Ecotoxicological Assessment of Chemical Fumigants Utilising an Earthworm (<Emphasis Type="Italic">Eisenia andrei</Emphasis>) Bioassay and Soil Microbial Communities

Fumigation is an important crop protection practice employed to control soil pathogens and diseases. Metham sodium and cadusafos are two commonly used soil fumigants for this purpose. However, little information is available on their effects on non-target soil organisms. The aim of the study was to determine the ecotoxicity of these chemical fumigants on earthworms (organismal responses and DNA damage) and soil microbial communities. Changes in soil microbial community function and structure were evaluated by means of Biolog? Ecoplates and phospholipid fatty acid (PLFA) analyses, respectively. Both fumigants had a significant (p < 0.05) negative impact on all earthworm endpoints. Earthworms did not reproduce; biomass was affected negatively and manifested significant DNA damage with metham sodium causing more pronounced effects in comparison to cadusafos. The fumigants had an inhibitory effect on microbial growth. No lasting effects were observed in the community structure but cadusafos had a pronounced effect on the microbial community functional diversity. Metham sodium and cadusafos had varying effects on earthworm and microbial endpoints. This illustrates the importance of using different bioindicators to get a better understanding of the overall effects on the soil ecosystem.     

In Vitro Mechanical Comparison of 2.0 and 2.4 Limited‐Contact Dynamic Compression Plates and 2.0 Dynamic Compression Plates of Different Thicknesses

Objective: To compare the bending structural stiffness and bending strength of thick and thin 2.4 mm limited contact dynamic compression plates (2.4 LC‐DCP), 2.0 mm LC‐DCP (2.0 LC‐DCP), and 2.0 dynamic compression plates (2.0 DCP). Study Design: In vitro mechanical study. Methods: Two thicknesses of 2.4 LC‐DCP, 2.0 LC‐DCP, and 2.0 DCP stainless‐steel plates were tested in 4‐point bending. Data were collected during bending until implants plastically deformed. Bending structural stiffness and bending strength were determined from load displacement curves. Mechanical properties were compared between plates and the effects of plate type, size, and thickness on stiffness and strength were assessed using ANOVA. Results: The thick 2.4 LC‐DCP implant was the stiffest and strongest; the thin 2.0 DCP implant was most compliant and weakest. Larger sized plates, thicker plates, and limited contact design of plates enhanced stiffness and strength. For the plates studied, plate size had a larger effect than plate type or thickness on stiffness and strength. Conclusion: Increasing the size (width) and thickness of plates increases both the bending structural stiffness and strength. For the plates studied, LC‐DCP implants were stiffer and stronger than DCP implants. Clinical Relevance: Plate bending structural stiffness and strength can be most effectively enhanced by using a larger sized plate, but gains can also be achieved by using a thicker plate and/or an LC‐DCP instead of a DCP implant when possible.     

A note on the reproductive performance of Damara,Dorper and Merino sheep under optimum management and nutrition for Merino ewes in the eastern wheatbelt of Western Australia

The reproductive performance of 48 Damara, 42 Dorper and 46 Merino ewes was evaluated under an optimum nutritional regime for Merino ewes that included one annual joining in a mixed (cropping and sheep) farming system in the eastern wheatbelt of Western Australia (W.A.) over a 3-year period. In 2005, when the Damara, Dorper and Merino ewes were aged between 8 and 9 months at joining and weighed 41.2, 42.4 and 33.3 kg with average body condition scores of 2.3, 2.4 and 1.8, respectively, their weaning rates were 71% (Damara), 81% (Dorper) and 13% (Merino). The Merino ewes had significantly lighter body weights and were lower conditioned (p < 0.001) resulting in significantly lower weaning rates (p < 0.001). In 2006, the Damara, Dorper and Merino ewes weighed 61.9, 69.5 and 61.6 kg at joining, with body condition scores of 2.8, 3.3 and 2.8, respectively, resulting in weaning rates of 52% (Damara), 122% (Dorper) and 117% (Merino). While the Damara and Merino weights and body condition scores were not different (p > 0.05), the Damara weaning rates were significantly lower compared with the Dorper and Merino groups (p < 0.001). The Dorpers were heavier and greater conditioned (p < 0.001); however, the weaning rates between the Dorper and Merino were not different (p > 0.05). In 2007, the Damara, Dorper and Merino ewes weighed 71.6, 77.1 and 70.2 kg at joining with body condition scores of 2.8, 2.8 and 2.5, respectively. Again, the Dorper ewes were heavier (p < 0.001) than the Damaras and Merinos, which were not different (p > 0.05). The Damara and Dorper had the same body condition while the Merino ewes were less and different (p < 0.05). However, there were differences in weaning rates between the three breeds (p < 0.001), of 64% (Damara), 105% (Dorper) and 134% (Merino). Over the 3-year period, under a nutritional management system optimal for Merino sheep and with one annual joining, with increasing age the Merino ewes weaned more lambs. However, while the Damara and Dorper ewes conceived and weaned relatively high lamb numbers when they were joined as lambs, their reproductive performance decreased over time. This nutritional regime resulted in increased levels of fatness of the Damara and Dorper ewes with no increase in reproduction rates under an annual joining system. A significant factor for the lower conception and weaning rates in the Damara ewes was the enlarged fat tail due to the increased fat levels, which made it difficult for the rams to impregnate the ewes.     

