Developing an Ecotoxicological Testing Standard for Predatory Mites in Australia: Acute and Sublethal Effects of Fungicides on Euseius victoriensis and Galendromus occidentalis (Acarina: Phytoseiidae)

Abstract

Laboratory bioassays for testing the effect of agrochemicals on Euseius victotiensis (Womersley) and Galendromus occidentalis (Nesbitt) on detached leaves of Glycine max (L.) (soybean) and Phaseolus vulgaris L. (French bean) were developed. The tests allowed standardized comparisons between mite species and leaf substrates, under "worst-case scenario" exposure, comparable with commercial pesticide application. Young juveniles, along with their initial food and the entire water supply, were sprayed to the point of runoff by using a Potter spray tower. The highest registered field rate concentration used on French bean was adjusted to deliver the same pesticide dose per higher runoff point spray volume on soybean. Cumulative mortality was assessed at 48 h, 4 d, and 7 d after spray application. Fecundity was assessed for 7 d from the onset of egg lay. Boscalid (Filan 500 WG), dithianon (Delan 700 WG), and kresoxim-methyl (Stroby 500 WG) caused no significant 7-d mortality or fecundity reduction to G. occidentalis or E. victoriensis compared with controls, and are classified as harmless to both species. Mancozeb (Mancozeb 750 WG) was highly toxic to both species, resulting in severe mortality and fecundity reduction and is considered incompatible with integrated pest management programs that use these species. Metiram (Polyram 700 WG) was highly toxic to E. victoriensis but only moderately toxic to G. occidentalis. Analyses of mortality proportions, including, and excluding unaccounted escapees, produced the same results. Test standardization on leaf substrates provides an alternative approach to standardization via residue on glass used by International Organisation for Biological and Integrated Control or Noxious Animals and Plants/West Palaearctic Regional Section regulatory testing in the European Union.

Seletividade de agrotóxicos usados na cultura da macieira a Neoseiulus Californicus (McGregor) (Acari: Phytoseiidae)1

“…Os fungicidas sobre os imaturos foram classificados como inócuos (classe 1, E < 30%) (Tabela 3). A aplicação de mancozebe sobre fêmeas A. andersoni (Chant), T. pyri, Galendromus occidentalis (Nesbitt), Euseius victoriensis (Womersley) resultou em um decréscimo da fecundidade, oviposição e mortalidade de imaturos (Cross & Berrie, 1996;Bernard et al, 2004). No Brasil, este fungicida causou alta mortalidade sobre I. zuluagai e não prejudicou a reprodução de E. alatus (Reis & Sousa, 2000).…”

Indirect Effects of Pesticides on Natural Enemies

“…Although similar to other pesticides, this may depend on the natural enemy type and species, timing of application (spatially and temporally), and life stage exposed. For example, mancozeb was shown to negatively affect fecundity and reproduction of the predatory mites, Amblyseius andersoni, G. occidentalis [42,152] and Euseius victoriensis [45] under laboratory and field conditions and benomyl indirectly inhibited reproduction of female Amblyseius fallacis [153] and G. occidentalis [148]. However, mancozeb did not indirectly affect longevity or reproduction of two leafminer parasitoids, Hemiptarsenus varicornis and Diglyphus isaea [57].…”

“…Certain pesticides (insecticides and fungicides) may also exhibit repellent activity [16,[41][42][43][44][45][46] or alter host plant physiology [13,47] thus indirectly affecting the ability of natural enemies to regulate existing arthropod pest populations [48].…”

“…Bostanian et al (2009) [154] reported that none of the fungicides evaluated including myclobutanil, propiconazole, fenhexamid, and pyraclostrobin, had any indirect effects on the fecundity of the predatory mite, G. occidentalis, and the fungicides captan, mancozeb, and myclobutanil did not indirectly affect longevity and fecundity of A. fallacis females [155]. Exposure to the fungicides boscalid and kresoxim-methyl, which are relatively 'newer' fungicides did not indirectly affect fecundity of both E. victoriensis and G. occidentalis [45]; and [148] found that exposure to the fungicides myclobutanil and trifloxystrobin resulted in no indirect effects on fecundity of G. occidentalis.…”

Genetically modified crops in Switzerland: implications for agrosystem sustainability evidenced by multi-criteria model

“…Like for the FR potato, it is expected that less fungicides could be applied compared to conventional orchards. Fungicide like mancozebe have shown to be toxic to insects like predatory thrips and mites (Bernard et al 2004;Li et al 2006), suggesting less pressure on those populations.…”