Iris yellow spot virus

Iris yellow spot virus was first discovered in the United States in 1989 infecting onions grown for seed in Idaho. The virus is a tospovirus, closely related to two serious virus diseases: tomato spotted wilt virus and impatiens necrotic spot virus. The disease is primarily a problem on onions (Allium spp.), garlic (Allium sativum), iris (Iris spp.) and lisianthus (Eustoma grandi-florum). IYSV is vectored by Onion thrips (Thrips tabaci). It is noted that the economic impact of iris yellow spot tospovirus in iris and leek is low in the Netherlands but this is not the case in Brazil on onion, as up to 100% loss has been observed in onion fields.

Iris
Symptoms are characterized by chlorotic spots which later developed into yellow and necrotic spots.

Onion
Plants show numerous eyelike spots on the leaves and flower stalks resulting in flower abortion.

Control
There is no known cure for IYSV. Once and infection is detected all affected plants should be culled and destroyed. All tools and equipment should be sanitised. Maintain optimal growing conditions for plants to prevent stress. Employ a crop rotation to avoid growing susceptible crops in infected soils. Weed regularly and control thrips movement and spread. Choose cultivars that are resistant to thrips and IYSV.