Adapted from the article “Observations on Krymsk 86 rootstock” by Joe Connell, UC Farm Advisor, Butte County in the September 2011 Sacramento Valley Almond News
Krymsk 86 is a peach-plum hybrid rootstock (Prunus persica x P. cerasifera) that originated in the Krasnodar region of Russia. As such, this hybrid rootstock is different than any other rootstock in use in the California almond industry. Now that it is planted in commercial orchards under many different conditions we are learning more about how it behaves when grafted to almond.
When grafted to peach, plum, or apricot it is thought to be tolerant of cold temperatures, drought, water logging, resistant to Phytophthora, and somewhat resistant to lesion nematodes. Grafted to almond in California, trees behave differently than almond grafted on peach or Marianna 2624 plum rootstocks.
The first trial in Butte County including this rootstock was planted in 2003. The Nonpareil trees on Krymsk 86 are larger than adjacent trees on Lovell peach. Krymsk 86 appears to be compatible with almond and it has a vigorous root system with good anchorage as a young tree. Krymsk 86 roots are susceptible to root knot nematodes, limiting usefulness on light textured soils where root knot can be a problem. Trees on Krymsk 86 are less vigorous than trees on peach roots in sandy soil.
Krymsk 86 appeared to be sensitive to wet, cold, and saturated soils with reducing root activity and nutrient uptake. In spring 2011, soils were wet and cold for an extended period causing trees to get a slow start. Several young orchards on Krymsk 86 had yellow trees for several reasons, none of which appeared fatal. In one young orchard on heavy clay adobe soil, wet saturated conditions likely denitrified available nitrogen resulting in a transient nitrogen deficiency. As soil dried out and warmed up they improved. In another orchard, the yellowing was interveinal chlorosis symptomatic of manganese deficiency. Yet another young orchard displayed both zinc and manganese deficiency symptoms, but an adjacent orchard on peach rootstock was also displaying manganese deficiency.
Under the same cold, wet conditions, some young yellow trees on Krymsk 86 displayed symptoms similar to the union mild etch (UME) problem. Once soils warmed and irrigation progressed some trees improve and put out a new flush of growth. UME is also a problem on Marianna 2624, and is more prevalent on varieties that are the least compatible with the rootstock such as Butte and Monterey. Leaves turn pale yellow and growth may stop. When severely affected, leaves roll and scorch on the margins, and trees may defoliate. Some trees die or remain very weak, but most recover the following year.
So, sometimes Krymsk 86 behaves somewhat like its plum half while other times it behaves like its peach parent. Whether it can tolerate extensive winter waterlogging like Marianna 2624, resist wood rots and blow-overs as the trees age, or tolerate oak root fungus better than peach roots will be discovered as these young orchards age.