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Bee pollination benefits for peach and nectarine

Extract from Bulletin 4298: Honeybee pollination

Peach (Prunus persica)

For many varieties, honey bees have a demonstrable beneficial effect

General:

Most varieties of peaches and nectarines are self-fruitful. That is, fruit will be formed after the plants flowers are pollinated with its own pollen. However, there are varieties that will not be able to do this and are called self-unfruitful - that is, very little fruit will set unless flowers are fertilised with pollen from another variety, and is usually best carried out by honey bees. Fruit set can range from 22% to 84% (Ref. 7).

Other research shows fruit set of most self-fertile peach varieties is between 10 to 25% whilst for nectarine it averages 10% to 20%. If you isolate flowers of market sold peaches, canning peaches and nectarines, the fruits set for the three types is 20.9, 21.7 and 15.7% and if they are open pollinated, the fruit set increases to 34.2 (up 64%), 34 (up 57%) and 26.5 (up 69%) respectively (Ref. 10).

In USA, varieties that need cross-pollination are: J. H. Hale; Earlihale; Hal-Berta; Candoka; Mikado (June Elberta).

High-density plantings:

A honey bee pollination system was developed for high-density orchard plantings (see the Beetubes section). High-density use of Beetubes or beehives are an important part of pollination when dormancy-breaking and thinning chemicals are used as part of this type of orchard management. Why? Because the dormancy-breaking chemicals bring most of the flowers out in a short period, high bee density is required to set fruit over a very short flowering before chemical thinning is required. Evenness of pollination is assured which means a short harvest period is also another outcome.

High-density peaches (919 to 1196 trees/ha) have been evaluated (Ref. 1) and compared with standard open vase systems (299 trees/ha). The open vasFFe systems usually range from 250 to 350 trees/ha. With high crop prices, high-density systems with high crop yields gave the best net returns but the relative advantages will decrease with low crop prices.

Flowers:

Flower shape varies amongst varieties and affects the way honey bees pollinate flowers. Most peaches have small flowers whilst those of nectarines are generally larger. Larger flowers are more favourable for honey bees to land upon - for example, cultivars Nectared, Red June, Nectarose, Redchief, Fantasia, Flavortop, Springcrest, Michelini, Frederica. Smaller flowers are unfavourable, especially those of cultivars Dixired, Early Redhaven, Redhaven, Loadel and Shasta (Ref. 9).

For smaller flowers, honey bees tend to work side-ways obtaining nectar between petals and stamens and tend to not contact stigmas for pollination. The larger flowers have stamens and petals in a position where the side-ways nectar gathering of honey bees is prevented and pollination occurs (Ref. 9).

Thinning fruit:

Armothin is a surfactant that kills late flowers reducing the amount of fruit setting. It has not presented any phytotoxic effect on foliage or fruits. Hand thinning can be reduced by 40% to 70%. Armothin must be applied when 30% to 60% anthesis (open flowers) is reached. Doses recommended are 1% to 2%; repeated application was a better alternative when variety had a profuse or prolonged flowering period (Ref. 2).

Armothin is a poly-fatty acid amine and when sprayed its action on fruit is concentration-dependent and negatively related to the percentage of open flowers. It burns petals, stamens and pistils reducing pollen germination by tissue damage. Used at 1% to 2%, flowering was reduced by 30%. Best yields were obtained at the end of bloom when 80% to 100% of flowers were open. The best concentration was between 1.5% and 2%. The chemical did not affect fruit and shoot growth dynamics (Ref. 3). Spray only the upper part of the tree when 75% flowering (Ref. 2).

Dormancy breaking:

Poor bud break is probably the most critical element in the performance of deciduous fruit trees under warm growing conditions with limited duration of winter chilling. The use of dormancy-breaking chemicals also enhances the growth of vegetative buds which competes for assimilates "food" which can lead to the poor retention of flowers and fruitlets.

Chemicals used are:

Dormex - Hydrogen cyanamide, a powerful agent that can have toxic effects on flower buds leading to reduced flowering and hence lower yields. Used at the rate of 0.5% to 1.5%. The "toxic" effect is the competition between flowers and vigorously growing vegetative shoots (Ref. 4).

