Behavioral Response of Grape Root Borer (Lepidoptera: Sesiidae) Neonates to Grape Root Volatiles

Abstract

Grape root borer, Vitacea polistiformis (Harris), is an oligophagous and potentially destructive pest of grape in commercial vineyards throughout much of the eastern United States. Larvae feed on vine roots, although little is known about their below-ground interactions with host plants. The behavioral response of groups of grape root borer neonates to stimuli from host and nonhost roots was evaluated in single and paired stimuli bioassays in which stimuli were presented in opposing wells attached to the bottom of petri dish arenas. Stimulus sources included root pieces and root headspace volatiles from 3309 and 420-A grape rootstocks (host) and apple (nonhost) and ethanol-based extracts of 3309 and 420-A roots. In single stimulus assays, significantly more larvae were recovered from wells containing grape roots, apple roots, grape extracts, and grape root volatiles than from control wells, but there was no significant response to volatiles collected from the headspace of apple roots. In paired stimuli assays, significantly more larvae were recovered from wells containing grape than apple roots. There was no difference in larval distribution between wells when 420-A and 3309 roots were presented simultaneously, although a significantly greater response to 3309 than 420-A root extract was recorded. When soil was added to the assays, significantly more larvae were recovered from wells containing grape roots than from those containing only soil, but this response was not detected in assays using buried apple roots. These results are discussed in relation to the plant-insect interactions between grape root borer larvae and their Vitaceae hosts.

Effects of Biotic and Abiotic Factors on Grape Root Borer (Lepidoptera: Sesiidae) Infestations in Commercial Vineyards in Virginia

“…Rijal et al (2013) showed that grape root volatiles may have an important role in larval food-Þnding, although the current study revealed no effects of rootstock. Soil texture, moisture, porosity, particle size, and compaction can affect the dispersion of behaviorally active host stimuli chemicals in the rhizosphere and also may inßuence the mobility and survival of root-feeding insect larvae (Villani andWright 1990, Gregory andJohnson 2006).…”

“…Bergh et al (2011) showed that neonate grape root borers responded positively to ethanol-based extracts of roots from several native Vitis species and commercial rootstocks, with indications of a stronger response to some. Subsequently, Rijal et al (2013) found that volatile emissions from roots were attractive to larvae. Although Harris et al (1994) noted higher levels of grape root borer infestations on older vines, All et al (1987) reported that 1-yr-old vines were infested and we have observed numerous instances of 3-to 5-yr-old vines supporting larval populations.…”

Volatiles released by Chinese liquorice roots mediate host location behaviour by neonate Porphyrophora sophorae (Hemiptera: Margarodidae)

“…Similarly to adult herbivores, neonate larvae are assumed to have an innate ability to differentiate stimuli from suitable host plants and stimuli from non‐host plants. Various studies have shown that neonate larvae of lepidopteran species orient towards odours released from their host plants primarily by olfaction . Polyphagous root‐feeding insects often use common primary metabolites to locate host plant tissues, whereas mono‐ and oligophagous species tend to use host‐specific secondary metabolites …”

“…The females tend to deposit the ovisacs 10–50 cm away from liquorice plants. Relatively indiscriminate oviposition site selection has been observed in other subterranean insect species, such as black vine weevil, Otiorhynchus sulcatus (F.), and grape root borer, Vitacea polistiformis (Harris) . After hatching, neonates move out of the soil and disperse on the soil surface in search of new hosts.…”

“…Relatively indiscriminate oviposition site selection has been observed in other subterranean insect species, such as black vine weevil, Otiorhynchus sulcatus (F.), and grape root borer, Vitacea polistiformis (Harris). 12,18 After hatching, neonates move out of the soil and disperse on the soil surface in search of new hosts. The host-searching strategy at ground level facilitates neonate dispersal over a much greater distance with lower energy cost compared with slow movement in the soil matrix.…”