Herbivore-induced plant volatiles emitted from avocado shoots infested by Oligonychus yothersi (Acari: Tetranychidae) increases the attraction of micro-coleopterans

Abstract

The avocado red mite, Oligonychus yothersi (McGregor) (Acari: Tetranychidae), is a polyphagous pest that causes damage to a wide range of plants. In Chile, is commonly found in avocado (Persea americana Mill.) orchards, and the plant damage is expressed as a reduction of photosynthetic activity in leaves, causing defoliation of trees under severe attack conditions. Oligota pygmaea (Solier) (Staphylinidae) and Parastethorus histrio (Chazeau) (Coccinellidae) microcoleopteran predators are found on 'Hass' avocado orchards, infested by O. yothersi. This study investigated the role of volatile compounds released by avocado in response to O. yothersi infestation in the tritrophic interaction avocado-O. yothersi-O. pygmaea-P. histrio. Plant volatiles were collected from live plants by headspace technique on Porapak Q traps and analyzed by gas chromatography coupled to mass spectrometry (GC-MS). In the chemical analysis, several chemical groups were identified including terpenes, aromatic compounds, and green leaf volatiles. Eight chemical compounds were detected only in the infested plants volatile profile, and differences were observed in the emission of 10 compounds between infested and uninfested plants (P < 0.05). The behavioral responses of the insects to plant volatiles were evaluated in a choice-test using a Y-tube as olfactometer. Uninfested plant volatiles were significantly attractive to O. yothersi, while infested plants volatile extract repelled the mites. Two compounds, R-limonene and α-pinene, elicit an attractant behavioral response from O. yothersi. Oligota pygmaea and P. histrio females registered a strong attraction to volatiles from infested plants, and the compounds (Z)-β-ocimene and methyl salicylate detected only in infested plant also were attractive to predators.

Volatile Profiling of Fifteen Willow Species and Hybrids and Their Responses to Giant Willow Aphid Infestation

“…The degree of infestation ( Figure 6) could also have contributed to different outcomes. The emission of HIPVs can qualitatively and quantitively vary depending on the population density of the insect feeding on host plants [72,73], with studies typically reporting a positive correlation between herbivore population density and VOC emission [74][75][76]. However, we only found a weak correlation between aphid infestation and VOC emission, and responding species and hybrids (except S. candida) were not heavily infested.…”

Galendromus occidentalis (Acari: Phytoseiidae) life table parameters on Oligonychus yothersi (Acari: Tetranychidae) colonies and its behavior to odors of mites, avocado shoots volatiles and synthetic compounds

“…Similarly, Shastani et al (2014) found that P. persimilis preferred synthetic MeSA at doses of 0.02-20 μg. However, P. histrio preferred MeSA concentration ranges 1-100 μg mL -1 , while O. pygmaea showed attraction at 1 and 10 μg mL -1 of synthetic MeSA (Rioja et al, 2018). Yet, when Shimoda (2010) offered synthetic MeSA (1 mg) vs. infested bean plants (P. vulgaris 'Nagauzuramame') with T. urticae, Neoseiulus californicus (Acari: Phytoseiidae) did not discriminate between these odor sources, showing that MeSA is an attractant for mite predators.…”

“…Our results reveal that G. occidentalis does not associate the HIPVs released by O. yothersi-infested avocado shoots (Table 4) with prey availability since they do not belong to the avocado system. In contrast, P. histrio and O. pygmaea are attracted to HIPVs emitted by O. yothersi-infested avocado shoots (Rioja et al, 2018). These predators use chemical cues from avocado-O.…”

“…As described in Rioja et al (2018) we used dynamic headspace technique with a positive/negative pressure air system. We performed collections for 24 h enclosing shoots into 1.5 L polyethylene terephthalate (PET) bottles cut vertically and sealed with Teflon tape.…”

“…Beetles Oligota pygmaea Solier (Coleoptera: Staphylinidae) and Parastethorus histrio Chazeau (Coleoptera: Coccinellidae) are observed preying all stages of O. yothersi on damaged and infested avocado trees (Hoy, 2011;Rioja et al, 2016). Since both coleopterans are dense-dependent, they require higher mite populations to establish themselves, and HIPVs released by O. yothersi-infested avocado recruit these predators (Rioja et al, 2018). The control of the red mite is achieved by pesticides usage, mineral oils, and aerial sulfur applications (Ripa and Larral, 2008).…”