Spraying with diluted lime sulphur in winter can help kill pests and fungal spores on benches and trees.

In my garden, the first month of winter means it’s time for the first of three ‘bench sprays’ of lime sulphur over the next three months. I like to do any spraying on the first weekend of the month. That way I remember to do the task and it just becomes part of my winter monthly routine. Mix 30ml of lime sulphur to one litre of water. Remove your trees, clean the benches then spray liberally. Be sure to hit the underside of the bench too. This will kill any fungal spores, as well as pests that are lurking around biding their time to attack.

It’s also a great time to hit the trees with the same ‘overwintering spray’ of 30ml/ 1litre lime sulphur to water. I only do this twice over the winter season in June and July. The trees will have a whitish look to them after the spraying, but this will diminish and disappear within a few weeks with watering and natural weathering. Same as the bench spray, this will kill any pests under flaky bark or fungal spores waiting to spawn.

NOTE: The over wintering spray is not an absolute essential for maintaining healthy bonsai. If your trees are thriving and are pest free, then there is no need to spray but if you do spray, there are a couple of very important steps to follow:

1. The first step is to water trees and pots thoroughly, so the soil is drenched, and all parts of the tree (trunk, branches etc) are wet prior to the application of diluted lime sulphur.
2. Place several layers of newspaper or similar around the base of each tree to protect the soil from any spray. Pay attention to ensure that the newspaper “hugs” the trunk of the tree so that it will catch excess spray dribbling down the trunk.
3. Mix lime sulphur with water. I use 30ml with 1 litre of water, some people use as little as 5ml with 1 litre of water.
4. Use a fine jet pump, spray the branches and trunks of the tree. Don’t drench the tree to the point that you have a huge river running down the trunk.
5. Leave the newspaper in place until all drops of lime sulphur have stopped falling from the tree. It is important to minimise the opportunity of lime sulphur entering the soil / root system. Don’t re-use the newspaper on another tree.

Now the contention… Of those people who choose to spray trees with diluted lime sulphur, some choose to only spray deciduous trees, others spray all trees (and their leaves). New growth that hasn’t hardened off may die off or be damaged by the spray. To my knowledge, no one sprays trees in flower (as it will likely destroy the flower).

Spray after the heat of the day so that it dries before the evening.