Biocontrol in insecticide sprayed crops does not benefit from semi‐natural habitats and recovers slowly after spraying

Abstract

To enhance biological pest control in crop fields, it is recommended to increase semi‐natural area on farm and decrease insecticide spraying. While the benefits of semi‐natural area for biocontrol in unsprayed fields are often demonstrated, it remains largely unknown if there are any benefits in real‐world, commonly sprayed crops. Here, we explored the combined effects of semi‐natural field margins and insecticide spraying on pest (cotton bollworm) egg predation in 53 Australian cotton fields and semi‐natural field margins across 2 years. We used predation experiments close to field edges to exclude functional groups of predators depending on their spatio‐temporal activity (diurnal vs. nocturnal and ground vs. canopy dwelling) and digital cameras to record natural enemy taxa responsible for predation. Ground predation was substantially higher than canopy predation and its magnitude in unsprayed crops with semi‐natural margins was similar to that within semi‐natural areas. In contrast, semi‐natural field margins did not benefit biocontrol in sprayed crop fields and did not influence recovery rate of biocontrol after spraying. Within ground‐dwelling predators, one dominant taxon contributed the most to biocontrol at a particular time and place. However, the dominant predator–prey interactions changed between day and night and fields with and without margins, thus indicating increased importance of additional predator taxa with increasing spatio‐temporal scales. Synthesis and applications. Our results show that semi‐natural margins benefit pest control only in unsprayed fields. Spraying at different time (e.g. during night) would not reduce the negative effects of insecticides because it would affect complementary group of nocturnal natural enemies that exert equally high biocontrol as diurnal ground‐dwelling predators. We highlight the need for management recommendations to simultaneously consider pros and cons of within‐field spraying and surrounding semi‐natural habitats to maximize their benefits in high‐input conventional production systems.

Species traits elucidate crop pest response to landscape composition: a global analysis

“…However, the steady increase in insect resistance to pesticides and transgenic crops might compromise the efficacy of these crop protection strategies in the future [48]. Moreover, agrochemicals can disrupt biological control [30,49], imposing multiple negative environmental and societal externalities [1]. The identification of locally adapted sustainable farming practices (e.g.…”

“…Local management is also expected to strongly influence pest abundance potentially modifying pest response to landscape composition (e.g. pesticide application and tillage [30,31]). However, this information was seldom available across the studies included in the present analysis, and it was therefore not considered.…”

Measuring What Matters: Actionable Information for Conservation Biocontrol in Multifunctional Landscapes

“…However, how much habitat is needed at one scale to support the function of the habitat at another scale is not well-understood. Furthermore, pesticide application at the landscape level should be taken into account in such cross-scale studies, to test the extent to which chemical suppression of natural enemy densities may be interfering with potential local benefits of pest control provision from natural habitat (Gagic et al, 2019). In fact, land-use intensity (including higher insecticide use) may be an even more important driver of landscape effects than resource availability (Jonsson et al, 2012).…”

Additive and interactive effects of pollination and biological pest control on crop yield

“…The predator exclosure treatment consisted of placing tanglefoot at the base of the stem (protected by sticky tape) to exclude ground‐dwelling predators. Ground‐dwelling predators are the main predators in the system and ants are the (dominant taxa that can contribute up to 94% of predation events Gagic, Hulthen, et al, ). Thus, hereafter we refer to the treatment as “ant exclosure”.…”