Friday, October 25, 2013

Hot Water Treatment for disease prevention at planting time

I am spending a lot of time in the bathroom these days! Specifically- soaking bags full of garlic cloves to get them ready to plant. I use my bathtub to do the hot water treatment on my garlic before I plant.
The hot water treatment kills the Garlic Bloat nematodes that I have found in some of my garlic. It also helps prevent spreading white rot. Last year it also seemed to help with garlic "cankers". These are soft brown spots on some of my cloves that make a bulb unsellable. The treated garlic didn't have cankers this year.

Here are the instructions that I successfully used last year and am using again:

There are usually four steps involved in hot water treatment of garlic cloves:
1. Pre-soak bath - Soak in water maintained at 100°F/38°C for 30-45 minutes. This
activates the nematodes in the clove and makes them more susceptible to the
heat treatment.  It also pre-warms the cloves so that the temperature of the hot-
water bath is easier to maintain.

2. Hot-water bath – Take the cloves immediately from the pre-soak and put them in
a 120°F/49°C hot-water bath.  Maintain this bath at  120°F/49°C for 20 minutes. 
The temperature of the hot-water bath will fall when the cloves are added.  You
need a system to quickly raise the temperature to 120°F/49°C without hot spots. 
Start timing when the temperature is stable at 120°F/49°C. 

The volume of water compared to the volume of the cloves is important.  If there
is too little water, the temperature will drop significantly when the cloves are
added.  Usually a ratio of 4-5 parts water to 1 part cloves is recommended.

3. Cool bath – Immediately submerse the cloves in a cool water bath for 10-20
minutes at 64-72°F/18-22°C. For very small lots running water can be used. Do
not use ice water as it is too cold.
4. Drying - Dry the cloves and plant within a week of treatment.  Do not try to store
treated cloves. These baths while reducing the nematode population, may
increase decay due to fungi especially if the seed is not dried and planted shortly
after treatment.

WARNING – Accurate time and temperature controls are required to successfully heat
treat garlic cloves!  One to two degrees Fahrenheit can make a difference.  Too high a
temperature or too long an exposure may injure or kill the garlic tissue, while too low a
temperature or too short an exposure may not kill the nematodes.

Karen's notes: This wasn't too hard once I got the hang of it. The key is using a good thermometer. I used a garden one that I dangled in the water using the holes of an old cheese grater to prop it up. (My thermometer is not submersible.) The cheese grater is layed on top of a heavy crock full of hot water so that it won't float around the tub or tip over.