Stocking rates of Trigona carbonaria for the pollination of greenhouse capsicums

Australian stingless bees contribute to the pollination of commercially important crops. Optimum bee stocking rates have, however, yet to be established. To determine stocking rates, five pollination trials were conducted. For each trial, 50 plants of Capsicum annuum L. var. grossum (L.) Sendt cv. Aries were placed in each of two glasshouses and a colony of T. carbonaria randomly assigned to one of the two glasshouses. The other glasshouse contained no bees and acted as a control. The grade and weight of fresh fruit increased by 26% and 24%, respectively, for plants subjected to bee pollination. To determine the number of pollination events required for optimum pollination, during the final trial, 110 flowers were randomly selected and covered with organza draw-string bags. The bags were removed between 10.00 and 11.00 h on the day of assessment to allow between one to ten pollination events to occur. A pollination event was deemed to have occurred each time a bee touched the stigma. There were no significant increases in pollen grain numbers on stigmatic surfaces after three pollination events. It was therefore determined that for optimum pollination to occur, T. carbonaria needed to come into contact with C. annuum stigmatic surfaces three times. The stocking rate was calculated from number of pollen foragers per hour, the mean number of foraging hours per day, the mean number of flowers that bees visited per hour, the number of flowers per plant in anthesis at any given time and the number of pollination events required to reach optimum pollination. The mean light intensity, temperature and relative humidity for all observations were 17869 Lx, 23°C and 47%, respectively and, under these conditions, one T. carbonaria OATH hive per ̃1900 C. annuum plants was optimal. This rate will, however, change depending on the ambient conditions, crop species and forager numbers.