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

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.

Increased capture efficiency of Scolytinae with modified semi-funnel trap model

Abstract Scolytinae species that, in high populations, can damage reducing wood production in forest crops. These beetles are monitored with traps baited with ethanol and increasing their efficiency can improve the integrated management of these insects. The objective was to evaluate the increase in the capture efficiency of Scolytinae with a semi-funnel trap model, in two experiments, one including wooden elements and other increasing the flight interception area and to correlate the numbers of these beetles collected with climatic factors. In the experiment 1, Eucalyptus urophylla S. T. Blake slats were directly attached to the collector flask and in another treatment, in addition to these slats, Cedrela sp. strips were inserted inside the bait holding hose. In the experiment 2, the insect interception area in the trap, originally 480 cm2, was expanded to 1,200 cm2 and compared with the model Pet–Santa Maria trap with an interception area of 550 cm2. Weekly collections were carried out between May 2018 and June 2019. The beetles collected were taken to the Wood Biodeterioration Laboratory of the Federal Rural University of Rio de Janeiro (UFRRJ) where they were sorted, identified at family level, counted and their number correlated with climatic factors. Statistical analyzes of the collected data were processed by the BioStat® 5.3 program. In the experiment 1 were collected 869 Scolytinae. The numbers of beetles collected per trap without modification, with E. urophylla slats and E. urophylla slats + Cedrela sp. strips were similar, 7.3 ± 3.8, 7.8 ± 6.2 and 7.7 ± 5.0 respectively. In the experiment 2 were collected 4,398 Scolytinae. Increasing the interception area of the beetles increased the efficiency of the semi-funnel trap, with 42.7 ± 20.5 Scolytinae collected compared to the original semi-funnel trap, 28.6 ± 12.6 and the Pet–Santa Maria, 20.4 ± 10.4, per trap. The number of Scolytinae did not correlate with climatic factors in the experiment 1 and it was correlated with temperature, relative humidity and wind speed, but not with precipitation, in the 2. The incorporation of E. urophylla slats or Cedrela sp. strips in the semi-funnel trap did not increase the number of beetles collected, but, the increase in the flight interception area and the temperature, relative humidity and wind speed were correlated with the number of beetles collected.

A New Repellent for Redbay Ambrosia Beetle (Coleoptera: Curculionidae: Scolytinae), Primary Vector of the Mycopathogen That Causes Laurel Wilt

The redbay ambrosia beetle, Xyleborus glabratus, was detected in Georgia, USA, in 2002 and has since spread to 11 additional states. This wood-boring weevil carries a symbiotic fungus, Harringtonia lauricola, that causes laurel wilt, a lethal disease of trees in the Lauraceae family. Native ambrosia beetles that breed in infected trees can acquire H. lauricola and contribute to the spread of laurel wilt. Since 2002, laurel wilt has devastated native Persea species in coastal forests and has killed an estimated 200,000 avocado trees in Florida. Since laurel wilt is difficult to manage once it has entered a susceptible agrosystem, this study evaluated piperitone as a candidate repellent to deter attacks by X. glabratus and other ambrosia beetles. Additionally, piperitone was compared to the known repellent verbenone as a potential cost-effective alternative. The repellent efficacy was determined by comparing captures in traps baited with commercial beetle lures containing α-copaene versus captures in traps baited with lures plus a repellent. In parallel 10-week field tests, the addition of piperitone reduced the captures of X. glabratus in α-copaene-baited traps by 90%; however, there was no significant reduction in the captures of native ambrosia beetles in ethanol-baited traps. In two replicate 10-week comparative tests, piperitone and verbenone both reduced X. glabratus captures by 68-90%, with longevity over the full 10 weeks. This study identifies piperitone as a new X. glabratus repellent with potential for pest management.

Piperitone (p-Menth-1-En-3-One): A New Repellent for Tea Shot Hole Borer (Coleoptera: Curculionidae) in Florida Avocado Groves

The tea shot hole borer, Euwallacea perbrevis, has been recently established in Florida, USA, where it vectors fungal pathogens that cause Fusarium dieback in avocado. Pest monitoring uses a two-component lure containing quercivorol and α-copaene. Incorporation of a repellent into IPM programs may reduce the incidence of dieback in avocado groves, particularly if combined with lures in a push-pull system. This study evaluated piperitone and α-farnesene as potential repellents for E. perbrevis, comparing their efficacy to that of verbenone. Replicate 12-week field tests were conducted in commercial avocado groves. Each test compared beetle captures in traps baited with two-component lures versus captures in traps containing lures plus repellent. To complement field trials, Super-Q collections followed by GC analyses were performed to quantify emissions from repellent dispensers field-aged for 12 weeks. Electroantennography (EAG) was also used to measure beetle olfactory response to each repellent. Results indicated that α-farnesene was ineffective; however, piperitone and verbenone were comparable in repellency, achieving 50-70% reduction in captures, with longevity of 10-12 weeks. EAG responses to piperitone and verbenone were equivalent, and significantly greater than response to α-farnesene. Since piperitone is less expensive than verbenone, this study identifies a potential new E. perbrevis repellent.

Modelling push-pull management of pest insects using repellents and attractive traps in fruit tree orchards

BACKGROUND

Push-pull with semiochemicals in pest management uses repellents to reduce response of pests to food-mate resources (push) and attractive traps to reduce populations (pull). Simulation models of push-pull can aid understanding of plant-insect interactions in nature and suggest hypotheses for field tests that improve management. A previous model indicated advantages of push-pull for controlling ambrosia beetle, Euwallacea fornicatus, pest of avocado trees. However, the simulated behavior of repellency was inconsistent with field observations.

RESULTS

We simulated individual-based movement of insects in push-pull to reveal relationships between parameters of radii (strength) of attractive traps, pest aggregations, and repellents with densities of each in an avocado orchard to visualize and understand the interactions and significance. Simulations indicated placement of traps along a 1-ha area periphery as a barrier resulted in similar trapping and mating as when traps were in a grid, either when insects originated randomly inside the plot or came from outside the plot. However, when insects originated from outside, both arrangements caught slightly more than when insects originated within the plot.

CONCLUSION

There were no differences in capture rates whether traps were spaced in a barrier along the plot's periphery or in a grid covering the plot. Push-pull was more effective than pull (mass trapping) alone. Repellent behavior of individuals when encountering a repellent radius was modelled by approximate 90° turns (right or left at random) when about to enter an infestation, consistent with earlier observations of effects of repellents on bark beetles orienting to aggregation pheromone. © 2022 Society of Chemical Industry.