This is a very quick disease and hard to control because it can penetrate cuticle and stomata. Start with sanitation. Remove all old leaves from the container when weeding. Space correctly so you can get air movement and sunshine to dry off the leaves quickly in the morning. Sanitize your shears after pruning each plant if you suspect you have boxwood blight.
- Elevate your calcium 7 times higher than magnesium 70% to 10% soil balance.
- Elevate your boron based on cation exchange capacity.
- Good sulfur levels with a higher soil PH.
- Foliar Sprays
- Fish fertilizer/carbon/rotated with a calcium silicate/boron mix.
Landscape’s biggest failures are low soil PH and poor drainage along with excessive irrigation.