Effect and mode of action of some systemic nematicides

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