ACTING on aphid behaviour to reduce virus yellows transmission to sugar beets. – AGIR

The project is structured around controlled-condition experiments aimed at evaluating the feeding behavior and virus transmission by Myzus persicae across different sugar beet varieties, along with field trials to assess the efficacy and feasibility of the proposed strategy combining both deterrent beet varieties and service plants.

At this stage of the project (year 2), an innovative high-throughput video-phenotyping method has made it possible to identify, among 96 sugar beet varieties, those that alter the locomotor behavior of Myzus persicae. High mobility was interpreted as a sign of resistance via an antixenosis mechanism. Four low-attractiveness (non-arrestant) varieties were selected, along with two arrestant control varieties. Subsequently, detailed analysis of feeding behavior was carried out using Electrical Penetration Graph (EPG) technology on these six varieties. The most discriminating feeding parameters were used to characterize varietal effects. In parallel with the EPG, choice tests under controlled conditions were used to compare aphid settling between pairs of the six varieties. At a later stage, service plants will be incorporated into the experimental setup to better understand how the combination of both levers (varieties and service plants) influences aphid behavior. The ability of these varieties to limit virus transmission is currently under evaluation. After virus acquisition (BYV or BChV) on infected source plants, aphids are transferred onto the test varieties, and transmission rates are assessed using ELISA assays. In addition, the mechanisms underlying resistance are being explored through the analysis of Volatile Organic Compounds (VOCs) and specialized metabolites produced by both highly arrestant and weakly arrestant varieties. A dynamic headspace sampling system will collect VOCs, and leaf discs will be harvested to analyze metabolites such as flavonoids, amino acids, and terpenes. These profiles will be compared between healthy and infected plants of each variety.

Field trials in experimental plots were initiated in the first year to assess the effects of two service plants—rough oat and Chinese radish—on M. persicae colonization. In the second year, three non-arrestant varieties and one arrestant variety were added to the setup. The effectiveness of each lever, alone and in combination, is measured based on aphid population dynamics and symptom intensity of yellows disease, from mid-April through September. ELISA tests confirm viral infections. Yield losses potentially linked to service plants or lower-performing beet varieties are accounted for in a cost/benefit/risk analysis. In the third year, these strategies will be tested at larger scale on farmers’ fields. The experimental design will compare these innovative practices with conventional protection methods to assess their potential to reduce aphicide treatments.

High-throughput video phenotyping revealed marked differences in the locomotor behavior of Myzus persicae aphids across the 96 tested sugar beet varieties. Extremes were identified, and based on several behavioral parameters—such as time spent immobile on the leaf disc, and the number of entries and exits from the disc—six contrasting varieties were selected for further study: two arrestant and four non-arrestant varieties. Complementary analyses using Electrical Penetration Graph (EPG) technology were conducted to evaluate aphid feeding behavior on these six varieties. No significant differences were detected: regardless of the variety, aphids spent approximately 40% of their time feeding from the phloem, and phases indicative of feeding difficulty were rare. These results do not corroborate those from the video phenotyping. However, choice tests supported the behavioral differences observed through video phenotyping, suggesting that this method captures broader aspects of aphid behavior than EPG, which is more focused on feeding.

Field trials were conducted to evaluate the effect of Chinese radish as a service plant on aphid populations and yellows symptoms. Weekly counts were performed on beet plants near radish rows and control beet rows. In the first year, low aphid pressure limited the ability to detect a significant effect of radish. Nevertheless, several technical limitations were identified: the radish cover was severely affected by the herbicide program and flea beetle attacks, which required an additional insecticide treatment.

