Behavioural responses of wheat stem sawflies to wheat volatiles

Abstract

Abstract1 Adult wheat stem sawflies Cephus cinctus, pests of cultivated cereals that also infests wild grasses, migrate into wheat fields where they oviposit in elongating, succulent stems.2 Volatiles released by wheat plants at susceptible stages were analyzed to determine potential semiochemical compounds. Seven major compounds were identified and quantified.3 A Y‐tube bioassay was developed to evaluate upwind orientation of adult sawflies in response to an airstream that passed over elongated wheat plants. The bioassay was also conducted with synthetic volatile compounds. The compounds were tested using a range of concentrations spanning those identified in the airstream passing over wheat plants.4 A significant number of adult females were attracted to wheat plants when given a choice of either purified air or the air passing over plants.5 A significant number of female C. cinctus were attracted to (Z)‐3‐hexenyl acetate, β‐ocimene, and (Z)‐3‐hexen‐1‐ol, but were repelled by 6‐methyl‐5‐hepten‐2‐one. Females did not respond to (E)‐2‐hexenal, or (E)‐2‐hexenyl acetate. The behavioural responses were concentration dependent; the highest tested concentration of (Z)‐3‐hexenyl acetate was repellent to females of this species.6 Adult males did not discriminate between air passing over wheat plants and air from a purified airstream. Males did not respond to any tested synthetic compound at any concentration.7 The present study demonstrates for the first time that adult females of wheat stem sawfly display innate behaviours in response to synthetic volatiles. These results provide a basis for the potential development of resistant wheat varieties and for the development of semiochemically‐based pest management.

Methyl Jasmonate Affects Population Densities of Phytophagous and Entomophagous Insects in Wheat

“…However, in our previous study, we found that the outcome of CJ on wheat stem sawflies is influenced by the sampling method, with more consistent results obtained from yellow sticky traps and indicating that CJ is repellent to wheat stem sawfly adults (Bayram and Tonğa, 2017). CJ-treated wheat plants release a group of HIPVs, one of which ((Z)-3-hexenyl acetate) repels the wheat stem sawfly C. cinctus at high doses while attracting it at lower concentrations (Piesik et al, 2008;Delaney et al, 2013). The same very high MEJA doses that we used in our study induced faster maturation of wheat plants in another study (Beltrano et al, 1998); therefore, in our field experiments, such faster growth may have limited the production of HIPVs like (Z)-3-hexenyl acetate, causing the compounds to remain at attractive (lower) concentrations after MEJA treatment.…”

Apion miniatum Germ. Herbivory on the Mossy Sorrel, Rumex confertus Willd.: Induced Plant Volatiles and Weevil Orientation Responses

“…This inference depends on the degree of VOC induction increasing with A. miniatum herbivory intensity on R. confertus and needs to be tested in the field. Piesik et al [28] found that only female Cephus cinctus Norton (Hynenoptera: Cephidae) were attracted to some concentrations of (Z)-3-HAC, (Z)-3-HOL, and the terpene ß-ocimene. Yet C. cinctus females were repelled by the highest tested concentration (8,400 ng·h -1 ) of (Z)-3-HAC.…”

“…All components (95% purity) were purchased from Sigma-Aldrich. The Y-tube system used was similar to that described by Piesik et al [28]. Each blend was tested at 5 concentrations (0, 1, 5, 25, 125 ng·min -1 ).…”

Differential preference of Capsicum spp. cultivars by Aphis gossypii is conferred by variation in volatile semiochemistry

“…This compound is released by wheat seedlings, along with (R) and (S)-6-methyl-5-hepten-2-ol and 2-tridecanone, that are heavily infested with the bird-cherry-oat aphid, Rhopalosiphum padi (Quiroz et al 1997). 6-Methyl-5-hepten-2-one is known to repel R. padi (Quiroz et al 1997), is attractive to the aphid parasitoids, Aphidius ervi (Du et al 1998) and A. funebris (Pareja et al 2007), and was also reported as a repellent of females of Cephus norton cintus, a wheat pest in North America (Piesik et al 2008). With regard to compounds other than 6-methyl-5-hepten-2-one produced by the nonpreferred SGHGB cultivar after infestation by A. gossypii, there are, up to now, no reports on their effects on aphids.…”