Deriving Economic Models for Pea Aphid (Hemiptera: Aphididae) as a Direct-Pest and a Virus-Vector on Commercial Lentils

Abstract

The pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), presents a dual threat to commercial pulse growers because it can inflict direct injury through feeding and indirect injury as a vector of two important viruses, Pea enation mosaic virus (PEMV) and Bean leafroll virus (BLRV). A decision support system is needed to help producers manage both of these threats in pulses. To address these gaps in lentil, Lens culinaris (Medikus) (Fabales: Fabaceae), we conducted field experiments near Moscow, Idaho in 2011 and 2012 with three objectives: 1) determine economic injury levels (EILs) for pea aphid in lentil based on the direct effects of their feeding on yield, 2) develop economic guidelines for treating aphids carrying PEMV or BLRV based on the impact on yield of virus inoculation at different times after crop emergence, and 3) provide a framework for using both of these decision tools as part of a comprehensive approach to pea aphid management in lentil. EILs were determined based on data from replicated field cage trials over 2 yr. Windows of economic vulnerability to viruses were determined based on artificial inoculation with viruses at different days after crop emergence over 2 yr. Both direct and indirect injury support tools can be parameterized with potential yields, market prices, and the costs of insecticide applications to guide treatment decisions. Together, the two tools comprise a decision support system for managing pea aphid acting as both a direct pest and as a vector of the viruses in lentils in the Palouse region of northern Idaho and southeastern Washington State.

Plant-mediated interactions between a vector and a non-vector herbivore promote the spread of a plant virus

“…This was revealed by higher parameter values associated with the direct pathway from S. lineatus to PEMV than the indirect pathways (figure 1). Greater susceptibility to infection in younger leaves is reported in plant pathosystems [18][19][20][21], a phenomenon that has also been reported in peas and is associated with PEMV management [41]. Herbivory by S. lineatus can also suppress anti-pathogen defences in this system [9], which may also provide additional context for the strong direct effects observed in the structural equation models.…”

Tri‐trophic interactions mediate the spread of a vector‐borne plant pathogen

“…In landscapes that produce legumes, such as the Palouse region (eastern Washington and northern Idaho), outbreaks of PEMV are economically devastating (Paudel et al. ). In the Palouse, pea aphids co‐occur with S. lineatus and H. convergens on P. sativum plants (see Appendix for more details).…”

“…PEMV infection occurs when a pair of mutualistic RNA viruses (an Enamovirus and Umbravirus) are transmitted during aphid feeding, with host infection occurring within hours (Chisholm et al 2018). In landscapes that produce legumes, such as the Palouse region (eastern Washington and northern Idaho), outbreaks of PEMV are economically devastating (Paudel et al 2018). In the Palouse, pea aphids co-occur with S. lineatus and H. convergens on P. sativum plants (see Appendix S1 for more details).…”

Population Dynamics and Yield Loss Assessment for Pea Aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), on Lentil in Morocco

“…Crop loss may depend upon species characteristics, landscape context, and patch size [7]. Pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), was first observed in Europe, from where it spread worldwide under temperate climate and now has a cosmopolitan distribution [8]. The pea aphid is an oligophagous herbivore that causes direct damage to plants by sucking sap from the tender leaves, stems and pods.…”