Improved termite resistance of wood by wax impregnation.

We investigated the effect of wax-treated and biocide-free wood specimens against three different termite species. A laboratory no-choice test with Reticulitermes banyulensis Clément was carried out in Valencia (Spain) under Mediterranean conditions for eight weeks. Scots pine sapwood (Pinus sylvestris L.) fully impregnated with distinct waxes was used. Two field trials were conducted with Coptotermes acinaciformis (Froggatt) and Mastotermes darwiniensis Froggatt in northern Queensland (Australia) with wax-impregnated beech (Fagus sylvatica L.) for 16 weeks. All three subterranean termites are of major economic importance in their respective regions. The results indicated that feeding pressure by the termites was sufficient within all trials for a valid test. Wax-impregnated Scots pine sapwood was classified as durable. No termites survived the test. The results showed an aging process under submersion conditions, which lead to a classification of moderately durable. The paraffin treatment showed good termite resistance under both test procedures, and was classified as durable. The Australian field trials showed a decreased mass loss of wax-treated beech, in which an amide wax showed excellent termite resistance. The results indicate a clear dependence of the termite resistance on the type and ratio of wax used and the feeding preferences of the specific termite species.

Spatial and diurnal pattern of protein foraging by Bactrocera tryoni (Froggatt) on a host plant

Background: Queensland fruit fly, Bactrocera tryoni, is the major pest fruit fly in Australia. Protein bait sprays, where insecticides are mixed with spot applications of a protein based food lure, are one of the sustainable pre-harvest fruit fly management strategies used in Australia. Although protein bait sprays do manage fruit fly infestation in the field, there is little science underpinning this technique and so improving its efficacy is difficult. Lacking information includes where and when to apply protein bait in order to best target foraging B. tryoni. As part of new work in this area, we investigated the effect of height of protein on tree and host plant fruiting status on the spatial and temporal protein foraging patterns of B. tryoni. MEthod: The work was conducted in the field using nectarine and guava plants and wild B. tryoni at Redland Bay, Queensland, Australia. Spot sprays of protein bait were applied to the foliage of randomly selected fruiting and non-fruiting trees. Each tree received protein bait spot sprays on the lower and higher foliage at 0530hrs. The number, sex and species of flies that fed on each protein spot were recorded hourly from 0600hrs through to 1800hrs.Results: For nectarines, there was a significant difference in the number of B. tryoni feeding on protein bait placed at different locations within the tree (ANOVA, F = 8.898, p = 0.001). More flies fed on protein placed on higher foliage relative to lower, irrespective of the fruiting status of the nectarine trees. A significant difference was also observed in the diurnal protein feeding pattern of B. tryoni (ANOVA, F = 2.164, p = 0.024), with more flies feeding at 1600hrs. Results for guava are still being collected and will be presented at the meeting.Conclusions: We conclude that B. tryoni effectively forages for protein at heights higher than 1.3m from ground, indicating greater efficacy of protein bait when applied at foliage higher in the canopy. Bactrocera tryoni actively forages for protein throughout the day, with a highest feeding peak at 1600hrs. The lack of significant difference in the spatial protein foraging pattern between fruiting and non-fruiting nectarine trees may be a real result, or may have resulted from the fruiting tree being very close (within 1 – 2 metres) of the non-fruiting tree. This hypothesis is being tested in the guava trial.

Host Susceptibility of Citrus Cultivars to Queensland Fruit Fly (Diptera: Tephritidae)

Citrus crops are considered to be relatively poor hosts for Queensland fruit fly, Bactrocera tryoni (Froggatt), as for other tephritid species. Australian citrus growers and crop consultants have reported observable differences in susceptibility of different citrus cultivars under commercial growing conditions. In this study we conducted laboratory tests and field surveys to determine susceptibility to B. tryoni of six citrus cultivars [(Eureka lemon (Citrus limon (L.) Osbeck); Navel and Valencia oranges (C. sinensis (L.) Osbeck); and Imperial, Ellendale, and Murcott mandarins (C. reticulata Blanco)]. The host susceptibility of these citrus cultivars was quantified by a Host Susceptibility Index, which is defined as the number of adult flies produced per gram of fruit infested at a calculated rate of one egg per gram of fruit. The HSI was ranked as Murcott (0.083) > Imperial (0.052) ≥ Navel (0.026) ≥ Ellendale (0.020) > Valencia (0.008) ≥ Eureka (yellow) (0.002) > Eureka (green) (0). Results of the laboratory study were in agreement with the level of field infestation in the four citrus cultivars (Eureka lemon, Imperial, Ellendale, and Murcott mandarins) that were surveyed from commercial orchards under baiting treatments against fruit flies in the Central Burnett district of Queensland. Field surveys of citrus hosts from the habitats not subject to fruit fly management showed that the numbers of fruit flies produced per gram of fruit were much lower, compared with the more susceptible noncitrus hosts, such as guava (Psidium guajava L.), cherry guava (P. littorale Raddi), mulberry (Morus nigra L.), loquat (Eriobotrya japonica (Thunb.) Lindl.), and pear (Pyrus communis L.). Therefore, the major citrus crops commercially cultivated in Australia have a relatively low susceptibility to B. tryoni, with Eureka lemons being a particularly poor host for this tephritid fruit fly.

Effect of citrus peel chemicals on Bactrocera tryonilarval survival

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is a major horticultural insect pest in Australia which significantly limits domestic and international market access for Australian horticultural produce. Citrus is one of the industries seriously affected by the fruit fly problem in Australia. This research investigated the effect of citrus peel essential oil chemicals on B. tryoni larval survival in five different commercially important Citrus species and cultivars as a way of better understanding fruit susceptibility. The fruits used were Murcott Mandarin, Navel orange, Eureka lemon, Valencia orange and yellow grapefruit. The essential oils of each citrus type were extracted using hydrodistillation and then mixed, at different concentrations, with artificial larval diets to which B. tryoni eggs were added. Surviving larvae were counted after five trial days. The same process was repeated for six essential oil components. Regression analysis of increasing oil concentration against larval survival showed that the crude oil blends of Navel orange, Eureka lemon and yellow grapefruit had significant negative effects on B. tryoni larval survival, but no such effects were seen for Murcott Mandarin and Valencia orange. Of the individual essential oil fractions, only D-limonene had a significant effect on B. tryoni larval survival, with this chemical being highly toxic at very low concentrations. The results of this study open up opportunities for incorporating B. tryoni resistance mechanisms into citrus through minor peel property changes which would not impact on the eating attributes of the fruit.