Relative efficiency of methods to estimate cabbage stem flea beetle (Psylliodes chrysocephala) larval infestation in oilseed rape (Brassica napus)

Abstract

BackgroundThe cabbage stem flea beetle (CSFB; Psylliodes chrysocephala) is an important pest of winter oilseed rape (OSR) crops in Europe. Damage is caused by adults feeding on young leaves and by larvae mining in the leaves and stems. The most common method to estimate the severity of CSFB larval infestation is by plant dissection, which is time consuming and labour intensive. Two alternative methods have been proposed: extraction of larvae from desiccating plants and counting the percentage of leaves with scars left by larvae on plant petioles. These methods are easy to implement and less time consuming than plant dissection but have not been properly validated.ResultsOSR plants were sampled in five different experiments and the two alternative methods tested; assessment of the total number of scars per plant as a predictor of the number of larvae was also tested. The number of larvae remaining in plants following various periods of desiccation was checked via plant dissection. We found that the desiccation method is efficient, giving reliable results after 7 days (76% of the total larvae extracted) with good accuracy in estimating the number of larvae per plant (±0.38 larvae per plant). The total number of scars also gives a reliable estimation of the number of larvae (r = 0.76, accuracy of ±1.01 larvae per plant).ConclusionOSR plant desiccation and the total number of scars per plant are reliable methods to estimate CSFB larval infestation and will facilitate monitoring of this cryptic pest stage. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Modelling the impact of cabbage stem flea beetle larval feeding on oilseed rape lodging risk

“…At Sites 1–4 larval pressure was examined via dissection of the stem and petioles, at Sites 5 and 6 larval pressure was assessed via passive desiccation 33,34 (Table 3).…”

“…32 For all sites where PGRs were applied as treatments, crops were assessed for application suitability by assessing whether crops exceeded a green area index (GAI) of 0.8 prior to stem extension. 18 2.2 Crop assessments and lodging risk calculations 2.2.1 Cabbage stem flea beetle larval pressure determination At Sites 1-4 larval pressure was examined via dissection of the stem and petioles, at Sites 5 and 6 larval pressure was assessed via passive desiccation 33,34 (Table 3).…”

Quantifying the impact of Psylliodes chrysocephala injury on the productivity of oilseed rape

“…These levels were selected to include the UK threshold of 25% leaf area damaged threshold for plants with two or fewer leaves 30 . The injury was done 25 days after sowing using a leather hole punch (3 mm diameter) to remove a controlled amount of leaf area (estimated by eye using a defined scoring system 47 ). Multiple holes were made at random, starting from the leaf/cotyledon tip and working towards the petiole, selecting either the leaf edge or an area between the edge and the midrib, until separated holes were no longer possible.…”

Integrated pest control in oilseed crops—new advances from the rapeseed research community

“…The automated detection of pests in OSR via sensors was tested and showed promise for early detection 13 ; this technology may take time to commercialize, but easier and faster methods to determine OSR pest infestation are available now which will make monitoring pest infestation easier for farmers and enable researchers to more easily determine the impact of different management methods on pest reduction. 14,15 Crop management factors such as undersowing companion plants was shown to reduce damage caused by CSFB in OSR 16 and rotation (or spatiotemporal separation of OSR fields via the proportion of OSR in the landscape) has also been shown to be important; CSFB, cabbage root fly (Delia radicum) and aphid abundance, damage or infestation decreases in crops with increasing distance from the nearest crop of OSR in the previous year. 17 Similar results were found for pollen beetle 18 and the cabbage seed weevil (CSW; Ceutorhynchus obstrictus) 18,19 importantly without negative impacts of distance on biocontrol by their specialist parasitoids.…”

“…These are in the pipeline; improved understanding of immigration behavior and the factors that drive infestation of the cabbage stem flea beetle (CSFB; Psylliodes chrysocephala ) 10,11 and pollen beetle ( Brassicogethes aeneus ) 12,13 will help to inform models to predict the timing, risk and spatial distribution of these insects, perhaps enabling targeted applications via precision agriculture. The automated detection of pests in OSR via sensors was tested and showed promise for early detection 13 ; this technology may take time to commercialize, but easier and faster methods to determine OSR pest infestation are available now which will make monitoring pest infestation easier for farmers and enable researchers to more easily determine the impact of different management methods on pest reduction 14,15 . Crop management factors such as undersowing companion plants was shown to reduce damage caused by CSFB in OSR 16 and rotation (or spatiotemporal separation of OSR fields via the proportion of OSR in the landscape) has also been shown to be important; CSFB, cabbage root fly ( Delia radicum ) and aphid abundance, damage or infestation decreases in crops with increasing distance from the nearest crop of OSR in the previous year 17 .…”