An Alfalfa-Related Compound for the Spring Attraction of the Pest Weevil Sitona Humeralis
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Patron: Her Majesty The Queen Rothamsted Research Harpenden, Herts, AL5 2JQ Telephone: +44 (0)1582 763133 WeB: http://www.rothamsted.ac.uk/ Rothamsted Repository Download A - Papers appearing in refereed journals Lohonyai, Zs., Vuts, J., Karpati, Zs., Koczor, S., Domingue, M.J., Fail, J., Birkett, M. A., Toth, M. and Imrei, Z. 2019. Benzaldehyde: an alfalfa- related compound for the spring attraction of the pest weevil Sitona humeralis (Coleoptera: Curculionidae). Pest Management Science. 75, p. 3153–3159. 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Research Article Received: 16 November 2018 Revised: 16 January 2019 Accepted article published: 30 March 2019 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/ps.5431 Benzaldehyde: an alfalfa-related compound for the spring attraction of the pest weevil Sitona humeralis (Coleoptera: Curculionidae) Zsófia Lohonyai,a,b József Vuts,a,c Zsolt Kárpáti,a Sándor Koczor,a Michael J Domingue,d József Fail,b Michael A Birkett,c Miklós Tótha and Zoltán Imreia* Abstract BACKGROUND: Sitona weevils (Coleoptera: Curculionidae) are a species complex comprising pests of many leguminous crops worldwide, causing damage to young plants as adults and to rootlets as larvae, resulting in significant yield losses. Timely detection of migrating adult weevils is needed to determine when deployment of control measures becomes necessary. With the aim of developing plant volatile-based lures for Sitona spp. detection, we investigated the responses of S. humeralis to host plant-related aromatic compounds. RESULTS: In olfactometer studies, both male and female S.humeralis responded positively to the odour of alfalfa flowers, a source of aromatic volatiles. In single sensillum recordings, basiconic sensilla located on the third and fourth terminal segments of the antennal club of both sexes were found to respond to benzaldehyde at doses of 10−5 and 10−4 g, suggesting that the weevil is able to detect this compound at the peripheral sensory level. In field studies, S. humeralis was attracted to benzaldehyde in the spring, but not in the autumn. CONCLUSION: Benzaldehyde, as described in this study, may be a suitable candidate for the development of monitoring tools for S. humeralis. © 2019 Society of Chemical Industry Keywords: Sitona; Curculionidae; plant volatile; chemical communication; benzaldehyde 1 INTRODUCTION The objective of this study was to develop aromatic host Sitona spp. weevils (Coleoptera: Curculionidae), which include volatile compound-based lures for the model species, S. humeralis. ∼ 100 species,1 are pests of legumes worldwide. Adults dam- Such lures may become a basis for the development of more age the foliage, which can weaken or kill the plant.2 Further- effective attractant combinations. In a previous report, alfalfa more, soil-dwelling developing larvae chew on rootlets and thicker flowers – which emit aromatic compounds characteristic of their root parts, which leads to primary damage to the nitrogen-fixing volatile profile – were tested for attractiveness to S. humeralis in olfactometer studies. We tested known synthetic aromatic nodules.3,4 Sitona humeralis Stephens is an important pest and alfalfa compounds (benzaldehyde, methyl-salicylate, 2-phenethyl a dominant species of its genus in alfalfa, Medicago sativa L. alcohol and phenylacetaldehyde)12,13 for their behavioural activity (Fabaceae), fields in Europe, Asia Minor, Iran and Central Asia; it is in the field. We tested the electroantennography (EAG) activity also present in several other leguminous crops as a member of the Sitona spp. complex.5 S. humeralis overwinters as an adult, becom- ing active again in early spring. Until recently, the only known field attractant for Sitona spp. ∗ Correspondence to: Z Imrei, Plant Protection Institute, Centre for Agricultural was 4-methyl-3,5-heptanedione, a male-produced aggregation Research, Hungarian Academy of Sciences, H-1022 Budapest, Hungary. E-mail: [email protected] pheromone component of S. lineatus L.6 The compound attracted S. macularis Herbst and S. humeralis in a preliminary study.7 a PlantProtectionInstitute,CentreforAgriculturalResearch,HungarianAcademy More recently, a bean-derived (Vicia faba L.) attractant blend of Sciences, Budapest, Hungary was described for S. lineatus, which in some cases increased trap b Faculty of Horticultural Science, SZIU, Budapest, Hungary catches in combination with 4-methyl-3,5-heptanedione in the autumn, but not in the spring.8 This and other findings9–11 suggest c Biointeractions and Crop Protection Department, Rothamsted Research, that within the genus Sitona there is scope for the development of Harpenden, UK both single- and multiple-species monitoring systems based on