Summary 1.Tropical rainforests are potential reservoirs of insects that could enhance crop pollination, but only a few instances of the provision of such services by tropical rainforest insects have been reported. Our field study aimed to determine the relative importance of such insects to the pollination of macadamia Macadamia integrifolia and longan Dimocarpus longan crops on the Atherton Tableland, north Queensland, Australia. 2. We quantified initial fruit set, a measure of pollination success, in treatments designed to assess the relative importance of the possible modes of pollination. The treatments were applied in orchards that varied in distance from rainforest, in order to compare the effects of the contrasting pools of available pollen vectors. We also recorded the insect species present and estimated the number of visits each made to flowers in crops near and far from rainforest. 3. For both crops there was an interaction between pollination treatment and distance from rainforest. Maximum fruit set was only achieved when pollen vectors had access to flowers and orchards were close to rainforest. Exclusion of pollinators near rainforest reduced initial fruit set to a greater extent than exclusion of pollinators far from rainforest. 4. We confirmed that pollen transfer in macadamia is by autogamous self-pollination and by pollen vectors, but our design did not distinguish among pollen vectors. The only abundant insects in macadamia orchards were honeybees Apis mellifera . There were more honeybee visits to macadamia flowers in orchards near rainforest than far from rainforest, but we detected no relationship between honeybee visits and initial macadamia fruit set in our sample of observations on a per raceme basis. More detailed studies are needed to identify the pollen vector responsible for enhanced pollination of macadamia near rainforest. 5. We established for the first time that pollen transfer in longan is by a combination of autogamous self-pollination, wind and bees. Longan flowers were visited by stingless bees and honeybees but only stingless bees had a positive relationship with initial longan fruit set and higher visitation rates near rainforest than far from rainforest. This suggests that enhanced pollination in longan near rainforest resulted primarily from a more abundant supply of stingless bees from the rainforest. 6. Synthesis and applications. By demonstrating that tropical rainforest can act as a reservoir of pollen vectors that benefit crops, our study highlights the existence of a largely unrecognized resource available to agriculture. At the same time our results make a significant contribution to the growing database of studies that underscore the importance of tropical rainforest conservation. Policy and management aimed at sustainable use of this resource would satisfy the goals both of agriculturalists, to improve crop yields, and conservationists, to conserve tropical rainforest.

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Plant pathogenic phytoplasmas found in grasses in northern Australia have the potential to adversely affect sugarcane production. To begin assessment of this threat, the number of grass species with phytoplasmas, the identity of those phytoplasmas, and their relationship with disease symptoms were determined. Sugarcane with and without symptoms of yellow leaf syndrome was included in the surveys. Molecular methods were used to detect and characterize phytoplasmas in grass species exhibiting symptoms typical of phytoplasma disease. Sugarcane samples were from the Ord River Irrigation Area, Western Australia, and Samford, Queensland. Samples of other grasses were from Wyndham, Kununurra and Broome, Western Australia, and Darwin, Northern Territory. Our survey identified four new phytoplasma host species and confirmed four known previously. Counting phytoplasmas, phytoplasma variants, and mixtures of phytoplasmas and variants, these eight host species had 33 different infections. Two phytoplasmas were new, cenchrus bunchy shoot which is related to Candidatus phytoplasma australiense, and sorghum bunchy shoot which is not closely related to any described phytoplasma. Twenty‐five phytoplasma isolates were detected in sugarcane. Of these, tomato big bud phytoplasma was the most common. In most cases no clear association between phytoplasmas and symptoms could be determined. None of the phytoplasmas in Australian sugarcane, but two in other grasses, were closely related to phytoplasmas associated with white leaf and grassy shoot diseases in Asian sugarcane. This study demonstrates that diversity of phytoplasmas and grass host species in northern Australia is greater than previously thought, and that symptoms alone are not always reliable indicators of phytoplasma presence or absence. It provides the groundwork to improve future field surveys, and for initiation of transmission trials to determine whether insect vectors capable of transmitting phytoplasmas from native grasses to sugarcane are present in the region.

Evidence regarding the effect of temperature and rainfall on gall‐inducing insects is contradictory: some studies indicate that species richness of gall‐inducing insects increases as environments become hotter and drier, while others suggest that these factors have no effect. The role of plant species richness in determining species richness of gall‐inducing insects is also controversial. These apparent inconsistencies may prove to be due to the influence of soil fertility and the uneven distribution of gall‐inducing insect species among plant taxa. The current study tested hypotheses about determinants of gall‐inducing insect species richness in a way different to previous studies. The number of gall‐inducing insect species, and the proportion of species with completely enclosed galls (more likely to give protection against heat stress and desiccation), were measured in replicate plots at five locations along a 500‐km N‐S transect in the seasonal tropics of the Northern Territory, Australia. There is a strong temperature–rainfall gradient along this transect during the wet season. Plant species lists had already been compiled for each collection plot. All plots were at low elevation in eucalypt savannah growing on infertile soils. There was no evidence to suggest that hot, dry environments in Australia have more gall‐inducing insect species than cooler, wetter environments, or that degree of enclosure of galls is related to protecting insects from heat stress and desiccation. The variable number of gall‐inducing insect species on galled plant species meant that plant species richness did not influence gall species richness. Confirmation is still required that low soil fertility does not mask temperature–rainfall effects and that galls in the study region are occupied predominantly in the wet season, when the temperature–rainfall gradient is most marked.

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