quickly, will stock up on kurstaki while we’re still in the EU.
Different strains of Bt target different types of insect. Kurstaki and aizawai both affect lepidoptera including cabbage whites but also other types of butterflies and moths. That plus evidence of resistance building up when over-used is possibly why it still isn’t licensed for home gardeners in the UK.
It’s available from several sellers on Ebay and Amazon under different brand names. There might be a couple more sources mentioned by other members if you use the Forum search.