Selectivity Assessment of Chlorfenvinphos Reevaluated by Including Physiological and Behavioral Effects on an Important Beneficial Insect

Abstract

Selectivity is an important factor in identifying candidate pesticides to be used in crop protection since it characterizes chemicals that, while being effective against target pests, exert an acceptable impact on the other components of the environment. Extrapolated to an integrated pest management (IPM) context, selectivity implies that candidate pesticides may preserve the ability of beneficial insects to significantly control target pest populations. In the present study, we assess the physiological selectivity of the organophosphate chlorfenvinphos, used to protect cruciferous crops against the cabbage root fly, Delia radicum (Diptera: Anthomyiidae), by investigating both the lethal and sublethal effects exerted on its main parasitoid Trybliographa rapae (Hymenoptera: Figitidae). The comparison of the median lethal doses showed that T. rapae was at least seven times less sensitive than D. radicum to chlorfenvinphos. However, longevity of parasitoids surviving a sublethal dose was reduced by half. The potential fecundity of females was decreased by 9.6 to 22.8%. Chlorfenvinphos also induced important behavioral changes in both sexes and reduced the chances for parasitoids to mate by more than 70%. While most behavioral changes were reversible, effects on mating and on fecundity were not, thereby suggesting long-term effects on the reproduction of the parasitoid. These cumulative effects of chlorfenvinphos would have dramatic consequences on the efficacy of parasitoids contacting such doses of chlorfenvinphos in the field and therefore there is question about the intrinsic selectivity of this insecticide.

Evidence of potential long term effects in (aquatic and terrestrial) invertebrates after short term pulsed exposure. Literature reviews on ecotoxicology of chemicals with special focus on plant protection products

“…A reduction of parasitoid lifespan could ultimately result in decreased reproductive output and diminished parasitism. A concurrent decrease in potential female fecundity was also observed in the days following chlorfenvinphos exposure, with fewer eggs dissected from the ovaries of exposed females at days 5 (17% reduction), 10 (10% reduction), 15 (21% reduction), and 20 (18% reduction) post-exposure (Alix, et al 2001). Experiments with multiple organophosphate and carbamate compounds indicate that brown lacewing populations are also potentially at risk from short-term, field-relevant exposures to plant protection products:…”

“…Trybliographa rapae parasitoids (Hymenoptera: Figitidae) were subjected to a single cuticular exposure of 300 ng chlorfenvinphos /insect (another OP), individuals exhibited reduced longevity (approximately 56% reduction for males and 48% reduction for females) (Alix, et al 2001). A reduction of parasitoid lifespan could ultimately result in decreased reproductive output and diminished parasitism.…”

“…EFSA reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors. Alix, et al, 2001 Final report CFT/EFSA/PPR/2008/01…”

Indirect Effects of Pesticides on Natural Enemies

“…It is possible that formulations such as emulsifiable concentrates (EC) and soluble powders (SP) may contain additives such as adjuvants, surfactants, solvents and/or carriers that are indirectly harmful to natural enemies [45,165]. Studies associated with how inert ingredients affect natural enemies are necessary in order to better understand the actual indirect impact of pesticides on natural enemies.…”

Efeito letal e subletais de inseticidas à Ageniaspis citricola Longvinovskaya (Hymenoptera: Encyrtidae)

“…Temperatura de 25 ± 2 ºC, UR de 70 ± 10% e fotoperíodo de 14 L: 10 E horas Efeitos subletais de abamectina sobre o parasitoide Ageniaspis citricola. Temperatura de 25 ± 2 ºC, UR de 70 ± 10% e fotoperíodo de 14 L: 10 E horasALIX et al, 2001;DECOURTYE;DELPUECH, 2007). Portanto, a menor proporção de fêmeas na população pode reduzir a eficácia do parasitoide no controle biológico de P. citrella ao longo do tempo, pois, somente as fêmeas são capazes de realizar o parasitismo de ovos e larvas de primeiro instar do insetopraga.…”