Characterization of impressions created by turfgrass arthropods on clay models

Abstract

Lepidopteran pests such as fall armyworm, Spodoptera frugiperda (JE Smith), and black cutworm, Agrotis ipsilon Hufnagel (both Noctuidae), are serious problems of turfgrass (Poaceae) in the USA. Several predators in turfgrass systems attack lepidopteran larvae; however, their predaceous activity is rarely recorded, as they leave hardly any evidence. Predaceous activity can be studied using clay models, an approach still rarely employed in turfgrass. Thus, assays were conducted to determine the types of impressions that common turfgrass arthropods leave on clay models simulating lepidopteran larvae. Nine impression types were characterized after exposing 16 arthropod taxa in enclosed arenas in the laboratory and one taxon in the field to two sizes of clay models, including scratches, paired marks, pricks, deep distortions, disturbed surfaces, detached segments, granulated surfaces, dents, and elongated scratches. Most arthropods produced scratches and paired marks, whereas granulated surfaces and elongated scratches were produced by only a few of the selected arthropods. To ensure that the impressions were correctly identified, non-expert volunteers reviewed the impressions, and they were accurately identified in >85% of the responses. Video recordings of arthropod interactions were captured to determine the behavior of the arthropods during their first interaction with the clay models. Most arthropods first interacted with the terminal rather than the middle regions of the models. There were no differences between their interactions with the large or small models, and they used their mouthparts as often as their legs. Knowledge of the impression types caused by common arthropods will improve the utilization of the clay model technique for field studies in turfgrass. This could contribute to improved management of natural enemies as part of an integrated pest management approach.

Influence of the Color, Shape, and Size of the Clay Model on Arthropod Interactions in Turfgrass

“…For clay model preparation, the same procedure as described previously was adopted, but only green-colored clay was used. Previous studies showed that predators interacted with green-colored clay models ( Low et al 2014 , Sam et al 2015 , Roels et al 2018 , Khan and Joseph 2021 , Long and Frank 2020 ). Elongated cylindrical- and rectangular octagonal-shaped models were prepared for the experiment.…”

“…Clay models were recovered from the field, transported to the laboratory, and stored at room temperature (21°C) until evaluation. The clay models were evaluated, referring to the impression types characterized by Khan and Joseph (2021) using a dissecting stereomicroscope (40×). The impression types were categorized as paired marks, scratches, detached segments, pricks, dents, and U-shaped marks.…”

“…Predator–prey interactions can be studied through various techniques, such as direct observations ( Pfannenstiel and Yeargan 2002 , Cabrera et al 2019 ), video recordings ( Zou et al 2017 , Manubay and Powell 2020 ), caged experiments ( Li et al 2017 ), live sentinel prey baits ( Tillman et al 2020 ), quantitative fatty acids ( Iverson et al 2004 ), stable isotopes ( Boecklen et al 2011 , Kamenova et al 2018 ), DNA in gut content ( Eitzinger et al 2019 , Oliveira-Hofman et al 2020 ), and impressions on clay models ( Bateman et al 2017 , Rößler et al 2019 , Khan and Joseph 2021 ). Among these techniques, the use of a clay model resembling insect prey is a cost-effective and emerging tool that could be utilized to estimate predation in various ecosystems ( Howe et al 2009 , Lövei and Ferrante 2017 , Rößler et al 2018 ), including forest ( Sam et al 2015 , Molleman et al 2016 , Gunnarsson et al 2018 , Hariraveendra et al 2020 ), agricultural ( Mansion-Vaquié et al 2017 , Denan et al 2020 ), and urban ecosystems ( Long and Frank 2020 , Nason et al 2021 , Pena et al 2021 ).…”

“…After the exposure, the clay models are recovered, and impressions created on the clay models are evaluated to estimate possible predatory interactions. Distinct impressions found on the clay model provide insights into understanding predator species and their activity and behavior ( Low et al 2014 , Khan and Joseph 2021 ).…”

“…Invertebrate and vertebrate predators interact with clay models and create distinct impressions ( Bateman et al 2017 , Lövei and Ferrante 2017 , Khan and Joseph 2021 ). Arthropod predators are active in the ground, especially on the temperate forest floor ( Ferrante et al 2017 ).…”