Sequential Isolation of Essential Oils Repellent to the Red Palm Weevil Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae)

The push-pull approach using semiochemicals in pest control requires both an attractant and a repellent. Many previous studies have arbitrarily tested one or more known insect repellents or plant essential oils (EOs) hoping to find repellents of an insect pest. We used a comprehensive approach that synergistically tests in the field numerous natural volatiles from commercial EOs to identify repellents of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae), a worldwide pest of palms and date palms. Volatiles from 79 EOs in slow-release devices were divided into five groups and tested in traps with attractive pheromone compared to traps with pheromone alone. EO-treatment groups exhibiting repellency due to significant trap shutdown, were further subdivided into subgroups of four EOs each and tested further. Two groups of four EOs (cypress, desert wormwood, elemi, and Eucalyptus citriodora) and (niaouli, nutmeg, oregano, and orange sweet), or their corresponding mixtures of major volatiles, caused pheromone trap reductions of up to 92%. Further tests showed that seven of the eight EOs are similarly repellent as the corresponding subgroup. This systematic approach of successively testing sub-fractions of EOs in the field for trap shutdown should be useful to identify repellents of other insect pests of crops.

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

The spherical mealybug, Nipaecoccus viridis (Hemiptera: Pseudococcidae), is a major global pest causing feeding damage to leaves and fruits of citrus varieties, soybean, mango, pomegranate, and grapevines. Females of the mealybug release a sex pheromone that was identified recently as a mixture of γ-necrodyl isobutyrate and γ-necrodol. The identification required synthesis based on a natural source of trans-α-necrodol, of unknown chirality, obtained from essential oil of Spanish lavender, Lavandula luisieri. To determine the chirality of the sex pheromone, here, we synthesize the γ-necrodyl acetate enriched in (+)-(S)-enantiomer and separate the enantiomers using a lipase enzyme. We confirm that the natural components, both in the mealybug and in the lavender essential oil, consist of (-)-(R)-enantiomers. Bioassays conducted in the lab and field show that males are attracted to (-)-(R)-γ-necrodyl isobutyrate alone.

Semiochemicals Affecting Attraction of Ambrosia Beetle Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) to Quercivorol: Developing Push-Pull Control

Euwallacea fornicatus (Eichhoff), the polyphagous shot hole borer (PSHB), is an ambrosia beetle infesting avocado Persea americana Mill. limbs in North America and Israel. We conducted field experiments with sticky traps in avocado orchards to develop push-pull semiochemical methods of managing PSHB. Traps baited with 10-fold increasing doses (0.01 to 100× or 1.26 µg to 12.6 mg/d) of attractant quercivorol were previously shown to increasingly capture female PSHB (males flightless). We converted trap catch of this relationship to a standardized effective attraction radius (EAR) that predicts capture power of baited-traps regardless of insect flight density. Earlier, piperitone and verbenone were shown to strongly inhibit attraction of PSHB to quercivorol-traps. We tested increasing numbers of 1× piperitone dispensers at 0.75-m distance surrounding a quercivorol-trap and found PSHB catch to decline exponentially. Increasing decadic doses (0.01 to 10×) of either verbenone or piperitone released at 1× quercivorol-traps caused a sigmoidal first-order kinetic-decay in catch. Verbenone (1×) placed at increasing distances (0, 0.25, 0.5, 1, and 2 m) from a 1× quercivorol-trap became increasingly ineffective in reducing catch of PSHB. We found no evidence that ethanol released from 7.5 to 480 mg/d affected attraction of PSHB, but Scobicia chevrieri (Villa and Villa) (Coleoptera: Bostrichidae) was increasingly attracted. Due to their relatively short-range (<0.5 m) inhibition of attractive sources, piperitone, and verbenone dispensers should be placed on avocado trunks where PSHB aggregations occur before the flight season.

