Pollen Beetle Brassicogethes Aeneus Research Articles

Factors driving the within‐plant patterns of resource exploitation in a herbivore

Abstract Selective pressures exerted on the feeding behaviour of animals have been extensively studied to understand their foraging patterns. In herbivores, specific within‐plant patterns of resource exploitation have been reported, but their determinants remain poorly understood. Here, we describe and decipher the determinants of the foraging pattern of the pollen beetle Brassicogethes aeneus, a pollinivorous insect that is a pest of oilseed rape Brassica napus. This insect feeds from flowers for almost all of its life cycle, except for a couple of weeks preceding blossoming. During this period, only flower buds are available and the insect destroys them to feed from the pollen they contain, causing serious yield losses. We found that during this critical period, pollen beetles exhibit a stereotypic intra‐inflorescence feeding pattern that depends on flower bud maturity. To explain this pattern, we first deciphered the selective pressures driving pollen beetles' feeding behaviour. Using a set of manipulative laboratory experiments, including behavioural experiments on plant tissues and artificial substrates, chemical characterization of plant tissues and performance experiments, we show that the pollen beetles' feeding behaviour does not seem to be driven by specialized metabolites or an attempt to reach an optimal nutrient balance, but rather by a process of maximization of total macronutrient intake. Next, using optimal diet choice models, we found that one aspect of the intra‐inflorescence feeding pattern, the preference for young over old flower buds, could be well‐explained through the lens of total macronutrient intake maximization per unit of time to access the resource. Our study provides new insights into small‐scale foraging patterns and highlights the need to characterize and assess the relative influence of several components of diet quality when deciphering selective pressures driving foraging patterns. Read the free Plain Language Summary for this article on the Journal blog.

Anther-Feeding-Induced RNAi in Brassicogethes aeneus Larvae

The biosafety aspect of applying double-stranded RNA (dsRNA) in crop pest management is rooted in dsRNA's mode of action, which displays nucleotide sequence-specificity to a particular region of a messenger RNA (mRNA), against which the insecticidal dsRNA is designed. This prominent and promising class of insecticides therefore has the potential to target a single pest species while conferring negligible effect on non-target organisms. Recent studies examining the effect of target-specific dsRNA in adults of the pollen beetle Brassicogethes aeneus, a major pest of oilseed rape (Brassica napus) crops in Europe, suggest the potential for developing a gene-silencing approach within integrated B. aeneus management. The present study examines the efficacy of target-specific dsRNA on target-mRNA silencing, and subsequent gene-silencing-induced mortality, in B. aeneus larvae, as this life stage represents a critical target for achieving optimal integrated B. aeneus control. Treatment applications occurred via feeding on dsRNA-treated anthers for 3 d. We observed variable gene-silencing efficacy, all target treatments having a significant or marginally significant effect after 3 d of dsRNA feeding, with greater variability at 6 d. These results further validated significant gene-silencing-induced mortality observed for one of the target treatments. Moreover, gene-silencing-induced mortality occurred at a quicker rate in B. aeneus larvae compared to what has been previously observed in B. aeneus adults. Finally, we consider refinements that must be made to B. aeneus larval bioassay setups to promote and strengthen future larval studies regarding this important crop pest species.

Widespread resistance of pollen beetles to pyrethroids in Czechia with no evidence for kdr mutation

The pollen beetle Brassicogethes aeneus (Fabricius, 1775) (Coleoptera: Nitidulidae) is one of the most important pests in oilseed rape (Brassica napus L. var. oleifera Moench) in Czechia. Wide-spread resistance development to pyrethroids in pollen beetle populations was documented in many European countries, including Czechia. The susceptibilities of 10 local pollen beetle populations originating from 10 localities in Czechia to lambda-cyhalothrin, tau-fluvalinate, thiacloprid, indoxacarb and chlorpyrifos were evaluated in 2017–2020 using glass vial bioassays. A high level of resistance to lambda-cyhalothrin was recorded in all the evaluated populations of the pollen beetle. The proportion of the populations resistant to tau-fluvalinate varied between years from 30% to 60%, and in 2018 and 2020, all the tested populations were classified as resistant. Despite the high level of resistance to pyrethroids, a kdr mutation known to cause resistance in the pollen beetle was not detected in any of the 244 tested individuals. In 2017–2020, the first local populations of the pollen beetle with decreased susceptibility to thiacloprid occurred. The LD90 of thiacloprid exceeded the field application dose in 100% and 90% of populations in 2018 and 2020, respectively. All the tested populations were susceptible to indoxacarb and chlorpyrifos. Cross-resistance between lambda-cyhalothrin and thiacloprid and between tau-fluvalinate and thiacloprid was found using data from 2017 to 2020. No cross-resistance between lambda-cyhalothrin and tau-fluvalinate was detected.

