The effect of foliar sprays of the synthetic auxin 3-5-6 TPA, on fruit drop, fruit size and seed development in three lychee (Litchi chinensis) cultivars: Tai So, Fay Zee Sui and Kwai Mai Pink.

Fruit drop in lychee can cause major yield losses in Australia, the severity varying with cultivar and season. Research in China, South Africa and Israel has demonstrated the potential for synthetic auxins used as foliar sprays to reduce fruit drop in lychee. Trials were initiated in Australia to test the efficacy of the synthetic auxin, 3-5-6 Trichloro-2-phridyl-oxyacetic acid (3-5-6 TPA) at 50 ppm on the cultivars Tai So, Fay Zee Sui and Kwai Mai Pink. Results indicate that in most cases the TPA reduced natural fruit drop however the size of the fruit at the time of application affects the response and the ideal application time varies with cultivar; approximately 13 mm fruit length in 'Kwai Mai Pink', 20 mm in 'Fay Zee Sui' and 27 mm in 'Tai So'. If applied too early in 'Tai So', it caused an increase in fruit drop. The TPA was most effective when natural fruit drop was high, reducing fruit drop from 74.7 to 34.9% in 'Kwai Mai Pink' and least effective when natural fruit drop was low. An increase in the percentage of fruit with poorly developed (chicken tongue) seed and slightly larger fruit size was also observed in treated trees.

The effect of 3-5-6 TPA on fruit drop and fruit size in the lychee (Litchi Chinensis) cultivars 'Fay Zee Siu' (feizixiao) , 'Kaimana', 'Kwai Mai Pink', 'Souey Tung' and 'Tai So' (Mauritus)

Fruit drop can cause major yield losses in Australian lychee orchards, the severity varying with cultivar and season. Research in China, South Africa and Israel has demonstrated the potential for synthetic auxins used as foliar sprays to reduce fruit drop in lychee. Trials tested the efficacy of the synthetic auxin 3-5-6 trichloro-2-phridyl-oxyacetic acid (TPA) applied as a foliar spray at 50 ppm on fruit drop and fruit size on the cultivars ‘Fay Zee Siu’, ‘Kaimana’, ‘Kwai Mai Pink’, ‘Souey Tung’ and ‘Tai So’. TPA reduced fruit drop when applied to fruit greater than 12 mm in length but increased fruit drop when fruit were smaller. Fruit size at the time of application had less effect on the response than the level of natural fruit drop. When natural fruit drop was high, TPA significantly reduced it; by up to 18.7 in ‘Fay Zee Siu’, 37.1 in ‘Kaimana’, 39.8 in ‘Kwai Mai Pink’, 15.1 in ‘Souey Tung’ and 7.7 in ‘Tai So’. TPA was less effective when natural fruit drop was low. TPA increased the number of large fruit and frequently increased the number of small fruit at harvest. The small fruit were associated with an increase in the retention of fruit with poorly developed (chicken tongue) seed. Average fruit size was generally larger (up to 12.7 in ‘Souey Tung’ and 22 in ‘Tai So’) with TPA applications.

Sirex woodwasp range expansion in Australia: performance and parasitism on two commercial pine species

Sirex woodwasp was detected in Queensland in 2009 and rapidly established in softwood plantations (Pinus radiata and P. taeda) in southern border regions. Biocontrol inoculations of Deladenus siricidicola began soon after, and adults were monitored to assess the success of the programme. Wasp size, sex ratios, emergence phenology and nematode parasitism rates were recorded, along with the assessment of wild-caught females. Patterns varied within and among seasons, but overall, P. taeda appeared to be a less suitable host than P. radiata, producing smaller adults, lower fat body content and fewer females. Sirex emerging from P. taeda also showed lower levels of nematode parasitism, possibly due to interactions with the more abundant blue-stain fungus in this host. Sirex adults generally emerged between November and March, with distinct peaks in January and March, separated by a marked drop in emergence in early February. Temperature provided the best correlate of seasonal emergence, with fortnights with higher mean minimum temperatures having higher numbers of Sirex emerging. This has implications for the anticipated northward spread of Sirex into sub-tropical coastal plantation regions. Following four seasons of inundative release of nematodes in Queensland, parasitism rates remain low and have resulted in only partial sterilization of infected females.

