Non‐invasive techniques for investigating and modelling root‐feeding insects in managed and natural systems

Abstract

1 Root-feeding insects are now considered to play a greater role in ecosystem processes than previously thought, yet little is known about their specific interactions with host plants compared with above-ground insect herbivores. Methodological difficulties associated with studying these insects in the soil, together with the lack of empirical and theoretical frameworks, have conventionally hindered progress in this area. 2 This paper reviews recent empirical and theoretical developments that have been adopted for studying root-feeding insects, focusing on the non-invasive techniques of X-ray tomography and acoustic field detection and how these can be integrated with new mathematical modelling approaches. 3 X-ray tomography has been used for studying the movements of several insects within the soil and has helped to characterize the host plant location behaviour of the clover root weevil, Sitona lepidus . Acoustic detection of soil insects has been used in various managed systems, ranging from nursery containers to citrus groves. 4 Mathematical modelling plays a complementary role for investigating root-feeding insects, illustrated by a number of published models. A model is presented for the movement of S. lepidus in the soil, which suggests that these insects undergo Lévy movements, similar to those recently demonstrated for above-ground organisms. 5 The future directions and challenges for investigating root-feeding insects are discussed in the context of the wider ecosystem, incorporating both above and below-ground organisms.

A possible ctenosauriscid archosaur from the Middle Triassic Manda Beds of Tanzania

“…The specimen was scanned at the NHM using a HMX-ST CT 225 System (Metris X-Tek, Tring, UK). The instrument utilises a cone beam projection system (see Johnson et al, 2007) with a four megapixel Perkin Elmer XRD 1621 AN3 HS detector panel. The x-ray and scan parameters were as follows: tungsten target; 225 kV; 185 mA; 0.5 mm focal spot; 3142 projections with 1.0 second exposure and a voxel size of 57 mm.…”

A simple in vitro method to study interactions between soil insects, entomopathogenic fungi, and plant extracts

“…Nevertheless, attempts have been made to get insight into soil pest insects' behaviour and ecology (van Herk & Vernon, 2007;Johnson et al, 2007;Mankin et al, 2008;Schumann et al, 2013). For this purpose, wireworm activity was assessed under choice and no-choice situations with single and combined treatments of the EPF and the garlic extract.…”

Automated image-based tracking and its application in ecology

“…These include infrared ( Figure IA,B), thermal infrared [50] (Figure IC; Movie S7 in the supplementary material online). X ray microtomography [55] [86), they are currently too slow for most automated tracking applications. Ught field cameras work at higher frame rates and there are several laboratories exploring if the; can be successfully incorporated into automated tracking systems (I.D.…”

“…Some imaging methods can even pass through physical structure, revealing the position of organisms either behind the structure or embedded within it, thus removing the problem of occlusions from physical habitat altogether. The behavior of small invertebrates within soil, for example, has been successfully quantified using highresolution X-ray microtomography, which works because biological tissue attenuates X-rays less than the surrounding soil matrix [55] (Box 2). Acoustic imaging (sonar) also permits imaging through relatively complex habitats, and is especially effective in aquatic environments.…”