Targeting a coatomer protein complex-I gene via RNA interference results in effective lethality in the pollen beetle Brassicogethes aeneus

The pollen beetle Brassicogethes aeneus is a serious pest of oilseed rape (Brassica napus) in Europe. Management of this pest has grown difficult due to B. aeneus’s development of resistance to pyrethroid insecticides, as well as the pressure to establish control strategies that minimise the impact on nontarget organisms. RNA interference represents a nucleotide sequence-based, and thus potentially species-specific, approach to agricultural pest control. The present study examined the efficacy of targeting the coatomer gene coatomer subunit alpha (αCOP), via both microinjection and dietary exposure to exogenous complementary dsRNA, on αCOP-silencing and subsequent mortality in B. aeneus. Beetles injected with dsRNA targeting αCOP (at 0.14 µg/mg) showed 88% and 100% mortality at 6 and 10 days post-injection, respectively; where by the same time after dietary exposure, 43%–89% mortality was observed in the 3 µg dsRNA/µL treatment, though the effect was concentration-dependent. Thus, the effect was significant for both delivery routes. In working towards RNA-based management of B. aeneus, future studies should include αCOP as a target of interest.

Evaluating the effect of seven plant essential oils on pollen beetle (Brassicogethes aeneus) survival and mobility

Plant essential oils (EOs) represent an area of interest for managing agricultural pests. We examined the insecticidal efficacy of seven plant EOs on the survival and mobility of the pollen beetle Brassicogethes aeneus, a primary pest of oilseed rape (Brassica napus) in Europe. Topical dosing tests showed the EO of the inner bark of Cinnamomum verum (cinnamon) to be the most effective EO examined in our study. Subsequent bioassays, exposing B. aeneus to oilseed rape plant surfaces sprayed with various concentrations of C. verum EO, additionally suggested a concentration threshold at which this EO may significantly control B. aeneus populations. We suggest that further studies on B. aeneus examine the effect of certain pure compounds associated with the most promising EOs (individually as well as in binary combinations) in order to reveal optimal chemical composition and ratios to exploit within a B. aeneus management framework.

Prospects for improved off-crop habitat management for pollen beetle control in oilseed rape

There is an urgent need to develop sustainable and environmentally benign integrated pest management (IPM) strategies for arable crops. The enhancement and manipulation of naturally occurring populations of the natural enemies of crop pests through habitat management for ‘conservation biological control’, as well as habitat management to manipulate populations of the pests themselves, have the potential to become major components of successful IPM strategies. We review the studies that have contributed to our current understanding of how the crop margin, local landscape, and regional landscape can influence pollen beetle Brassicogethes aeneus (syn. Meligethes aeneus) (Coleoptera: Nitidulidae) abundance and damage to oilseed rape crops (Brassica napus), and the efficacy of their natural enemies. We also discuss how habitat management across these multiple scales may improve pollen beetle control, reducing the need for insecticide use and contributing towards sustainable production of this important crop which is grown on increasing areas for both food and fuel.

Semiochemical-based alternatives to synthetic toxicant insecticides for pollen beetle management

There is an urgent need to develop sustainable pest management systems to protect arable crops in order to replace the current over-reliance on synthetic insecticides. Semiochemicals are insect- or plant-derived chemicals that are used by organisms as information signals. Integrated pest management tools are currently in development that utilise semiochemicals to manipulate the behaviour of pest insects and their natural enemies to provide effective control of pests within the crop. These innovative tools usually require fewer inputs and can involve multiple elements, therefore reducing the likelihood of resistance developing compared with use of synthetic toxicants. We review here the life cycle of the pollen beetle Brassicogethes aeneus (previously known as Meligethes aeneus) which is a pest insect of oilseed rape (Brassica napus) and describe the current knowledge of any behaviour mediated by semiochemicals in this species. We discuss the behavioural processes where semiochemical-based control approaches may be appropriate and consider how these approaches could be incorporated into an integrated pest management strategy for this important arable crop.