Common aphid vectors of LYSV are the green peach aphid (Myzus persicae) and the black bean aphid (Aphis fabae). Other aphids have been shown to experimentally inoculate host plants

Collect symptomatic plant tissue by visual survey.

Survey Sample Collection:

Leaves: Remove leaf tip samples from the second youngest leaf on symptomatic plants.

Bulbs: Remove bulb from the symptomatic plants of interest.

No specific signs are present.

Leek: In leek, LYSV causes irregular yellow striping on the leaves, particularly near the base, but not confined to this area. In certain instances, entire leaves can turn yellow. Diseased plants are drier with soft, limp, and/or deformed leaves.

Garlic: In garlic, LYSV causes light yellow striping on the distal part the leaves, which can lead to dwarfing of the entire plant. The virus also causes bulbs to be smaller and malformed, which results in yield loss.

Allium crops infected with LYSV are more susceptible to weather conditions like frost, and do not keep well post-harvest.

Enzyme Linked Immunosorbent Assay (ELISA): Agdia and AC diagnostics have commercially available double antibody sandwich (DAS) ELISAs for LYSV available using polyclonal antisera. Neither of the commercial ELISA tests have been validated for regulatory purposes at this time, however. This test is to be used for screening only. Positive results will need to be verified using molecular methods.

Leek Yellow Stripe Virus could be confused with Iris Yellow Spot Virus (IYSV) depending on the expression of symptoms. Both of these viruses infect leek, but IYSV is a tospovirus, not a potyvirus. The main hosts of IYSV are onion and shallot, but the virus has the capacity to infect leek as well (Smi IYSV is not known to infect any variety of garlic). IYSV also causes chlorotic (yellow) lesions on unfurled leaves, but the lesions are distinctly diamond-shaped instead of continuous down the lamina as with LYSV. Iris yellow spot virus typically only infects leaves, compared to LYSV which infects bulb tissue with ease. IYSV vector transmission also differs from LYSV. Iris yellow spot virus is vectored by the onion thrips (Thrips tabaci ). IYSV is also established in many states, and is not considered an exotic pest.

Another easily confused virus is Onion Yellow Dwarf Virus (OYDV). OYDV is also a potyvirus with similar symptoms to LYSV. Like LYSV, streaking starts at the base of the leaf and can spread to complete yellowing of the entire leaf. Leaves are sometimes flattened and fall over often. OYDV is transmitted by the same two species of aphids and via vegetative propagation, and is often found in complex with LYSV. The OYDV virus forms thread-like particles about 722 to 820 nm long. To distinguish which virus is present in a symptomatic plant, it is best to use molecular diagnostics.

Indicator Hosts:
Allium porrum: Yellow leaf stripes are observed with infection of LYSV.

Chenopodium amaranticolor and C. quinoa: Diagnostic symptoms of LYSV include chlorotic local lesions that become green rings when leaves senesce.

Celosia argentea: Brown necrotic local lesions are observed with infection of LYSV.

ELISA: Wei et al. (2006) extracted sap from the affected plant and tested for LYSV with general potyvirus monoclonal antibodies from Agdia Inc. (Elkhart, Indiana). This diagnostic should be verified with RT-PCR or sequencing to confirm it is LYSV and not another potyvirus.

Immunoelectromicroscopy: Virus particles are trapped from crude leaf extracts on copper grids in 0.1 M phosphate buffer at pH 7.0 for 15 minutes. Grids are washed with 1:50 dilution of LSYV antiserum for 15 minutes. Decorated virus particles are then stained with 1% (weight/volume) of uranyl acetate (Dovas et al., 2001).

Molecular:
RT-PCR: RT-PCR was performed using specific primers designed from the consensus regions of the coat protein genes of Leek yellow stripe virus (Fajardo et al., 2001). Pappu et al. (2008) also provide specific details on RT-PCR and primers for Leek Yellow Stripe Virus.

LYSV has been reported in garlic in Washington and Oregon (Pappu et al., 2005; Gieck et al., 2007).