Phytoseiulus persimilis response to herbivore-induced plant volatiles as a function of mite-days

Abstract

The predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae), uses plant volatiles (i.e., airborne chemicals) triggered by feeding of their herbivorous prey, Tetranychus urticae (Acari: Tetranychidae), to help locate prey patches. The olfactory response of P. persimilis to prey-infested plants varies in direct relation to the population growth pattern of T. urticae on the plant; P. persimilis responds to plants until the spider mite population feeding on a plant collapses, after which infested plants do not attract predators. It has been suggested that this represents an early enemy-free period for T. urticae before the next generation of females is produced. We hypothesize that the mechanism behind the diminished response of predators is due to extensive leaf damage caused by T. urticae feeding, which reduces the production of volatiles irrespective of the collapse of T. urticae population on the plant. To test this hypothesis we investigated how the response of P. persimilis to prey-infested plants is affected by: 1) initial density of T. urticae, 2) duration of infestation, and 3) corresponding leaf damage due to T. urticae feeding. Specifically, we assessed the response of P. persimilis to plants infested with two T. urticae densities (20 or 40 per plant) after 2, 4, 6, 8, 10, 12 or 14 days. We also measured leaf damage on these plants. We found that predator response to T. urticae-infested plants can be quantified as a function of mite-days, which is a cumulative measure of the standing adult female mite population sampled and summed over time. That is, response to volatiles increased with increasing numbers of T. urticae per plant or with the length of time plant was infested by T. urticae, at least as long at the leaves were green. Predatory mites were significantly attracted to plants that were infested for 2 days with only 20 spider mites. This suggests that the enemy-free period might only provide a limited window of opportunity for T. urticae because relatively low numbers of T. urticae per plant can attract predators. Leaf damage also increased as a function of mite-days until the entire leaf was blanched. T. urticae populations decreased at this time, but predator response to volatiles dropped before the entire leaf was blanched and before the T. urticae population decreased. This result supports our hypothesis that predator response to plant volatiles is linked to and limited by the degree of leaf damage, and that the quantitative response to T. urticae populations occurs only within a range when plant quality has not been severely compromised.

A key volatile infochemical that elicits a strong olfactory response of the predatory mite Neoseiulus californicus, an important natural enemy of the two-spotted spider mite Tetranychus urticae

“…Individual G-tests were conducted to evaluate whether each of four replicates (20 individuals/replicate) in an experiment differed from a 50:50 distribution between the two odor sources (** P \ 0.01, * P \ 0.05, NS not significant). For details, see the text 2000b; Ishiwari et al 2007;van Wijk et al 2008), plant cultivar (Dicke et al 1990b), plant age (Takabayashi et al 1994), herbivore density (Maeda and Takabayashi 2001) and infestation level (Nachappa et al 2006). The potential influences of these factors may make it difficult to compare behavioral studies that focus on predator response to volatile infochemicals from e.g.…”

<p class="HeadingRunIn"><strong>Prey consumption and functional response of <em>Neoseiulus</em> californicus and <em>Neoseiulus longispinosus</em> (Acari: Phytoseiidae) on <em>Tetranychus urticae</em> and <em>Tetranychus kanzawai </em>(Acari: Tetranychidae)</strong></p>

“…Recent research shows that these chemical volatiles were produced by plants infected by herbivores; the volatiles emitted from the plant are called "HIPVs" (herbivore-induced plant volatiles) (Takabayashi et al 1994;Shimoda et al 2005;Nachappa et al 2006;Dicke & Baldwin 2010;Dicke 2015). "HIPVs" comprise a complex mixture of tens up to more than 200 compounds, the composition of which may vary with herbivore species, herbivore developmental instar, plant tissue, and abiotic conditions (Dicke 2015).…”

Olfactory responses of Neoseiulus cucumeris (Acari: Phytoseiidae) to odors of host plants and Frankliniella occidentalis (Thysanoptera: Thripidae)–plant complexes

“…These results suggest that the predators were capable of exploiting herbivore-induced volatiles form T. tabaci-infested cucumber leaves as a foraging cue (Satoshi and Takeshi 2008). The predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae) (Shimoda and Dicke 1999;Maeda et al 2000;Maeda and Takabayashi 2001;Nachappa et al 2006;Wijk et al 2008) urticae (Acari, Tetranychidae) were studied in greenhouse, and an average of 79.5% of the predators were found on infested plants, indicating that these attract about four times as many predators as do clean plants. Hence, P. persimilis preferred odors from infested cucumber plants to odors from clean cucumber plants (Janssen 1999).…”