Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi. Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis. Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling.Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperaturespublishedVersio

Effects of limited volatiles release by plants in tritrophic interactions

We introduce a mathematical model to describe the tritrophic interaction between crop, pest and the pest natural enemy where the release of Volatile Organic Compounds (VOCs) by crop is taken into account. The VOCs may be considered as an indirect defence mechanism of the plant as they attract the pest natural enemies toward the attacked plants. The model dynamics is studied through qualitative analysis and numerical simulations. The factors that may enhance pest disappearance are identified. In particular, we show that VOCs may have a beneficial effect on the environment since their release may be able to stabilize the model dynamics. Specifically, for the parameter values that we have explored, this effect can arise only when both the phenomena of VOCs basic plant release and VOCs plant release due to pest attack are present

Effects of limited volatiles release by plants in tritrophic interactions

We introduce a mathematical model to describe the tritrophic interaction between crop, pest and the pest natural enemy where the release of Volatile Organic Compounds (VOCs) by crop is taken into account. The VOCs may be considered as an indirect defence mechanism of the plant as they attract the pest natural enemies toward the attacked plants. The model dynamics is studied through qualitative analysis and numerical simulations. The factors that may enhance pest disappearance are identified. In particular, we show that VOCs may have a beneficial effect on the environment since their release may be able to stabilize the model dynamics. Specifically, for the parameter values that we have explored, this effect can arise only when both the phenomena of VOCs basic plant release and VOCs plant release due to pest attack are present

Effect of three isolates of Pandora neoaphidis from a single population of Sitobion avenae on mortality, speed of kill and fecundity of S. avenae and Rhopalosiphum padi at different temperatures

We studied the effect of three Pandora neoaphidis isolates from one Sitobion avenae population, three temperatures, and two aphid species namely S. avenae and Rhopalosiphum padi on (i) aphid mortality, (ii) time needed to kill aphids, and (iii) aphid average daily and lifetime fecundity. A total of 38% of S. avenae and 7% of R. padi died and supported fungus sporulation. S. avenae was killed 30% faster than R. padi. Average daily fecundity was negatively affected only in S. avenae inoculated with, but not killed by, P. neoaphidis. Nevertheless, lifetime fecundity of both aphid species inoculated and sporulating with P. neoaphidis was halved compared to lifetime fecundity of surviving aphids in the control. Increased temperature resulted in higher mortality rates but did not consistently affect lethal time or fecundity. Results suggest that (i) temperature effects on virulence differ between isolates, even when obtained within the same host population, and (ii) even though an isolate does not kill a host it may reduce its fecundity. Our findings are important for the understanding of P. neoaphidis epizootiology and for use in pest-natural enemy modelling

Can aphids be controlled by fungus? A mathematical model

The control of insect pests in agriculture is essential for food security. Chemical controls typically damage the environment and harm beneficial insects such as pollinators, so it is advantageous to identify targetted biological controls. Since predators are often generalists, pathogens or parasitoids are more likely to serve the purpose. Here, we model a fungal pathogen of aphids as a potential means to control of these important pests in cereal crops. Typical plant herbivore pathogen models are set up on two trophic levels, with dynamic variables the plant biomass and the uninfected and infected herbivore populations. Our model is unusual in that (i) it has to be set up on three trophic levels to take account of fungal spores in the environment, but (ii) the aphid feeding mechanism leads to the plant biomass equation becoming uncoupled from the system. The dynamical variables are therefore the uninfected and infected aphid population and the environmental fungal concentration. We carry out an analysis of the dynamics of the system. Assuming that the aphid population can survive in the absence of disease, the fungus can only persist (and control is only possible) if (i) the host grows sufficiently strongly in the absence of infection, and (ii) the pathogen transmission parameters are sufficiently large. If it does persist the fungus does not drive the aphid population to extinction, but controls it below its disease-free steady state value, either at a new coexistence steady state or through oscillations. Whether this control is sufficient for agricultural purposes will depend on the detailed parameter values for the system

Effect of strip cropping on carabid beetle and staphylinids

Strip cropping is a cropping method used in agriculture to regulate agroecosystem functions such as nutrient and water dynamics, while there is little knowledge on its impact on beneficial arthropods in northern conditions and biological pest control potential they offer.. Over a two-year period (2018 and 2019), we experimented on an organic cabbage (Brassica oleracea) – faba bean (Vicia faba) strip cropping system. The experimental setup consisted of three 270m2 plots, representing monocrops of faba bean and cabbage, and a plot of alternating strips of the two. Carabid beetles (Coleoptera: Carabidae) and staphylinids (Coleoptera: Staphylinidae) were sampled by pitfall trapping using three one-week trapping periods over each of the two growing seasons. We examined the effects of cabbage – faba bean strip cropping on carabid beetle activity density and genus richness and staphylinid activity density. Our results show that this particular strip cropping system has the potential to increase carabid beetle activity density and genus richness, but not that of the staphylinids

Can aphids be controlled by fungus? A mathematical model

The control of insect pests in agriculture is essential for food security. Chemical controls typically damage the environment and harm beneficial insects such as pollinators, so it is advantageous to identify targetted biological controls. Since predators are often generalists, pathogens or parasitoids are more likely to serve the purpose. Here, we model a fungal pathogen of aphids as a potential means to control of these important pests in cereal crops. Typical plant herbivore pathogen models are set up on two trophic levels, with dynamic variables the plant biomass and the uninfected and infected herbivore populations. Our model is unusual in that (i) it has to be set up on three trophic levels to take account of fungal spores in the environment, but (ii) the aphid feeding mechanism leads to the plant biomass equation becoming uncoupled from the system. The dynamical variables are therefore the uninfected and infected aphid population and the environmental fungal concentration. We carry out an analysis of the dynamics of the system. Assuming that the aphid population can survive in the absence of disease, the fungus can only persist (and control is only possible) if (i) the host grows sufficiently strongly in the absence of infection, and (ii) the pathogen transmission parameters are sufficiently large. If it does persist the fungus does not drive the aphid population to extinction, but controls it below its disease-free steady state value, either at a new coexistence steady state or through oscillations. Whether this control is sufficient for agricultural purposes will depend on the detailed parameter values for the system

Flower reservoirs in stone fruit orchards: creating self- regulating systems with a low input strategy

Promotion of biodiversity has great potential to contribute to organic fruit growing by increasing and facilitating natural pest control. Flower strips are a known management strategy used in orchards and vegetable production and used to provide habitat for beneficial insects increasing biocontrol of pests and pollination of crop plants. However, in organic stone fruit production perennial flowers strips are not as widely implemented because of the logistical challenges (for example additional machinery) and high efforts needed for maintenance of flowers strips. Pest population build up in orchards is facilitated by enclosures and therefore there is a need to promote biocontrol agent’s diversity and abundance in orchards as well as pollination. In this project, we will exploit our large experience in Agroecology, to promote biodiversity and natural pest control in organic orchards with a low input strategy. The overall goal of this research project is to test whether flower reservoirs implemented in areas adjacent to the tree rows and in anchoring areas where tractors do not transit can provide similar benefits as those provided by flower strips in the orchard alley, while reducing the logistical challenges and maintenance efforts needed from farmers, and therefore, increasing its acceptance and implementation