Floral biology of Macadamia integrifolia (Macadamia
Dr Elizabeth M. Exley, Department of Entomology, The University of Queensland Grant details
23 March 1988
Experiments carried out with travel and salaries monies provided by the A.F.F. are listed below.
Experiments were performed only in orchards due to the inaccessibility of racemes of trees in natural locations. Furthermore, since the refugia of wild macadamia trees are small, they no longer represent "natural" situations.
l. Pollinating insect diversity and abundance in 11
macadamia orchards in Queensland and NSW.
The eleven orchard sites surveyed for diversity and abundance of pollinating insects are shown on Fig 1.
A mean of greater than 90% of macadamia flower visitors belonged to two species of social bees, honey bees (Apis mellifera) or Trigona bees (Trigona carbonaria). The abundance of insects other than honey bees was correlated with the extent of surrounding vegetation.
2. Pollinating insect diversity, abundance and behaviour
at one site (Closeburn) for the full duration of the flowering season.
Honey bees and Trigona bees were present through the entire flowering season of macadamia. Other insects were rare at the beginning of the flowering season (July) but common later in the flowering season (October).
Results show that whereas honey bees forage for nectar, Trigona bees visit the flowers mainly for pollen. This results in Trigona bees coming into contact with the stigma of the macadamia flower more often than honey bees, suggesting they are more efficient pollinators.
3. Foraging preferences of the two major pollinating
insects (viz honey bees and Trigona bees) to determine which bee
species visit racemes in sunny and/or shady positions and on both
heavily and lightly flowering trees.
No statistical analysis is yet completed but it appears that both honey bees and Trigona bees forage equally actively in open sunny positions and shady positions.
4. Relative pollinator efficiency of the two major
insect visitors by covering racemes with a wire mesh that allows
only the smaller Trigona bees to forage and assessing the resulting
initial nut set and final nut set.
Macadamia racemes visited only by Trigona bees showed high initial nut set suggesting these bees are efficient pollinators. Data for final nut set is not yet available.
5. Determining the relationship between the number
of bee visits and the initial and final nut set by bagging racemes
and removing the bags for varying periods each day for the full
duration of raceme life.
Treatments that resulted in higher levels of insect visitation also had higher initial nut set. Data for final nut set is not yet available.
B. EXPENDITURE STATEMENT
Salaries (for period 7 July 1987 to 30 Oct 1987)
345 hours at $9.52 / hour $3284.24
Travel 1255 km at $0.21 / km $263.60