Abstract
Agricultural expansion at the cost of natural or semi-natural habitats is simplifying human-dominated landscapes. As croplands provide a large resource of food to herbivores, pest damage may increase, but such large-scale patterns across regions are little known. Here, we used two years of maize field data from 102 counties (each 1318 km2 on average) across Shandong Province in China to study the spatial distribution of two major co-occurring maize pests: the putative habitat specialist the Asian Corn Borer (Ostrinia furnacalis) (ACB) and the generalist Yellow Peach Moth (Conogethes punctiferalis) (YPM). We used Spatial Analysis by Distance Indices (SADIE) to assess the spatial distribution patterns of these pests and their relation to landscape factors. In both 2016 and 2017, the aggregation and abundance of the ACB was positively correlated with the proportion of maize on the county level, whereas the YPM exhibited the opposite pattern, i.e., a negative correlation with maize proportion. The ACB abundance was below the economic threshold level when maize was <31% in 2017, whereas the YPM abundance was below the threshold when maize was >27% (in 2016) or 23% (in 2017). Maize plant presence was the main determinant of the abundance of the ACB, while the YPM appeared to benefit from further resources in non-crop habitats. These contrasting distribution patterns suggest that the two pests are driven by their different resource requirements. In more diversified landscapes, pest control may need to focus primarily on the generalist consumer, the YPM, whereas in maize-dominated landscapes, the specialist consumer, the ACB, is dominant and needs attention.
Highlights
Agricultural expansion at the cost of natural or semi-natural habitats is simplifying human-dominated landscapes
While most studies on spatial distribution have only been carried out at the farm scale, studies conducted at the landscape scale or even more, the regional scale across a large area are critical for our understanding of the large-scale effects of habitat change on pest populations
There is a marked absence of empirical work examining the effects of landscape change on the spatial distribution of specialist and generalist herbivores across regions
Summary
Agricultural expansion at the cost of natural or semi-natural habitats is simplifying human-dominated landscapes. Maize plant presence was the main determinant of the abundance of the ACB, while the YPM appeared to benefit from further resources in non-crop habitats These contrasting distribution patterns suggest that the two pests are driven by their different resource requirements. Empirical studies show that the www.nature.com/scientificreports effects of increasing cultivated or host crop areas on pest abundance are either positive or negative, with no clear trend (reviewed by Veres et al.[13]). These contrasting results may be related to the differences between ecological specialists and generalists, which may respond to host patch configuration differently. There is a marked absence of empirical work examining the effects of landscape change on the spatial distribution of specialist and generalist herbivores across regions
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