Dealing with insect pests is one of the biggest challenges facing the cultivation of oilseed rape (Brassica napus, OSR). Insect pests are usually controlled using insecticides, but the increasing occurrence of insecticide‐resistant populations and the socio‐economic context argue against the sole use of these substances. Plant resistance is a classical and proven alternative crop protection strategy that is the basic tool of integrated pest management. However, no insect‐resistant OSR cultivar is currently available on the market. Here, I review some of the constraints that make phenotyping for insect resistance particularly challenging with OSR and give perspectives to develop this resistance. Some studies have proved that breeding OSR for insect resistance could be achieved, and three strategies have been considered: introducing resistance transgenes into the OSR genome, exploiting natural variation in resistance already present in B. napus and introgressing resistance from other brassicaceous species. The white mustard, Sinapis alba, seems a particularly promising source of resistance against most of the OSR insect pests.

Root-feeding insect herbivores are of substantial evolutionary, ecological and economical importance. Plants defend themselves against insect herbivores through a variety of tolerance and resistance strategies. To date, few studies have systematically assessed the prevalence and importance of these strategies for root–herbivore interactions across different plant species. Here, we characterize the defense strategies used by three different grassland species to cope with a generalist root herbivore, the larvae of the European cockchafer Melolontha melolontha. Our results reveal that the different plant species rely on distinct sets of defense strategies. The spotted knapweed (Centaurea stoebe) resists attack by dissuading the larvae through the release of repellent chemicals. White clover (Trifolium repens) does not repel the herbivore, but reduces feeding, most likely through structural defenses and low nutritional quality. Finally, the common dandelion (Taraxacum officinale) allows M. melolontha to feed abundantly but compensates for tissue loss through induced regrowth. Thus, three co-occurring plant species have evolved different solutions to defend themselves against attack by a generalist root herbivore. The different root defense strategies may reflect distinct defense syndromes.

BACKGROUND: Development of accurate pest monitoring systems is essential for the establishment of integrated pest management strategies. Information about the pest behavior during the colonization process, as well as the sex and reproductive status of the colonizing population often are lacking and hinder their development. The cabbage stem flea beetle (CSFB, Psylliodes chrysocephala) can cause the complete destruction of oilseed rape crops (OSR, Brassica napus). In the present study, the colonization process of OSR fields by the CSFB was studied.RESULTS: More individuals were caught on the outward facing side of the traps than the side of the trap facing towards the crop at the field border and catches were higher on the trapping units at the center of the field than at its border, suggesting that more beetles were entering than leaving the crop. Catches were higher on lower traps placed near to the crop than on those positioned further from the ground and also were higher during the day than late afternoon and night. The sex‐ratio of individuals caught was skewed towards males and sexual maturity was acquired for females during the experiment. Integration of sampling data with local meteorological data showed that the catches correlated mostly with air temperature and relative humidity.CONCLUSION: This study provides new information about the dispersion of the CSFB in OSR fields during the colonization process, and highlights correlations between local meteorological factors and activity of the CSFB, and represent a new step towards implementing monitoring strategies against this pest. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

For many phytophagous insects, oviposition plays a key role in the selection of an appropriate host. A more comprehensive understanding of the factors influencing this behaviour in pest insects provides a basis for the development of new management strategies. Herein, the determinants of oviposition were assessed in the cabbage stem flea beetle, Psylliodes chrysocephala (Coleoptera: Chrysomelidae), an insect specialized on the Brassicaceae family and a major pest of oilseed rape crops in Europe. To this end, a controlled condition experiment was conducted, in which a range of host plants exhibiting varying degrees of acceptability for feeding were presented to mature females. A superior host, Brassica rapa pekinensis, an intermediate one, Brassica napus, and a non‐host plant, Iberis amara, were used. An additional treatment involved wrapping the plants in micro‐perforated plastic bags to prevent feeding on aerial parts. The results demonstrated that contact with the host plant, and more particularly feeding, stimulated oviposition, with this effect being more pronounced in B. napus. Indeed, for the same amount of feeding, females laid significantly more eggs when feeding on B. napus than when feeding on B. rapa pekinensis. Additionally, a sequential experiment demonstrated that the intensity of oviposition is subject to rapid adaptive changes, as it is exclusively dependent on the current dietary conditions, with no influence of past dietary regimens. The quantification of macronutrients indicated the potential influence of plant‐digestible carbohydrates on these outcomes. Further investigation is required to determine the impact of the plant nutritional quality and defences on oviposition.