Pesticides and Arthropods: Sublethal Effects and Demographic Toxicology
Pesticidi i artropode: subletalni efekti i demografska toksikologija
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Author
Marcic, Dejan
Keywords
PesticidesArthropods
Sublethal effects
Life tables
Demographic toxicology
Pesticidi
artropode
subletalni efekti
tablice života
demografska toksikologija
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Show full item recordAbstract
Insecticides and acaricides designed to control primary harmful insects and mites
may also variously affect some other arthopods present in an (agro)ecosystem (e.g. secondary
pests, predators, parasitoids, saprophytes, bioindicators, pollinators). Apart from insecticides
and acaricides, arthropods may also be affected by the activity of other pesticides
(fungicides, herbicides, etc.). Regardless of whether they are deemed desirable or not, the
effects that pesticides have on arthopods need to be quantified as closely as possible through
appropriate experimental procedures. Data acquired in tests designed to determined
LD50/LC50 values are inadequate for evaluation of pesticide effectiveness in the field as pesticides
also cause various sublethal effects, generally disregarded in such investigations.
The sublethal effects of pesticides refer to any altered behaviour and/or physiology of individuals that have survived exposure to pesticides at doses/concentrations that can be lethal
(within range causing mortality in an experimental population that exceeds mortality in
an untreated population) or sublethal (below that range). Pesticides affect locomotion and
mobility, stimulate dispersion of arthropods from treated areas, complicate or prevent their
navigation, orientation and ability to locate hosts, and cause changes in their feeding, mating
and egg-laying patterns. Sublethal pesticide effects on arthropod physiology reflect
on the life span, rate of development, fecundity and/or fertility, sex ratio and immunity of
surviving individuals. Different parameters are being used in arthropod bioassays to determine
sublethal effects (ED50/EC50, LOEC, NOEC, total effect index). Compared to acute toxicity
tests, these parameters improve the quality of evaluation and create a more accurate
view of the effects of a pesticide. However, such approach covers mainly fecundity/fertility
alone, while all other sublethal effects remain unaccounted for. Besides, it refers to an evaluation
of individuals, rather than populations, and it is the latter that are required for a more
reliable evaluation of effectiveness of pesticides in real life. A demographic-toxicological
approach has been proposed therefore as a way of integrating the effects that a toxicant
may cause at population level, which includes the construction of life tables and computation
of population growth parameters, including intrinsic rate of increase (rm) as a crucial
parameter. Compared to other laboratory toxicity tests, the demographic-toxicological bioassay
has been found superior in terms of a capacity to evaluate overall effects of pesticides,
and such approach in evaluating pesticide effects is crucial for environmentally-based
programmes of integrated plant protection and a competent evaluation of ecotoxicological
risks of pesticide applications. Insekticidi i akaricidi namenjeni suzbijanju primarnih štetnih vrsta insekata i grinja deluju
na različite načine i na druge artropode (sekundarne štetne vrste, predatore, parazitoide, saprofite, bioindikatore, polinatore) sa kojima dolaze u kontakt u (agro)ekosistemu. Pored insekticida i akaricida, artropode su osetljive i na delovanje drugih pesticida (fungicida, herbicida).
Bez obzira da li ih posmatramo kao poželjne ili nepoželjne, efekte pesticida na artropode treba
što preciznije kvantifikovati primenom odgovarajućih eksperimentalnih postupaka. Rezultati dobijeni testovima dizajniranim za određivanje LD50/LC50 vrednosti nisu dovoljni za procenu efektivnosti pesticida u polju, jer pesticidi izazivaju i različite subletalne efekte, koje ovi testovi ne uzimaju u obzir. Subletalni efekti pesticida obuhvataju promene ponašanja i/ili fiziologije jedinki preživelih ekspoziciju delovanju pesticida u dozama/koncentracijama koje mogu da
budu letalne (u opsegu koji u eksperimentalnoj populaciji uzrokuje smrtnost veću od smrtnosti
u kontroli) ili subletalne (ispod ovog opsega). Pesticidi utièu na lokomotornu aktivnost i
mobilnost, podstiču disperziju sa tretiranih površina, otežavaju ili onemogućavaju navigaciju,
orijentaciju i pronalaženje domaćina, menjaju ponašanje karakteristično za način ishrane, parenje
i polaganje jaja. Subletalni efekti pesticida na fiziologiju atropoda ispoljavaju se kroz uticaj
na dužinu života, brzinu razviæa, fekunditet i/ili fertilitet, odnos polova, imunitet preživelih
jedinki. U testovima sa artropodama, koriste se razlièiti parametri za iskazivanje subletalnih efekata
(ED50/EC50, LOEC, NOEC, indeks totalnog efekta). U poređenju sa testovima akutne toksičnosti,
ovi parametri poboljšavaju kvalitet evaluacije i pružaju jasniju sliku o efektima pesticida;
međutim, ovakav pristup uglavnom uzima u obzir samo fekunditet/fertilitet, dok drugi subletalni
efekti ostaju neregistrovani. Pored toga, reč je o evaluaciji na nivou jedinke, a ne na nivou
populacije, kakva je neophodna za pouzdaniju procenu efektivnosti pesticida u realnim uslovima.
Kao način za integraciju efekata koje neki toksikant može da izazove na nivou populacije
predložen je demografsko-toksikološki pristup, tj. konstruisanje tablica života i izračunavanje
parametara populacionog rasta, među kojima centralno mesto pripada prirodnoj stopi rasta
populacije (rm). U poređenju sa drugim laboratorijskim postupcima testiranja toksičnosti, demografsko-
toksikološki biotest se pokazao kao superiorniji u proceni ukupnih efekata pesticida;
ovakav pristup evaluaciji efekata pesticida suštinski je značajan za ekološki zasnovanu integralnu
zaštitu bilja i kvalitetnu procenu ekotoksikološkog rizika primene pesticida.