Diel rhythm of volatile emissions of males and females of the peach fruit fly Bactrocera zonata

Fruit flies in the genus Bactrocera are among the most destructive insect pests of fruits and vegetables throughout the world. A number of studies have identified volatiles from fruit flies, but few reports have demonstrated behavioral effects or sensitivities of fly antennae to these compounds. We applied a recently developed method of automated headspace analysis using SPME (Solid Phase Microextraction) fibers and GC-MS (gas chromatography mass spectrometry), termed SSGA, to reveal volatiles specific to each sex of B. zonata that are emitted in a diel periodicity. The volatiles released primarily at dusk were identified by GC-MS and chemical syntheses as several spiroacetals, pyrazines, and ethyl esters. Solvent extraction of male rectal glands or airborne collections from each sex, followed by GC-MS, showed that certain of the volatiles increase or decrease in quantity sex-specifically with age of the flies. Electroantennographic (EAG) analysis of dose-response indicates differences in sensitivities of male and female antenna to the various volatiles. Our study provides a comprehensive analysis of the volatile chemicals produced and released by B. zonata and their antennal responses. The possible pheromone and semiochemical roles of the various volatiles released by each sex and the difficulties of establishing behavioral functions are discussed.

Monitoring and mass-trapping methodologies using pheromones: the lesser date moth Batrachedra amydraula

The lesser date moth (LDM) Batrachedra amydraula is a significant pest of date palm fruits. Previously, detection and monitoring of the pest was inaccurate due to high costs of sampling with lifting machines. We report a practical system for detection and monitoring of LDM based on pheromone traps and relevant models. Dose-response experiments with LDM pheromone traps indicated a 1 mg lure is optimal for monitoring. Delta traps with adhesive covering their entire inner surface gave the highest captures while trap colour was unimportant. Sampling pheromone traps throughout the night indicated male flight began at 1:00-2:00 and reached a peak 2 h before sunrise. Monitoring traps exposed all year long in Israel revealed three generations with different abundance. Trapping transects in a date plantation indicated interference from a monitoring trap became minimal at distances >27 m away. Inter-trap distances closer than this may lower efficiency of monitoring and mass trapping in control programs. Our estimate of the circular effective attraction radius (EARc) of a 1 mg delta trap for LDM (3.43 m) shows this bait is among the most attractive compared with baits for other insects. We developed encounter-rate equations with the pheromone trap EARc to model the interplay between population levels, trap density and captures that are useful for detection of invasive LDM and its control by mass trapping. The integrated methodologies are applicable to many pest species.

Analyzing diurnal and age-related pheromone emission of the olive fruit fly, Bactrocera oleae by sequential SPME-GCMS analysis

The olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), uses 1,7-dioxaspiro[5.5]undecane ("olean"), produced primarily by females, as a sex pheromone. We used sequential solid phase microextraction-gas chromatography mass spectrometry (SPME-GCMS) analysis to show that female olive flies release about 1000 ng of pheromone at the onset of scotophase for several weeks, while males release about 1/100 as much during the first week after eclosion. The present research demonstrates details of employing SPME-GCMS with the partially known pheromone system of the olive fruit fly as a model for pheromone identification and diurnal release patterns in insects, especially fruit flies. The sequential SPME-GCMS method will readily allow detection and semi-quantification of semiochemicals released by insects in minute amounts throughout the diurnal cycle.

Inhibition of LTB4 binding to human neutrophils by nordihydroguaiaretic acid

Nordihydroguaiaretic acid (NDGA) was investigated for its ability to interact with leukotriene B4 receptors on human polymorphonuclear leukocytes (hPMNs). 3H-LTB4 binding to specific receptors was reduced in a dose-dependent manner with maximal reduction at 100 microM NDGA and an IC50 of about 50 microM. Binding of another inflammatory stimulus. N-formyl-norleucyl-leucyl-phenylalanine (FNLP) was not affected by similar treatment. Chemotaxis and enzyme release stimulated by LTB4 and oligopeptide were inhibited by NDGA. In addition, LTB4-triggered inflammation in vivo in mice was inhibited by systemic administration of NDGA. These data suggest that LTB4 receptor antagonism may contribute to inhibition of inflammation by NDGA.