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Asymptomatic Host Plant Infection by the Widespread Pathogen Botrytis cinerea Alters the Life Histories, Behaviors, and Interactions of an Aphid and Its Natural Enemies

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People and Wildlife Research Group, School of Biological Sciences, University of Reading, Whiteknights, Reading, Berkshire RG6 6AJ, UK
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Fakulti Biosumber dan Industri Makanan, Universiti Sultan Zainal Abidin, Besut Terengganu 22200, Malaysia
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School of Biological Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK
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School of Agriculture, Policy and Development, University of Reading, Whiteknights, Reading, Berkshire RG6 6AR, UK
*
Author to whom correspondence should be addressed.
Insects 2018, 9(3), 80; https://doi.org/10.3390/insects9030080
Received: 9 May 2018 / Revised: 23 June 2018 / Accepted: 3 July 2018 / Published: 6 July 2018
Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and structure of insect communities. Changes in host plants may have direct effects on the life-histories of their insect herbivores, which can then influence their value as prey to their natural enemies. While there have been many studies that have explored the effects of infection when plants show symptoms of disease, little is understood about how unexpressed infection may affect interactions at higher trophic levels. We examined how systemic, asymptomatic, and seed-borne infection by the ubiquitous plant pathogen Botrytis cinerea, infecting two varieties of the lettuce Lactuca sativa, affected aphids (the green peach aphid, Myzus persicae) and two widely used biocontrol agents (the parasitoid Aphidius colemani and the ladybird predator Adalia bipunctata). Lettuce varieties differed in host plant quality. Asymptomatic infection reduced chlorophyll content and dry weight of host plants, irrespective of plant variety. Aphids reared on asymptomatic plants were smaller, had reduced off-plant survival time and were less fecund than aphids reared on uninfected plants. Parasitoids showed reduced attack rates on asymptomatically infected plants, and wasps emerging from hosts reared on such plants were smaller and showed reduced starvation resistance. When given a choice in an olfactometer, aphids preferentially chose uninfected plants of one variety (Tom Thumb) but showed no preference with the second (Little Gem) variety. Parasitoids preferentially chose aphids on uninfected plants, irrespective of host plant variety, but ladybirds did not show any such preference. These results suggest that the reduced quality of plants asymptomatically infected by Botrytis cinerea negatively affects the life history of aphids and their parasitoids, and alters the behaviors of aphids and parasitoids, but not of ladybirds. Fungal pathogens are ubiquitous in nature, and this work shows that even when host plants are yet to show symptoms, pathogens can affect interactions between insect herbivores and their natural enemies. This is likely to have important implications for the success of biological control programs. View Full-Text
Keywords: aphid; parasitoid; predator; Myzus persicae; Aphidius colemani; Adalia bipunctata; Lactuca sativa; lettuce; biological control aphid; parasitoid; predator; Myzus persicae; Aphidius colemani; Adalia bipunctata; Lactuca sativa; lettuce; biological control
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Ngah, N.; Thomas, R.L.; Shaw, M.W.; Fellowes, M.D.E. Asymptomatic Host Plant Infection by the Widespread Pathogen Botrytis cinerea Alters the Life Histories, Behaviors, and Interactions of an Aphid and Its Natural Enemies. Insects 2018, 9, 80.

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