Imidacloprid – olive orchard “guardian”

Abstract

Pojava otpornosti populacije štetnika na organofosfate i metilkarbamate, inhibitore acetilkolinesteraze, dovela je do njihove slabije učinkovitosti i uvjetovala da ih neonikotinoidni insekticidi istisnu iz uporabe. Imidakloprid je najvažniji neonikotinoid, a odlikuje se niskom postojanosti u tlu, visokom insekticidnom aktivnosti i niskom toksičnosti u sisavaca. Neurofiziološke studije su potvrdile da je on agonist postsinaptičkih nikotinskih acetilkolinskih receptora, pri čemu izaziva najprije stimulaciju postsinaptičkih membrana, a nakon toga para lizu prijenosa živčanih impulsa. U Hrvatskoj se imidakloprid često koristi u maslinicima Istre i kvarnerskih otoka kao efi kasno sredstvo u zaštiti nasada maslina protiv različitih nametnika. Progresivno povećanje proizvodnje i primjene pesticida u poljoprivredi predstavlja veliku opasnost za onečišćenje okoliša, osobito podzemnih voda. Kada pesticid uđe u okoliš ovisan je o mnogim fi zikalnim i kemijskim procesima. Procesi sorpcije jedni su od glavnih faktora koji utječu na postojanost i pokretnost pesticida u okolišu. U ovome radu opisani su postupci sorpcije i razgradnje imidakloprida i njihova ovisnost o karakteristikama tla u četiri maslinika Istre i kvarnerskih otoka. Sastav i svojstva tla (veličina čestica, udio organskih tvari, kiselost tla) imaju izrazit utjecaj na postupke sorpcije i razgradnje imidakloprida. Sorpcija imidakloprida je jača, a razgradnja brža u tlu s višim udjelom gline i humusa te nižoj kiselost tla. Razgradnja imidakloprida u tlu se odvija sporo i kontinuirano. S vremenom poluraspada iznad 110 dana, imidakloprid se može svrstati u postojane pesticide. Uslijed česte primjene ipak predstavlja potencijalnu opasnost zbog ulaska u ciklus kruženja tvari u okolišu s posljedičnim štetnim djelovanjem na biljni i životinjski svijet, a time i na čovjeka.Neonicotinoids are increasingly replacing the organophosphate and methylcarbamate acetylcholinesterase inhibitors which are losing their eff ectiveness due to the selection for resistant pest populations. Imidacloprid is the most important neonicotinoid with low soil persistence, high insec cidal potency and rletively low mammalian toxicity. Neurophysiological studies have confi rmed that imidacloprid is an agonist at the postsynaptic nicotinic acetylcholine receptors which stimulates the postsynaptic membrane first and then paralyses nerve conduction. In Croatia, imidacloprid is commonly used in olive growing areas, including Istria and Kvarner islands, as an eff ective mean of olive fruit fly infestation control. Once a pesticide is introduced into the environment it can be infl uenced by many physical and chemical processes. Pesticide sorption processes are undoubtedly one of the major factors aff ecting the persistence and movement in the environment. This paper describes sorption and degradation processes of imidacloprid and investigates the relationships between soil properties and sorption and degradation characteristics in four soils, representative of northern Adriatic region, namely island Krk and a coastal Istrian region. Soil content and properties (particle size, content of organic matter, acidity) have a great eff ect on sorption of imidacloprid onto soil particle. Sorption and degradation of imidacloprid increase in soil with higher clay and organic matter content and with lower acidity. The imidacloprid degradation processes are continuous, though not very rapid. According to half-life of more than 110 days, imidacloprid is classified as persistant pesticide. However, it’s liberate usage can disturb environmental cycling and thus adversely aff ect non-target organisms, including plant and animal species. In this way, imidacloprid may also impose a risk to the human health

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