No abstract

Weed Manager is a model-based decision support system to assist arable farmers and advisers in weed control decisions on two time scales: within a single season and over several years in a rotation. The single season decision is supported by a wheat crop and annual weed growth simulation, with a multi-stage heuristic decision model. The rotational aspect uses a model of seed population dynamics, with decisions optimised using stochastic dynamic programming. Each time scale has its own user interface within a single program integrated into the ArableDS framework, which provides data sharing between several decision support modules. Weed Manager was used by about 100 farmers and consultants in the 2005-2006 and 2006-20077 seasons.

No abstract

Marine algae produce a variety of secondary metabolites that function as herbivore deterrents. Algal metabolites, however, often fail to deter damage by some herbivores such as mesograzers that both live and feed on their host alga. In addition, the degree to which intraspecific chemical variation in an alga affects a mesograzer's feeding behavior and its ability to deter predators is poorly understood. The red alga Portieria hornemannii contains the secondary metabolites apakaochtodene A and B, which have been shown to vary in concentration among sites on Guam and act as significant deterrents to fish feeding. On Guam, the sea hare Aplysia parvula preferred and grew best when fed its algal host P. hornemannii. However, high concentrations of P. hornemannii crude extract and the pure compounds apakaochtodene A and B acted as feeding deterrents to A. parvula. Despite differences among sites in the levels of apakaochtodenes A and B, A. parvula showed no significant preference for P. hornemannii from any one location. Aplysia parvula found on P. hornemannii sequestered apakaochtodenes, and both whole animals and body parts were unpalatable to reef fishes. Sea hares found on the red alga Acanthophora spicifera, which contains no unpalatable secondary metabolites, had no apakaochtodene compounds and were eaten by fishes. This observation is consistent with the hypothesis that diet-derived algal metabolites in sea hares play a role in deterring predation.

With increasing interest in feed-based methane mitigation strategies and regional legal directives aimed at methane production from the agricultural sector, identifying local sources of biological feed additives will be critical for rendering these strategies affordable. In a recent study, the red alga Asparagopsis taxiformis harvested offshore Australia was identified as highly effective for reducing methane production from enteric fermentation. Due to potential difference in methane-reduction potential and the financial burden associated with transporting the harvested seaweed over long distances, we examined locally sourced red seaweed A. taxiformis and brown seaweed Zonaria farlowii for their ability to mitigate methane production when added to feed widely used in the Californian dairy industry. At a dose rate of 5% dry matter (DM), California-sourced A. taxiformis and Z. farlowii reduced methane production by up to 74% (p < 0.05) and 11% (p < 0.05) during in vitro rumen fermentation, respectively. No effect on CO 2 production was observed for either seaweed. The measured decrease in methane production induced by A. taxiformis and Z. farlowii amendment, suggest that these local macroalgae are indeed promising candidates for biotic methane mitigation strategies in California, the largest milk producing state in the United States. To determine their real potential as methane mitigating feed supplements in the dairy industry, their effect in vivo will need to be investigated.