Speed of action and toxicity of acylurea insect growth regulators against Spodoptera exempta (Walk.) and Spodoptera littoralis (Boisd.) larvae: Effect of inter-moult age

Ultra-low volume (ULV) spray bioassays at droplet densities (20–80 drops cm^?2) corresponding to field deposits were used to determine the efficacy of two acylurea insect growth regulators, teflubenzuron (‘Nomolt®’) and flufenoxuron (‘Cascade®’) against three different age groups of third-instar Spodoptera exempta and Spodoptera littoralis larvae. While no response (mortality and/or abnormal moulting with impaired ability to feed) was observed with one-day-old larvae until 48 h after treatment, two-day-old larvae showed some response (27–93% abnormal moulting and 3–10% mortality when larvae were sprayed; 80–100% abnormal moulting and up to 83% mortality when larvae and plants were sprayed) after 24 h and up to 100% mortality at 120 h. Studies with non-feeding, pre-moult larvae showed that cuticular uptake of acylureas was sufficient to affect an appreciable proportion of larvae after 24 h, with up to 100% mortality at 120 h. More detailed studies with pre-moult S. littoralis larvae showed that, while a few larvae which moulted between 1 and 5 h after treatment showed abnormal moulting to the L4 stage, a much larger proportion of larvae which moulted 6–20 h after treatment were affected. Previous studies with S. exempta have shown that different larval instars show similar levels of sensitivity to acylureas. The present work suggests that, while the age distribution within instars has little influence on the end-point mortality of acylureas, it can profoundly modify the speed of response, the majority of larvae within an instar being effectively controlled at the moult following treatment. The significance of these observations in relation to the crop protection activity of acylureas against field populations of Spodoptera larvae is discussed.     

Diversifying native pinewoods using artificial regeneration

Little is known about broadleaf establishment within the nativepinewoods of Scotland, yet such information is critical to currentrestoration initiatives. A 2-year field trial was set up toassess the growth and performance of seedlings of four broadleavedspecies within different developmental stages of Pinus sylvestris(Scots pine) woodland in the Scottish Highlands. The developmentalstages included stem initiation (establishment stage), stemexclusion (thicket/pole stage) and canopy break up (old-growthcanopy), providing sites of varying shade and resource availability.It was predicted that differences in establishment between siteswould occur due to species-specific differences in ‘tolerance’of shade, low-nutrient availability and poor soil drainage.Analysis of trial results showed high survival but growth rates(relative stem height and basal diameter growth) declined rapidlyin year two. In year two, Ilex aquifolium achieved the highestmean growth rates in the stem exclusion stands (average 15 percent light) where there was a lower percentage of Phytomyzailicis (holly leaf miner) infection and frost damage. Sorbusaucuparia exhibited generalist behaviour with similar growthand performance across all stand treatments. Betula pubescensmaintained similar growth rates across stand types but was moresusceptible to insect damage in deeper shade. Overall, Alnusglutinosa grew more successfully than the other species andachieved highest mean growth rates in canopy break up (average44 per cent light) and stand initiation (average 71 per centlight) stages. Broadleaf establishment within pinewood standsis challenging on account of acidic nutrient-poor soil regimes,and in places, poor drainage, aggressive understorey competitionand canopies that restrict light availability and insect herbivory.Forest restoration techniques, including matching species tosite, accelerating establishment and using framework species(individuals of high field performance that are able to restoresite productivity and nutrient cycles), are discussed.