Armobreak - improved flowering occurred with addition of KNO₃. Armobreak is used at the rate of 1% with KNO₃ at 5% (Ref. 4).

Pollen:

Optimum temperature for ripening and release of pollen from anthers (dehiscence of anthers) was above 25C. The optimum humidity for ripening and release was between 50% and 70% (Ref. 5). Airborne pollen is virtually zero at 2.5 grains/m³ (Ref. 5).

In a peach orchard an average 600 g of pollen/hive was trapped over the flowering period (Ref. 5). Honey bees carried 15.3 mg of pollen/bee. Notable quantities of pollen produced (Ref. 9).

The number of pollen grains per anther varied from 450 to 2800 and the number of pollen grains per flower ranged from 15 000 to 101 400. The number of anthers per plant varies. Peaches sold through markets generally have 32 to 39 anthers/flower (average 1300 grains/anther and 47 000/flower), canning peaches have 30 to 38 anthers/flower (av. 1500 grains/anther and 55 000/flower) and nectarines have 33 to 40  anthers/flower. A few varieties have 28 to 30 anthers/flower (Ref. 9).

Pollen production varies greatly during consecutive years and differences between cultivars in given years were usually smaller than differences between years of the same varieties (Ref. 9).

Nectar:

Notable quantities of nectar produced. The range of nectar production is from 5 to 45 mg/flower, with canning peaches tending to produce more nectar (Ref. 9).

Sugar content of nectar is between 30% and 50% and the percentage is dependent upon the weather (Ref. 9).

Honey production:

Colony population increased but no surplus of honey was stored (Ref. 5).

Hives per hectare:

1 to 2 hives/ha for young trees, 2.5 hives/ha in older orchards.

Foraging:

Foraging activity was positively correlated with temperature and negatively with relative humidity.

Hives placed into peach orchards in Victoria had on 41% of observations more than 100 bees/minute flying from the hive entrance, and 10% of observations showed 200 bees/minute flying from the hive entrance (Ref. 5).

The maximum number of bees/tree was 3.6 with an average of 1.2 bees/tree visiting the peach flowers. All insects visiting peach flowers were honey bees (Ref. 5). Honey bees visited 3.74 flowers/minute and each visit lasted 20.5 seconds (Ref. 6).

The number of bee visits to flowers ranged from 4 to 107 during 15 minute observations. Canning peaches averaged 53 bee visits/15 minutes, whilst market sold peaches averaged 28 bee visits to flowers in 15 minutes. As much as 1 to 30 honey bee visits can be expected on each opened flower in day-time hours on those days when weather is favourable for bee activity (Ref. 9).

Pollen collectors were higher than nectar collectors in the morning (9 am) whilst in the late afternoon, nectar collectors out-numbered pollen collectors (Ref. 6).

Other pollinators:

Apis cerana: 8.9 visits/flower/minute; duration of visit was 5.56 seconds/flower and bees carried 12.2 mg of pollen from flowers (Ref. 6).

Review of bee pollination benefits:

• A significant 2.9 times increase in fruit set (9.5% to 27.6%: P< 0.01) and a significant 2.6 times increase in weight (18.2 kg/tree to 46.6 kg/tree: P<0.05) of variety Crawford in open and bee-excluded plots. Beehives were no more than 14 m from trees (Ref. 5).

• The activity of honeybees increased substantially the rate of fruit set on open standing flowers (Ref. 8).

• Fertilisation was always higher on uncaged branches with intensive bee visitation than on cages with no bee visits. Canning peach plants are less sensitive to the absence of honey bees. Uncaged branches produced 1.3 times higher fruit set than cages branches. Fruit sold through the markets (non-canning varieties) were more sensitive to the absence of honey bees. Fruit set on uncaged branches was 1.6 times higher fruit set than on caged ones. Nectarines yield was much higher with honey bees with uncaged flowers showing 2.3 times higher fruit set than those flowers on caged branches (Ref. 9).

