The role of spiders as predators of two lepidopteran Brassica pests

Spiders are thought to play a significant role in limiting pest outbreaks in agroecosystems such as vineyards, orchards and cotton. The diversity and impact of spiders in vegetable crops are less well understood, although there is evidence that predators may be important for suppression of lepidopteran pests in Brassica crops, particularly early in the season before parasitoids become established. Sampling was conducted in early season plantings of Brassicas in the Lockyer Valley (South East Queensland, Australia) in order to determine the most commonly occurring spider families. The most numerous were Theridiidae, which were more strongly associated with cauliflower and poorly associated with cabbage. The Lycosidae and Clubionidae/Miturgidae (formerly in the ‘catch-all’ family Clubionidae) also occurred commonly. Lycosidae (and to a lesser extent Salticidae) had above average abundance in Chinese cabbage and below average abundance in broccoli compared with average abundance for these spider families; Clubionidae/Miturgidae had above average abundance in cauliflower. Laboratory studies were then conducted to explore the predatory capacity of these three most commonly occurring spider families. All three were capable of feeding on larvae of the diamondback moth, Plutella xylostella (Linnaeus), and cabbage cluster caterpillar, Crocidolomia pavonana (Fabricius), under laboratory conditions. Theridiidae, which are thought to prey on small pests such as leafhoppers and aphids, were able to successfully attack larvae up to five times their body size. Predation rates varied from an average of 1.7 (SE = 0.47) (1.6 control corrected) larvae consumed over a 24 h period in the case of the Theridiidae, to 3.3 (SE = 0.60) larvae for the Clubionidae/Miturgidae

Improved statistical methods for estimating infestation rates in quarantine research when hosts are naturally infested

Trading partners often require phytosanitary or quarantine treatments for fresh horticultural produce to ensure no economically important pest species are moved with the imported product. When developing such treatments, it is essential that the level of treatment efficacy can be determined. This is often based on the mortality of the total number of target pests exposed to treatment, but in naturally infested products this number is not always known. In such cases, the infestation rate and subsequently an estimate of the number of pests are obtained directly from a set of untreated control samples of the host product. The International Plant Protection Convention (IPPC) Secretariat has provided 2 formulas for these situations that place an interval around the point estimate obtained from the control samples to obtain an estimate of the infestation rate. However, these formulas do not allow a confidence level to be assigned to the estimate, and there are concerns with the assumptions regarding the distribution and the measure of variability used in the formulas. In this article, we propose 2 alternative formulas. We propose that the lower one-sided confidence limit should be applied to all infestation datasets that are approximately normally distributed. As infestation data are sometimes skewed, it is proposed the lower one-sided modified Cox confidence limit is applied to data approximately log-normal distributed. These well-recognized formulas are compared to the formulas recommended by the IPPC and applied to 3 datasets involving natural infestation

Hyperspectral imaging to non-destructively predict citrus chilling injury

Queensland lemons are exported at low (i.e. <3°C) temperature to meet market access protocols. While the fruit generally tolerate these conditions, skin damage consistent with chilling injury (CI) is occasionally encountered and results in significant economic and reputational loss. The robustness of fruit to withstand export handling is inherently variable and difficult to predict. This study evaluated the potential of hyperspectral imaging to detect and predict CI in fruit before it was visible to the human eye. Seeded and seedless Eureka lemons were sourced from a north Queensland orchard. They were treated with either 2.6 or 18.5 parts per million (ppm) ethylene gas at 20.4 or 28.9oC for 5 days to hasten the loss of green skin colour, as per commercial degreening practice. The degreened fruit were stored at 1.9oC for 5 weeks to simulate seafreight to export markets, followed by 10 days at 20oC to assess CI under typical retail display conditions. Spectral data was collected within 2-3 h after harvest, degreening or cold storage. Three near infrared (NIR) devices were used; Bruker Matrix-F for spot assessment; Pika NIR 320 and Pika XC2 for hyperspectral imaging, covering wavelengths from 830-2500 nm, 900-1700 nm and 400-1000 nm, respectively. The supervised classification method of linear discriminate analysis was applied to the spectra collected from the Bruker Matrix-F, whereas partial least squares discriminant analysis (PLS-DA) was used to analyse spectra and images obtained from the Pika XC2 and NIR 320 instruments. The results showed that there is potential for NIR hyperspectral imaging to predict CI in seeded and seedless Eureka lemons, when assessed after degreening and particularly after cold shipment. Spectra collected after degreening and cold storage demonstrated reasonable levels (i.e. 70%) of correct classification. The highest correct classification was obtained for scans taken after storage and is likely due to CI having been induced in the fruit. Spectra collected 2-3 h after harvest using the Bruker Matrix-F device were not analysed due to fruit damage from the technique itself. Future research is needed to explore wavelength selections to refine, verify and develop models against an independent prediction set that combines the two varieties. The maximum level of spatial and/or spectral binning for the hyperspectral images that results in minimal loss of information should also be investigated. Once models are tested and validated successfully at a laboratory level, there would be scope for RD&E investment in a model that could be integrated into handheld or in-line NIR sensors to assist industry in grading out sensitive fruit batches that lack robustness to withstand export

