Cereal Aphid Colony Turnover and Persistence in Winter Wheat

Abstract

An understanding of spatial and temporal processes in agricultural ecosystems provides a basis for rational decision-making with regards to the management and husbandry of crops, supporting the implementation of integrated farming strategies. In this study we investigated the spatial and temporal distribution of aphid pests (Sitobion avenae and Metopolophium dirhodum) within winter wheat fields. Using an intensive sampling programme we investigated distributions at both the small (single shoot) and large (field) scales. Within two fields, a grid with 82 locations was established (area 120 m by 168 m). At each location, 25 shoots were individually marked and aphid counts by observation conducted on 21 and 22 occasions as the crop matured, resulting in 43,050 and 45,100 counts being conducted in the two fields respectively. We quantified field scale spatial distributions, demonstrating that spatial pattern generally emerged, with temporal stability being both species- and field- dependent. We then measured turnover of colonies at the small (individual shoot) and large (field) scales by comparing consecutive pairs of sampling occasions. Four turnover categories were defined: Empty (no aphids recorded on either occasion); Colonised (aphids recorded on the second occasion but not the first); Extinction (aphids recorded on the first occasion but not the second); Stable (aphids recorded on both occasions). At the field scale, population stability soon established, but, at the small scale there was a consistently high proportion of unoccupied shoots with considerable colonisation and extinction and low stability. The redistribution of aphids within the crop at the local scale is a vulnerability which could be used to disrupt population development – by mediating exposure to ground-active natural enemies and by incurring a metabolic cost caused by the physiological demands to re-establish on a nearby host plant.

Dropping to escape: a review of an under‐appreciated antipredator defence

“…There is also the additional risk of simply being pursued and consumed by the original predator. Strikingly, from a population perspective, incidents of dropping can lead to important changes in the spatial organisation of prey (Minoretti & Weisser, 2000;Fievet et al, 2007;Winder et al, 2014) and it is likely that such changes may increase the susceptibility of remaining prey to future attacks (Agabiti et al, 2016).…”

“…Predators will suppress prey populations in part through the costs of induced defensive behaviours -such as dropping -alongside their direct consumptive effects (Nelson & Rosenheim, 2006). Several studies have drawn attention to a synergistic effect -mediated by dropping -of foliar-foraging and ground-based predators controlling prey (Winder, 1990;Grez, Zaviezo & Mancilla, 2011;Winder et al, 2014Winder et al, , 1994. Predator interactions could be particularly important in developing biological pest control (Crowder & Jabbour, 2014), where it may also be the case that the role of parasitoids has previously been under-appreciated (Schmidt et al, 2003).…”

Annual predictions of the peak numbers of Sitobion avenae infesting winter wheat

“…; Winder et al. ). The factors that affect population growth include abiotic conditions (Dean ; Sengonca et al.…”

“…In Europe, there are two species, Sitobion avenae (F.) and Rhopalosiphum padi (L.), which infest the ears of cereals of which the former is dominant in Central Europe. Biology and factors determining the population growth of S. avenae have been extensively studied, including detailed studies on the population dynamics of this aphid in the field (Ankersmit and Carter 1981;Simon et al 1991;Sengonca et al 1994b;Winder et al 2015). The factors that affect population growth include abiotic conditions (Dean 1974;Sengonca et al 1994a;Ma and Ma 2012;Jeffs and Leather 2014), host plant (Watt 1979;Honek and Martinkova 1999) and clonal variation in aphid populations (Huang et al 2013;Dai et al 2014).…”

When parasitoids deal with the spatial distribution of their hosts: consequences for both partners

“…In their natural environment, A. rhopalosiphi females encounter very contrasted aphid aggregation levels during their life or through generations, as detailed above. Given that aphids move and develop rapidly, A. rhopalosiphi females must be able to respond to a highly ephemeral distribution of aphids (Winder et al, 2014). Aphidius rhopalosiphi females perceive host patch density within the environment through interpatch travel time, and modify their response according to their previous acquired experience (Outreman et al, 2005;Muratori et al, 2008).…”