Last winter, I applied the biodynamic spray called Horn Manure to my no dig garden, which certainly seems to have benefitted the pear tree (which was not decimated by pear midge for the first time).
The days suggested to be favourable in early 2018 for such an application are:
3rd -4th March.
These dates are root days in the Maria Thun calendar when the moon is descending in its monthly cycle.
However, others also allude to a damp, cloudy day as being beneficial so, if dry sunny conditions are indicated for the above dates, others may be more appropriate.
In reality, little clear data exists suggesting that a huge difference will arise from treating the soil on a specific day, so one suspects that treating the soil and the trees sometime before spring is better than no treatment.
Please read the February 2017 blog entry on this subject for further details on how to prepare dynamised horn manure.