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Wireworms (Agriotes sp.) represent a significant global threat in agriculture as soil-dwelling insect pests. Previous field observations have indicated varying susceptibilities of different potato varieties to wireworm attacks. In this laboratory study, we used three potato varieties known for displaying contrasted levels of susceptibility: Monalisa (high), Spunta (moderate) and Charlotte (low). We tested two groups of hypotheses: (1) wireworms display higher feeding activities when fed on a susceptible variety, which is also linked to faster larval development; (2) the most susceptible varieties are also the most attractive for wireworms, which can be explained by differences in their emissions of volatile organic compounds (VOCs), that guide larval foraging behaviour. Based on the results of our bioassays, we confirm our first hypothesis: wireworms feeding activity was higher on Monalisa tuber (i.e. longer galleries, lower weight gain of tubers), and these wireworms gained more weight and size than those that fed on the Charlotte variety, after 50 weeks of feeding. Based on our behavioural assays, we found that wireworms exhibit greater attraction towards Spunta tubers as opposed to those of Monalisa and Charlotte. The volatile collection analyses reveal a complex blend of 63 VOCs from potato tubers but do not suggest significant differences across the three varieties. The volatile profiles were however different between the two tuber phenological stages considered here. This study provides insights into the mechanisms of host detection and selection by wireworms. [ABSTRACT FROM AUTHOR]

Numerous studies have shown that an increase of environmental temperature could directly disturb insect larval development. Natural enemies of insect pests, particularly predators of aphid populations, are not spared. Following temperature predictions of Belgian climate change scenario, the goal of this study is to measure life-history traits, such as the mass, body length and aphid consumption (Acyrthosiphon pisum (Harris, 1776)) (Hemiptera: Aphididae) of Episyrphus balteatus (De Geer, 1776) (Diptera: Syrphidae) larvae under three constant temperature treatments (i.e. 20, 23, and 26 °C). We detected no significant differences between 20 °C and 23 °C on the hoverflies larval development, their aphidophagous potential, as well as their mortality, pupation and emergence rates, while 26 °C had a deleterious effect on these parameters and the fitness of E. balteatus except for the total of consumed aphid per larva. Therefore, the high temperature could be disadvantageous for larval predation efficiency of E. balteatus. The outcomes of this study provide a new overview about ecological features of E. balteatus in the context of biological control under Belgian climate change. [ABSTRACT FROM AUTHOR]

Abstract: The performance of predators of plant pests is mainly driven by their ability to find prey. Recent studies suggest that rising atmospheric carbon dioxide (CO2) concentrations will affect the semiochemistry of plant–insect relationships, possibly altering prey‐finding behaviour. In the present study, we test the hypothesis that higher atmospheric CO2 concentrations affect the oviposition behaviour of an aphidophagous hoverfly and alter the development of its larvae. We also test the hypothesis that volatile compounds released by the plant–aphid association are modified under elevated CO2. Broad bean plants infested with pea aphids are grown under ambient (450 ppm) or elevated CO2 (800 ppm) concentrations. Plants raised under each treatment are then presented to gravid hoverfly females in a dual‐choice bioassay. In addition, emerging Episyrphus balteatus larvae are directly fed with aphids reared under ambient or elevated CO2 conditions and then measured and weighed daily until pupation. Odours emitted by the plant–aphid association are sampled. A larger number of eggs is laid on plants grown under ambient CO2 conditions. However, no significant difference is observed between the two groups of predatory larvae grown under different CO2 concentrations, indicating that the CO2 concentration does not affect the quality of their aphid diet. Although plant volatiles do not differ between the ambient and elevated CO2‐treated plants, we find that the quantity of aphid alarm pheromone is lower on the plant–aphid association raised under the elevated CO2 condition. This suggests that an alteration of semiochemical emissions by elevated CO2 concentrations impacts the oviposition behaviour of aphid predators. [ABSTRACT FROM AUTHOR]

