Location: Temperate Tree Fruit and Vegetable Research
Project Number: 2092-22000-022-023-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: May 3, 2021
End Date: May 2, 2025
Objective:
1) Assess whether treatment with afidopyropen affects Potato Leafroll Virus (PLRV) transmission by green peach aphid on potato.
2) Examine the feeding/probing behavior of green peach aphid on potato relative to treatment with afidopyropen.
Approach:
1) We will use monoclonal parthenogenetic colonies, one viruliferous and one non-viruliferous. Colonies will be initiated from a single female collected from Moxee Farm in Wapato, Washington. The PLRV inoculate used to generate viruliferous colonies is currently maintained in colony at the Eigenbrode lab at the University of Idaho and was originally isolated in southern Idaho. We will use potted potato (cv. Russet Burbank) plants in experimental assays. Plants assigned the insecticide treatment will be sprayed with afidopyropen using a CO2-pressurized backpack sprayer at a rate of 221.8 ml/ha mixed with 75.80 l water as the carrier, 18 h prior to usage in experiments. For acquisition assays, 15 non-viruliferous 3rd or 4th instar aphids will be placed in clip cages on a symptomatic leaf of each of 10 PLRV-infected potato plants per treatment type, either untreated (control) or treated with afidopyropen. Aphid mortality will be checked 48 h after the acquisition access period, and up to 10 surviving aphids transferred individually to uninfected eight-day-old potato plants. The receiving plants will be treated or untreated in the same manner as the infectious plants, so that aphids will be placed on either two untreated or two treated plants in sequence. Transferred aphids will remain in clip cages for a five-day inoculation access period, after which mortality will be recorded, all remaining aphids removed, and the test plants maintained in insect exclusion cages within the greenhouse for 42 d. We will then collect leaf tissue from each test plant for rt-PCR to determine whether plants are infected or uninfected with PLRV. For inoculation assays, one viruliferous 3rd or 4th instar aphid will be placed on an uninfected eight-day-old potato plant leaf within a clip cage for a 48-h inoculation access period. Ten replications will be completed per untreated or afidopyropen-treated regimen. After 48 h, aphid mortality will be recorded, all aphids removed, and plants maintained within insect-exclusion cages in the greenhouse for 42 d prior to rt-PCR assay for PLRV infection.
2) We will use an EPG to characterize the feeding and probing behaviors associated with afidopyropen treatment using a system currently at the Wapato lab, placing one aphid each on two untreated and two afidopyropen-treated potato plants (cv. Russet Burbank). We will use newly emerged adults for assays, glued onto a 25.4-µm diameter gold wire attached to brass nails using silver glue (1:1:1 water, white glue, and silver flake). Then the brass nails will be attached to the EPG amplifier, an electrode inserted in the soil of a potted test plant, and aphids placed on the underside of the third leaf from the apex to complete the circuit. Thereafter, wavelengths will be recorded for 48 h or until aphid mortality. We will continue assays until we have reach 15–20 replicates per treatment. Wavelength components will be characterized in the following manner: C (stylet pathway phase), E1 (phloem phase sieve element salivation), E2 (phloem phase sap ingestion and salivation), E1e (extracellular watery salivation), F (derailed stylet mechanics), and G (xylem ingestion) (Tjallingii 1990).
