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Abstract

Global potato production is limited by the adverse effects of virus disease. Of particular significance are the aphid borne viruses; Potato Leaf Roll Virus (PLRV) and Potato Virus Y (PVY). PLRV is a circulative or persistent virus, requiring its aphid vector to feed for a prolonged period to acquire and transmit the virus. As a result, its vectors are limited to potato-colonising species such as the peach-potato aphid (Myzus persicae) and the potato aphid (Macrosiphum euphorbiae). Contrastingly, PVY is a stylet borne or non-persistent virus and can be acquired and transmitted in seconds by aphids making exploratory probes on plants they land on. It can, therefore, be vectored by both colonising and non-colonising aphids and 65 aphid species are currently known to be capable of PVY transmission. Significant yield loss in the season of infection is rare for both viruses, but in crops grown from infected seed tubers yield reductions of up to 50% have been recorded (Valkonen, 2007). Consequently, the potato industry is dependent on the production of healthy, certified seed potatoes with low (<6%) to zero viral infection levels (The Seed Potatoes (England) Regulations, 2015). Production of virus-free seed potatoes to the standard required is challenging, particularly for non-persistent viruses that can be transmitted before insecticides can act, but insecticide resistance and the withdrawal of key active ingredients in recent years has further added to the difficulty. Novel virus vector management solutions are urgently needed for growers to ensure the availability of high-grade seed potatoes. ‘Stimulo-deterrent diversion’ or ‘push-pull’ is a pest management strategy that utilises a variety of behaviour modifying cues, both visual and olfactory, to divert pest species away from their target (‘push’) and towards a trap area where they can be more easily controlled (‘pull’), and has proved effective in the control of medical, veterinary and crop pests. Push strategies include the use of intercropping and the application of essential oils that actively deter pests or mask crop plant olfactory cues, and the application of mulches to obscure visual cues. This approach has been successfully used to control a range of Lepidopteran, Coleopteran and Thysanopteran pests (Balaso et al., 2019). Several potential components for a push-pull strategy to control aphid vectors of potato viruses have been identified, including repellent companion plants and essential oils, attractive trap plants, visually attractive crop borders and visually repellent mulches. Push-pull promises to be particularly effective for the suppression of non-persistent viruses, which are rapidly lost when aphid vectors make exploratory probes after landing on trap crop plants. This ensures that aphids are virus free, even if they should progress to the crop itself. Overall Aim: To develop a push-pull strategy for the effective management of aphid pests in seed and ware crop potatoes. The central hypothesis is that aphid vector behaviour can be successfully manipulated and modified to produce an effective means to reduce levels of potato virus transmission to commercially acceptable levels.

Description

Objective 1: Determine positive & negative behavioural responses (e.g., landing behaviour and accuracy) of each aphid species to visual cues (colour, plot size and geometry).

Objective 2: Determine positive & negative behavioural responses (e.g., landing behaviour) of each aphid species to one or more plant essential oils and/or companion crops and to commonly applied plant protection products.

Objective 3: Investigate aphid landing behaviour within prototype push-pull systems in glasshouse, small plot and commercial conditions.

Objective 4: Optimise push-pull systems e.g., modifying plant mixes within trap crop, spatial arrangement of trap crop plants, use of novel formulations of plant essential oils (nano-formulations and microencapsulation technologies) as repellents. Objective 5: Field evaluation of optimised push-pull system in commercial crops over multiple seasons.