Tim A. Heard

Antimicrobial activity of honey from the stingless bee Trigona carbonaria determined by agar diffusion, agar dilution, broth microdilution and time‐kill methodology

Aims:  The aim of this study was to determine the spectrum of antimicrobial activity of 11 samples of stingless bee honey compared to medicinal, table and artificial honeys.

Factors influencing flight activity of colonies of the stingless bee Trigona carbonaria (Hymenoptera: Apidae)

Temporal patterns of flight activity and influence of climatic variables on activity of colonies of the potentially useful crop pollinator, Trigona carbonaria Smith, were investigated. Colonies of T. carbonaria were active all the year at the experimental site but the daily activity period was longer in the warmer months. Intensity of daily flight activity was greatest in September and least in May. Temperature and radiation were the most important variables affecting flight activity. They impose thresholds on activity, with flight occurring only at temperatures greater than 18°C and radiation greater than 15 W m-2. Temperature and radiation also influence the intensity of activity above the thresholds. Relative humidity, vapour pressure, cloud cover and wind speed had no significant effect. A variable measuring the hours from daily peak of activity was significantly correlated with flight activity, indicating an intrinsic diel pattern of activity. Daily variation in flight activity, representing the influence of unmeasured variables, was also significant.

The future of pollinators for Australian agriculture

Agriculture in Australia is highly dependent on insect pollination, in particular from the introduced western honeybee, Apis mellifera. Most agricultural pollination is provided as an unpaid service by feral A. mellifera and native insects. A smaller proportion of agricultural pollination is provided as a paid service by beekeepers. Insect pollination is threatened by misuse of insecticides and the loss of remnant vegetation, but most potently by the likelihood that the honeybee mite, Varroa destructor, will enter the country. Now is the time to prepare for the effect of these changes, and international experience with pollinator decline should serve as a guide. We need to protect and manage our remnant vegetation to protect wild pollinators. Insurance against declining A. mellifera will come through the development of management practices for alternative pollinator species. By developing native insects as pollinators we can avoid the risks associated with the importation of additional introduced species.

Worth the risk? Introduction of legumes can cause more harm than good: an Australian perspective

Weeds are serious threats to Australias primary production and biodiversity conservation. For example, a recent Australia Bureau of Statistics survey found that 47% of farmers across Australia have a significant weed problem. A literature review revealed that legumes represent a significant proportion of the national weed problem and most serious Australian legume weeds are exotic thicket-forming species that were deliberately introduced for their perceived beneficial properties, such as for shade and fodder, or even quite trivial reasons, such as garden ornamentals. The low economic value of the rangelands most of these species infest, compared with control costs, hinders chemical and mechanical control of these weeds, such that biological control, which takes time, is expensive to implement and has no guarantee of success, may represent the only economically viable alternative to abandoning vast tracts of land. We argue that, because the behaviour of an introduced species in a novel environment is so hard to forecast, better predictive techniques should be developed prior to further introductions of plant species into novel environments. We also discuss the potential of legumes currently being promoted in Australia to become weeds and suggest the recent trend of exporting Australian Acacia spp. to semiarid regions of Africa risks history repeating itself and the development of new weed problems that mirror those posed by Australian Acacia spp. in southern Africa.

Behaviour and pollinator efficiency of stingless bees and honey bees on macadamia flowers.

SUMMARYBehavioural observations and experiments on pollinator efficiency of stingless bees, Trigona carbonaria, and honey bees, Apis mellifera, visiting flowers of macadamia, Macadamia integrifolia, growing in orchards in Australia were performed. Stingless bees mainly collected pollen and this activity resulted in intimate contact with the stigma. Honey bees mainly collected nectar and came into contact with the stigma less often. Racemes which were enclosed in cages which excluded honey bees but allowed visitation by the smaller stingless bees yielded a nut set equal to that on open-pollinated racemes, showing that these bees are efficient pollinators. Honey bees worked flowers more quickly than stingless bees, visiting more flowers in a given time. Both bee species responded to racemes rich in pollen and nectar by remaining longer at those racemes and visiting more flowers on them.

Anti-staphylococcal activity of C-methyl flavanones from propolis of Australian stingless bees (Tetragonula carbonaria) and fruit resins of Corymbia torelliana (Myrtaceae).

