Agriculture Reference
In-Depth Information
be applied over an extended time during bloom and early fruit development.
This long period allows you to see how many fruits have been formed and to
accurately remove just enough fruit to ensure annual crops of large fruits.
Organic apple orchardists have more limited chemical thinning options.
Researchers have tried salt (sodium chloride) and vinegar, but they have not
produced consistently effective or reliable results. The most popular thinning
agents at this time are a combination of oil (usually fish oil) and liquid lime
sulfur (LLS). Fish oil and LLS sprays proved so successful in Washington
State trials that some conventional growers have adopted the practice.
A typical thinning spray consists of 2.5 percent fish oil and 2 to 4 percent
liquid lime sulfur. Use the lower rates when you expect fruit set to be lower.
Use the higher rates if you expect a particularly heavy fruit set. According
to Cornell University, Crocker's Fish Oil (Quincy, Washington), was used in
their thinning trials, although other fish oil products may be equally as ef-
fective. In thinning trials, fish oil was somewhat more effective than miner-
al crop oils. California researchers reported that soybean and cottonseed oil
were more effective thinning agents than was fish oil.
CHOOSING THE RIGHT THINNER
As of this writing, fish oil was not registered as a thinning agent in Cali-
fornia, and researchers there found that soybean and cottonseed oil
were more effective than fish oil. Note that not all liquid lime sulfur
products are approved for thinning by certified organic fruit growers.
Check all of your oil and sulfur products to ensure that they are ap-
proved for thinning before applying them.
When to spray.
Washington State fruit specialists recommend applying a
fish oil/LLS spray during bloom. Unfortunately, at that time you do not yet
