Impact of cypermethrin on feeding behaviour and mortality of the spider Pardosa amentata in arenas with artificial ‘vegetation’

Abstract

Pesticides can modify invertebrate movement and feeding behaviour which could reduce predation in agroecosystems. Previous assays have exposed the spider Pardosa amentata (Clerck) to the synthetic pyrethroid cypermethrin and monitored prey items consumed in small containers (requiring very little movement to capture prey). The current study used larger arenas containing artificial 'vegetation' (a plastic analogue) to encourage spiders to hunt and capture prey. The period 24 h after exposure produced greatest variability in prey item consumption between treatments and was used to examine treatment effects. At this time, cypermethrin reduced prey consumption rates but these effects did not persist. Findings did not suggest that the presence of artificial vegetation in arenas modified prey consumption rates, which was consistent for individuals treated with cypermethrin and a control group. This is despite the majority of pesticide-treated individuals exhibiting both ataxia and paralysis of the hind legs (these effects persisting for a maximum of 3 and 6 days respectively). These findings were consistent for both sexes. Spider longevity under starvation conditions was not significantly reduced by cypermethrin exposure but overall females survived longer than males. The findings are discussed in the context of the arenas used and the ecology of this common predator.

Effects of insecticide exposure on movement and population size estimates of predatory ground beetles (Coleoptera: Carabidae)

“…In particular, Bayley and Baatrup22 found changes in movement of an isopod that corresponded to those seen in the first and second video tracking experiments with S. quadriceps (increases in distance moved, maximum velocity, percentage time moving), although the period of exposure was much longer (22 h). Hyperactivity resulting from sublethal insecticide exposure usually appears to compromise the ability of predators to feed,4, 23, 26 but at least one study suggests a short‐term benefit of stimulation for location of hosts by a parasitoid 25. The third (repeated‐measures) video tracking experiment indicated inhibition of S. quadriceps movement and an increase in meander 240 min after lambda‐cyhalothrin exposure.…”

“…Pest resurgence and secondary pest outbreaks are among the best‐known undesirable consequences of insecticide use,1 and are often attributed to high mortality of predators and parasitoids. However, arthropod responses to sublethal insecticide exposure are both common and varied 2–4. For example, estimates of natural enemy population size sometimes paradoxically increase following insecticide applications 5, 6…”

Evaluation of decreasing deltamethrin concentration in the treatment of olive logs: effects on the olive bark beetle and its associated parasitoids

“…The near absence of new reproduction galleries excavated in deltamethrin treated logs (Table 1), although insecticide dosage along the experimental setup was reduced approximately 10-fold, could be explained by a repellent effect of the insecticide, already reported for pyrethroid insecticides (Pen˜a et al 1998;Rodrı´guez et al 2003a;Rose et al 2005;Shaw et al 2006). Other possible effects of the insecticide which would explain the absence of new reproduction galleries could be a delayed effect on mortality or modification of the beetle behaviour when locating the olive logs.…”

“…Log treatment before colonization is ostensibly an attractive strategy, because logs can be sprayed in the olive orchard before they are brought to log piles. However, the application of synthetic insecticides may induce some adverse effects, harm associated parasitoids or repel the beetles and thus transfer the problem to other places (Rose et al 2005;Shaw et al 2006).…”

Acute and long‐term effects of selective insecticides onMicromus tasmaniaeWalker (Neuroptera: Hemerobiidae),Coccinella transversalisF. (Coleoptera: Coccinellidae) andNabis kinbergiiReuter (Hemiptera: Miridae)

“…In addition, selective insecticides may impact negatively on beneficial invertebrates by modifying behaviour or movement (e.g. reduced feeding or avoidance) (Shaw et al 2006), which were not directly tested in this study. Walthall and Stark (1997) argued that population growth rate factors, such as the intrinsic rate of increase (rm) and more recently (Stark et al 2007) the delay in population growth index, are superior predictors of population response to toxicant exposure than acute mortality estimates.…”