I came across this suggestion for the organic control of white rot in alliums, and as it is such a common problem on allotments, it will be of interest to others.
This method of organic control of white rot was suggested by an expert on alliums, Professor Fred Crowe, Oregon State University, after ongoing tests.
When white rot has infected allium roots and bulb, it forms thousands of little black seed like, sclerotia, which fall off and remain in the soil, unless the infected bulb, roots and the adjacent soil have been removed and sterilised. When the sclerotia infected ground is dug over, the sclerotia will be distributed throughout the digging depth. These sclerotia will become dormant over the Winter, but in the Spring will germinate as soon as they sense the presence of allium roots close by.
The control method is to trick the dormant sclerotia into thinking that there is an allium growing beside it, by watering on a ground-up garlic bulb solution of 1 part garlic solution to 1000 parts water, say one ground-up garlic bulb to a watering can of water. Apparently, you should be able to taste and smell the garlic in the solution. It should be applied when the ground temperature is between 10c and 20 c with an optimum temperature of 15c.
It should be watered onto the ground that you intend to use for alliums, during the preceding year while the ground is moist and warm.
It is also possible to use garlic powder which you can find in Asian food shops and health food stores. This should be applied at a rate of 250 lb to the acre. Roughly 125 Kg per 4000 sq m, or roughly 30 gm per sq m if my arithmetic is correct. This has the advantage of having been sterilised and unable to pass on any allium infections but is not so effective.
Has anyone tried this method and how effective was it?
The above is my summary of a transcription of a lecture that he gave. The transcription is rather heavy going but is on line here
http://www.bcseeds.org/white-rot.php