Age estimation of barramundi (Lates calcarifer) over multiple seasons from the southern Gulf of Carpentaria using FT-NIR spectroscopy

The age of whole otoliths from barramundi (Lates calcarifer) obtained from the southern Gulf of Carpentaria were estimated using Fourier transform near-infrared (FT-NIR) spectroscopy. Otoliths from 1716 barramundi collected in 2006, 2009 and 2012–2015 were used in this study. Partial least-squares regression models (PLS-R) and multiple linear regression models (MLR) were developed from the diffuse reflectance spectra and the age was obtained from traditional sectioned otoliths. Calibration models were built up over consecutive years (2012–2015) by using a subset of the samples and used to predict the age of the remaining samples and samples from the following year. Results suggest that when seasonal (temporal) variability is incorporated into the calibration model, FT-NIR has the ability to predict barramundi age (validation R2 ranged from 0.73 to 0.78; RMSEP ranged from 6.92 to 7.64 months). The predicted age class was within 1 year of the reference age in over 96% of the samples. These models were also able to predict the age of otoliths from 2006 and 2009, which were retrieved from long-term storage (validation R2 ranged from 0.77 to 0.84; RMSEP ranged from 8.66 to 10.88 months). The results from this study have shown the potential for barramundi from the southern Gulf of Carpentaria to be aged quickly and accurately by using FT-NIR

Protein feeding of Queensland fruit fly Bactrocera tryoni and cucumber fly Zeugodacus cucumis (Diptera: Tephritidae) on non-host vegetation: effect of plant species and bait height

Perimeter-baiting of non-crop vegetation using toxic protein baits was developed overseas as a technique for control of melon fly, Zeugodacus (Zeugodacus) cucurbitae (Coquillett) (formerly Bactrocera (Zeugodacus) cucurbitae), and evidence suggests that this technique may also be effective in Australia for control of local fruit fly species in vegetable crops. Using field cage trials and laboratory reared flies, primary data were generated to support this approach by testing fruit flies' feeding response to protein when applied to eight plant species (forage sorghum, grain sorghum, sweet corn, sugarcane, eggplant, cassava, lilly pilly and orange jessamine) and applied at three heights (1, 1.5 and 2 m). When compared across the plants, Queensland fruit fly, Bactrocera tryoni (Froggatt), most commonly fed on protein bait applied to sugarcane and cassava, whereas more cucumber fly, Zeugodacus (Austrodacus) cucumis (French) (formerly Bactrocera (Austrodacus) cucumis), fed on bait applied to sweet corn and forage sorghum. When protein bait was applied at different heights, B. tryoni responded most to bait placed in the upper part of the plants (2 m), whereas Z. cucumis preferred bait placed lower on the plants (1 and 1.5 m). These results have implications for optimal placement of protein bait for best practice control of fruit flies in vegetable crops and suggest that the two species exhibit different foraging behaviours

Evaluation of the efficacy of commercial disinfectants against Fusarium oxysporum f. sp. cubense Race 1 and Tropical Race 4 propagules

Panama disease caused by Fusarium oxysporum f. sp. cubense (Foc) has devastated banana production worldwide. This work aimed to determine effective disinfectants against two races of Foc, race 1 and tropical race 4 (TR4), for implementation with on-farm biosecurity procedures against this disease following the outbreak of TR4 in North Queensland in 2015. A total of 32 commercial disinfectants were screened and their activity was assessed after ≤ 30 sec, 5 min, 30 min and 24 hr of contact with a Foc suspension containing 105/ml chlamydospores without and with soil added (0.05 g/ml). Of the disinfectants tested, the quaternary ammonium compounds containing ≥ 10% active ingredient were found to be the most effective against both Foc races. These products, when used at a 1:100 dilution, completely inhibited the survival of all Foc propagules across all the contact times regardless of the absence or presence of soil. The bioflavonoids product EvoTech 213 and bleach (10% sodium hypochlorite) used at a 1:10 dilution also eliminated all Foc propagules across all the contact times. None of the detergent-based or miscellaneous products tested were completely effective against both Foc races even used at a 1:10 dilution. Soil decreases the efficacy of disinfectants and therefore must be removed from contaminated items before treatments are applied

Cucumber volatile blend, a promising female-biased lure for Bactrocera cucumis (French 1907) (Diptera: Tephritidae: Dacinae), a pest fruit fly that does not respond to male attractants

