Alternatives to neonicotinoids to control yellowing in beet crops

In an update of its 2018 Opinion on alternatives to neonicotinoids, ANSES identified 22 solutions for controlling aphids and yellowing disease in sugar beet crops. These control measures may take over from neonicotinoid products, which have been banned since 2018 but whose use was reintroduced for beet seed treatments under a waiver in 2020. These alternative solutions, whose effectiveness is good but insufficient when they are used alone, will require an integrated control approach or even a change in cultivation practices to be sufficiently effective.

In 2020, large populations of aphid vectors of yellowing viruses invaded beet crops. This situation led to the use under a waiver of neonicotinoid products for the coating of beet seeds, in the absence of other sufficiently effective control measures for this sector. To keep producers and the sugar industry from having to deal with the consequences of this problem again, ANSES received a request from the Ministry of Agriculture to identify available effective alternatives for reducing aphid populations infesting sugar beets.

Four short-term solutions were identified: two conventional plant protection products with insecticidal properties and two practices to be implemented on cropped land to reduce aphid populations. These practices consist of mulching and organic fertilisation, with the aim of controlling nitrogen inputs. 

In addition to these solutions available for immediate use, 18 other control measures should become available within the next two to three years. The marketing authorisations for certain plant protection products used for other crops may also be extended.

Most of the alternative solutions considered as potential replacements for neonicotinoids have good but insufficient effectiveness, when used alone, to reduce levels of damage to an acceptable economic threshold. ANSES therefore recommends supporting research and development efforts to adapt the solutions identified for other crops to the case of sugar beets, and testing combinations of solutions as part of an integrated control approach, in the context of epidemiological surveillance.   

A range of complementary control measures

To identify these measures of control, the group of experts analysed more than 3,800 references from the scientific literature, noting that few of these studies investigated the control of beet aphids. The experts nonetheless identified several technical solutions, both existing and yet to be developed. “Various types of solutions were identified. The use of several combined products or methods should be considered to achieve a sufficient level of effectiveness and prevent aphids from developing resistance”, affirms Hervé Jactel, the chair of the Working Group in charge of the expert appraisal. The solutions include synthetic and natural plant protection products, micro-organisms, aphid insect predators and parasitoids (which lay their eggs inside aphids), vegetable and mineral oils, which provide beets with physical protection, methods for stimulating the plants’ natural defences, the selection of beet varieties resistant to yellowing viruses and lastly, methods combining the cultivation of beets with that of other plants, whose role is to keep aphids from accessing the beet plants or encourage the action of aphid arthropod predators or parasitoids. 

Appropriate alternatives for beets

This expert appraisal supplements the Report published by ANSES in 2018 on alternatives to neonicotinoids (PDF): “For the first expert appraisal, we had an overview of the situation, with 130 uses analysed”, explains Emmanuel Gachet, scientific coordinator of the expert appraisal and Head of the Expert Assessment of Biological Risks Unit of ANSES's Plant Health Laboratory. “Here, we have focused on the two main aphid species responsible for transmitting yellowing viruses – the green peach aphid (Myzus persicae) and the black bean aphid (Aphis fabae) – to identify rapidly available solutions for sugar beets”. This expert appraisal focused on the effectiveness, sustainability and operational feasibility of the alternative solutions. Some are still under development; moreover, some of those that are regulated have not yet been approved at European level. ANSES reiterates that prior to their use, plant protection products should be assessed in terms of their effectiveness and the associated risks to human health and the environment, including pollinators, before any marketing authorisation may be issued for the use in question. It also stresses the need to consider combining the available solutions, as part of an agro-ecological approach, in particular with a view to crop diversification.