Population-level effects of abamectin, azadirachtin and fenpyroximate on the predatory mite Neoseiulus baraki

Abstract

The coconut production system, in which the coconut mite Aceria guerreronis is considered a key pest, provides an interesting model for integration of biological and chemical control. In Brazil, the most promising biological control agent for the coconut mite is the phytoseiid predator Neoseiulus baraki. However, acaricides are widely used to control the coconut mite, although they frequently produce unsatisfactory results. In this study, we evaluated the simultaneous direct effect of dry residue contact and contaminated prey ingestion of the main acaricides used on coconut palms (i.e., abamectin, azadirachtin and fenpyroximate) on life-history traits of N. baraki and their offspring. These acaricides are registered, recommended and widely used against A. guerreronis in Brazil, and they were tested at their label rates. The offspring of the exposed predators was also evaluated by estimating the instantaneous rate of population increase (r i ). Abamectin compromised female performance, whereas fenpyroximate did not affect the exposed females (F0). Nonetheless, fenpyroximate strongly compromised the offspring (F1) net reproductive rate (R0), intrinsic rate of population growth (r i ), and doubling time (DT). In contrast, fenpyroximate did not have such effects on the 2nd generation (F2) of predators with acaricide-exposed grandparents. Azadirachtin did not affect the predators, suggesting that this acaricide can be used in association with biological control by this predatory species. In contrast, the use of abamectin and fenpyroximate is likely to lead to adverse consequences in the biological control of A. guerreronis using N. baraki.

Pesticides and passive dispersal: acaricide‐ and starvation‐induced take‐off of the predatory mite Neoseiulus baraki

“…One hundred female predatory mites were released on each PVC disc, and were daily provided with epidermal fragments of coconut perianth (ca. 1 cm 3 ) containing between 80 and 100 coconut mites ( A. guerreronis ) at different developmental stages . The mites were reared under controlled conditions of 27.0 ± 0.5 0 C and 75.0 ± 10.0% relative humidity (RH), with a 12‐h photoperiod; the same conditions were used for all bioassays.…”

“…This response minimizes acaricide exposure and therefore will benefit the predatory mite survival when fleeing the chemical challenge. This response takes place even though the predatory mite is able to sustain the physiological cost associated with higher tolerance to acaricides compared with the coconut mite . This behavioural outcome and consequences have been reported in other insect species and have potential management implications .…”

“…The acaricides were used at the following single rates corresponding to their respective maximum label rate registered for the coconut mite in Brazil: 13.5 mg a.i./L for abamectin, 30.0 mg a.i./L for azadirachtin, and 100 mg a.i./L for fenpyroximate. These label rates were sublethal concentrations for the predatory mite, as previously demonstrated, and no mortality was observed during the bioassays.…”

“…The wind‐mediated passive dispersal of N. baraki may also be affected by acaricides used against its prey, including the coconut mite, and so this mite species is useful as a model to test pesticide effects on passive dispersal. The biopesticides abamectin and azadirachtin, in addition to the conventional (specific) acaricide fenpyroximate, are frequently used against the coconut mite in the Neotropics, leading to sublethal exposure of N. baraki . Therefore, we hypothesized that sublethal exposure of the phytoseiid predator to these compounds and starvation may interfere with its passive dispersal via wind.…”

“…[27][28][29][30] Nonetheless, some of the acaricides used against the coconut mite compromise the survival and/or performance of its phytoseiid predator N. baraki. [31][32][33][34] The wind-mediated passive dispersal of N. baraki may also be affected by acaricides used against its prey, including the coconut mite, and so this mite species is useful as a model to test pesticide effects on passive dispersal. The biopesticides abamectin and azadirachtin, in addition to the conventional (specific) acaricide fenpyroximate, are frequently used against the coconut mite in the Neotropics, leading to sublethal exposure of N. baraki.…”