The proposed combination of levers addresses a real need within the sugar beet sector to improve crop protection against Myzus persicae, the aphid vector responsible for transmitting yellows viruses. Adoption of the strategy by farmers is anticipated at the end of the project if results are satisfactory, and knowledge transfer is an integral component of the project. To align with the needs of the sugar beet industry, the current objectives of the Ecophyto II+ plan, and the upcoming Ecophyto 2030 plan, the strategy developed must aim to fully or partially replace aphicide treatments depending on the level of risk in a given year. In addition, the work on video phenotyping could potentially be adopted by seed companies to accelerate the varietal selection process by introducing a new selection criterion based on aphid feeding behavior, as a complement to classical resistance/tolerance screening. Finally, research on Volatile Organic Compounds (VOCs) and secondary metabolites could contribute to the identification of repellent compounds against M. persicae, and may pave the way for the development and future availability of new biocontrol products for farmers.

Gabin Mardoc, Yuan Gao, Silène Lartigue, Vincent Calcagno, Fabienne Maupas, et al.. Identification of Sugar Beet Cultivars Exhibiting Antixenosis Through High-Throughput Video-Phenotyping of Aphid Behavior.. 20èmes rencontres de Virologie Végétale (RVV)., Jan 2025, Aussois (FR), France. ?hal-05144362?

Audrey Fabarez. AGIR sur le comportement des pucerons pour réduire la transmission virale de la jaunisse de la betterave sucrière. Journée d'animation - Écophyto Maturation, Dec 2024, Paris, France. 2025. ?hal-05143943?

Context and objectives :
The ban of neonicotinoids as seed treatments to manage aphids transmitting sugar beet yellows viruses constitutes a major challenge for farmers and sugar beet industries. Previous studies (ex : PNRI, Modefy) have shown that sugar beet varieties and certain companion plants can influence the behaviour of Myzus persicae, considered as the main vector of yellows viruses. Some sugar beet varieties alter the feeding behaviour of the aphid, and are less favourable to its establishment. Some companion plants can also reduce aphid populations on sugar beets through mechanisms that are not yet well identified. The main objective of this project is to combine these two levers, to identify strategies that would limit both the attractiveness of beets and the acquisition of viruses by aphids. At the beginning, the project is at a TRL 4 because previous experiments on varieties, sustaining the very encouraging preliminary results, have been done under controlled conditions. The identification of promising sugar beet varieties and companion plants will be pursued under controlled conditions, and the best combinations will be tested in experimental plots (years 1 and 2), and in the field (years 3). At the end, the project will reach a minimum of TRL 6.

Method :
Sugar beet varieties selection will be carried out with high-throughput video-phenotyping, electro-penetrography, and virus transmission tests. The selection of combinations of varieties and companion plants will be carried out though aphid choice tests and trials in experimental plots. The selected combinations will then be deployed at the field-scale to evaluate their global interest. The identification of Volatile Organic Compounds (VOC) and non-volatile metabolites that have an effect on aphid behaviour will allow to explore new solutions.

End users :
The final users are sugar beet farmers, and the transfer of knowledge could be done by the French Technical Institute for Sugar beet (ITB) (articles, trial visits…). The output of this project could also be useful for other sectors.

Relevance and durability of the solution :
Four aphicide treatments are allowed in 2024 on sugar beets. Two molecules are used : one with a waiver request each year (120 days), will no longer be usable in 2025, and the second is a molecule for many crops with a high risk of emergence of resistance. The strategy tested in this project could replace some or all the aphicide treatments carried out according to the risk of each campaign. These strategies could help them to save aphicide treatments for campaigns with a low to moderate risk. In high-risk years, it could allow them to limit yield losses. The strategy falls into the category of indirect control/prophylactic methods with the main objective of reducing virus transmission by aphids, as opposed to direct control methods based on pest elimination. Thus, this strategy is part of the cultivation system transition by reconsidering sugar beet protection against aphids and yellows viruses.

Consortium :
This project is coordinated by the ITB, which provides operationnal management of the PNRI with INRAE which provides scientific management. Thanks to its expertise in sugar beet cultivation, it acts as technical support to the other partners. The project is based on the scientific expertise of the partners with complementary skills, from virus to farmer field.