PEACH AND NECTARINE
Prunus persica (L.) Batsch, family RosaceaeThe peach and the nectarine (P. persica var. nectarina (Ait.) Maxim.) differ primarily in that the nectarine has a smooth skin, but the peach is covered with needlelike hairs or fuzz. Nectarines are known as a single factor mutation of the peach. Nectarine-like fruit has been obtained from peach trees and peaches have been found on nectarine trees (Philp and Davis 1936).
The farm value of the 1970 peach crop was $176.3 million compared to $10 million for nectarines. Peaches are grown on about 200,000 acres, 81,810 acres of which are in California. Nectarines are produced almost exclusively in California on 7,790 acres (Kitterman and Nelson 1971).
Plant:
The deciduous trees, set in the orchard about 20 feet apart, are usually trimmed to 8 to 16 feet in height (fig. 142). There are scores of cultivars only recognizable by the type of fruit they produce. Flowering occurs at about the same time each spring on all cultivars except for a few early and late blooming cultivars. The plant usually requires some winter chilling to promote normal growth and flower development in the spring. Freestone cultivars, those with fruits that break away easily from the stone or seed, are much more popular for the fresh market than the clingstone type in which the flesh of the fruit is firmly attached to the stone. The freestone 'Elberta' cv. has been the most popular of all cultivars, but it is being replaced by firmer, more attractive cultivars. The highly perishable fruit must be harvested at a precise stage of ripening.
[gfx] FIGURE 142.- Peach orchard in bloom.
Inflorescence:
The many attractive pink or reddish blossoms of the peach and nectarine appear in the spring at about the time leaf development begins (fig. 143). The structure of the flower is ordinary in that sepals are present but small; there are usually five rather oval petals, 25 to 40 mm across, and 15 to 30 pollen-laden anthers surrounding the single erect pistil through which the pollen tube reaches a single ovary, which contains two ovules. Following fertilization, only one ovule normally develops at the expense of the other, leading to the development of a one- seeded stone. As a result, the fruit develops asymmetrically (Stewart et al. 1967). The peach ovary is covered with a dense coat of hairs. The nectarine ovary is usually bare, similar to that of the plum (figs. 144, 145).
Most cultivars produce pollen at the time the stigma is receptive. Nectar is secreted at the base of the corolla. The flowers are highly attractive to honey bees and other pollen- and nectar-collecting insects. The fact that only one ovule must be fertilized for a peach fruit to set as compared to hundreds of ovules in other fruit such as melons or papayas, enormously simplifies the pollination of the peach.
Normally, the flowers are fully closed at 6 a.m., but most of them are open by 10 a.m., and all are open by noon. They do not close at night; they may stay open and the stigma may be receptive for 3 days (Randhawa et al. 1963).
[gfx] FIGURE 143.- Peach blossoms.
FIGURE 144.- Longitudinal section of 'Babcock' peach flower, x 4.
FIGURE 145. - Longitudinal section of 'Perfection' nectarine flower, x 4.Pollination Requirements:
Considering the economic importance of the peach crop, surprisingly little has been done about its pollination requirements. There are many references to fruit production (for example, Cullinan 1937, Hedrick 1917, USDA 1967), which usually state that most cultivars are self-fertile and a few are self-sterile (Kanato et al. 1967, Lagasse 1926). Many self- sterile cultivars have been largely or completely eliminated from the market, regardless of their other good qualities, because interplanting of cultivars and insect pollination are necessary in their production. These include 'Alamar', 'Candoka', 'Chinese Cling', 'Hal-berta', 'J. H. Hale', 'June Elberta', 'Mikado', and a few others. Unfortunately, the references to the self-sterility of such cultivars has tended to draw attention away from the "self-fertile" cultivars and the possibility that they might not be capable of fertilizing themselves without the aid of an outside agency.
