By Nate Jameson
The decision-making process for choosing a scion/rootstock combination involves multiple factors. The process starts by answering the following questions:
Question 1: New planting or resetting?
If the block is being reset, is still profitable and will stay in production for several years, then I suggest the grower stay with the existing combination currently planted.
If the block is not profitable, then the grower needs to determine why.
Question 2: Why is it not profitable?
- Is this due to a subpar nutrition program?
- Is this due to a subpar insect management program?
- Is this due to heavy nematode infection?
- Is this due to heavy phytopthora infection?
- Is this due to canker?
- Is this due to HLB?
- Is this because the existing variety has lost value?
- Is the existing rootstock/scion combination a good choice in this location?
- Is the electrical conductivity (a measure of the salt content in the water) of the irrigation increasing due to increased salinity?
- Is the soil pH within acceptable ranges for citrus?
- Are there other factors specific to that grove location?
Chances are the lack of profitability is some combination of the above and not a single factor. Since it is usually not a single factor, it’s important to recognize what the other contributing factors are as part of the decision-making process. Replacing one scion/rootstock combination with a different combination will not fix a poor nutrition or phytopthora management program. Good horticultural practices are more important than they have ever been, and surviving HLB requires all of us to become the best horticultural managers possible. If we as growers don’t address all the issues, just changing a rootstock will not necessarily be profitable.
So, once all the above horticultural needs have been addressed, the next question is:
Question 3: Fresh fruit or juice fruit?
Some rootstocks are better for mandarins and others are better for round oranges, so the scion selection becomes part of choosing the right rootstock.
Question 4: What soil type is the tree being planted in?
Flatwoods-, Ridge- and calcareous-type soils all have different effects on the decision-making process. Considering all the factors is important because what works for a juice grower on Ridge soils may not work for a fresh fruit grower on Flatwoods soils.
Nate Jameson operates Brite Leaf Citrus Nursery in Lake Panasoffkee, Florida.
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