Multi‐scale mosaics in top‐down pest control by ants from natural coffee forests to plantations

Abstract

While top‐down control plays an important role in shaping both natural and agricultural food webs, we lack insights into how top‐down control effects vary across spatial scales. We used a multi‐scale survey of top‐down control of coffee pests and diseases by arboreal ants to examine if colony location creates a small‐scale mosaic in top‐down control around trees and if the strength of that control varies between sites at the landscape scale. We investigated pest and disease levels on coffee shrubs at different distances from shade trees with and without a Crematogaster spp. ant colony in 59 sites along a coffee management intensity gradient in southwestern Ethiopia. Within sites, ants significantly suppressed herbivory and coffee leaf rust at distances less than 10 m from nesting trees. Top‐down control varied between sites, with stronger top‐down control of free‐feeding herbivory near ant colonies at sites with lower management intensity and stronger top‐down control of a skeletonizer at sites with higher canopy cover. We conclude that the strength of top‐down control by ants is highly heterogeneous across spatial scales, as a consequence of the biology of the predator at the small scale and herbivore density or changes in herbivore–ant interactions at the landscape scale.

Lessons from Ethiopian coffee landscapes for global conservation in a post-wild world

“…In Ethiopia, arboreal Crematogaster ants are seen as an annoyance by coffee berry pickers, but actually provide a service of supressing herbivory levels on coffee leaves (Fig. 3a : bottom 75 ).

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“…Middle: A hyperparasite (white) supresses the growth of coffee leaf rust (orange) from the rainy to the dry season 73 . Bottom: Herbivory is lower on coffee shrubs below shade trees with nests of Crematogaster ants 75 . b Globally, there are many underexplored beneficial interactions: There are many studies on birds predating on herbivores and on pollination by bees, fewer on interactions with ants and mycorrhizal fungi, and very few on more cryptic interactions for example from parasitoids, hyperparasites, bats and beneficial microbes, let alone studies on multiple interactions or three-way interactions.…”

Monitoring of Natural Enemies (Hymenoptera) on Different Lands Use: Study from Agroforestry, Community Forest, and Pioneer Land

“…Because of various advantages, insects from the order Hymenoptera have been used extensively in previous research on natural enemies (Koul & Dhaliwal, 2003;Honek et al, 2018;Tougeron et al, 2018;Triyogo et al, 2020). In both natural and agricultural cropping systems, hymenopteran insects play key roles as predators and parasitoids that feed on phytophagous insects (Wielgoss et al, 2014;Stüber et al, 2021). Hymenopteran predators and parasitoids are effective natural enemies that can attack prey and parasitized hosts at various stages, reducing the number of phytophagous in an ecosystem (Koul & Dhaliwal, 2003;Halim et al, 2018).…”