Arthropods, nontarget

Naranjo, S.E., G. Head, and G.P. Dively. 2005. Field studies assessing arthropod nontarget effects in Bt transgenic crops Introduction. Environ. Entomol. 34 1178-1180. 

Fenvalerate is extremely toxic to representative nontarget aquatic organisms and to some beneficial terrestrial arthropods at concentrations substantially lower than those recommended to control pestiferous insects. Toxic effects are associated primarily with the 2.S, a.S -isomcr and are exacerbated at low temperatures. Birds, mammals, and terrestrial plants are normally tolerant. 

Riedl, H. and S.A. Hoying. 1980. Impact of fenvalerate and diflubenzuron on target and nontarget arthropod species on Bartlett pears in northern California. Jour. Econ. Entomol. 73 117-122. 

Widespread use of mirex may lead to altered population structure in terrestrial systems, with resurgence or escalation of nontarget pests due to selective mirex-induced mortality of predators (NAS 1978). For example, populations of immature horn flies and rove beetles, two species of arthropods normally preyed upon by fire ants, were higher in mirex-treated areas than in control areas (Howard and Oliver 1978). Conversely, other species, such as crickets, ground beetles, and various species of oil-loving ants, were directly affected and populations were still depressed or eliminated 14 months posttreatment (NAS 1978), whereas fire ants recovered to higher than pretreatment levels, as judged by mound numbers and mound size (Summerlin et al. 1977). 

Keywords Aquatic organisms Ecotoxicology Nontarget arthropods Synthetic pyrethroid... 

Not surprisingly, considering their highly efficacious and broad-spectrum insecticidal activity, SPs are highly toxic to honeybees and other nontarget arthropods. High levels of toxicity to aquatic arthropods have been reported [5]. Although of relatively low toxicity to birds, fish are also sensitive, probably because of a less... 

Table 8 Summary of laboratory nontarget arthropod toxicity endpoints...

The field nontarget arthropod data for pyrethroids summarized in Table 9 indicate that for all pyrethroids there was an initial reduction in abundance for some species shortly after application. There was a trend of more marked effects at the higher full field application rates with less marked affects at the lower drift rates tested (e.g., Deltamethrin, bifenthrin, and esfenvalerate). Also there was a trend of greater selectivity (i.e., fewer taxa affected) at lower drift rates (e.g., /amMa-cyhalothrin and Deltamethrin). For nearly all the pyrethroid field studies, either full or partial recovery of affected taxa was reported by the end of the field study or growing season, and in some cases for certain taxa, recovery occurred within 1-3 weeks. 

Table 9 Summary of nontarget arthropod field/semifield studies (app = application)... 

Some toxic consequences of neonicotinoids for nontarget beneficial aquatic and terrestrial arthropods such as bees can be expected since these creatures have nicotinic acetylcholine receptors as functional components of the cholinergic system similar to those of insect pests. Surprisingly, neonicotinoid toxicity to numerous nontarget insect species and wildlife marker vertebrates, for example, rainbow trout, is lower than expected. In general, the environmental safety of neonicotinoids surpasses that of other insecticides. 

The analysis of environmental risk assessments of 50 pesticides revealed that risks to birds and mammals often were not fully addressed. EMs could be useful for filling this gap, but should also be useful for aquatic organisms and nontarget arthropods, particularly in relation to questions of recovery. A major obstacle to the full use of EMs is the lack of clear protection goals in terms of population-level effects. Validation is key to the acceptance of models in the regulatory context, and guidance is needed for the assessment of EMs and their outputs (Chapter 11). 

Terrestrial vertebrates (birds and mammals) were the group of organisms for which an acceptable risk most often failed to be fully demonstrated, with 25 substances (50%) in list 2, followed by nontarget arthropods, with 14 (28%) substances, and aquatic organisms, with 12 (24%) substances (Figure 11.1). 

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