By Aaron Himrod
Although there is a current lack of true resistance to HLB, making appropriate variety choices does have a significant impact on grove performance and profitability. Compromises among the various factors will have to be made. Take note of the most limiting factors in your grove and make your selection with these in mind. HLB exacerbates stresses that may have previously been adequately tolerated, so today’s limiters can be quite different than 2004! This is still the most important step in your decision process.
Cost and availability will vary depending on variety royalty structure as well as rootstock amplification method. Many newer rootstocks are only available in significant quantities through tissue culture propagation. Growers should expect to pay more for trees propagated in this manner and must order these trees well in advance. Care should be taken, as many newer varieties do not have as long of a tested history as others.
Many growers seem to be noticing improved results from vigorous, precocious bearing selections planted at higher densities than traditional settings. HLB reduces vigor and tree size, so this change does not likely present the horticultural problems that many foresee.
In our own nursery, the majority of current production is made up of US-802, US-942, X-639, Kuharske, rough lemon, and UFR-4 rootstocks. The scions are mostly nucellar Valencia, OLLs, Vernia and Hamlin. With the suite of rootstocks and scions that we have narrowed down, we feel like we have a group that includes at least one scion and rootstock that will lead to the ultimate goal of performance for most citrus sites. Observations and grower feedback support their use due to their compatibility, availability and performance under current conditions in combination with modern growing practices such as enhanced root nutrition. Synergies are being noticed among some of these varieties.
Other choices are certainly available, and a different combination might be your best option. Your own tolerance of risk and existing variety performance will help guide your decision.
Trees must get to their breakeven point sooner than they did in the days before HLB. Expecting 18-plus years of useful life out of a tree anymore is unrealistic and likely unnecessary.
High levels of HLB tolerance/resistance from improved genetics in the next eight to 10 years is probable. In the meantime, replacing less productive trees with healthy, vigorous resets at higher densities seems to be the best path toward economic success.
Aaron Himrod operates Himrod Citrus Nursery in Bowling Green, Florida.
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