Spatial and numerical relationships of arthropod communities associated with key pests of maize

Abstract

Pest management largely focuses on managing individual pest species with little concern for the diverse communities that co-occur with key pests and potentially shape their population dynamics. During anthesis, we described the foliar arthropod communities on 53 maize farms throughout the region of eastern South Dakota. The resulting communities were examined for trends in local associations in the abundances of taxa with key pests in the system (rootworms [Diabrotica spp.], European corn borers [Ostrinia nubilalis], aphids and Western bean cutworm [Striacosta albicosta]) using regression analyses. Regional spatial clustering in the abundances of key pests with members of the community was explored using Moran's I test statistic. The distributions of rootworms and European corn borer were mapped. A total of 37 185 arthropods representing at least 91 taxa were collected in South Dakota maize; there was an average of 5.06 predators and 8.29 herbivores found per plant. Key pests were never found at economically threatening levels (with one exception for Diabrotica). Numerous species were consistently numerically associated with each of the key pests across the farms during anthesis. Occasionally, these pests shared species with which they were locally associated with; for example, coccinellid egg abundances were predictive of the abundances of all key pest species except rootworm adults. Spatial analysis across the region suggested that species co-occurred with key pests based on local characteristics surrounding the fields, rather than as a result of regional characteristics. Exceptions were documented; namely aphids and Western bean cutworms that spatially clustered with a handful of other members of the community. The results of the study point out that the abundances of key pests of maize were interconnected through indirect associations in the abundances of other members of the community. These associations may be useful for manipulating maize agroecosystems to minimize the effects of maize pests.

Effects of clothianidin‐treated seed on the arthropod community in a mid‐Atlantic no‐till corn agroecosystem

“…As discussed previously, the lack of available prey or hosts during the first 4 weeks of corn growth probably delayed colonization and subsequent population buildup of many predators and parasitoids. When correlating arthropod abundance with predominant herbivores on corn plants at anthesis, aphid populations corresponded with numerical responses to multiple predators including coccinellids, anthocorids, spiders, syrphids, and carabids . Likewise, thrips, aphids and cicadellids were the most prevalent herbivores in our study, and the foliar and aerial sampling data showed reductions in thrips that coincided with reductions in anthocorids.…”

“…When correlating arthropod abundance with predominant herbivores on corn plants at anthesis, aphid populations corresponded with numerical responses to multiple predators including coccinellids, anthocorids, spiders, syrphids, and carabids. 54 Likewise, thrips, aphids and cicadellids were the most prevalent herbivores in our study, and the foliar and aerial sampling data showed reductions in thrips that coincided with reductions in anthocorids. In some cases, exposure to neonicotinoids can also influence natural enemies' ability to find hosts.…”

“…At anthesis, abundances of arthropods were not significantly different from those observed in the control community. Arthropod communities also tend to be the most abundant and diverse at this stage in corn phenology . The decline in non‐target effects over time was likely linked to the decreasing titer of clothianidin in the plants.…”

“…Arthropod communities also tend to be the most abundant and diverse at this stage in corn phenology. 53,54 The decline in non-target effects over time was likely linked to the decreasing titer of clothianidin in the plants. Recent work determined that clothianidin concentrations in plant tissue (root and seedling) decline rapidly in the first 20 days after planting, with less than 1.5% of the applied clothianidin being taken up by the plant.…”

Assessment of unanticipated unintended effects of genetically modified plants on non‐target organisms: a controversy worthy of pursuit?

“…Moreover, data should be gathered in a targeted manner focusing on testable risk hypotheses formulated during the problem formulation phase of ERA (Raybould 2006). To optimize the usefulness of field trials, EFSA recommends to target those taxa which are considered the most informative to ERA and which are expected to be sufficiently abundant to support sound statistical analyses (Duan et al 2006;Rauschen et al 2010;Comas et al 2013Comas et al , 2015Romeis et al 2014;Lundgren et al 2015), and to perform field trials with sufficient plot size and replication (Candolfi et al 2000;Perry et al 2009;Semenov et al 2013;van der Voet and Goedhart 2015).…”