Chapter 2: Almonds


Chapter 2: Almonds


ALMOND
Prunus amygdalus Batsch, family Rosaceae

Almond production in the United States is limited almost exclusively to California, which produces more than one-third of the world supply of almonds (Anonymous 1969b). In 1971, 169,000 acres of bearing trees were reported.

The average annual production in the United States for 1958-68 was 740 pounds of meat (the edible portion of the fruit) per acre, ranging from 568.5 to 944.4 lb/acre (Anonymous 1969a). The 1970 farm value of the crop was $80.1 million.

Plant:

The deciduous almond resembles the peach in its general size, manner of growth, blossoms, and leaves. The blossoms, however, appear earlier in the spring than peach blossoms, usually before the leaves develop. The fruit also resembles the peach in structure, the thin leathery inedible hull (mesocarp) corresponding to the flesh of the peach (Kester 1969). This hull splits at maturity, revealing the usually thin shell with its edible kernel (meat) inside. Thus, we eat the flesh of the peach and discard the pit and enclosed kernel, while the hull of the almond is discarded and the kernel of the nut is eaten. This may be consumed raw, roasted, or toasted, whole or sliced, alone, or in candy, confections, or prepared dishes.

An almond tree may remain in production 50 years or more. The trees are usually planted 20 to 30 feet apart. Because of the self- incompatibility of commercial cultivars, the orchards are usually planted with two rows of the main cultivar and one of the pollenizer cultivars. Almonds prosper where summer temperatures are hot and dry, but they require chilling during dormancy, with a minimum of freezing weather after mid-February. Immature fruit may be killed at 31deg F. During flowering, fair weather with daytime temperatures above 57 deg is essential to permit flight of pollinating insects. For these reasons, the area in the United States where almonds can be successfully grown is limited primarily to the Sacramento and San Joaquin Valleys of California.

'Nonpareil' is planted more than any other cultivar and accounts for more than half of the almond production. The 'Kapareil', developed and deriving its name from the 'Eureka' and the 'Nonpareil', is a good pollenizer for the 'Nonpareil' (Kester et al. 1963). The 'Nonpareil' shell is thin (shelling 60 to 70 percent meat), and the nuts ripen in late August or early September. The 'Texas' or 'Texas Prolific' is the second most important cultivar. It shells only 40 to 45 percent meat, blooms several days to 1 week after 'Nonpareil,' and ripens in late September or October. Other cultivars include the following (Griggs 1970*, p. 186):

Early
'I.X.L.', 10 'Jordanolo', 'Ne Plus Ultra', 'Peerless'.

Mid-season
'
Cressey', 'Davey', 'Drake', 'Kapareil', 'Merced', 'Nonpareil', 'Norman', 'Paxman', 'Price Cluster', 'Profuse', 'Vesta'.

Late
'Ballico', 'Butte', 'Emerald', 'Empire', 'Mission' ('Texas'), 'Ripon', 'Ruby', 'Thompson', 'Tioga', 'Wawonal', 'Yosemite'.

Very Late
'Tardy Nonpareil.'

__________
10 'Jordanolo' , 'I.X.L.', and 'Drake' are no longer being planted, but there are significant acreages of bearing trees of these cultibvars.

Inflorescence:

The 1- to 11/2-inch almond flower has a single pistil with two ovules (fig. 35). One or both of the ovules may develop into fruits; however, a "double" is not desired in commercial production. The ovary is in a floral cup formed by the green bracts, the five pinkish petals, and the 10 to 30 stamens. Nectar is secreted within the cup. The pollen, which is not windblown, is produced on the anthers that loosely surround the stigma. The abundant flowers open from late January to late March (Vansell and Griggs 1952*, Vansell and DeOng 1925), but primarily from mid-February to mid-March. The crop is harvested in the fall.

Honey bees visit the flowers eagerly for both nectar and pollen.Honey produced from almonds is of poor quality and when harvested from the hive is used in the bakery trade. It is usually left in the hive as feed for the bees. The nectar and pollen stimulate honey bee brood-rearing. Nectar foragers are active on almonds throughout the day if weather permits, but pollen foragers are most active during midday. The honey bee is the primary insect visitor to almond flowers.

[gfx] FIGURE 35. - Longitudinal section of 'Mission' (Texas') almond flower, x 6.

Pollination Requirements:

The almond flower is self-incompatible. A pollen tube of a flower of the same tree, the same cultivar, and sometimes of certain other cultivars, will not grow down the style (Kester 1969). Hatch (1886) noted that trees of the 'Languedoc' cultivar near seedling trees of other parentages always produced heavier crops than when in solid blocks. According to Griggs and Iwakiri (1964), all almond cultivars grown in California require cross-pollination to produce a crop. These authors also stated that under weather conditions favorable for honey bee flight the individual flower is most receptive to cross-pollination the day following opening and remains decreasingly receptive the next 3 or 4 days. Flowers not cross-pollinated shed in about a month (Kester and Griggs 1 959a). A few pairs of almond cultivars are cross-incompatible. If a grower wants to grow these, he should plant at least one other cultivar as a pollenizer (Griggs 1970*).

