Arthropod-Plant Interactions (2015) 9, 187-195

Billy A. Krimmel and Alfred G. Wheeler Jr. (2015)
Host-plant stickiness disrupts novel ant–mealybug association
Arthropod-Plant Interactions 9 (2), 187-195
Abstract: Ants commonly engage in facultative mutualisms with honeydew-excreting homopterans such as mealybugs and other scale insects. Attendant ants obtain a high-energy carbohydrate of predictable availability, while the homopteran trophobiont gains protection from natural enemies and potential benefits of sanitation (honeydew removal), maintenance of host-plant quality, and transport. In a California, USA, arboretum, we observed large numbers of dead and dying Argentine ants (Linepithema humile) that had become entrapped on viscid flower buds and flowers of South African species of Erica as they attempted to tend a South African mealybug (Delottococcus confusus). Mealybugs on viscid ericas were found on clusters of small buds before they had become sticky (and later in other areas that minimized exposure to stickiness). As buds developed, they became viscid, enclosing mealybugs within sticky flower parts and precluding further attendance by ants. Ants, however, were able to tend mealybugs without disruption on nonsticky ericas. Counts (n = 118)of haphazardly chosen stems of sticky ericas showed that significantly more dead ants were present on mealybug-infested stems. We suggest that evolutionary histories help explain the disparate outcomes for ants and mealybugs on sticky ericas. The Argentine ant lacks an evolutionary history with sticky ericas, whereas the native South African mealybug presumably shares an evolutionary relationship with species of Erica in South Africa's Cape Floristic Region. We propose that the mealybug's behavior and waxy coating are adaptations for circumventing plant stickiness. Our observations might represent the first documentation of plant stickiness disrupting an ant–homopteran association.
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Link to article at publishers website
Database assignments for author(s): Alfred G. Wheeler

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Linepithema humile		U.S.A. (SW)