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
NutsIndustry Update: American Pistachio Growers 2015 Conference
March 23, 2015
Industry flying high as a billion-pound crop looms at the end of the decade. Read More
CitrusCalifornia Unveils $1 Billion Drought Package
March 23, 2015
Governor, legislative leaders, announce $1 billion emergency drought legislation. Read More
CitrusFeed A Bee Campaign Aims To Plant 50 Million Flowers
March 23, 2015
Bayer CropScience announces program to increase forage opportunities for critical pollinators. Read More
FruitsBe On High Alert For Leaffooted Bug
March 18, 2015
Now is the time to start scouting for leaffooted bug in almond orchards. Read More
NutsHoneybee Forage Program Helps Bees And Growers
March 10, 2015
Project Apis m. is targeted at improving bee health with the help of California almond growers. Read More
Biocontrols 2015 Conference
CitrusGrowers Go In-Depth At Biocontrols 2015 Conference & Tradeshow
March 9, 2015
The first-of-its-kind event brought growers, researchers, regulators, and suppliers together for a two-day discussion on the latest biocontrols tools and technologies. Read More
FruitsNo Federal Water For California’s Central Valley Growers – Again
February 27, 2015
Skimpy snowpack leads Bureau of Reclamation to make unprecedented announcement that there will be a zero initial allocation for the second year in a row. Read More
The Latest
NutsWhy You Should Use Low-Rate Applications Of Potassium
March 26, 2015
These rates provide growers a low-cost method comparable to conventional applications. Read More
Disease ControlBacterial Spot Can Make Almonds Unmarketable
March 24, 2015
Management strategies can help you mitigate losses from this nasty almond disease. Read More
CitrusFarm Bureau Says WOTUS Rule Would Ignore Exemptions
March 24, 2015
Common farming practices may be vulnerable to Clean Water Act enforcement under the rule. Read More
NutsIndustry Update: American Pistachio Growers 2015 Confer…
March 23, 2015
Industry flying high as a billion-pound crop looms at the end of the decade. Read More
CitrusCalifornia Unveils $1 Billion Drought Package
March 23, 2015
Governor, legislative leaders, announce $1 billion emergency drought legislation. Read More
CitrusFeed A Bee Campaign Aims To Plant 50 Million Flowers
March 23, 2015
Bayer CropScience announces program to increase forage opportunities for critical pollinators. Read More
FruitsBe On High Alert For Leaffooted Bug
March 18, 2015
Now is the time to start scouting for leaffooted bug in almond orchards. Read More
NutsHoneybee Forage Program Helps Bees And Growers
March 10, 2015
Project Apis m. is targeted at improving bee health with the help of California almond growers. Read More
FruitsNo Federal Water For California’s Central Valley Grower…
February 27, 2015
Skimpy snowpack leads Bureau of Reclamation to make unprecedented announcement that there will be a zero initial allocation for the second year in a row. Read More
FruitsMaximize Produce Profits By Focusing On Soil Health
February 27, 2015
Cover crops are just one of the ways you can help boost your trees’ and vines’ performance and your bottom line. Read More
FNV logo
CitrusPMA Announces Funding For Major Produce Marketing Progr…
February 26, 2015
The produce industry is getting into brand marketing in a big way. The Produce Marketing Association (PMA) has announced the launch of a new promotional campaign - FNV - designed to take a page from the marketing strategies of big-money consumer brands like Nike and Apple. Read More
CitrusFDA, Federal Partners Develop New Method For Attributin…
February 25, 2015
Data was analyzed from nearly 1,000 outbreaks to assess which categories of foods were most responsible for making people sick. Read More
CitrusBiocontrols 2015: Exhibition Sneak Preview
February 25, 2015
We take a look inside the exhibit hall at the Biocontrols 2015 Conference & Tradeshow. Read More
NutsA Better Way To Gauge Chilling Hours
February 24, 2015
Using a new system, the chill portions model, can improve growers’ accuracy. Read More
CitrusNew App Helps Identify Insects, Diseases, And Nutrient …
February 24, 2015
Spensa Technologies launches app that helps growers take control of pests and improve soil nutrients. Read More
Crop ProtectionFMC Launches Biological Fungicide With New Mode Of Acti…
February 18, 2015
The broad spectrum fungicide, Fracture, is labeled for prevention and control of powdery mildew, botrytis, and brown rot blossom blight. Read More
CitrusNew Desalination Technology May Be The Answer To Califo…
February 18, 2015
Researchers plan to address concerns with a process that will examine ways to turn seawater into drinkable water. Read More
NutsWalnuts May Improve Memory
February 18, 2015
A University of California-Los Angeles study found greater cognitive function in participants who ate walnuts. Read More