A profitable almond crop depends upon the cross-pollination of practically all flowers. The grower wants the heaviest possible set of almonds, because there is no fruit-thinning problem and nuts with small kernels are in greatest demand (Griggs 1953*). (By comparison, 5 percent of the blossoms on an apple tree can produce an economic yield.) The failure of any almond flowers to be cross-pollinated reduces yield by just that much. Only the bees that carry pollen from a flower of one cultivar to another receptive flower contribute to fruit-set. Not all flowers set, and several must be cross-pollinated for every almond expected (Kester 1958). To obtain a maximum crop of almonds, essentially 100 percent of the flowers must be cross-pollinated (Kester and Griggs 1959b). The bee population should therefore be sufficiently heavy that repeated visits to every flower occur and the bees must "shop around;" that is, they should not only visit many flowers on one tree but also must visit between cultivars to obtain their loads of nectar and pollen. In this way, the pollen is spread from one tree to another to the maximum extent.

Pollinators:

The honey bee is practically the only pollinating insect of economic importance on almonds, and growers throughout the world have been urged to use it (Ferreres in Mexico, 1947; Gagnard in Algeria, 1954; Griggs in California, 1970*; Muttoo in India, 1950; Purdie and Winn in Australia, 1964, 1965). The importance of a heavy honey bee population cannot be overemphasized. Almond blossoming occurs when days are short and cool, other pollinators are absent, and the honey bee colonies are frequently in their weakest condition of the year. The weather is most likely to be unsettled, and temperatures often restrict bee activity to 1 to 3 hours at midday.

Although only 1 grain of pollen is theoretically necessary to set an almond fruit (Tufts 1919), the pollen must come from another compatible cultivar at just the right time. Bees often visit scores of blossoms on a tree before moving to another if nectar or pollen is plentiful, yet maximum transfer of the pollen between appropriate trees is necessary. This calls for a heavy bee concentration on the trees. An orchard with a bee population that permits the colonies to store surplus almond honey would be questionably low for maximum pollination and maximum almond production. The more a bee is forced to "shop around" between trees to acquire a load of food, the more effective it becomes as a pollenizer of almonds.

As pointed out by Brittain (1933), the adjoining acreages can influence forager effectiveness, so that the area within one-half mile or so, and not only the orchard alone, must be considered the unit when calculating the pollinator force necessary for the orchard.

Most almond growers recognize that cross-pollination by bees is essential, and they make some effort to provide this service to the flowers. Frequently, too few colonies are obtained, they are not sufficiently populous in field bees, they are not properly distributed for maximum efficiency in visiting all flowers, or the bees become damaged by pesticides before their services on the crop are completed. Sometimes, only a few weak colonies near the orchard are depended upon to set the almond crop rather than the adequate number of populous colonies distributed uniformly throughout the orchard. Frequently, "bargain prices" are paid for truck loads of 100 or more colonies unloaded in one easily accessible place (for the beekeeper), and where the bees have a choice of other than almond flowers to visit.

Sometimes, the grower is unable to locate an uncommitted beekeeper or one who wants to supply bees. Such a situation was recognized in 1970 when growers were told (Anonymous 1970) that bees were scarce due to pesticide losses and the reluctance of beekeepers to supply bees for pollination. The growers were further told that the situation was likely to continue; therefore, they should consider contracts for 1971 and even future years to assure themselves of bees.

The most serious problems appear to be (1) the low rental fee which is established largely by the beekeeping industry itself, (2) colonies of inadequate strength, and (3) colonies not strategically placed or properly serviced to provide adequate pollination. The beekeeper tends to feel that higher pollination fees would only invite competition by other beekeepers. He therefore charges little if any more than the $5 to $10 recommended 40 years ago (Phillips 1930). The statistics indicate that there are not sufficient mobile colonies in California or in nearby adjoining states to satisfactorily pollinate the current almond orchards.

Pollination Recommendations and Practices:

The literature on almond pollination leaves no doubt about the need for an ample supply of bees to pollinate the flowers. There is no other choice than to have honey bees perform this task. The question is one of quantificationÑhow many bees?

Vansell and Griggs (1952*) recommended that there be either one pollenizer row of trees for every three rows of the main variety, or two rows of pollenizer trees for each two of the main variety. Then they recommended that two to three strong colonies of honey bees be used per acre. Woodrow (1932), Purdie and Winn (1964), and Sheesley and Poduska (1970a, b, c) showed that strong colonies were much more effective than weak ones, particularly at lower temperatures, such as those likely to occur during almond blossom time.

Griggs et al. (1952*) counted 20 to 30 bees on each of two almond trees caged with a colony of honey bees. The weather was favorable for bee activity at the time the counts were made. Griggs and Iwakiri (1960) counted 150 to 200 bees per tree in the open, which they considered fair to good bee activity. There were seven colonies per acre (half of them were weak, half were strong) supplied to the orchard in which the counts were made.

