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

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.

Molecular characterization of a first begomovirus associated with lentil (Lens culinaris) from India

A disease of lentil with symptoms of distortion, mottling and chlorosis in the leaves, shortening of internodes and excessive branching was noticed in lentil at Kanpur, India, during 2012-2014. Results of polymerase chain reaction and reverse transcriptase polymerase chain reaction employed to detect suspected RNA and DNA viruses indicated involvement of a geminivirus, which was further characterized by sequencing of full genome amplified by rolling circle amplification. Analysis of full length DNA-A revealed 96.4-96.7% nucleotide similarity with bitter gourd yellow vein virus (BGYVV) isolates and tomato leaf curl New Delhi virus (ToLCNDV) isolate. As per the recent revision of begomovirus species demarcation criteria, if a new virus isolate shares ≥91% nt sequence identity with any other isolate of an existing species, it should be treated as an isolate of that species, even if it is <91% identical to all other isolates from that species. This made BGYVV an isolate of ToLCNDV and resulted in the de-recognizing of the BGGYV. Hence, the present virus has been named as a strain of ToLCNDV and designated as Tomato leaf curl New Delhi virus-Lentil-[India:Kanpur:Lentil:2014] with the acronym as ToLCNDV-Lentil-[IN:Knp:Len:14]. This is the first report of a begomovirus found associated with a disease in lentil from India.