Shallot latent virus

Shallot latent virus (Carlavirus latensascalonici) is a viral pathogen of the genus Carlavirus that specifically affects crops within the Allium family. As a systemic plant virus, it infects the host’s vascular system, causing chronic stress that often manifests with very subtle or no external signs, hence the term "latent".

The primary hosts of this virus include shallots, bulb onions, and garlic. The virus is highly persistent in vegetative propagules, meaning infected bulbs or sets will inevitably produce infected plants in the next season. This cycle makes it a significant issue for commercial onion growers who rely on bulb multiplication for their crop cycles.

The symptoms of the infection are often mild and can include mosaic-like patterns, slight leaf chlorosis, and occasionally plant dwarfing. In many cases, infected onions appear stunted with reduced bulb development compared to healthy specimens. The economic damage manifests in lower yields and poor storability of the harvested crop.

Transmission occurs through two main routes: insect vectors and mechanical contact. Aphids are the primary insect vectors, transmitting the virus in a non-persistent manner while feeding on plant sap. Additionally, human activities such as pruning, thinning, or handling bulbs can facilitate the spread of the virus within a field or greenhouse setting.

Effective management requires an integrated approach focusing on prevention and sanitation. Growers should implement strict screening of planting material, utilizing virus-indexed bulbs whenever possible. Furthermore, managing aphid populations using biological or chemical control and disinfecting gardening tools are essential practices to minimize the risk of spreading the pathogen.