• Peach variety Crawford. Honeybees were the only insects observed in this experiment. (D. F. Langridge et al. Aust. J. Exp. Agric. An. Husb. 17 (1977))

Peach variety Crawford. Honeybees were the only insects observed in this experiment. (D. F. Langridge et al. (1977) Aust. J. Exp. Agric. An. Husb. 17)

Attribute	Caged trees	Open trees	Statistical significance of difference
% fruit set	9.5	27.6	P<0.01
Harvested fruit	18.2 kg	46.6 kg	P<0.05
Fruit with split stones (%)	23.4	18.6	Not significant
Stones without kernels (%)	53	32.8	Not significant

References:

1. TITLE: Do high density systems really pay? - Evaluation of high density systems for cling peaches
   AUTHOR: DeJong, T. M.; Tsuji, W. and Grossman, Y. L.
   JOURNAL: Proceedings 6^th Symposium on integrating in orchard canopy, rootstocks and environmental physiology in orchard systems. Acta Hort. 451: 599-604 (1997).

2. TITLE: Evaluation of two promising peach chemical thinners in Chile
   AUTHOR: Lemus, G.
   JOURNAL: Proceedings 4^th International Peach Symposium, Acta Hort 465: 663-671 (1998).

3. TITLE: Armothin, A peach blossom thinning agent: 5 years of experience
   AUTHOR: Baroni, G.; Costa, G. and A. Ramina
   JOURNAL: Proceedings 4^th International Peach Symposium, Acta Hort 465: 673-677 (1998).

4. TITLE: Effect of dormancy breaking agents with Armobreak in the peach
   AUTHOR: Erez, A. and Yablowitz, Z.
   JOURNAL: Proceedings V, International Symposium on temperate fruits Acta Hort 441: 183-190 (1997).

5. TITLE: A study on pollination of dessert peaches cv Crawford
   AUTHOR: Langridge, D. F.; Jenkins, P. T. and Goodman, R. D.
   ABSTRACT: The availability of pollen for fertilisation of Crawford peaches and its dispersal by wind and by honey bees was studied in the laboratory and in a peach orchard. Optimum conditions for ripening and dehiscence of anthers were provided when temperatures were above 25C and humidity was below 70% Relative Humidity. There was virtually no airborne pollen in the open orchard or inside a cage placed around a peach tree. Flight activity of bees was related to ambient temperatures and bee visits to peach trees were low compared with those of cherries or apples. On trees to which bees had access there was 2.9 times increase in percentage of flowers that set fruit and a 2.6 times increase in weight of fruit harvested as compared with trees from which bees were excluded.
   JOURNAL: Aust. J. of Exp. Agric. and Animal Husbandry 17: 697-699 (1977).

6. TITLE: Foraging ecology of Apis cerana and A. mellifera L. in pollinating stone fruit crops
   AUTHOR: Mattu, V. K.; Chaudhary, D. K. and Kumar, L.
   ABSTRACT: Distribution, abundance and foraging activity of insect pollinators visiting stone fruit crops in Shimla Hills of the northwest Himalayas revealed that Apis cerana and A. mellifera were the most abundant pollinators on cherry, peach and almond. Syrphus sp., Eristalis spp., Halictus sp,. Fannia sp., Musca domestica (house flies) and Dolichopus sp. were the other pollinators visiting these crops. Peak foraging activity of A. cerana occurred an hour earlier than A. mellifera. In both species, the number of pollen collectors was higher than nectar collectors in the morning (9 am), but later in the afternoon nectar collectors outnumbered pollen collectors. A. cerana visited significantly more peach (8.9) and almond (6.5) flowers per minute compared to A. mellifera (3.74, 4.59). A. mellifera spent more time per flower (8.58, 20.5, 17.19 seconds) on cherry, peach and almond and carried more pollen (14.68, 15.25 mg) from cherry and peach compared to time spent (6.47, 5.56, 10.98 seconds) and pollen carried (13.56, 12.15 mg) by A. cerana. Both species preferred to forage on middle branches of cherry and top branches of peach tree, while in almond, top and middle branches were equally preferred. Foraging activity was positively correlated with temperature and negatively with relative humidity.
   JOURNAL: Pest Management and Economic Zoology 2(1): 35-3 (1994)9.

