Georgia Trials Offer Rootstock Choices

Ernie NeffRootstocks

Since launching in 2013-14, southern Georgia’s citrus industry has grown to about 2,000 acres of commercial citrus, primarily cold-hardy satsumas.

Ongoing citrus rootstock trials being conducted by University of Georgia (UGA) Cooperative Extension in Lowndes County hold promise for increased yields, improved fruit quality and greater disease resistance.

Jake Price, UGA Extension agent and Lowndes County Extension coordinator, has six local citrus rootstock/variety trials with varying objectives. The trees are custom-produced by U.S. Department of Agriculture (USDA)-certified citrus nurseries in Florida according to Price’s specifications.

The oldest trial, planted in 2014, is growing Owari satsuma trees on 10 standard and new trifoliate hybrid rootstocks. The goal of this trial is to give growers more rootstock options. Currently, most citrus in Georgia is grown on Poncirus trifoliata rootstocks such as Rubidoux, Rich 16-6 or Flying Dragon. The trifoliate hybrid rootstocks being tested were developed by Kim Bowman, rootstock geneticist of the USDA’s Agricultural Research Service in Fort Pierce, Florida.  

Trial No. 2, planted in 2016, is examining early maturing satsuma varieties on Rubidoux rootstock.

Trial No. 3, planted in 2018, is examining two satsuma/changsha hybrids called Orange Frost and Artic Frost.

Trial No. 4, planted in 2018, is testing the Sugar Belle mandarin on four rootstocks.

Trials No. 5 and 6, planted in 2020, will evaluate Silverhill satsuma and Tango mandarin on newly released rootstocks that have tolerance to HLB.

The trials will determine how newly developed citrus rootstocks affect different varieties in terms of tree yield, fruit quality, disease resistance, tree size and cold hardiness. Rubidoux rootstock is being used in the trials to compare with a number of other hybrid rootstocks developed by the USDA and the University of Florida. Many of these rootstocks have shown tolerance to HLB.

“Many of these rootstocks being evaluated have never been evaluated on satsumas anywhere,” said Price. “If HLB becomes a problem in Georgia, we will have data on how Georgia-grown satsumas and Tangos perform on the newer HLB-tolerant rootstocks.”

All of the trees in the rootstock and variety trials have survived the state’s winters thus far.

“Hopefully our data will help new growers decide what rootstocks they want to use when they are planting their groves,” Price said.

More information about early results from the rootstock trials can be found here.

Source: University of Georgia College of Agricultural & Environmental Sciences

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