Cassava witches broom

Cassava witches broom is a severe plant disease affecting cassava plantations globally. It causes significant economic damage by inducing morphological abnormalities in the plant, ultimately hindering the development of tubers, which are the main agricultural product of this crop.

The disease is caused by phytoplasmas, specialized bacteria that colonize the phloem tissue of the host plant. These pathogens disrupt the hormonal balance of the plant, leading to the characteristic excessive growth of axillary buds. Transmission occurs primarily through sap-sucking insects like leafhoppers, which act as vectors by carrying the pathogen between plants.

Visual symptoms are highly distinctive and often appear as a cluster of thin, stunted, and proliferated shoots. Instead of developing a strong, main stem, the infected cassava plant becomes bushy with shortened internodes and yellowed leaves. This state effectively prevents the plant from partitioning sufficient starch to the roots, resulting in low or non-existent yield.

Environmental conditions play a crucial role in the development and spread of the disease. Warm, tropical climates favor the rapid multiplication of insect vectors, allowing the phytoplasma to sweep across large areas. Furthermore, the use of infected stem cuttings for propagation is a primary factor in the transmission of the disease to new fields.

Effective management strategies focus on integrated pest management and strict phytosanitary practices. Key steps include

• the use of certified disease-free planting material;
• rogueing and destruction of symptomatic plants;
• vector population control using insecticides;
• application of resistant or tolerant cultivars where available.