Articles
PREDICTION OF BITTER PIT
Our yearly production is about 400.000 tons.
Reckoning with the varieties of the grown apples we can say that nearly 40 % are susceptible to very susceptible to bitter pit, and 60 % are not too much affected by this disease.
We have calculated that in some years the losses by bitter pit will be up to 10–15 % of the production.
That will be 10 to 15 millions of guilders from direct and indirect losses by bitter pit. (Direct losses will be the apples that are affected by bitter pit, and indirect losses are a result of decrease of prices when there are pitted apples on the market.) As you will understand these are enough reasons for the fruitgrowers to ask a prediction whether there will be bitter pit or not.
In the Netherlands we have fruitgrowing areas in the south-western part on marine clay soils, in the middle on river basin soils and in the south on sandy and loess soils.
As it is accepted bitter pit has to do with potassium and calcium levels in the plant.
We can translate the area in high potash and calcium levels in the south-west, much variation in potash and calcium in the middle, and high potash and low calcium levels in the sandy soils.
Since I was working at an advisory service station in the middle of the Netherlands on research in the relations between soil, fertilizing, and storage problems, I was already long involved in bitter pit (24, 71–77, 93, 94). We have set up a basis for the interpretation of the results of leaf analysis for several purposes.
One of these was a basis for prediction of bitter pit in advance.
This I will show you in the next figure: