Effect and mode of action of some systemic nematicides

In this study, nematicidal effects, mode of action and specific characters of some systemic nematicides were studied, in search of substitutes for the widely used soil fumigants that require high dosages. The thesis comprises:- a review of literature,- development of techniques,- a test for nematicidal effectiveness of agricultural chemicals,- a detailed study of two systemic nematicides in vitro and in vivo,- a study of some important side-effects of the two systemic nematicides.Review of literatureThe main groups of test animals (nematodes and arthropods) and the systemic and fumigant categories of nematicides are briefly reviewed, and a scheme of the principal interactions between nematicide, fauna, flora and soil is given (Fig. 1). The literature review stresses:- the great increase in crop yields possible by soil disinfection,- the desirability of replacing currently used nematicides applied at dosages of 100-1000 kg a.i. per ha,- the effect of systemic nematicides on the relation plant/nematodes at dosages of 1-10 kg a.i. per ha,- the controversial opinions on mode of action of systemic nematicides, - the lack of information on residues and side-effects,- the selectivity of techniques for testing nematicides, which thus may not detect effective chemicals.Development of techniquesMaterials and methods are briefly indicated. Special attention was given to the development of new screen techniques. Three biological assays, called 'penetration inhibition' test (PI test), 'therapeutic' test (T test) and 'gall index' test (GI test) were developed or modified to meet the requirements for effective and rapid screening of all known types of nematicides, with emphasis on systemics (Fig. 2, 7 and 10).The PI test measures inhibition of invasion by Ditylenchus dipsaci in stem sections of Vicia faba (Fig. 3 - 6; Table 1). The T test can also be used like the PI test - to measure inhibition of invasion by D. dipsaci - but can be also used to measure the therapeutic effect of substances in Lycopersicum esculentum infested by D. dipsaci (Fig. 8 and 9; Tables 2 and 3). The GI test measures the effect on gall formation of L. esculentum by Meloidogyne incognita (Fig. 11; Table 4).Nematicidal effectiveness of some biocidesThis general screen as a basis for appraisal and choice between compounds for further study was made with the PI test. Tables 5 and 6 and Fig. 12 summarize details and results.Thirtyfour of 60 preparations tested were effective with an EC-50 (median effective concentration) of 50 mg/litre (ppm) or less. The very active materials were organophosphates and organocarbamates and are known to inhibit acetylcholinesterase; they comprise a group of 17 compounds with an EC-50 of 1 ppm or less. Of those materials, the following had not previously been recorded as nematicidal: dichlorvos, methiocarb, trichlorphon, pyrazophos, fenitrothion. However, three known nematicidal active compounds showed an EC-50 above 50 ppm: α-terthienyl, benomyl and dinitro-o-cresol (Table 5).Oxamyl, an organocarbamate, and phenamiphos, an organophosphate, were chosen on the basis of these results and of other properties for further study on their effects and mode of action.Effects of oxamyl and phenamiphos in vitroBoth chemicals had direct effects on nematodes (contact action), including protrusion of stylets, and shortening, swelling and wrinkling of their body, resulting in aberrant undulations and reduced mobility (Fig. 13 -16). The symptoms of poisoning, however, were reversible for oxamyl, but less so for phenamiphos.When D. dipsaci was permanently exposed to solutions of the preparations, the nematode was initially affected but recovered gradually in oxamyl concentrations up to 64 ppm. Phenamiphos did not allow recovery - not even at 0.1 ppm - during 21 days' exposure (Fig. 17; Table 7).When D. dipsaci was washed with water, nematodes treated with 1000 ppm a.i. oxamyl for 24 hours recovered in 2 days; even after 4 days' treatment with oxamyl solutions at 10000 ppm a.i. nematodes in the L-4 stage could recover. The effects of phenamiphos were less reversible; after 24 hours' treatment in 100 ppm a.i. the nematodes did not regain normal behaviour, but nematodes did recover after treatment with 10 ppm a.i. Recovered nematodes could reproduce normally (Fig. 18-21; Tables 8 and 9).The effects observed and those noted in the literature indicate that the effects were caused by inhibition of acetylcholinesterase or other neuro-enzymes.Effects of oxamyl and phenamiphos in soil and plantsSoil drenches with aqueous solutions of both preparations reduced Pratylenchus penetrans in plant roots or even eradicated them, and also reduced nematode densities in soil. Phenamiphos, particularly, is less effective in organic soils. Root dips and foliage sprays (without preventing soil contamination) were effective, but basipetal transport of the substances could not be demonstrated. Also within plants, the effects of oxamyl on nematodes were reversible and of phenamiphos irreversible.At low temperatures, at low dosages and in the first weeks after soil was drenched, oxamyl was superior as a nematicide to phenamiphos, either to control nematodes inside or outside the roots of the test plants. At high temperatures, for high dosages and longer periods, the reverse was true (Fig. 22 - 24; Tables 10-14).The effect of the two substances on nematodes in microplots sown with Lolium perenne (Fig. 25-27) were generally similar to those obtained in vitro and in drench treatments: this was true for several species of nematodes and microarthropods, although saprozoic mites were less susceptible (Fig. 28 and 29; Tables 17 and 18). Phenamiphos caused a greater and longer effect than oxamyl, although oxamyl too greatly reduced populations for several weeks after treatment. Plant growth was best on oxamyl plots as phenamiphos was apparently phytotoxic to L. perenne.The same treatments on fallow soil confirmed that the substances had an almost equal, direct effect on the nematodes as for nematodes in soil in which L. perenne was growing (Fig. 3 1 ; Table 20).Some specific effects of oxamyl and phenamiphosOxamyl persisted less in soil than phenamiphos (Fig. 33; Table 22); in fact oxamyl was so transient that low-temperature application increased the nematicidal effect markedly.Experiments in vivo with sublethal concentrations of oxamyl and phenamiphos suggest that hardly any resistance could be expected with these systemics. About 9 successive generations of D. dipsaci were tested for resistance in one year.Sprays with oxamyl were not toxic to plants while phenamiphos was relatively toxic (Fig. 34), with differences from species to species of plant.A test in vitro on toxicity to fungi showed that oxamyl has no fungitoxic properties and phenamiphos has (Table 25).Both substances reduced Rhizobium trifolii nodulation on red clover plants infested by P.penetrans (Fig. 35).General conclusionsSystemic nematicides are useful for preventing nematodes from attacking crops, by preventing penetration of nematodes or even by eradicating nematodes that have already entered roots, stems or leaves. The nematicidal effects and persistance is somewhat greater for phenamiphos than for oxamyl.Apparently they not only influence nematodes through the plant (by systemic action), but also in the soil (by contact).Systemic nematicides may also prevent damage to plants by microarthropods.As to residues, oxamyl seems less dangerous to the environment than phenamiphos, because oxamyl is quickly broken down to biologically inactive substances. The combination of short persistence and reversibility of the poisoning effect makes oxamyl - in contrary to phenamiphos - nematostatic rather than nematicidal

Parsing in Dialogue Systems using Typed Feature Structures

The analysis of natural language in the context of keyboard-driven dialogue systems is the central issue addressed in this paper. A module that corrects typing errors and performs domain-specifc morphological analysis has been developed. A parser for typed unification grammars is designed and implemented in C++; for description of the lexicon and the grammer a specialised specification language has been developed. It is argued that typed unification grammars and especially the newly developed specification language are convenient formalisms for describing natural language use in dialogue systems. Research on these issues is carried out in the context of the Schisma project, a research project of the Parlevink group in linguistic engineering; participants in Schisma are KPN Research and the University of Twente. The aims of the Schisma project are twofold: both the accumulation of knowledge in the field of computational linguistics and the development of a natural language interfaced theatre information and booking system is envisaged. The Schisma project serves as a testbed for the development of the various language analysis modules necessary for dialogue systems

Biochar versus hydrochar as growth media constituents for ornamental plant cultivation

[EN] Biochar and hydrochar have been proposed as novel materials for providing soilless growth media. However, much more knowledge is required before reliable advice can be given on the use of these materials for this purpose. Depending on the material and the technology applied (pyrolysis or hydrothermal carbonization), phytotoxicity and greenhouse gas emissions have been found for certain chars. In this study, our aim was to assess the feasibility of three chars as substrate constituents. We compared two biochars, one from forest waste and the other from olive mill waste, and a hydrochar from forest waste. We studied how chars affected substrate characteristics, plant performance, water economy and respiratory CO2 emission. Substrates containing biochar from forest waste showed the best characteristics, with good air/water relationships and adequate electrical conductivity. Those with biochar from olive mill waste were highly saline and, consequently, low quality. The substrates with hydrochar retained too much water and were poorly aerated, presenting high CO2 concentrations due to high respiratory activity. Plants performed well only when grown in substrates containing a maximum of 25 % biochar from forest waste or hydrochar. After analyzing the char characteristics, we concluded that biochar from forest waste could be safely used as a substrate constituent and is environmentally friendly when applied due to its low salinity and low CO2 emission. However, biochar from olive mill waste and hydrochar need to be improved before they can be used as substrate constituents.This study was funded by the Polytechnic University of Valencia (Projects on New Multidisciplinary Research; PAID-05-12). We thank Molly Marcus-McBride for supervising the English.Fornes Sebastiá, F.; Belda Navarro, RM. (2018). Biochar versus hydrochar as growth media constituents for ornamental plant cultivation. Scientia Agricola (Online). 75(4):304-312. https://doi.org/10.1590/1678-992X-2017-0062S304312754Abad, M., Noguera, P., & Burés, S. (2001). National inventory of organic wastes for use as growing media for ornamental potted plant production: case study in Spain. Bioresource Technology, 77(2), 197-200. doi:10.1016/s0960-8524(00)00152-8Bargmann, I., Martens, R., Rillig, M. C., Kruse, A., & Kücke, M. (2013). Hydrochar amendment promotes microbial immobilization of mineral nitrogen. Journal of Plant Nutrition and Soil Science, 177(1), 59-67. doi:10.1002/jpln.201300154Bargmann, I., Rillig, M. C., Buss, W., Kruse, A., & Kuecke, M. (2013). Hydrochar and Biochar Effects on Germination of Spring Barley. Journal of Agronomy and Crop Science, 199(5), 360-373. doi:10.1111/jac.12024Bedussi, F., Zaccheo, P., & Crippa, L. (2015). Pattern of pore water nutrients in planted and non-planted soilless substrates as affected by the addition of biochars from wood gasification. Biology and Fertility of Soils, 51(5), 625-635. doi:10.1007/s00374-015-1011-6Belda, R. M., Lidón, A., & Fornes, F. (2016). Biochars and hydrochars as substrate constituents for soilless growth of myrtle and mastic. Industrial Crops and Products, 94, 132-142. doi:10.1016/j.indcrop.2016.08.024Costello, R. C., & Sullivan, D. M. (2013). Determining the pH Buffering Capacity of Compost Via Titration with Dilute Sulfuric Acid. Waste and Biomass Valorization, 5(3), 505-513. doi:10.1007/s12649-013-9279-yFernandes, C., & Corá, J. E. (2004). Bulk density and relationship air/water of horticultural substrate. Scientia Agricola, 61(4), 446-450. doi:10.1590/s0103-90162004000400015Fornes, F., Belda, R. M., Carrión, C., Noguera, V., García-Agustín, P., & Abad, M. (2007). Pre-conditioning