Article

PC‐Plant Protection: optimizing chemical weed control1

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Abstract

In Denmark, a political decision was taken to achieve, before 1997, a 50% reduction in the bulk of active ingredients in pesticides consumed, compared with average consumption in the period 1981/1985. To meet this requirement, a computer-based decision support system has been developed. In order to minimize doses, the system combines the concept of factor adjusted doses and expert knowledge. Herbicide doses are adjusted on the basis of the sensitivity of different weed species and their growth stages. Based on actual field observations, the system suggests suitable herbicides, the normal dose, the actual dose, prices per ha, etc. In future, doses will probably also be factor-adjusted according to climatic conditions, competitive ability of cereal cultivars and soil type. The need for control of individual weed species (thresholds) is based on expert knowledge. Ongoing long-term studies on seed production by weeds, competition studies etc. will hopefully help to establish more exact models for economic thresholds. After satisfactory validation through field trials, the system will be continuously updated with new findings in weed research. The system has been on the market in Denmark since spring 1991.

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... Finally, decision rules for site-specific weed management are needed which determine the correct dose and herbicide mixture for each position in the field. So far, decision support systems give a recommendation for uniform weed control applications across the total field based on the average weed infestation level (Rydahl and Thonke, 1993). None of these models take into account the heterogeneous distribution of weeds within the field. ...
Chapter
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Site specific crop protection or precision crop protection is an integral component of precision farming which basically depends on measurement and understanding of variability. Site specific crop protection is an enabled technology and based on information and focused decision. The components include Remote Sensing (RS), Geographical Information System (GIS), Global Positioning System (GPS), soil testing, yield monitors and Variable Rate Technology (VRT). The available technologies enable us in understanding the variability and by giving site specific crop protection recommendations we can manage the variability that make site specific crop protection viable. The disease or insect affected crop and normal crops give different tonal variation in imageries. After image analysis found the great variability in tonal variation on the imagery. Normal crops give red, bright red and dark red colour with smooth texture but pests affected area give pink, yellow and yellow pinkish red colour with irregular shape and rough texture. This helps farmers to pay immediate attention towards pest infestation and manage crop by spraying chemicals. Thermography allows the quantitative analysis of spatial and dynamic physiological information on the plant status. Infrared thermography is used to study spatial variability of stomatal conductance, to schedule irrigation, for monitoring of temperature stress in plants, to screen for mutants with altered stomatal control and for assessment of plant-pathogen interaction by monitoring patterns of surface leaf temperature. Site specific crop protection is a system that is designed to strengthen farming management, providing farmers improved means to spot weak productivity zones and react before they become loses, increasing yields for the farmer and reducing annual production costs and adverse environmental impacts.
... ha-') last spraying before or during anthesis; against aphids, only if needed. "Herbicide application as recommended by PC-Plant Protection (Rydahl 1993). 'Fertilizer was drilled in beneath and between cereal rows before sowing. ...
Article
The field mycobiota associated with malt barley was characterized over a period of 2 years, and changes in the mycobiota present on different cultivars were evaluated after treatment with pesticides or no treatment. The study showed that spraying, with pesticides did not result in changes in the composition of field mycobiota compared with the pesticide-free barley. The determining factor on the mycobiota was the location. The dominant species on barley was Alternaria infectoria Simmons. The most frequent Fusarium species detected were F. tricinctum (Corda) Sacc. and F. avenaceum (Fr.) Sacc. Results implied an interaction between Alternaria and Fusarium on the surface of the kernels. Keywords: pesticide-free malt barley, dematiaceous fungi, Alternaria infectoria, Fusarium.
... Boyle & Fairchild (1997) noted that, within plant communities, competitive processes will interact with herbicides in the sense that there may be a primary phytotoxic effect of the herbicide on the target species with a secondary, indirect, effect of the herbicide on the individual plant due to the altered competition from neighbours. At reduced rates of herbicide application, competitive processes may play a key role in determining the outcomes of herbicide application , and an understanding of the interaction is important in recommending reduced rates of application (Haas 1989; Rydahl & Thonke 1993; Christensen 1994). ...
Article
Summary • The estimation of dose–response relationships is an integral and legally necessary part of the routine regulatory process for herbicides. For each herbicide, plants of both target and non-target species are exposed to different levels of the chemical, and effects on mortality and performance expressed as LD50 and ED50 values (respectively, the dose at which 50% of plants die and the dose at which plants show a 50% response to herbicide). Thereafter, LD50 and ED50 values may provide comparative information between herbicides and species. There is little published on the effects of plant density on dose–response relationships. • We used the herbicide 2,4-D amine and Agrostemma githago as a model system to investigate the effects of plant density on the dose–response relationship (ED50) between 2,4-D and A. githago biomass measured as fresh weight. • Plants were grown in a controlled environment room at both low and high densities (two and 64 plants per pot) for 2 weeks, sprayed with 2,4-D using a precision sprayer, and then harvested after a further 2 weeks. The ED50 values were significantly greater when the plants were grown at high density (616 g active ingredient ha−1) than those grown at low density (42 g active ingredient ha−1); a 15-fold difference. • Mathematically, it was shown that a simple multiplicative relationship exists between ED50 and dose received when plants are grown at different densities, all other conditions being equal. • To explore the underlying effects of competitive processes arising from different densities, we experimentally investigated three phases where competition could be influencing the response of plants: (i) before spraying, (ii) at the time of spraying and (iii) after spraying. We used a sequential series of experiments to determine which phase was contributing most to the observed difference between ED50 values obtained from plants grown at low and high density. • It was shown that the competition between plants after spraying was the most likely phase to have contributed to the observed difference in ED50 values between the two densities. • These results demonstrate that trials used in the pesticide regulatory process ought to test not only different doses of pesticide but also different densities of plants (both crop and weed).