Bactrocera cucumis (French 1907), the ‘cucumber fruit fly’, is a horticultural pest in Australia that primarily infests cucurbits and has also been recorded from tomatoes, papaw and several other hosts. It does not respond to known male lures, cue-lure and methyl eugenol, making monitoring and control difficult. A cucumber volatile blend lure was recently developed in Hawaii and found to be an effective female-biased attractant for the melon fly B. cucurbitae. This lure was field tested in north Queensland, Australia in McPhail traps in comparison with orange ammonia, Cera Trap® and a control, and was found to more consistently trap B. cucumis than the other lures. B. cucumis were caught at 41% of the cucumber volatile lure trap clearances, compared with 27% of the orange ammonia, 18% of the Cera Trap and 16% of the control trap clearances. The cucumber volatile lure was more attractive to B. cucumis in low population densities and also trapped B. cucumis earlier on average than the other lures. Data analysed from the site with highest trap catches (Spring Creek) showed that the cucumber volatile lure caught significantly more B. cucumis than the other traps in four of the 11 trap clearance periods, and for the remaining clearances, no other trap type caught significantly more flies than the cucumber volatile lure. The cucumber volatile lure had a strong female-biased attraction but it was not significantly more female-biased than orange ammonia or Cera Trap. Cucumber volatile lure traps were cleaner to service resulting in better quality specimens than the orange ammonia trap or Cera Trap. These findings have potential implications for market access monitoring for determining pest freedom, and for biosecurity monitoring programmes in other countries that wish to detect B. cucumis early

Evaluation of the efficacy of commercial disinfectants against Fusarium oxysporum f. sp. cubense Race 1 and Tropical Race 4 propagules

Panama disease caused by Fusarium oxysporum f. sp. cubense (Foc) has devastated banana production worldwide. This work aimed to determine effective disinfectants against two races of Foc, race 1 and tropical race 4 (TR4), for implementation with on-farm biosecurity procedures against this disease following the outbreak of TR4 in North Queensland in 2015. A total of 32 commercial disinfectants were screened and their activity was assessed after ≤ 30 sec, 5 min, 30 min and 24 hr of contact with a Foc suspension containing 105/ml chlamydospores without and with soil added (0.05 g/ml). Of the disinfectants tested, the quaternary ammonium compounds containing ≥ 10% active ingredient were found to be the most effective against both Foc races. These products, when used at a 1:100 dilution, completely inhibited the survival of all Foc propagules across all the contact times regardless of the absence or presence of soil. The bioflavonoids product EvoTech 213 and bleach (10% sodium hypochlorite) used at a 1:10 dilution also eliminated all Foc propagules across all the contact times. None of the detergent-based or miscellaneous products tested were completely effective against both Foc races even used at a 1:10 dilution. Soil decreases the efficacy of disinfectants and therefore must be removed from contaminated items before treatments are applied

High-Density Espalier Trained Mangoes Make Better Use of Light

Mango productivity and fruit quality in Australia can be improved through transforming low-density plantings to high-density plantings and intensive training systems. Several planting density and training systems were established in Australia to investigate optimizing light interception and distribution, yield and fruit quality, and to reduce tree vigor and biennial bearing through the manipulation of canopy architecture. In this research, we studied light relations and yield in conventional low-density commercial orchards of different ages and investigated light relations and yield of ‘National Mango Breeding Program NMBP1243’, ‘Keitt’ and ‘Calypso’ grafted to ‘Kensington Pride (KP)’ rootstock in a replicated experiment. Trees were trained to five planting systems: high-density espalier and conventional, medium-density single leader and conventional, and low-density conventional. Our study in commercial orchards showed that maximum yield was ~16,000 kg/ha when light interception reached ~49% and declined at higher levels of light interception. In the high-density intensive training systems, we found that light interception increased with canopy volume, with high-density espalier training systems intercepting more available light compared to medium-density training systems and low-density conventional trees. Yield/ha increased to ~50,000 kg/ha in espalier training systems when light interception was ~40%. Light interception, canopy volume and yield/ha varied between varieties

Cucumber volatile blend, a promising female-biased lure for Bactrocera cucumis (French 1907) (Diptera: Tephritidae: Dacinae), a pest fruit fly that does not respond to male attractants

Bactrocera cucumis (French 1907), the ‘cucumber fruit fly’, is a horticultural pest in Australia that primarily infests cucurbits and has also been recorded from tomatoes, papaw and several other hosts. It does not respond to known male lures, cue-lure and methyl eugenol, making monitoring and control difficult. A cucumber volatile blend lure was recently developed in Hawaii and found to be an effective female-biased attractant for the melon fly B. cucurbitae. This lure was field tested in north Queensland, Australia in McPhail traps in comparison with orange ammonia, Cera Trap® and a control, and was found to more consistently trap B. cucumis than the other lures. B. cucumis were caught at 41% of the cucumber volatile lure trap clearances, compared with 27% of the orange ammonia, 18% of the Cera Trap and 16% of the control trap clearances. The cucumber volatile lure was more attractive to B. cucumis in low population densities and also trapped B. cucumis earlier on average than the other lures. Data analysed from the site with highest trap catches (Spring Creek) showed that the cucumber volatile lure caught significantly more B. cucumis than the other traps in four of the 11 trap clearance periods, and for the remaining clearances, no other trap type caught significantly more flies than the cucumber volatile lure. The cucumber volatile lure had a strong female-biased attraction but it was not significantly more female-biased than orange ammonia or Cera Trap. Cucumber volatile lure traps were cleaner to service resulting in better quality specimens than the orange ammonia trap or Cera Trap. These findings have potential implications for market access monitoring for determining pest freedom, and for biosecurity monitoring programmes in other countries that wish to detect B. cucumis early