Almond-Marianna 2624 Performance

John Edstrom
UCCE Farm Advisor

Stan Cutter
Nickels Estate

Prior research at Nickels Soil Lab suggested that some almond varieties can be quite productive when planted on Marianna 2624 plum rootstock. However, this rootstock has a considerable dwarfing effect on most varieties and requires tighter tree spacing to realize its maximum bearing potential. Yield potential of M2624 is generally considered to be less than like varieties on peach rootstocks. Given sites with Oak Root Fungus or heavy/wet soils, plum root is preferred. Mission, Ruby and Padre cultivars have shown excellent compatibility with M2624. However, the Butte variety has shown inconsistent performance on M2624 in the field.

This test planting was established in 1989 to evaluate 4 almond cultivars in a close planted hedgerow on M2624 rootstock. Commercially harvestable replications were designed into the test to collect yield data. Butte, Mission, Ruby and Padre almonds were planted as single rows at 10' x 20' spacings for 218 trees/acre.

Yields declined significantly in this planting in 1999 (Table I). Although frost was reported in nearby orchards the cropping pattern in this block and within individual trees did not suggest frost greatly hurt yields. Frost may have had some affect but yield decline was also due to alternate bearing following a record crop last season. Ruby led the four varieties in production at 2050 lbs/ac, followed by Padre at 1838 lbs/ac, Butte at 1715 lbs/ac, and Mission at 1500 lbs/ac. Kernel sizes (Table II) were within the normal range given the yields except for Butte. Butte kernels appeared somewhat shriveled this year (particularly given the modest yield) which may reflect the marginal M2624 compatibility of this variety. We have not found this affect on kernels before.

All four varieties continue to perform satisfactorily on M2624 rootstock, with few tree losses occurring. Some canopy expansion is still required to adequately fill allotted space and reach optimum bearing potential. The large 1998 crop limited shoot growth last year limiting canopy expansion. Overall tree vigor is limited with this rootstock. The twenty feet distance between rows for M2624 appears too wide given the shallow soil at this test site and dwarfing effect of plum rootstock. A more appropriate row width would be 18 feet at this site.

Suckering (typically troublesome with M2624) has been reduced by deeper tree planting. Growers considering M2624 blocks may want to special order trees high budded to allow deeper planting to help prevent root suckers and also employ an aggressive sucker removal program in early years to limit longterm troubles.

On the more positive side, M2624 production levels in 1999 equaled those of the same varieties on Lovell rootstock planted nearby at 15' x 20' on a somewhat deeper soil. Also, Padres on M2624 are not leaning over in these short statured trees like Padres on Lovell.

The leaf scorch symptoms reported here previously for the Butte variety on M2624 did not develop this season. During some years marginal leaf necrosis forms in mid summer on random limbs in scattered trees. Affected trees appear smaller in size while individual limbs affected show reduced vigor and defoliate before harvest. No disease organism, salt, fertilizer, chemical, or other cause has been found to explain this symptom. This problems seems to be separate from the mild etch malady afflicting young trees on M2624 in many commercial orchards. Numerous growers in 1999 reported problems resembling mild etch/leaf burn symptoms with Butte, Mission and others on M2624 in 2^nd and 3^rd leaf orchards. Mild etch has not been found in this test.

Table I.

Yield Lbs/Ac -- 1991-1999

Table II.

Kernel size

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Copyright © 1999 Colusa County Cooperative Extension, Univ. of California
Last modified: September 01, 2000