Ecological and pest-management implications of sex differences in scarab landing patterns on grape vines

• Published in: PeerJ (San Francisco, CA) Vol. 5; p. e3213
• Main Authors: González-Chang, Mauricio, Boyer, Stéphane, Lefort, Marie-Caroline, Nboyine, Jerry, Wratten, Steve D
• Format: Journal Article
• Language: English
• Published: United States PeerJ, Inc 27-04-2017; PeerJ; PeerJ Inc
• Subjects: Adults; Animal Behavior; Biodiversity and Ecology; Coleoptera; Costelytra zealandica; Defoliation; Ecology; Entomology; Environmental Sciences; Flight; Flight activity; Foliage; Gender differences; Generalised linear models; Horticulture; Landing behavior; Landing behaviour; Leaves; Males; Management; Melolontha melolontha; Melolonthinae; Pest control; Phenols; Pheromones; Seasonal variations; Seasons; Sex differences; Sex ratio; Species; Statistical analysis; Vines; Vineyards; Vitis vinifera; Wineries & vineyards; Zoology; New Zealand; Generalised linear models; Vineyards; Melolonthinae; Sex-ratio; Landing behaviour; Entomology; Zoology, Melolonthinae; Ecology; Subjects Animal Behavior
• ISSN: 2167-8359; 2167-8359
• DOI: 10.7717/peerj.3213

Melolonthinae beetles, comprising different white grub species, are a globally-distributed pest group. Their larvae feed on roots of several crop and forestry species, and adults can cause severe defoliation. In New Zealand, the endemic scarab pest
(White) causes severe defoliation on different horticultural crops, including grape vines (
). Understanding flight and landing behaviours of this pest can help inform pest management decisions.
Adult beetles were counted and then removed from 96 grape vine plants from 21:30 until 23:00 h, every day from October 26 until December 2, during 2014 and 2015. Also, adults were removed from the grape vine foliage at dusk 5, 10, 15, 20 and 25 min after flight started on 2015. Statistical analyses were performed using generalised linear models with a beta-binomial distribution to analyse proportions and with a negative binomial distribution for beetle abundance.
By analysing
sex ratios during its entire flight season, it is clear that the proportion of males is higher at the beginning of the season, gradually declining towards its end. When adults were successively removed from the grape vines at 5-min intervals after flight activity begun, the mean proportion of males ranged from 6-28%. The male proportion suggests males were attracted to females that had already landed on grape vines, probably through pheromone release.
The seasonal and daily changes in adult
sex ratio throughout its flight season are presented for the first time. Although seasonal changes in sex ratio have been reported for other melolonthines, changes during their daily flight activity have not been analysed so far. Sex-ratio changes can have important consequences for the management of this pest species, and possibly for other melolonthines, as it has been previously suggested that
females land on plants that produce a silhouette against the sky. Therefore, long-term management might evaluate the effect of different plant heights and architecture on female melolonthine landing patterns, with consequences for male distribution, and subsequently overall damage within horticultural areas.