ornamental plants to drought by means of saline water irrigation as related to salinity tolerance. Scientia Horticulturae, 113(1), 52-59. doi:10.1016/j.scienta.2007.01.008Fornes, F., Belda, R. M., & Lidón, A. (2015). Analysis of two biochars and one hydrochar from different feedstock: focus set on environmental, nutritional and horticultural considerations. Journal of Cleaner Production, 86, 40-48. doi:10.1016/j.jclepro.2014.08.057Fornes, F., & Belda, R. M. (2017). Acidification with nitric acid improves chemical characteristics and reduces phytotoxicity of alkaline chars. Journal of Environmental Management, 191, 237-243. doi:10.1016/j.jenvman.2017.01.026Fornes, F., Belda, R. M., Fernández de Córdova, P., & Cebolla-Cornejo, J. (2017). Assessment of biochar and hydrochar as minor to major constituents of growing media for containerized tomato production. Journal of the Science of Food and Agriculture, 97(11), 3675-3684. doi:10.1002/jsfa.8227Fornes, F., Carrión, C., García-de-la-Fuente, R., Puchades, R., & Abad, M. (2010). Leaching composted lignocellulosic wastes to prepare container media: Feasibility and environmental concerns. Journal of Environmental Management, 91(8), 1747-1755. doi:10.1016/j.jenvman.2010.03.017GARCIADELAFUENTE, R., CARRION, C., BOTELLA, S., FORNES, F., NOGUERA, V., & ABAD, M. (2007). Biological oxidation of elemental sulphur added to three composts from different feedstocks to reduce their pH for horticultural purposes. Bioresource Technology, 98(18), 3561-3569. doi:10.1016/j.biortech.2006.11.008Genty, B., Briantais, J.-M., & Baker, N. R. (1989). The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence. Biochimica et Biophysica Acta (BBA) - General Subjects, 990(1), 87-92. doi:10.1016/s0304-4165(89)80016-9Hoitink, H. A. J., Stone, A. G., & Han, D. Y. (1997). Suppression of Plant Diseases by Composts. HortScience, 32(2), 184-187. doi:10.21273/hortsci.32.2.184Libra, J. A., Ro, K. S., Kammann, C., Funke, A., Berge, N. D., Neubauer, Y., … Emmerich, K.-H. (2011). Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis. Biofuels, 2(1), 71-106. doi:10.4155/bfs.10.81Mazuela, P., Salas, M. del C., & Urrestarazu, M. (2005). Vegetable Waste Compost as Substrate for Melon. Communications in Soil Science and Plant Analysis, 36(11-12), 1557-1572. doi:10.1081/css-200059054Méndez, A., Paz-Ferreiro, J., Gil, E., & Gascó, G. (2015). The effect of paper sludge and biochar addition on brown peat and coir based growing media properties. Scientia Horticulturae, 193, 225-230. doi:10.1016/j.scienta.2015.07.032Nieto, A., Gascó, G., Paz-Ferreiro, J., Fernández, J. M., Plaza, C., & Méndez, A. (2016). The effect of pruning waste and biochar addition on brown peat based growing media properties. Scientia Horticulturae, 199, 142-148. doi:10.1016/j.scienta.2015.12.012Sáez, J. A., Belda, R. M., Bernal, M. P., & Fornes, F. (2016). Biochar improves agro-environmental aspects of pig slurry compost as a substrate for crops with energy and remediation uses. Industrial Crops and Products, 94, 97-106. doi:10.1016/j.indcrop.2016.08.035Smith, B. R., Fisher, P. R., & Argo, W. R. (2004). Growth and Pigment Content of Container-grown Impatiens and Petunia in Relation to Root Substrate pH and Applied Micronutrient Concentration. HortScience, 39(6), 1421-1425. doi:10.21273/hortsci.39.6.1421Solaiman, Z. M., Murphy, D. V., & Abbott, L. K. (2011). Biochars influence seed germination and early growth of seedlings. Plant and Soil, 353(1-2), 273-287. doi:10.1007/s11104-011-1031-4Steiner, C., & Harttung, T. (2014). Biochar as a growing media additive and peat substitute. Solid Earth, 5(2), 995-999. doi:10.5194/se-5-995-2014Tian, Y., Sun, X., Li, S., Wang, H., Wang, L., Cao, J., & Zhang, L. (2012). Biochar made from green waste as peat substitute in growth media for Calathea rotundifola cv. Fasciata. Scientia Horticulturae, 143, 15-18. doi:10.1016/j.scienta.2012.05.018Vaughn, S. F., Eller, F. J., Evangelista, R. L., Moser, B. R., Lee, E., Wagner, R. E., & Peterson, S. C. (2015). Evaluation of biochar-anaerobic potato digestate mixtures as renewable components of horticultural potting media. Industrial Crops and Products, 65, 467-471. doi:10.1016/j.indcrop.2014.10.04