d Department of Entomology, Pennsylvania State University, University Park, PA, plant-derived attractants. USA Pest Manag Sci (2019) www.soci.org © 2019 Society of Chemical Industry www.soci.org Z Lohonyai et al. Table 1. Legume-related aromatic compounds field-tested for the attraction of Sitonahumeralis, and their known electrophysiological or behavioural activity in other weevil species Compound Species Type of response Reference 2-Phenethyl alcohol Ceutorhychus assimilis Payk. Electrophysiological Evans and Allen-Williams14 Phenylacetaldehyde Ceutorhychus assimilis Payk. Electrophysiological Blight et al.15 Evans and Allen-Williams14 Tanymecus dilaticollis Gyllenhal Electrophysiological Toshova et al.16 Benzaldehyde Ceutorhychus assimilis Payk. Electrophysiological Blight et al.15 Myllocerinus aurolineatus Voss Behavioural in olfactometer Sun et al.17 Tanymecus dilaticollis Gyllenhal Electrophysiological Toshova et al.16 Methyl salicylate Ceutorhychus assimilis Payk. Electrophysiological Blight et al.15 Evans and Allen-Williams14 Anthonomus musculus Say Electrophysiological Szendrei and Rodriguez-Saona18 Tanymecus dilaticollis Gyllenhal Electrophysiological Toshova et al.16 Eugenol Anthonomus grandis grandis Boheman Behavioural in field Armstrong19 of benzaldehyde (the only compound with field activity) using chances of accidental positive results, strengthening the statistics. whole-antenna EAG and single sensillum recordings (SSR) to Prior to each experiment, all glassware was washed with Teepol™ confirm its sensory detection. A legume-related volatile com- detergent, rinsed with acetone and distilled water, and baked in an pound, eugenol,13 was also included in the study, because it oven overnight at 130 ∘C. Perspex components were washed with elicited behavioural responses from other weevil species (Table 1) Teepol™ solution, rinsed with 80% ethanol solution and distilled and evoked electrophysiological responses in S. humeralis (Zs. water, and left to air dry. The olfactometer was surrounded by Lohonyai, unpublished). Further field trapping tests were carried black paper and illuminated from above using diffuse uniform out to determine the level of attraction to particular candidate lighting from two 18 W/35 white fluorescent light bulbs shaded compounds. with a piece of red acetate. A single beetle was introduced into the middle of the olfactometer at each test period. Charcoal-filtered air was pumped into the glass chambers at a rate of 100 mL min−1, 2 MATERIALS AND METHODS then drawn through the central hole of the olfactometer at a 2.1 Four-arm olfactometry rate of 300 mL min−1 using another vacuum pump (Charles Austen A Perspex four-arm olfactometer was used to determine beetle Pumps Ltd, Byfleet, UK), and thereby pulled through each of the behavioural responses to alfalfa floral headspace (Fig. 1),20 which four side arms (75 mL min−1 arm−1), and subsequently exhausted consisted of three layers held together with plastic nuts and bolts. from the laboratory. Each beetle was given 2 min to acclimatise, ∘ Both the top and bottom discs had a diameter of 156 mm and after which the experiment was run for 16 min at 24 C, the ∘ a thickness of 5 mm, and were fitted with a filter paper base olfactometer being rotated by 90 every 4 min to control for any to provide traction for the walking insect. The middle part was directional bias. The olfactometer was divided into four regions 180 mm in diameter, 7 mm thick and was manufactured to include corresponding to each of the four arms, and the time spent in each four side areas or arms (each 55 mm long × 5 mm high) situated arm by a single beetle was recorded (N = 10/sex). at 90∘ to each other. The areas narrowed towards the perimeter and were connected to glass chambers with Teflon™ tubing, via 2.2 Electroantennography a 3 mm diameter hole at the end of each of the four arms. One Feral S. humeralis weevils were collected at Biatorbágy and Tököl, of the glass chambers contained four flower heads on a live M. (Pest County, Hungary). An antenna from a live female or male sativa (treatment) and the other three were empty and acted adult S. humeralis was excised at the base and mounted between as controls. The use of three empty control arms reduced the two glass capillaries containing 0.1 M KCl solution. A constant humidified airflow of ∼ 0.7 L min−1 was directed towards the antenna, which was placed at ∼ 3 mm from the exiting airflow from a Teflon™-coated steel tube. One of the electrodes was grounded, and the other was connected to a high-impedance DC amplifier (IDAC-232; Ockenfels Syntech GmbH, Kirchzarten, Germany). Test compounds dissolved in 10 μL hexane were administered to a 5 × 5 mm piece of filter paper inside a Pasteur pipette. Stimulus treatments consisted of pushing 1 mL of air through the Pasteur pipette into the air stream flowing towards the antenna.