7. TITLE: Low temperature injury in peach and nectarine cultivars
   ABSTRACT: Winter hardy and late blooming peach and nectarine varieties can be grown successfully in Hungary. In some years even the most hardy varieties can be damaged by low temperatures. Thirty fresh market type-peach, 4 processing clingstone peach and 26 nectarine varieties were tested in Szatymaz, Southern Hungary, in an important peach growing area. In 1995, 2 to 5 days prior to blooming -7C caused 8% (Cresthaven) to 97% (Regina) damage to ballon stage flowers. In the winter of 1996/97 the temperature dropped to -20C, causing 9% (Lacika fele) to 89 % (Armking) of flower buds to be damaged. In April 1997, in the first days of blooming 7% (Cresthaven) to 97% (Domiziana) of the flowers were damaged by -5C. There was a correlation between the rate of damage and the start of flowering. In case of early blooming cultivars the rate of damage was higher not only in the flowering period but in winter as well, compared to late blooming cultivars. The yield was determined not only by frost damage, but by density of flower buds and by fruit set. The density of flower buds varied between 0.22 pcs/cm (Maria Luisa) and 1.10 pcs/cm (Armking). Fruit set of open pollinated flowers ranged from 22% (Cresthaven) to 84% (Primerose). Based on the characteristics studied the best varieties were selected for growing.
   AUTHOR: Z. Szabo, J. Nyeki, I. Szel, A. Pedryc, L. Szalay.
   JOURNAL: Fourth International Peach Symposium, Vols 1 - 2, Acta Horticulturae 465: 399-404 (1998).

8. TITLE: Open pollination and autogamy (self-fertilisation) of peach and nectarine varieties
   ABSTRACT: As many as 150 varieties of peaches and nectarines have been studied in Hungary by our team during the period of 1960-1996. The main objective was the assessment of the conditions of fertilisation and fruit set, as for the comparison of natural self-pollination and open pollination.
   The rate of fruit set from open pollination showed the highest values in peaches amongst all stone fruits. The rates of fruit set through autogamy or open pollination, both varied considerably according to growing site, season and variety. The effect of the growing season, that is, the weather during the blooming period, prevailed over the varietal tendencies.
   Fruit set from either self-pollination or open pollination was always inferior in nectarines than in peaches for both fresh market type or processing clingstones. Natural self-pollination produced lower fruit set than artificial self-pollination, moreover, the activity of honeybees increased substantially the rate of fruit set on open standing flowers.
   AUTHOR: J. Nyeki, Z. Szabo, A. Andrasfalvy, M. Soltesz, J. Kovacs.
   JOURNAL: Fourth International Peach Symposium, Vols 1 - 2, Acta Horticulturae 465: 279-284 (1998).

9. TITLE: Studies on the bee pollination of peach and nectarine
   ABSTRACT: Peaches and nectarines produce notable amounts of both nectar and pollen to attract bees to flowering trees. Data on: (1) pollen production by 17 peach and nectarine cultivars in 1983 and 1984 in Hungary (1 table); and (2) number of bee visits to open flowers of 12 peach cultivars and 7 nectarine cultivars during 1982, 1984 and 1989 in Hungary (3 tables) are presented. Factors affecting pollination of flowers by bees, including flower shape, relative position of anthers, type of pistil [gynoecium], anther size, pollen size, nectar and pollen production are discussed.
   AUTHOR: P. Benedek and J. Nyki.
   JOURNAL: Proceedings of the third international peach symposium, Beijing, China, 6-10 September 1993, Acta Horticulturae 374: 169-17 (1996)6.

10. TITLE: Fruit set of self and pollen pollinated peach flowers under Hungarian ecological conditions
    AUTHOR: Nyeki, J. and Szabo, Z.
    JOURNAL: Proceedings of the third international peach symposium, Beijing, China, 6-10 September 1993, Acta Horticulturae 374: 177-18 (1996)0.

Page reviewed: March 2006