Honey bee colony strength standards
As with any early-blooming crop, it can be difficult to get strong colonies in time for apple bloom. As much as possible, colonies should have large adult populations and plenty of brood (see Chapter 7, page 51). Mayer et al. (1986) and Ambrose (1990) recommend a minimum strength standard of six frames of brood covered by adult bees. Such a colony will have about 20,000 bees.
Managing honey bee hives for apple pollination
In smaller orchards, colonies should be placed in groups of 4–6 at 150-yard (137 m) intervals. With larger orchards, colonies should be placed in groups of 8–16 at 200–300-yard (183–275 m) intervals, start- ing about 100 yards (92 m) from the edges. Young trees, with fewer blossoms, are less attractive to bees than older trees, so in young orchards the grower may have to increase hive numbers in order to compensate (Mayer et al., 1986).
150 Chapter 17
Fig. 17.4. Plan 3 calls for a solid planting of the pollenizer every fourth row.
(Source: Carol Ness.)
Colonies should not be kept at the apple orchards year-round.
Instead, they should be moved in after about 5% of the orchard is in bloom or when the first king blooms open. Such a delay will encour- age bees to focus on the crop rather than learn to visit competing plants.
Pollen dispensers (hive inserts) are devices that fit at the entrance of bee hives and hold pollen of desirable pollenizer varieties in such a way that bees dust themselves with the pollen as they leave the hive.
Although dispensers have a questionable record (Jay, 1986; Mayer et al., 1986), many apple growers use them. Like crabapples, pollen dis- pensers are an attractive remedy for old solid-block orchards with no pollenizers planted nearby (Anonymous, 1983; Mayer and Johansen, 1988). In general, inserts are warranted when weather restricts the blooming of pollenizers and the activity of the bees.
It is necessary to use only pure, hand-collected apple pollen in dispensers; cured, pollen-laden anthers are even better (Mayer et al., 1986). Bee-collected pollen pellets will not pollinate apple flowers, even though they are easily obtained from pollen traps at hive entrances. Lycopodium powder is sometimes used to dilute pollen, but it agitates bees and is no longer recommended. High-quality
Apple 1511
Fig. 17.5.Plan 4 has two pollenizer rows next to four rows of the main apple variety. (Source: Carol Ness.)
pollen for inserts is available commercially. Pollen should be kept refrigerated until use, and inserts should be replenished with about a teaspoon of pollen every few hours while bees are actively flying. A bee density rate of two bee hives per acre (5 ha21) is recommended if one is relying on inserts for pollination (Mayer et al., 1986).
Orchard mason bees as apple pollinators
Orchard mason bees (O. cornifrons, O. lignaria lignaria, and O. lig- naria propinqua) (Chapter 12) are potential apple pollinators. O. lig- naria lignaria, and O. lignaria propinqua land directly on the anthers and stigma of the blossom, thus maximizing the chance of successful pollination (Torchio, 1985). Honey bees, on the other hand, sometimes land on the flower petals before approaching the sexual column. In a comparison of orchard bees and honey bees in Japan, orchard bees visited more apple flowers per minute and con- tacted the sexual column 26 times more frequently (Batra, 1982).
Orchard bees are most promising in cases where honey bees are not available or in those varieties that honey bees work inefficient- ly, such as ‘Delicious’. In North Carolina, O. lignaria lignaria,
152 Chapter 17
Table 17.5.Recommended bee densities for apple.
No. of honey bee hives acre21(ha21) Reference
1(2.5) Humphry-Baker (1975); Crane and Walker (1984); Ambrose (1990); Kevan (1988)
2 (5) Mayer et al. (1986)
0.25, 0.5, 1, 2 (0.6, 1.2, 2.5, 5) McGregor (1976)
1–2 (2.5–5) Levin (1986)
0.4–2 (1–5) Kevan (1988)
0.8–1.2 (2–3) British Columbia Ministry of Agriculture, Fisheries, and Food (1994)
1.5–5 (4–12.5) Scott-Dupree et al. (1995)
1.5 (3.7) Literature average
Other measures and bees 20–25 honey bees per tree
per observation min Mayer et al. (1986) 75 honey bees leaving hive
entrance min21 Ambrose (1990); Mayer et al. (1986) 1 honey bee per 1000 flowers Palmer-Jones and Clinch (1968) 6 honey bee visits per flower Petkov and Panov (1967) 250 orchard bees acre21(618 ha21) Torchio (1985)
2834 orchard bees acre21(7000 ha21) Batra (1982)
O. lignaria propinqua, and O. cornifrons improved fruit-set, seed number, and fruit shape in ‘Delicious’ apples, even in areas of orchards that already had honey bee hives (Kuhn and Ambrose, 1984). In spite of these favourable studies, orchard mason bee man- agement has not reached practical large-scale levels. Recurring prob- lems include the timing of bee emergence with apple bloom, the dispersal of females away from the orchard after release, and disease contamination in nest materials.
Soil-nesting bees (non-Nomia) as apple pollinators
Populations of non-managed soil nesters range from abundant to insignificant. Some soil nesters are good apple pollinators where they occur in large numbers. In Maryland, the introduced A. pilipes villo- sula is active during apple bloom. It forages in cool, damp weather, and works from before dawn to after dusk (Batra, 1994). Small-scale culturing methods are worked out (S.W.T. Batra, unpublished report).
Leafcutting bees as apple pollinators
Managed leafcutting bees (M. rotundata) will visit apple blossoms in Washington, but they fly only when temperatures are greater than 75°F (24°C) (D.F. Mayer, unpublished data). Moreover, the bees must be incubated starting 21 days before bloom, and it is not easy to predict apple bloom.
Apple 1531
Flowering
The male (staminate) and female (pistillate) flowers of asparagus (Asparagus officinalis) usually develop on different plants, although some perfect flowers occur. Early-stage flowers are similar and have both male and female organs. One set of organs usually aborts, leaving the flower, and plant, either male or female. Male flowers (Fig. 18.1) are slightly larger than the females (Fig. 18.2) and open first. The flower has six major segments, six stamens (poorly developed in the pistillate flower), and a three-lobed pistil (poorly developed in the sta- minate flower). Both kinds of flowers have nectaries at the base of the corolla. The individual whitish-green flowers are pendulous, bell- shaped, and about !f in (0.6 cm) long. Flowers produce nectar and pollen and attract bees.