Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies

Appendix D. A table showing longevity, fecundity, and intrinsic rate of increase of Aphis glycines reared on soybean produced under three different agricultural management systems in the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, during 2003.

A table showing longevity, fecundity, and intrinsic rate of increase of Aphis glycines reared on soybean produced under three different agricultural management systems in the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, during 2003

Appendix C. A table showing large- and small-size predators and parasitoids for different combinations of agricultural management system and predator manipulation treatments within the large field cages in the aphid population increase experiment at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, 2003.

A table showing large- and small-size predators and parasitoids for different combinations of agricultural management system and predator manipulation treatments within the large field cages in the aphid population increase experiment at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, 2003

Appendix B. A table showing ANOVA results for fixed and random effects and slicing tests results of the effect of agricultural management system and predator manipulation treatments on Aphis glycines within large field cages at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, 2003.

A table showing ANOVA results for fixed and random effects and slicing tests results of the effect of agricultural management system and predator manipulation treatments on Aphis glycines within large field cages at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, 2003

Appendix E. A table showing MANOVA results for the effect of agricultural practices on the five more-abundant Aphis glycines foliar predators at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, during 2003.

A table showing MANOVA results for the effect of agricultural practices on the five more-abundant Aphis glycines foliar predators at the Kellogg Biological Station Long Term Ecological Research site, Michigan, USA, during 2003

Effects of plant age (PA) on naturally occurring populations of <i>A. glycines</i> and predators in the experimental plots.

<p>Bars present mean (+1 SE) of (A) log₁₀– transformed number of aphids/plant, from a sample of 10 random plants per plot in each date, and (B) total number or predators/25 sweeps, from four samples/plot. PA 1–3 refers to the oldest to the youngest plant age, respectively. Horizontal lines indicate the dates when the manipulative trials were conducted.</p