Sex Pheromone of the Invasive Mealybug Citrus Pest, Delottococcus aberiae (Hemiptera: Pseudococcidae). A New Monoterpenoid with a Necrodane Skeleton

Abstract

Native to sub-Saharan Africa, Delottococcus aberiae De Lotto (Hemiptera: Pseudoccidae) is an invasive mealybug that has been recently reported in Europe seriously damaging citrus production in eastern Spain. In this study, we isolated and determined the structure of the sex pheromone of D. aberiae, to provide a highly specific and effective lure for detecting, monitoring and potentially controlling this pest. The volatile profile of D. aberiae virgin and mated females was studied by aeration and collection of effluvia in Porapak-Q. The resulting extracts were analyzed by gas chromatography coupled to mass spectrometry (GC-MS), revealing a candidate compound specific of virgin females. GC-MS and nuclear magnetic resonance spectroscopy data evidenced a new compound, (4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)methyl acetate, with an unusual β-necrodol skeleton. This compound was synthesized and shown to be attractive to male D. aberiae in both laboratory and field experiments. A GC analysis using an enantioselective stationary phase and polarimetry analyses of the synthetic enantiomers showed the natural compound emitted by virgin females to be the (-)-enantiomer.

Latest Developments in Insect Sex Pheromone Research and Its Application in Agricultural Pest Management

“…Sex pheromones comprise sex attractant pheromones, which induce upwind oriented movements to the conspecific individual, and courtship pheromones, which elicit a variety of close-range responses in the insect partner [ 12 , 13 ]. Since the first pheromone discovery, the rapid progress of methodologies developed to identify new pheromones, mainly GC, GC-MS, NMR, electrophysiological techniques [electroantennography (EAG), gas chromatography coupled to electroantennography (GC-EAD), single sensillum recordings (SSR), and coupled GC-SSR], have allowed the identification of thousands of compounds as insect sex pheromones [ 14 ] ( Table 2 contains new sex pheromones and sex pheromone components recently identified from insect pests in the period 2010–2020 and the corresponding references [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]). In addition, an interdisciplinary approach involving advances in analytical chemistry, neurophysiology, genetics, and molecular biology have improved our understanding of insect chemical communication and behavior to the level of discrete neural circuits [ 8 ].…”

Scientific and technological developments in mating disruption of scale insects

“…Unnatural stereoisomers in general have no biological activity or are slightly active (Einhorn et al 1990;Zhang et al 2004;Millar et al 2012;Tabata et al 2017a; and their presence in the mixture does not negatively affect the biological activity of the pheromone. Thus, in many cases it is not necessary to remove the opposite enantiomer generated during pheromone synthesis to be employed in pest management programs and racemates are perfectly active (Hinkens et al 2001;Zada et al 2003;El-Sayed et al 2010;Vacas et al 2019), which is economically favourable for their implementation. Possible inhibitory effects were reported in a rather few cases: the (S)isomer of solanone might be responsible for the weak activity of the racemic solanone in the field for Aulacaspis murrayae Takahashi (Ho et al 2014).…”

“…The classical methods employed since the 1970s for the isolation and identification of sex pheromones consist mainly of volatile collection and chromatographic techniques. For this purpose, an abundant supply of insects is needed because virgin females of scale species release smaller amounts of pheromone, i.e., 0.2-10 ng/day (Levi- Zada et al 2014;Tabata & Ichiki 2015;Vacas et al 2019) and 75 ng/day as the maximum reported (Tabata et al 2012), than female moths, which release 0.3-25 ng/h (Lacey & Sanders 1992;Anfora et al 2005). This implies that tens of thousands (Zada et al 2003) and even hundreds of millions (Roelofs et al 1977) of female-day equivalents (quantity of pheromone collected from one female each day) have to be sampled to obtain enough crude quantity that allows isolation of the target compound and the employment of spectroscopic techniques for its identification.…”

Absolute Configuration of the Spherical Mealybug Nipaecoccus viridis Sex Pheromone, γ-Necrodyl Isobutyrate: Chemoenzymatic Synthesis and Bioassays

“…In 2019, (2,2,3,4-tetramethylcyclopent-3-ene-1-yl)­methanol (γ-necrodol) and γ-necrodyl isobutyrate were found to be released by females of the spherical mealybug N. viridis, while (4,5,5-trimethyl-3-methylenecyclopent-1-en-1-yl)­methyl acetate (β-necrod-1-en-1-yl methyl acetate) (Figure ), with an unusual β-necrodol skeleton, was found in Delottococcus aberiae (De Lotto) (Hemiptera: Pseudococcidae) . α-Necrodols and their acetate derivatives were also found in two other plant species: Lavandula luisieri (Rozeira) Riv.…”