Weather data in its raw form frequently contains irrelevant and noisy information. Often the hardest task in model development, regardless of the technique used, is translating independent variables from their raw form into data relevant to a particular model. A sequential or cascading temporal correlation analysis was used to identify weather sequences that were strongly correlated with aphid trap catches recorded at Lincoln, Canterbury, New Zealand, over 1982-2000. Trap catches in the previous year and 13 weather sequences associated with eight climate variables were identified as significant predictors of aphid trap catch during the autumn flight period. The variables were used to train artificial neural network (ANN) models to predict the size of autumn aphid migrations into cereal crops in Canterbury. Such models would assist cereal growers to make better informed and more timely pest management decisions. ANN predictive performance was compared with multiple regression predictions using jackknifed data. The ANN gave superior prediction compared with multiple regression over 13 jackknifed years.
Environmental and social crises in agriculture have led to growing recognition that more ecologically sustainable and socially just food and agricultural systems are needed. This thematic number of the International Journal of Agriculture and Natural Resources gathers the papers submitted to the workshop “Challenges for agroecology development for the building of sustainable agri-food systems,” an OECD Co-operative Research Programme-sponsored conference. The aim of the workshop was to promote the transition from conventional agriculture towards agroecology as a science, practice and social movement through sharing the experiences of different OECD countries: Australia, Canada, Chile, Colombia, Hungary, Italy, Netherlands, Norway, Spain, Sweden and the United States. The main topics discussed at the workshop included i) agroecology development in OECD countries: local experiences and international collaboration; ii) agroecology as a social movement and related public policies; iii) agroecology education to promote sustainable agri-food systems; and iv) science, innovation and technologies in agroecological systems. While not a comprehensive assessment of the state of agroecology in OECD countries, this thematic number integrates diverse perspectives on some main research and policy advances and uncovers some existing gaps in agroecology practice as an approach for transitioning towards ecologically sustainable and socially just agricultural systems
The influence of infective juveniles (IJs) concentration, soil texture, IJ-host distance and organic matter (OM) content, at different decomposition degree, on the activity of the nematode Steinernema feltiae isolate Lican Ray (LR) was examined using Galleria mellonella larvae. Bioassays were conducted in tubes of varied length, filled with soil of different textures, placed either vertically or horizontally. In the concentration assay, highest IJ concentrations caused maximum larval mortality in all soil types (440, 2,200 and 4,400 IJs in clay, loam and sandy loam). In the second assay, soil texture (loam, clay or sandy loam) interacted significantly with IJ-host distance (10, 20, 30, 40 cm, horizontally; 30, 50, 70 cm, vertically), and distances of 30 cm or more affected IJ effectiveness on the control of G. mellonella. The effect was stronger in clay and sandy loam than in loam soils, where IJ moved up to 40 cm horizontally and 70 cm vertically. In the third assay, OM content (0, 2, 4, 6 and 8%) and its decomposition degree (initial, medium and advanced) did not interact to influence IJ movement in all treatments that contained any percentage of OM (2-8%). Only in the soil with no OM, IJ did not cause death of larvae at all. These results show the potential of S. feltiae LR to be used in different soil textures, as long as the content of soil OM allows its dispersal and host infection, in order to optimize the pest-control activity of the nematode.
In Canterbury the cereal aphid (Rhopalosiphum padi) has a bimodal annual flight pattern with peaks in autumn and late spring The autumn peak coincides with the migration of aphids into autumn and winter sown wheat The timing magnitude and duration of flights vary dramatically from year to year and can have important implications for the management of this aphid in cereals Twenty years of climatic and aphid flight data were used to train a neural network to obtain a model to predict the date and size of aphid migrations in cereal crops in Canterbury New Zealand The model provided an exceptional fit to the ten years of training data but gave disappointingly poor prediction for the eight years of validation data Possible reasons for poor prediction of validation data are given and suggestions are made concerning future developments
Background Steinernema feltiae is an entomopathogenic nematode used in biological control programs with a global distribution. Populations of this species show phenotypic plasticity derived from local adaptation and vary in different traits, such as location and host penetration. The aim of this work was to describe a Chilean isolate of this nematode species, using integrative approaches. Methods Nematode morphological and morphometric studies were conducted along with molecular analysis of nuclear genes. The symbiotic bacterium was also identified by sequencing the 16S rRNA gene. Some ecological characteristics were described, including the temperature requirements for the nematode life cycle and the effect of soil water content for optimal reproduction. Results Morphometric characterization revealed a large intra-specific variability. The isolate identity was also corroborated with the analysis of nuclear genes. Based on the 16S gene, its symbiont bacteria, Xenorhabdus bovienii, was identified. The lowest, optimal and highest temperatures found to limit the infestation and reproduction on Galleria mellonella were 10, 20 and 30 °C, respectively; the emergence from the host larvae occurred approximately 10 days after inoculation. Differences were observed in offspring, and 120 infective juveniles (IJ)/larva was the most prolific dose at 20 °C. The soil water content did not affect the number of IJ invaders, penetration efficacy and IJ emergence time or offspring per larva, but it caused a delay in achieving full mortality at the permanent wilting point with respect to saturation and field capacity. Conclusions For the first time, a Chilean isolate of S. feltiae is described in detail considering morphological, molecular and ecological aspects. The isolate was shown to be efficient in soil containing water, with optimal temperatures ranging from 15 to 25 °C for host infestation and production of an abundant offspring; these characteristics would allow its potential use as control agents in a wide geographical area of the country.
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