GLASSHOUSE POLLINATION STUDIES:
Grieve (1879) discounted the need for or value of bees in a glasshouse. Conners (1922b, 1926) reported that peaches in a glasshouse failed to set unless pollinated by hand or bees because of a lack of air currents to sway the blossoms and cause the stamens to come in contact with the stigma. Coote (1895) also showed that when trees were grown in the greenhouse with bees to visit the flowers a heavy set resulted. Vermeulen and Pelerents (1965) obtained 84 fruits per tree in a glasshouse with bees but only five per tree with bees absent. Thompson (1940) reported on the value of bees to peaches in greenhouses in England.BAGGING AND WIND POLLINATION STUDIES:
Conners (1917) reported that trees of 'Belle', 'Early Crawford', 'Elberta', and 'Greensboro' cvs. caged to exclude insects set fruit readily. Later, he (1922a )mentioned the 'Susquehanna' as being self-sterile and that he discarded three other selections for that reason. Crandall (1920) found that more than twice as man: bagged flowers set fruit if they were hand pollinated than if bagged only. Detjen (1945) performed a similar experiment with similar results, that is, flowers bagged and hand pollinated set more fruit than did open flowers, but flowers bagged only, without additional pollination, set fewer flowers. He felt that buffeting of the flowers by wind was sufficient to dislodge the pollen and transfer it to the stigma. Sharma (1961) reported that while bagged peach flowers "gave a commercial set without pollination insects," the set was higher on unbagged branches. Kerr (1927) bagged branches of 27 cultivars and found that 19 were "sufficiently self fruitful, 5 did not set enough and 2 were unfruitful".Both Chandler (1951*) and Langridge (1969) reported that there is little airborne peach pollen.INSECT POLLINATION STUDIES:
Factual tests on the relation of insects to pollination of peaches are woefully inadequate although numerous tests have given indications, and conclusions have been drawn, on the relation of insects to set of fruit of peaches. For example, MacDaniels and Heinecke (1929) stated: "Most peach varieties are self-fertile and present no pollination difficulties except that attributable to lack of sufficient insects at blooming time to accomplish self-pollination. "Bulatovic and Konstantinovic (1962) obtained better set on various species with exposed flowers than with selfed flowers, and they concluded that there was slightly more fruit set on all cultivars when visited by bees.
Rather thorough studies were conducted by Marsha et al. (1929) who summarized their findings with the statement, "Enough has been written to show the satisfactory crops from either self-sterile or self-fertile varieties of orchard fruits cannot be obtained unless there are plenty of honey bees or other pollen-carrying insects working in the orchard at the time the trees are in bloom." Murneek (1937) also stated that "Whether variety is self-sterile or self-fertile insects are equally necessary for proper pollination and setting of fruit. Chandler (1951*) stated that the pollen must be applied to the stigma by insects that visit the flowers. Jorgense and Drage (1953) listed peaches as "largely self-fruitful, but "bees are necessary" in their pollination. Khan (1930) also concluded that cross-pollination is necessary to obtain good yields and that bees are the chief agent for cross-pollination.
Boller (1953) stated that "Some pollination occurs' without the help of bees, probably by shaking of the flowers by the wind. Whether we get enough self-pollination by this means is unknown. We do know that a small number of bees can do a lot of self-pollinating since almost every visit to a flower results in self- pollination."
H. W. Fogle (personal commun., 1971) stated that the flowers are receptive to pollination 4 to 7 days, depending upon the weather, but the set is unlikely "unless a bee or similar insect enters the flower and spreads the pollen around."
These references indicate that, although the actual data are sparse, pollinating insects are of value even for the self-fertile cultivars of peaches.
Some growers consider thinning of a heavy set of fruit to be a greater problem than pollination (Snyder et al. 1952); however, thinning the fruit after flowering is easier than getting fruit to set if the flowers are gone and the set is inadequate.
Pollinators:
The degree of pollination actually accomplished by wind as compared to insects is unknown. Also, if, as some references indicate, wind alone is insufficient and insects are needed, the number of visitors is unknown. If the weather is clear and mild, the bees will visit the flowers throughout much of the day; however, if the weather is cold or wet, bees may be absent. In visiting the nectaries in the base of the flower, the bee either pushes one or more anthers against the stigma or rubs against it. In either case, pollen is transferred to the stigma. If the cultivar is self-fertile, a high population of bees would not be needed to set an adequate crop (Boiler 1963). Should the population of bees in the area be inadequate, honey bees can be transported and placed in the orchard. The evidence indicates that their presence in the orchard is important. Randhawa et al. (1963) considered the honey bee most important as a pollinator of peaches. Yokozawa and Yasui (1957) reported that when the weather was generally cloudy and rainy the Diptera were the most common floral visitors, but during clear weather the Hymenoptera were more frequently observed on the flowers.
Pollination Recommendations and Practices:
Numerous horticulturists have indicated that bees are beneficial to peaches, and most State bulletins recommend to growers that action be taken to increase the number of insect pollinators in the orchard. The growers are fortunate in that the peach flowers are attractive and ample pollination is obtained free when conditions are favorable, with bees coming long distances.
Newell (1903) urged the keeping of honey bees near peach orchards. Jorgensen and Drage (1953) considered bees necessary. Kelly (1964) made a study relating to cost of peach growing in Pennsylvania and found that an average of only one hive per 16 acres was used.
Benner (1963) recommended one strong colony of honey bees for each three to five acres of orchard just coming into bearing but stated that in older orchards one good colony of bees for each acre might be needed.
Several hundred colonies of honey bees are rented annually for pollination of peaches in New Jersey (J. C. Matthenius, Jr., personal commun., (1970). Most growers, however, take no action in relation to pollination of the crop.
