Why Using Neonicotinoids Against Sugar Beet Aphid Pests May Not Be Necessary

Abstract

Due to the continuing problem of the infestation of sugar beet crops in the UK by aphids, more especially the peach potato aphid, Myzus persicae, a major vector of sugar beet yellow viruses, Defra has decided to allow derogation of the application of the neonicotinoid insecticide thiamethoxam as an emergency control measure during the 2022 growing season. This insecticide is one of the few remaining synthetic compounds to which the species has yet to become resistant. Here the author argues that because of the likely evolution of such resistance in the near future, and because of concerns of the use of such chemicals against non-target beneficial animals, notably bees, Defra should urgently re-fund research into the use of primary parasitic wasps (parasitoids) as natural control agents of this and other pest aphid species. Such agents are known from previous molecular-based researches to have high efficacy, both in M. persicae and the grain aphid, Sitobion avenae (≥50% parasitism in natural field populations). To reduce the probability of M. persicae evolving resistance to one of the last modern neonicotinoid insecticides left in the 'armoury' of growers, especially including those of sugar beet, alternative control approaches need to be re-considered urgently, preferably involving the cessation of such chemical treatments altogether (a practice clearly driven by commercial considerations by the pesticide manufacturing industry) due to environmental concerns. Chief amongst these is the long-term impact of pesticides on non-target arthropods within the environment, and especially pollinators like bees. Such an approach can be implemented mainly by employing natural biological control agents. In this way, adequate aphid, and hence viral control may be provided, i.e. below the economic damage threshold of around 10–15% yield loss normally considered for aphid attack (for example, in the case of sugar beet yellows in 2021 in eastern England, the estimated loss was 8%, so that the economic threshold of 9% was not met; whilst at the same time eliminating pesticide usage. This must surely be good in the long-term for both growers and consumers alike. In the author's view, the government via Defra needs to continue funding work on natural control agents of aphid pests urgently, both in terms of their efficacy as well as their more general biology and genetics. Ultimately, an insect pest can only be effectively combated if a wide knowledge base is available in relation to its fundamental biology, behaviour, genetics and ecology, whereupon the most rational, cost-effective and indeed most relevant control approaches can then be implemented.