Abstract: Most phytoviruses use insect vectors to spread and infect the surrounding crop plants. Because atmospheric gas concentrations alter the physiology and metabolism of plants, we hypothesize that the concentration of carbon dioxide (CO2) affects the spread of viruses, due to modifications in the feeding behavior of the vector. Tobacco plants, Nicotiana tabacum L. (Solanaceae), and green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), were cultivated under ambient (450 p.p.m., termed aCO2) and elevated (800 p.p.m., eCO2) concentrations of CO2. For each atmospheric condition, we first evaluated the ability of the Potato virus Y to spread in a small experimental design, from a central infected tobacco plant to two surrounding circles of healthy plants in presence of aphid vectors for 7 days. The number of aphids recovered on each plant and the infection status of the plants (i.e., healthy vs. infected) were assessed at the end of the experiment. We also evaluated the ability of aphids to transmit the virus under the two experimental atmospheres, by immediately transferring a single insect from an infected plant to a healthy one. The presence of virus in healthy plants was then determined. We found that aphid dispersal, as well as the associated spread of viruses, did not differ between the two atmospheres. On the other hand, we found that aphids grown under eCO2 were more efficient in transmitting viruses to healthy plants compared to aphids reared under aCO2 conditions. The results of this experiment indicate that: (1) the ability of an aphid vector to spread a phytovirus is not affected by the level of CO2 at short time and spatial scales, but (2) the concentration of CO2 may affect plant defenses or the feeding behavior of herbivorous insects, resulting in more efficient viral transmission from the vector to the host plant. [ABSTRACT FROM AUTHOR]

In response to a predator attack, many Aphidinae species release an alarm pheromone, which induces dispersal behavior in other individuals within the colony. The major component of this pheromone is the sesquiterpene (E)-β-farnesene (Eβf), but variations occur between aphid species. In the present work, we collected, identified, and quantified the alarm pheromone of Aphis craccivora Koch (Hemiptera: Aphididae), before quantifying the escape behavior induced in the neighboring individuals. We compared the semiochemistry and associated behavior of alarm signaling with two other aphid species: Myzus persicae (Sulzer) (Hemiptera: Aphididae) and Aphis fabae Scopoli (Hemiptera: Aphididae). Eβf was the only volatile found for each species. M. persicae produces a higher quantity of Eβf (8.39 ± 1.19 ng per individual) than A. craccivora (6.02 ± 0.82 ng per individual) and A. fabae (2.04 ± 0.33 ng per individual). Following exposure to natural doses of synthetic Eβf (50 ng and 500 ng), A. craccivora respond more strongly than the two other Aphidinae species with 78% of the individuals initiated alarm behavior for 500 ng of Eβf. [ABSTRACT FROM AUTHOR]

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In response to a predator attack, many Aphidinae species release an alarm pheromone, which induces dispersal behavior in other individuals within the colony. The major component of this pheromone is the sesquiterpene (E)-β-farnesene (Eβf), but variations occur between aphid species. In the present work, we collected, identified, and quantified the alarm pheromone of Aphis craccivora Koch (Hemiptera: Aphididae), before quantifying the escape behavior induced in the neighboring individuals. We compared the semiochemistry and associated behavior of alarm signaling with two other aphid species: Myzus persicae (Sulzer) (Hemiptera: Aphididae) and Aphis fabae Scopoli (Hemiptera: Aphididae). Eβf was the only volatile found for each species. M. persicae produces a higher quantity of Eβf (8.39 ± 1.19 ng per individual) than A. craccivora (6.02 ± 0.82 ng per individual) and A. fabae (2.04 ± 0.33 ng per individual). Following exposure to natural doses of synthetic Eβf (50 ng and 500 ng), A. craccivora respond more strongly than the two other Aphidinae species with 78% of the individuals initiated alarm behavior for 500 ng of Eβf., (© The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America.)