The mortality of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) neonate larvae in relation to drop-off and soil surface temperature: The dangers of bungy jumping

The first larval instar has been identified as a critical stage for population mortality in Lepidoptera, yet due to the body size of these larvae, the factors that contribute to mortality under field conditions are still not clear. Dispersal behaviour has been suggested as a significant, but ignored factor contributing to mortality in first-instar lepidopteran larvae. The impact that leaving the host plant has on the mortality rate of Helicoverpa armigera neonates was examined in field crops and laboratory trials. In this study the following are examined: (1) the effects of soil surface temperature, and the level of shade within the crop, on the mortality of neonates on the soil after dropping off from the host plant; (2) the percentage of neonates that dropped off from a host plant and landed on the soil; and (3) the effects of exposure to different soil surface temperatures on the development and mortality of neonates. The findings of this study showed that: (1) on the soil, surface temperatures above 43°C were lethal for neonates, and exposure to these temperatures contributed greatly to the overall mortality rate observed; however, the fate of neonates on the soil varied significantly depending on canopy closure within the crop; (2) at least 15% of neonates dropped off from the host plant and landed on the soil, meaning that the proportion of neonates exposed to these condition is not trivial; and (3) 30 min exposure to soil surface temperatures approaching the lethal level (>43°C) has no significant negative effects on the development and mortality of larvae through to the second instar. Overall leaving the plant through drop-off contributes to first-instar mortality in crops with open canopies; however, survival of neonates that have lost contact with a host plant is possible, and becomes more likely later in the crop growing season.

Hanging drop: An in vitro air toxic exposure model using human lung cells in 2D and 3D structures

Using benzene as a candidate air toxicant and A549 cells as an in vitro cell model, we have developed and validated a hanging drop (HD) air exposure system that mimics an air liquid interface exposure to the lung for periods of 1 h to over 20 days. Dose response curves were highly reproducible for 2D cultures but more variable for 3D cultures. By comparing the HD exposure method with other classically used air exposure systems, we found that the HD exposure method is more sensitive, more reliable and cheaper to run than medium diffusion methods and the CULTEX (R) system. The concentration causing 50% of reduction of cell viability (EC50) for benzene, toluene, p-xylene, m-xylene and o-xylene to A549 cells for 1 h exposure in the HD system were similar to previous in vitro static air exposure. Not only cell viability could be assessed but also sub lethal biological endpoints such as DNA damage and interleukin expressions. An advantage of the HD exposure system is that bioavailability and cell concentrations can be derived from published physicochemical properties using a four compartment mass balance model. The modelled cellular effect concentrations EC50(cell) for 1 h exposure were very similar for benzene, toluene and three xylenes and ranged from 5 to 15 mmol/kg(dry weight) which corresponds to the intracellular concentration of narcotic chemicals in many aquatic species, confirming the high sensitivity of this exposure method. (C) 2013 Elsevier B.V. All rights reserved.

Presence of Nicotinamide Adenine Dinucleotide–Independent Haemophilus paragallinarum in Mexico

Two isolates of Haemophilus paragallinarum were obtained from a layer chicken in Mexico. The isolates were confirmed as H. paragallinarum by polymerase chain reaction and conventional biochemical identification. The isolates were nicotinamide adenine dinucleotide (NAD) independent—growing on blood agar without the need of a nurse colony as well as on a complex medium that lacked both NAD and chicken serum. Both isolates were pathogenic, causing the typical clinical signs of infectious coryza in susceptible chickens. One isolate was Page serovar B/Kume serovar B-1 and the other isolate was Page serovar C/Kume serovar C-2. The isolates were associated with a field outbreak that involved an egg drop of 20% over a 3 wk period and a doubling of weekly mortality (from 0.1% to 0.2%). This is the first report of NAD-independent H. paragallinarum outside South Africa and is the first time that NADindependent H. paragallinarum of serovar B has been reported. Abbreviations: NAD ¼ nicotinamide adenine dinucleotide; NAM ¼ nicotinamide; PCR ¼ polymerase chain reaction; TM ¼ complete growth medium without chicken serum or nicotinamide adenine dinucleotide; TM/SN ¼ complete growth medium that contains both chicken serum and nicotinamide adenine dinucleotide