The studies indicate that at least two to three strong colonies per acre may be required for maximum production of almonds. The colonies should be distributed within the orchard in small groups one-tenth mile apart. Each colony should have at least 800 in2 of brood and a cluster of bees that covers most of the frames in a two-story deep-frame hive. The colonies should be in the orchard at the beginning of flowering and should remain until flowering on the main cultivar has ended.

Whether more colonies per acre or closer placement of the groups of colonies within the field will result in greater net increase to the grower has not been determined. In the San Joaquin Valley of California, a commonly held idea is that almond production at bloom time can be increased more with less investment by having adequate bees than with any other expenditure, all other factors being equal. In general, this would indicate that not enough colonies are being used for maximum production of almonds.

LITERATURE CITED:

ANONYMOUS.
1969a. DO WE HAVE A CROP? Almond Facts 34(2): 12.

______ 1969b. PRICE RECOMMENDATIONS MADE. Almond Facts 34(4): 24-25.

______ 1970. BUZZZZ. Almond Facts 35(1): 27.

BRITTAIN, W. H.
1933. APPLE POLLINATION STUDIES IN THE ANNAPOLIS VALLEY, N.S., CANADA, 1928-1932. Canada Dept. Agr. Bul. 162, n.s., 198 pp.

FERRERES, L. P.
1947. [POLINIZACION DEL ALMENDRO POR LOS INSECTOS.] Rancho Mex. 3(18): 17-20, 75. [In Spanish.]

GAGNARD, J. M.
1954. SYSTEMATIC CHARACTERS AND THE STERILITY IN ALMONDS CULTIVATED IN ALGERIA.] Algeria Inst. Agr. Ann. 8(2): 163. [In French] Abstract in Bee World 39: 192.

GRIGGS, W. H., and IWAKIRI, B. T.
1960. ORCHARD TESTS OF BEEHIVE POLLEN DISPENSERS [TRAPS] FOR CROSS-POLLINATION OF ALMONDS, SWEET CHERRIES, AND APPLES. Amer. Soc. Hort. Sci. Proc. 75: 115-128.

______and IWAKIRI, B. T.
1964. TIMING IS CRITICAL FOR EFFECTIVE CROSS-POLLINATION OF ALMOND FLOWERS. Calif. Agr. 18: 6 - 7.

HATCH, A. T.
1886. ALMOND. Calif. State Bd. Hort. Rpts. 1885-86, pp. 324 - 326.

KESTER, D. E.
1958. MAJOR FACTOR IN 1958 CROP LOSSES WAS RAIN DURING BLOSSOMING SEASON. Almond Facts 23(6): 6-7.

______ 1969. ALMONDS. In Handbook of North American Nut Trees. North. NUt Growers' Assoc. (Knoxville, Tenn.), pp. 302-314.

______ASAY, R., and SERR, E. E.
1963. THE KAPAREIL ALMOND. Calif. Agr. Expt. Sta. Bul. 798, 13 pp.

______and GRIGGS, W. H.
1959a. FRUIT SETTING IN THE ALMOND: THE PATTERN OF FLOWER AND FRUIT DROP. Amer. Soc. Hort. Sci. Proc. 74: 214-219.

______and GRIGGS, W. H. 1959b. FRUIT SETTING IN THE ALMOND: THE EFFECT OF CROSS- POLLINATING VARIOUS PERCENTAGES OF FLOWERS. Amer. Soc. Hort. Sci. Proc. 74: 206 - 213.

MUTTOO, R N.
1950. HONEY BEES AND FRUIT CROPS. Indian Jour. Hort. 7(3/4): 17 - 20.

PHILLIPS, E. E.
1930. HONEYBEES FOR THE ORCHARD. N.Y. (Cornell) Agr. Col. Ext. Bul. 190, 24 pp.

PURDIE, J. D., and WINN, R. A.
1964. ALMOND POLLINATION-HONEY BEE ACTIVITY. So. Austral. Jour. Agr. 68(5): 152 - 157.

______and WINN, R. A.
1965. ALMOND POLLINATION: HONEY BEE ACTIVITY. Austral. Bee Jour. 46: 17 -19.

SHEESLEY, B., and PODUSKA, B.
1970a. GRADING BEE COLONY STRENGTH. Almond Facts 35(5): 22-24.

______and PODUSKA, B.
1970b. STRONG HONEYBEE COLONIES PROVE VALUE IN ALMOND POLLINATION. Calif. Agr. 24(8): 4 - 6.

______and PODUSKA, B.
1970C. RELATIVE VALUES OF HONEYBEES COLONIES FOR ALMOND POLLINATION. Gleanings Bee Cult. 98(8): 486-491.

TUFTS, W. P.
1919. ALMOND POLLINATION. Calif. Agr. Expt. Sta. Bul. 306: 337-366.

VANSELL, G. H., and DEONG, E. R.
1925. A SURVEY OF BEEKEEPING IN CALIFORNIA AND THE HONEYBEE AS A POLLINIZER. Calif. Agr. Expt. Sta. Cir. 297, 22 PP.

WOODROW A. W.
1932. THE COMPARATIVE VALUE OF DIFFERENT COLONIES OF BEES IN POLLINATI0N. Jour. Econ. Ent. 25: 331-336.


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