BACKGROUND: Insecticides are essential, though controversial tools in modern pest management. Insecticides can slow the spread of key vector‐borne plant pathogens, but often lead to inconsistent results given that insecticide use is generally focused on acute toxicity under no‐choice conditions. Here, we analysed the lethal (survival) and sublethal (feeding behaviour) effects of six commercial products (acetamiprid, deltamethrin, spinosad, sulfoxaflor, pyrethrin and kaolin) on Philaenus spumarius, vector of the bacterium Xylella fastidiosa. Furthermore, we assessed the impact of insecticides displaying different degrees of acute toxicity against spittlebugs (highest to lowest: acetamiprid, pyrethrin and kaolin) on the transmission of X. fastidiosa by P. spumarius under both free‐choice and no‐choice conditions.RESULTS: Deltamethrin, acetamiprid and to a limited extent pyrethrin significantly altered the feeding behaviour of P. spumarius. Deltamethrin and acetamiprid were highly toxic against P. spumarius, but the mortality induced by exposure to pyrethrin was limited overall. By contrast, spinosad, sulfoxaflor and kaolin did not significantly impact P. spumarius feeding behaviour or survival. Under no‐choice conditions, both pyrethrin and acetamiprid reduced the X. fastidiosa inoculation rate compared with kaolin and the control. On the other hand, pyrethrin reduced transmission, but acetamiprid failed to significantly affect bacterial inoculation under free‐choice conditions.CONCLUSION: Pyrethrin was the only compound able to reduce X. fastidiosa transmission under both free‐choice and no‐choice conditions. Xylella fastidiosa management strategy based exclusively on the evaluation of insecticide acute toxicity under no‐choice conditions would most likely fail to prevent, or slow, bacterial spread. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Philaenus spumarius L., the main vector of Xylella fastidiosa (Wells) in Europe, is a univoltine species that overwinters in the egg stage, and its nymphs emerge in late winter or spring. Predicting the time of egg hatching is essential for determining the precise times for deploying control strategies against insect pests. Here, we monitored P. spumarius eggs from oviposition to egg hatching together with the daily temperatures and relative humidities at four field locations that were located at different altitudes in central Spain. The collected data were used to build a growing degree day (GDD) model to forecast egg hatching in the Iberian Peninsula. Furthermore, the model was validated with field observations that were conducted in Spain. The model was then used as a decision-support tool to calculate the optimum timing for applying control actions against P. spumarius. Our results suggest that controlling nymphs at two different dates would target the highest percentages of nymphal populations present in the field. Our model represents a first step for predicting the emergence of nymphs and adopting timely control actions against P. spumarius. These actions could limit disease spread in areas where X. fastidiosa is present.

Introduction: Canola (Brassica napus L.) is one of the most important crops worldwide. Turnip yellows virus (TuYV), transmitted by aphids, is one of the most damaging viruses affecting canola crops and is challenging to control. With the prediction of more intense and prolonged drought events due to future climate change, an additional factor may extensively impact the epidemiology of plant diseases. This study aimed to understand the impact of drought on canola plants infected with TuYV and to explore the relationship between virus infection and drought.Methods: Two glasshouse experiments were conducted: 1. Competition: Four plants (two infected, two non-infected) were grown in the same pot. 2. No Competition: One plant was grown per pot. In both experiments, infected and non-infected canola plants were exposed to well-watered conditions, water stress (simulated drought), and terminal drought. Various plant traits were recorded, including biomass, leaf area, height, number of leaves, chlorophyll content, water use efficiency, and virus symptom expression.Results: Both virus infection and water stress reduced dry biomass, leaf area, and height. Virus infection alone reduced canola biomass by up to 49% compared to non-infected, well-watered controls. Under water stress or terminal drought, the biomass of TuYV-infected plants was further reduced by up to 71% and 65%, respectively. Virus infection also reduced the number of leaves, although water treatment alone did not. Chlorophyll content was higher in water-stressed and terminal drought plants compared to well-watered ones, while virus infection reduced chlorophyll content. The impact of drought and virus infection was more pronounced when plants were under competition.Discussion: Given the expected increase in prolonged and frequent droughts in many canola-growing regions due to climate change, a significant detrimental effect on canola production due to the combined influence of drought and TuYV is anticipated. This study underscores the need for developing mitigation strategies to protect canola production in a changing climate.

Philaenus spumarius represents the primary vector of the bacterium Xylella fastidiosa in Europe; hence, control measures are directed toward it, with a need for alternatives aligned with the agricultural sustainability criteria. Entomopathogenic ascomycetes (EA) show promise by infecting P. spumarius via endophytic colonization, though their sublethal effects on behavior remain understudied. This study assessed the effects of Metarhizium brunneum strain EAMa 01/58-Su on P. spumarius survival and feeding behavior, using the Electrical Penetration Graph technique. We provide the first evidence of endophytic colonization of olive plants by EA, occurring in both treated and distant untreated leaves. Foliar application enabled the dual establishment of M. brunneum as both epiphytic and endophytic, significantly disrupting vector feeding. Insects fed on M. brunneum sprayed leaves showed a more total and unsuccessful probing events, longer non-probing (np) periods, and reduced xylem contact (Xc) duration. Additionally, successful xylem probing (with xylem ingestion) was significantly delayed. Interestingly, a reduction in waveform N events and their duration in M. brunneum— non-sprayed leaves was detected, suggesting a systemic effect of the fungal colonization on the plant preference by the vector that could ultimately disrupt Xf retention mechanisms. In contrast, the drench application of M. brunneum in the olive saplings did not result in endophytic colonization or significant effects on the insect behavior compared with control plants. These findings provide the basis for future experiments on Xf transmission and support the potential of M. brunneum as a biocontrol agent beyond its conventional use against vector populations on cover crops.