Article
It has been established that weeds are spatially aggregated with a spatially varying composition of weed species within agricultural fields. Site-specific spraying therefore requires a decision method that includes the spatial variation of the weed composition and density. A computerized decision method that estimates an economic optimal herbicide dose according to site-specific weed composition and density is presented in this paper. The method was termed a ‘decision algorithm for patch spraying’ (DAPS) and was evaluated in a 5-year experiment, in Denmark. DAPS consists of a competition model, a herbicide dose–response model and an algorithm that estimates the economically optimal doses. The experiment was designed to compare herbicide treatments with DAPS recommendations and the Danish decision support system PC-Plant Protection. The results did not show any significant grain yield difference between DAPS and PC-Plant Protection; however, the recommended herbicide doses were significantly lower when using DAPS than PC-Plant Protection in all years. The main difference between the two decision models is that DAPS integrates crop–weed competition and estimates the net return as a continuous function of herbicide dose. The hypothesis tested is that the benefit of using lower herbicide doses recommended by DAPS would disappear after a few years because weed density will increase and thus require higher doses. However, the results of weed counting every year did not confirm this hypothesis.
Article
Initiatives such as Videotext and forecasting models resulted in a relatively fast introduction of computer technology on to farms at the end of the 1980s. In several countries there were developments to create models for supervised control and data exchange became digital. Most models were developed for diseases that could expand very rapidly, or diseases that should be controlled regularly. In the 1990s, development of weather-related Decision Support Systems (DSSs) began. It is important to use the optimal way to disseminate information to the target group; which can differ between or even within countries. The use of DSSs results in a lower risk of crop damage by diseases and pests, and a lower input of active substances, from the use of adjusted dosages. Future developments may include the possibility of implementing a number of DSS-models into a Geographical Information System, which will support precision agriculture by providing adjusted spraying advice based on plot-specific characteristics. The success of DSSs is despite its development occurring independently in a number of countries. The speed of development of these systems would have been substantially faster had there been real cooperation between countries or groups of researchers. In order to withstand funding reductions, it is necessary for the development of new DSSs that collaboration between researchers and research groups internationally increases significantly in the near future.
Article
A major concern of producers has always been how to reduce the amount of inputs required for crop production while maintaining or improving yields. One area of research addressing this issue is site-specific weed management (SSWM). The objective of this research was to evaluate the possibility of using SSWM herbicide applications to reduce overall production costs when site-specific weed populations are known. Weed populations of three soybean fields (B-East, B-South, B-North), located at the Black Belt Branch Experiment Station, Brooksville, MS, were estimated in 1998 and 1999. Sampling occurred July 8–9, 1998 (8 weeks after planting), and June 30–July 1, 1999 (6 WAP). An established 10 m 10 m Universal Transmercator (UTM) grid coordinate system was used to divide the fields into 100 m2 cells, with the sample point located in the center of each cell. Optimal herbicide recommendations were obtained for each sample location within each field by subjecting the weed information to the Herbicide Application Decision Support System (HADSS). An average of the weed populations for the entire field was also subjected to HADSS to obtain an optimal recommendation for a broadcast application for comparison purposes. Data from 1998 resulted in 25% and 15% of the field not requiring a herbicide treatment for the B-North and B-South when compared to the whole-field recommendations to receive broadcast treatments. However, B-East received a no treatment recommendation for the whole-field analysis. The no treatment recommendation was attributed to the sicklepod population exceeding a level deemed economically controllable by HADSS. However, when SSWM recommendations were generated, 49% of the field received no treatment recommendation, while 51% resulted in a herbicide application as an economical choice. In 1999, glyphosate-resistant transgenic soybean was used, thereby increasing the POST herbicide treatment options available in HADSS. Herbicide treatment recommendations resulted in 100%, 56%, and 91% of the total area requiring herbicide treatments for B-East, B-North, and B-South, respectively. Comparing the projected net returns for each field can develop a better estimate of the value of SSWM. In 1998, data from the B-East resulted in a projected net return increase of $21.63 ha–1 over that of the broadcast application. Estimated net return increased $21.63 ha–1 over that of the broadcast application. Estimated net return increased 5.42 ha–1 at B-North, with simulated SSWM applications over broadcast applications, and $14.67 ha–1 increase at B-South. Net returns for 1999 resulted in only a $14.67 ha–1 increase at B-South. Net returns for 1999 resulted in only a 0.32 ha–1 increase by using SSWM for B-East, but a 21.00 and21.00 and 13.56 ha–1 increase for B-North and B-South, respectively. The extra expenses of SSWM, such as sampling and technology costs, are not included in the net returns calculations and, when included, would reduce the difference between SSWM and conventional methods. This research has demonstrated the potential value of SSWM from an economic standpoint; environmental benefits through reductions in herbicide applications are also apparent.