Timing of fungicide applications for control of husk spot caused by Pseudocercospora macadamiae in macadamia

Pseudocercospora macadamiae is an important pathogen of macadamia in Australia, causing a disease known as husk spot. Growers strive to control the disease with a number of carbendazim and copper treatments. The aim of this study was to consider the macadamia fruit developmental stage at which fungicide application is most effective against husk spot, and whether application of copper-only applications at full-size fruit developmental stage toward the end of the season contributed to effective disease control. Fungicides were applied to macadamia trees at four developmental stages in three orchards in two subsequent production seasons. The effects of the treatments on disease incidence and severity were quantified using area under disease progress curve (AUDPC) and logistic regression models. Although disease incidence varied between cultivars, incidence and severity on cv. A16 showed consistent differences between the treatments. Most significant reduction in husk spot incidence occurred when spraying commenced at match-head sized-fruit developmental stage. All treatments significantly reduced husk spot incidence and severity compared with the untreated controls, and a significant positive linear relationship (R2 = 73%) between AUDPC and severity showed that timing of the first fungicide application is important for effective disease control. Application of fungicide at full-size fruit stage reduced disease incidence but had no impact on premature fruit drop.

Nitrogen use for high productivity and sustainability in cashew.

Interest in cashew production in Australia has been stimulated by domestic and export market opportunities and suitability of large areas of tropical Australia. Economic models indicate that cashew production is profitable at 2.8 t ha-1 nut-in-shell (NIS). Balanced plant nutrition is essential to achieve economic yields in Australia, with nitrogen (N) of particular importance because of its capacity to modify growth, affect nut yield and cause environmental degradation through soil acidification and off-site contamination. The study on a commercial cashew plantation at Dimbulah, Australia, investigated the effect of N rate and timing on cashew growth, nut production, N leaching and soil chemical properties over five growth cycles (1995-1999). Nitrogen was applied during the main periods of vegetative (December-April) and reproductive (June-October) growth. Commercial NIS yields (up to 4.4 t ha-1 from individual trees) that exceeded the economic threshold of 2.8 t ha-1 were achieved. The yield response was mainly determined by canopy size as mean nut weight, panicle density and nuts per panicle were largely unaffected by N treatments. Nitrogen application confined to the main period of vegetative growth (December-April) produced a seasonal growth pattern that corresponded most consistently with highest NIS yield. This N timing also reduced late season flowering and undesirable post-November nut drop. Higher yields were not produced at N rates greater than 17 g m-2 of canopy surface area (equating to 210 kg N ha-1 for mature size trees). High yields were attained when N concentrations in Mveg leaves in May-June were about 2%, but this assessment occurs at a time when it is not feasible to correct N deficiency. The Mflor leaf of the preceding November, used in conjunction with the Mveg leaf, was proposed as a diagnostic tool to guide N rate decisions. Leaching of nitrate-N and acidification of the soil profile was recorded to 0.9 m. This is an environmental and sustainability hazard, and demonstrates that improved methods of N management are required.

Mixture Effects of Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) to Lung Carcinoma Cells via a Hanging Drop Air Exposure System

A recently developed hanging drop air exposure system for toxicity studies of volatile chemicals was applied to evaluate the cell viability of lung carcinoma A549 cells after 1 h and 24 h of exposure to benzene, toluene, ethylbenzene and xylenes (BTEX) as individual compounds and mixtures of 4 or 6 components. The cellular chemical concentrations causing 50% reduction of cell viability (EC50) were calculated use a mass balance model and came to 17, 12, 11, 9, 4 and 4 mmol/kg cell dry weight for benzene, toluene, ethylbenzene, m-xylene, o-xylene and p-xylene respectively after 1 h of exposure. The EC50 decreased by a factor of four after 24 h of exposure. All mixture effects were best described by the mixture toxicity model of concentration addition, which is valid for chemicals with the same mode of action. Good agreement with the model predictions were found for benzene, toluene, ethylbenzene and m-xylene at four different representative fixed concentration ratios after 1 h of exposure but lower agreement to mixture prediction was obtained after 24 h of exposure. A recreated car exhaust mixture, which involved the contribution of the more toxic p-xylene and o-xylene, yielded an acceptable but lower quality prediction as well.