LITERATURE CITED:
BENNER, B.
1963. FRUIT AND VEGETABLE FACTS AND POINTERS: PEACHES. United Fresh Fruit and Vegetable Assoc., Washington, D.C., 3d rev. and expanded ea., p. 11 (total pagination not known).BOILER, C. A.
1953. POLLINATION OF STONE FRUITS. Oreg. State Hort. Soc. Proc. 45: 122-125.BULATOVIC, S., and KONSTANTINOVIC, B.
1962. THE ROLE OF BEES IN THE POLLINATION OF THE MORE IMPORTANT KINDS OF FRUIT IN SERBIA. In 1st Internatl. Symposium on Pollination Proc., Copenhagen, Aug. 1960. Commun. 7, Swedish Seed Growers' Assn., pp. 167 - 172.CONNERS, C. H.
1917. METHODS IN BREEDING PEACHES. Amer. Soc. Hort. Sci. 14th Ann. Mtg. Proc.: 126-127.______ 1922a. PEACH BREEDING A SUMMARY OF RESULTS. Amer. Soc. Hort.. Sci. I9th Ann. Mtg. Proc: 108-115.
______ 1922b. FRUIT SETTING OF THE J. H. HALE PEACH. Amer. Soc. Hort.. Sci. 19th Ann. Mtg. Proc.: 147-151.
______ 1926. STERILITY IN PEACHES. Hort. Soc. N.Y. Mem. 3: 215-221.
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1937. IMPROVEMENT OF STONE FRUITS. U.S. Dept. Agr. Yearbook 1937: 665-748.DETJEN, L. R.
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1879. BEES AS FERTILIZING AGENTS. Gard. Chron. 11: 204.HEDRICK, U. P.
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1930. SOME OBSERVATIONS ON THE POLLINATION OF PEACHES (PRUNUS PERSICA BENTH. AND HOOK.). Agr. Jour. India 25(6): 492-494.KITTERMAN, J M., and NELSON, G.
1971. 1970 CALIFORNIA FRUIT AND NUT ACREAGE. Calif. Crop and Livestock Rptg. Serv., 19 pp.LAGASSE, F. S.
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1969. EFFECTS OF TEMPERATURE, HUMIDITY, AND CAGING ON THE CONCENTRATION OF FRUIT POLLEN IN THE AIR. Austral. Jour. Expt. Agr. Anim. Husb. 9:549-552.MACDANIELS L. H., and HEINICKE, A. J.
1929. POLLINATION AND OTHER FACTORS AFFECTING THE SET OF FRUIT WITH SPECIAL REFERENCE TO THE APPLE. N.Y. (Cornell) Agr. Expt. Sta. Bul. 497, 47 pp.MARSHALL, R. E., JOHNSTON, S., HOOTMAN, H. D., and WELLS, H. M.
1929. POLLINATION OF ORCHARD FRUITS IN MICHIGAN. Mich. Agr. Expt. Sta. Spec. Bul. 188, 38 pp.MURNEEK, A. E.
1931. POLLINATION AND FRUIT SETTING. Mo. Agr. Expt. Sta. Bul. 379, 28 pp.NEWELL, W.
1903. THE RELATION OF BEES TO FRUIT GROWING. Ga. State Hort. SOc. Proc. 27: 58-66.PHILP G. L., and DAVIS L. D.
1936. PEACH AND NECTARINE GROWING IN CALIFORNIA. Calif. Agr. Ext. Sen. Cir. 98, 62 pp.RANDHAWA, G. S., YADAV, I. S., and NATH, N.
1963. STUDIES ON FLOWERING, POLLINATION AND FRUIT DEVELOPMENT IN PEACH GROWN UNDER SUBTROPICAL CONDITIONS. Indian Jour. Agr. Sci. 33(2): 129-138.SHARMA, P. L.
1961. THE HONEYBEE [APIS INDICA] POPULATION AMONG INSECTS VISITING TEMPERATE-ZONE FRUIT FLOWERS AND THEIR ROLE IN SETTING FRUIT. Bee World 42: 6-7.SNYDER, J. C., BRANNON, D. H., and HARRIS, M. R.
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1940. THE IMPORTANCE OF BEES IN AGRICULTURE. Bee Craft 22(250): 6-7.UNITED STATES DEPARTMENT OF AGRICULTURE.
1967. GROWING PEACHES EAST OF THE ROCKY MOUNTAINS. U.S. Dept. Agr. Farmers' Bul. 2205, 24 pp.VERMEULEN, L., and PELERENTS, C.
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1957. [STUDIES ON THE POLLINATION OF PEACH.] 1. INSECT VISITORS TO THE FLOWERS OF PEACH.] Hort. Assoc. Jap. Jour. 26(3): 185-191. [In Japanese, English title and summary.]