Propolis of Australian stingless bees (Tetragonula carbonaria, Meliponini) originating from Corymbia torelliana (Myrtaceae) fruit resins was tested for its antimicrobial activities as well as its flavonoid contents. This study aimed at the isolation, structural elucidation and antibacterial testing of flavanones of C. torelliana fruit resins that are incorporated into stingless bee propolis. Flavanones of this study were elucidated by spectroscopic and spectrometric methods including UV, 1D and 2D NMR, EI-MS, ESI-MS and HR-MS. The results indicated known C-methylated flavanones namely, 1 (2S)-cryptostrobin, its regioisomer 2 (2S)- stroboponin, 3 (2S)- cryptostrobin 7-methyl ether, and 6 (2S)- desmethoxymatteucinol, and known flavanones 4 (2S)- pinostrobin and 5 (2S)- pinocembrin as markers for C. torelliana fruit resins and one propolis type. Ethanolic preparations of propolis were shown to be active against Staphylococcus aureus (ATCC 25923) and to a lesser extent against Pseudomonas aeruginosa (ATCC 27853). C. torelliana flavanones inhibited the growth of S. aureus therefore contributing to the antibacterial effects observed for Australian stingless bee propolis extracts.

Pollination biology of cashew in the Northern Territory of Australia.

Aspects of the pollination biology of cashew Anacardium occidentale L. (Anacardiaceae) were investigated at a site of potential commercial production. A mean of 442.9 flowers were produced per panicle of which 32.1 (7.3%) were hermaphrodite, the remainder being male. Mean initial fruit set was 5.0 per panicle, representing a percentage fruit set of 15.5%. The absence of either male or hermaphrodite flowers at any particular stage of flowering did not limit fruit set. Diversity of insect flower visitors, attracted by nectar rewards, was great, but only a few species were common. Three species of potentially efficient pollinators were tested for their pollinator efficiency which was found to be high for honey bees, Apis mellifera, and a native fly, Ligyra sp. Only 25% of flowers were pollinated in 1987, but this increased to 98% owing to a corresponding increase in the natural populations of insect visitors. Wind and night flying insects played no role in pollination. Although 98% of flowers were pollinated, initial fruit set averaged only 15.5%. This suggests that factors other than pollination limit fruit set. However, pollination is important and the insect pollinators will need protection from insecticide applications and destruction of breeding sites.

Stingless bee keeping in Australia: snapshot of an infant industry

Results of this survey of the keeping of stingless bees in Australia in 1998/1999 showed that this new activity is growing rapidly. Responses came from over 250 stingless bee keepers with more than 1400 colonies. The industry is concentrated in coastal Queensland with Trigona carbonaria being the most common species kept. Rates of future colony increase expected by survey participants (15-18% per annum) were low compared with increases achieved by experienced beekeepers (30%), but both indicate that the industry could grow rapidly over the next two decades. Enjoyment, conservation, crop pollination (mainly macadamia nut), honey production and hive sales were the major reasons for keeping stingless bees.

Ambient temperature influences Australian native stingless bee (Trigona carbonaria) preference for warm nectar.

The interaction between flowers and insect pollinators is an important aspect of the reproductive mechanisms of many plant species. Several laboratory and field studies indicate that raising flower temperature above ambient can be an advantage in attracting pollinators. Here we demonstrate that this preference for warmer flowers is, in fact, context-dependent. Using an Australian native bee as a model, we demonstrate for the first time a significant shift in behaviour when the ambient temperature reaches 34°C, at which point bees prefer ambient temperature nectar over warmer nectar. We then use thermal imaging techniques to show warmer nectar maintains the flight temperature of bees during the period of rest on flowers at lower ambient temperatures but the behavioural switch is associated with the body temperature rising above that maintained during flight. These findings suggest that flower-pollinator interactions are dependent upon ambient temperature and may therefore alter in different thermal environments.

Pollinator requirements and flowering patterns of Macadamia integrifolia

A study of insect pollination of macadamia, Macadamia integrifolia Maiden & Betche (Proteaceae) was undertaken in southern Queensland. Both initial nut set and final nut set increased with increasing insect visitation. Pollination was not limiting yield at this site, however, as racemes exposed to 6 h of bee visitation per day had similar final nut set to racemes constantly exposed (10 h of bee visitation). Honey bees and Trigona spp. bees visited the racemes in approximately equal numbers at the site. Approximately 50 bee visits were made per day to the racemes exposed for 6 h. Individual flowers remained attractive to insects for approximately 3 days. Hence approximately 150 visits per raceme are required to ensure adequate pollination. The flowers on a raceme opened over a period of approximately 7 days with peak opening at around day 2. Flowers opened during the day, peaking in the early afternoon.