Milam stem-pitting

Milam stem-pitting is a serious disorder in citrus trees associated with specific isolates of the Citrus tristeza virus (CTV). This viral pathogen targets the plant's vascular tissue, effectively obstructing the flow of water and nutrients, which leads to a gradual decline in the tree's health.

The disease primarily affects various species within the Citrus genus, with significant impacts observed in orchards utilizing susceptible rootstocks such as Milam. The rootstock-scion combination plays a critical role in the expression of the disease, making the tree's genetic background a key factor in susceptibility.

Visible symptoms include the development of pits, grooves, and depressions on the woody cylinder beneath the bark of the trunk and main branches. Infected trees often exhibit canopy thinning, reduced vigor, leaf chlorosis, and smaller fruit size, which significantly compromises the overall productivity of the plantation.

Transmission occurs through insect vectors, most notably aphids (such as Toxoptera citricida), which spread the virus while feeding. Human-mediated transmission is also a major concern, as the virus can be easily spread through the propagation and grafting of infected plant material into healthy rootstocks.

Managing Milam stem-pitting requires a strict integrated approach. Since there is no curative treatment for infected trees, prevention is the primary strategy. Growers should focus on using certified virus-free nursery stock, implementing rigorous aphid control programs, and performing regular orchard surveys to rogue out any symptomatic trees as soon as they are identified.