How To Choose Almond Rootstocks

Trials in Stanislaus County indicate that Lovell may show signficantly more verticillium wilt symptoms than other rootstocks. This photo shows verticillium  wilt symptoms on second-leaf Nonpareil on Lovell. (Photo credit: Roger Duncan)
Trials in Stanislaus County indicate that Lovell may show signficantly more verticillium wilt symptoms than other rootstocks. This photo shows verticillium wilt symptoms on second-leaf Nonpareil on Lovell. (Photo credit: Roger Duncan)

Editor’s Note: Roger Duncan is a pomology farm advisor with University of California Cooperative Extension in Stanislaus County.

Like hamburgers, almond trees can be served your way. Growers have the option of special ordering their trees with the variety they want and the rootstock they need. Unfortunately, many almond growers just order “the usual” without studying the menu.

Nemaguard is vigorous, immune to rootknot nematode, compatible with all commercial almond varieties, doesn’t sucker much, has decent anchorage, and growers are familiar with it. However, there are many situations in which Nemaguard struggles or just may not be the best choice. As we continue to replant back into old orchard ground, it may be a good idea to rotate to a different rootstock to lessen the effects of replant problems.

Nemaguard is prone to lime-induced chlorosis (yellowing/iron deficiency) in alkaline soils. It is also susceptible to salt toxicity (sodium, chloride, and boron), asphyxia from saturated soils, Phytophthora root rot, oak root fungus, crown gall, and “heart rot” from various wood decay fungi. Despite the name “Nemaguard,” this rootstock is susceptible to ring and root lesion nematodes. The susceptibility to ring nematode leads to the risk of bacterial canker in second-generation orchards replanted into sandy soil. Lovell may be slightly better in clay loam soils, but it has all the other drawbacks of Nemaguard plus more crown gall, and is highly susceptible to rootknot nematode.

Check Out Hybrids
Over the past 20 years, several hybrid rootstocks have become commercially available in California and are gaining in popularity. These include peach x almond, peach x plum, and other more complex hybrid rootstocks. The best known peach x almond (PxA) hybrid rootstock in California is Hansen, a product of the University of California (UC) breeding program. Another UC PxA hybrid, Nickels, is superior to Hansen but is more difficult to find.

Commercial nurseries also sell their own proprietary PxA rootstocks. There are subtle differences among these PxA hybrids, but as a group they are very vigorous and are the most tolerant rootstocks to alkaline and saline soils. On the negative side, they tend to be very susceptible to root diseases, including Phytophthora, crown gall, and Armillaria (oak root fungus). Most are also highly susceptible to ring nematode and therefore bacterial canker.

In the Sacramento Valley, where soils are often heavier and annual rainfall totals can be three to six times what falls in the San Joaquin Valley, the almond industry is quickly converting to Krymsk 86, a peach x plum hybrid originally from Russia. Although widespread commercial experience with this rootstock is still limited, so far this rootstock has performed well in these conditions. Krymsk 86 appears to have superior anchorage compared to Nemaguard and Lovell. Krymsk 86 also appears to perform well in heavy soils and is as tolerant to Phytophthora as Marianna 2624. It may be less suitable for sandy soils where rootknot nematodes are present. Krymsk 86 is a little less vigorous than Nemaguard and may lend to slightly tighter spacing.

Viking is easily the best rootstock choice for sites prone to bacterial canker (shown here oozing through bark). (Photo credit: Roger Duncan)
Viking is easily the best rootstock choice for sites prone to bacterial canker (shown here oozing through bark). (Photo credit: Roger Duncan)

Viking And Atlas
Another rootstock gaining in popularity is Viking, a complex hybrid of peach, almond, plum, and apricot. Viking appears to have all the best attributes of Nemaguard but has fewer weaknesses. Like Nemaguard, Viking is well adapted to well-drained loam and sandy loam soil. Viking is slightly more vigorous than Nemaguard and is also immune to rootknot nematode. Viking rarely suckers, appears to have better anchorage than Nemaguard, and is apparently compatible with all commercial almond varieties. In addition, Viking is more tolerant of alkaline soils than Nemaguard and Lovell and is also tolerant of ring nematode. The largest problem we have noticed with Viking is its sensitivity to dehydration during handling at the nursery and at planting. This has occasionally resulted in new trees failing to push after planting.

We are currently monitoring other rootstocks in UC field trials to determine their potential fit in our production system. Empyrean 1 (also known as Barrier 1) has vigor similar to PxA hybrid rootstocks but without many of the disease problems. It also appears to be somewhat tolerant of alkaline soils and maybe ring nematode, but our experience is still very limited.

Atlas is another rootstock of interest. It is a complex hybrid similar to Viking, but the horticultural characteristics are different. Atlas is more susceptible to ring nematode and alkaline soils than Viking but it appears to have better yield efficiency than other rootstocks tested and appears to be more tolerant of alkaline soil than Nemaguard.