Chapter
For precision weed management decision rules are needed that take into account spatial and temporal variability of weed populations and weed-crop interactions. The following chapter describes different decision rules for online and offline site-specific weed management. Those decision rules use crop-weed competition models, dose-response functions, weed population models and cost functions to calculate the best intensity of weed control for each field section. It is shown that herbicide input and weed control costs can be significantly reduced when farmers use those models in combination with modern sensor and application technologies.
Article
The Danish Integrated Farm Management System is a PC-based system developed by the Danish agricultural advisory service covering all management and control aspects of a farm. It consists of a joint module linking a number of sector modules (cattle production, plant production, economy, pig production and buildings/machinery). The sector module for plant production provides facilities for detailed planning, decision support and control, including all subjects of a complete cultivation plan for each individual field. The fertilizer plan and the crop protection plan provide detailed specifications within the overall cultivation plan. For decision support there are advanced sub-modules for fertilization, crop protection and grassland management. PC-Plant Protection is an optional and fully integrated sub-module of The Integrated Farm Management System, or a self-contained program product.
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Les essais biologiques sont des expériences planifiées en vue d'estimer la force d'un ou plusieurs stimuli comparativement à une norme (ou standard) et ce, en employant l'information fournie par les réponses d'un matériel biologique soumis à certaines mensurations (et comptages). Bien quils soient un sujet apparemment spécialisé attirant de rares statisticiens, ils sont aussi, par maints côtés remarquablement propres à faire réfléchir sur des aspects importants de la pratique de la biométrie comme de l'inférence statistique. Dans cet article, nous montrons comment les essais biologiques peuvent jeter de la lumière sur la pratique de la statistique, en relation spécialement avec les plans d'expériences, l'emploi des tests de signification, la présence d'observations aberrantes (outliers), et autres sujets relatifs à l'interprétation des données. Tout d'abord nous esquissons une logique des essais de dilution, et des tests de validité nécessaires pour les interpréter. La classe importante des essais de radio-immunité fournit d'excellents exemples de problèmes se rapportant au choix de la courbe de réponse, à la variance des réponses, à la méthode d'estimation, et à la nécessité de reconnaitre 'des paramètres de second niveau'? Le plan d'expérience influe à la fois sur la pertinence et sur la précision d'un essai, ce qui peut être mis en évidence sur des exemples très simples. De nos jours, l'analyse statistique se fera ordinairement avec un calculateur. Nous insistons à la fois sur la nécessité d'un 'logiciel' qui programme pour les besoins courants et sur l'erreur qu'on commet quand on croit que des statisticiens non professionnels ont seulement besoin d'une programmation très simple. L'essai biologique n'implique guère de théorie statistique abstraite, mais - parce que ses problèmes peuvent être jugés sans avoir de connaissances détaillées de biologie - c'est un arrière plan excellent pour l'enseignement de la statistique pratique et pour la compréhension des réalités de l'inférence statistique.
Article
The principles of parallel-line assay were employed lo assess the influence of various additives on the herbicidal activity of alloxydim-sodium, fluazifop-butyl and sethoxydim on winter barley (Hordeum vulgare L. cv. Igri). The dose-response curves of the herbicides were parallel, only differing in their horizontal location, i.e., the relative potencies of the herbicide preparations were independent of the dose-response level considered. Except for one herbicide-additive combination, increasing the concentration of the additives in the spray solution increased herbicide activity. The prospects of using the parallel-line assay in studies examining the effect of additives on the activity of herbicides and its application in other kinds of herbicide studies are discussed. Méthode d'estimation de l'influence d'adjuvants sur l'efficacite de certains herbicides appliqués en pulvérisation foliaire
Three years field experience with an advisory computer system applying factor-adjusted doses
  • M Baandrup
BAANDRUP, M. (1989) Three years field experience with an advisory computer system applying factor-adjusted doses. In Brighton Crop Protection Conference-Weed? 1989, pp. 555-560. BCPC, Croydon (GB).
Plant breeding and PC-Plant Protection
  • M Baandrup
BAANDRUP, M. (1992) [Plant breeding and PC-Plant Protection.] Dansk Froaul4, 69-70 (in Danish).
Bioassay and the practice of statistical inference Reduced herbicide doses in Denmark and the development of the concept of factor-adjusted doses
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FINNEY, D.J. (1979) Bioassay and the practice of statistical inference. International Statistical Review 47, 1-12, KUDSK, P. (1989) Reduced herbicide doses in Denmark and the development of the concept of factor-adjusted doses. In Brighton Crop Protection Conference-Weeds, pp, 545-554.
[Yield response to reduced dosages in winter cereals
  • S Christensen
Reduced herbicide doses in Denmark and the development of the concept of factor adjusted doses. InBrighton Crop Protection Conference-Weeds
  • P Kudsk