Iris yellow spot

Iris yellow spot virus (IYSV) is a destructive plant virus belonging to the genus Orthotospovirus. It is recognized as one of the most economically significant pathogens affecting allium crops globally, leading to substantial yield losses in both onions and garlic.

The host range of IYSV primarily includes onions, garlic, shallots, and chives. Furthermore, the virus can infect a wide variety of ornamental plants, such as irises, and numerous weed species, which act as primary sources of inoculum when commercial fields are not in season.

Symptoms typically present as diamond-shaped or spindle-shaped chlorotic lesions on the foliage and flower stalks. As the disease progresses, these spots often develop necrotic centers, causing the leaves or scapes to weaken, bend, and eventually collapse, which severely disrupts the plant's ability to photosynthesize.

The primary vector for IYSV is the onion thrips (Thrips tabaci). The virus is acquired by larvae feeding on infected tissue and is transmitted by both larvae and adults. Environmental conditions such as dry and warm weather facilitate rapid thrips reproduction, leading to explosive outbreaks of the virus across fields.

The impact of this disease is profound, resulting in reduced bulb size, poor quality, and limited marketability. In severe cases, the entire harvest may be compromised, making it essential for growers to implement robust integrated pest management (IPM) practices to mitigate the risks.

• Implement aggressive onion thrips control using rotated insecticide classes.
• Practice strict weed management to eliminate alternative host sites.
• Ensure spatial separation between new crops and mature, infected allium fields.
• Sanitize equipment and eliminate crop debris immediately after harvest.
• Use tolerant or resistant onion cultivars where locally available.