Pages: 1 2

Topics: , , , , ,

Leave a Reply

Nuts Stories
CitrusFederal Judge Blocks Clean Water Rule
August 28, 2015
  According to RISE (Responsible Industry For A Sound Environment), a federal judge in North Dakota has blocked implementation of Read More
money
CitrusMonsanto Drops Current Bid For Syngenta Acquisition
August 27, 2015
Even with a revised proposal that sweetened the pot to $46.2 billion, financial expectations still fall flat. Read More
NutsAlmonds Contribute Little To Carbon Emissions
August 25, 2015
Compared to other nutrient-dense foods, the carbon footprint of almonds is small. Read More
NutsAlmond Board Continues Legacy Of Funding Important Research
August 25, 2015
A $2.5 million investment in third-party research aims to improve almond farming sustainability. Read More
Virginia Tech campus in Blacksburg
CitrusCounting Down The Top U.S. Colleges For Natural Resources And Conservation
August 25, 2015
STEM-fueled area of study presents wide field of opportunity for future grads. Read More
FruitsClimatologist: Do Not Count On El Niño To End California Drought
August 25, 2015
 In a California Department of Food and Agriculture blog post, California state climatologist, Michael Anderson, urged growers to be mindful Read More
CitrusMaps Show Impending Impact From WOTUS
August 19, 2015
Plots indicate expansion of EPA’s reach across Pennsylvania, Virginia, and Montana. Read More
The Latest
CitrusWhole-Farm Revenue Protection Insurance To Be Available…
August 31, 2015
USDA offers greater flexibility for beginning, organic and fruit and vegetable growers. Read More
drought management; irrigation; water management
CitrusClear Up Misconceptions About Water Use In Ag
August 31, 2015
Those in the industry need to to clear up misconceptions about water use in agriculture. Read More
NutsGrowers Claim Pistachio Trees Diseased – Nursery …
August 30, 2015
Whatever the cause, pistachio trees are suffering from Pistachio Bushy Top Syndrome, and tens of thousands of acres in California and Arizona will have to be replanted. Read More
CitrusFederal Judge Blocks Clean Water Rule
August 28, 2015
  According to RISE (Responsible Industry For A Sound Environment), a federal judge in North Dakota has blocked implementation of Read More
money
CitrusMonsanto Drops Current Bid For Syngenta Acquisition
August 27, 2015
Even with a revised proposal that sweetened the pot to $46.2 billion, financial expectations still fall flat. Read More
NutsAlmonds Contribute Little To Carbon Emissions
August 25, 2015
Compared to other nutrient-dense foods, the carbon footprint of almonds is small. Read More
NutsAlmond Board Continues Legacy Of Funding Important Rese…
August 25, 2015
A $2.5 million investment in third-party research aims to improve almond farming sustainability. Read More
Virginia Tech campus in Blacksburg
CitrusCounting Down The Top U.S. Colleges For Natural Resourc…
August 25, 2015
STEM-fueled area of study presents wide field of opportunity for future grads. Read More
FruitsClimatologist: Do Not Count On El Niño To End Californi…
August 25, 2015
 In a California Department of Food and Agriculture blog post, California state climatologist, Michael Anderson, urged growers to be mindful Read More
CitrusMaps Show Impending Impact From WOTUS
August 19, 2015
Plots indicate expansion of EPA’s reach across Pennsylvania, Virginia, and Montana. Read More
branches covered in ice
CitrusWicked Winter Coming This Way Says Latest Farmer’s Alma…
August 17, 2015
Super El Niño-influenced weather patterns align to paint a less-than-pretty portrait. Read More
woman smashing an alarm clock with a hammer
CitrusDon’t Become A Time Crunch Casualty
July 31, 2015
Finding the balance between work life and home life is easier said than done for GenNext Growers. Read More
Disease ControlNew Disease Control Tools For Fruit And Nut Growers
July 29, 2015
Apple scab is a big problem for growers in the Midwest and East. But, a new fungicide boasts efficacy against Read More
CitrusUSDA Expands Crop Insurance Options For Fruit And Nut G…
July 24, 2015
The USDA announced the expansion of crop insurance to provide additional options for fruit and nut producers. The Supplemental Coverage Read More
CitrusInternational Report Confirms 2014 As Earth’s Warmest Y…
July 21, 2015
Scientific compilation notes climate markers continue to show global warming trend. Read More
non-gmo label leafy greens
CitrusGMO Labeling Battle Moves To House Floor
July 21, 2015
The Safe and Accurate Food Labeling Act of 2015 was passed by the Agriculture Committee last week and will head Read More
CitrusEl Niño Could Be Strongest In 50 Years
July 14, 2015
In the latest AccuWeather report, Brett Anderson, senior meteorologist with AccuWeather says El Niño has strengthened over the past few Read More
EquipmentJohn Deere Gator Giveaway Winner Announced
July 13, 2015
Meister Media Worldwide (MMW) is proud to announce the winner of this year’s Gator Giveaway contest. The Gator Giveaway contest Read More