The banana plant, technically the world’s largest herb, relies entirely on its underground structure for survival and growth. This central hub is the corm, a large, thickened stem often mistaken for a bulb or rhizome. All true roots, which are fibrous, emerge directly from this corm, anchoring the plant and absorbing water and nutrients. Damage to the corm or its roots is fundamentally fatal because this structure is the plant’s vegetative heart, responsible for producing new shoots and sustaining the entire plant.
Pathogenic Fungi and Bacteria
The most globally significant killer of the banana root system is the soil-borne fungus responsible for Fusarium Wilt, often called Panama Disease. The fungus, Fusarium oxysporum f. sp. cubense (Foc), invades the plant through the root hairs and progresses into the primary roots. Once inside, the fungus colonizes the xylem vessels, the plant’s vascular channels responsible for transporting water and nutrients.
The fungal growth, combined with the plant’s defensive attempt to wall off the infection by producing gums and gels, physically blocks the flow of water. This internal blockage leads to the characteristic wilting and yellowing of the leaves, causing the plant to starve and dehydrate from the root up. The most aggressive strain, Tropical Race 4 (TR4), attacks a wide variety of banana types. Once the soil is infested with its durable resting spores, called chlamydospores, the pathogen can remain viable for decades.
Bacterial wilts also pose a significant threat to the corm and root integrity. Moko Disease, caused by the bacterium Ralstonia solanacearum, enters the plant through the roots or wounds and causes progressive yellowing and collapse of leaves. This bacterium systemically infects the vascular tissue, causing a brown or black discoloration within the corm when cut open. Unlike fungal wilt, bacterial infections lead to a wet rot, which rapidly reduces the corm to a foul-smelling, decaying mass, destroying the root-producing tissue.
Destructive Pests of the Root System
The burrowing nematode, Radopholus similis, is a microscopic threat considered the most damaging nematode pest in commercial banana production. These endoparasites tunnel through the root and corm tissues, creating cavities within the cortex. As they feed, they cause distinct reddish-brown lesions that eventually coalesce, leading to severe root necrosis and decay.
The destruction of the root cortex severely compromises the plant’s ability to absorb water and nutrients, resulting in poor growth and smaller fruit bunches. The extensive damage to the anchoring roots weakens the structure, making the plant highly susceptible to toppling over, especially when bearing a heavy bunch of fruit. Secondary fungal and bacterial infections often enter through the lesions, accelerating root rot and plant decline.
Another major pest is the Banana Corm Weevil (Cosmopolites sordidus), whose larvae cause the most extensive damage. The adult female lays eggs in the base of the pseudostem or corm, and the resulting grubs bore deep into the corm’s interior. These tunnels interfere with the plant’s vascular system, impeding sap movement, which leads to wilting and leaf yellowing.
In heavy infestations, the corm becomes riddled with tunnels, hollowing out the plant’s base and promoting secondary fungal decay. This internal structural failure is a primary cause of plant “fallout,” where the weakened plant snaps off at the base. The weevil damage also inhibits the corm’s ability to initiate new roots and suckers, severely shortening the productive life of the banana mat.
Environmental Conditions
External environmental factors can kill banana roots by creating conditions unfavorable for the plant’s physiology. Waterlogging, which occurs when the soil becomes saturated for prolonged periods, rapidly depletes the oxygen supply in the root zone. Banana roots require oxygen for aerobic respiration; the lack of it forces the roots to switch to a less efficient anaerobic process, leading to energy deficits and the accumulation of toxic compounds.
This oxygen deprivation causes the existing roots to weaken, rot, and die off, resulting in a shallow, deteriorating root system. While the plant may attempt to adapt by forming adventitious roots and internal air channels called aerenchyma, continuous waterlogging causes the root system to collapse. Similarly, exposure to extreme cold or frost can directly kill the corm tissue. The corm contains significant water stores and soft cells, which are highly susceptible to freezing damage and subsequent rot.
Methods for Intentional Removal
For homeowners seeking to remove an unwanted banana plant permanently, two primary methods target the corm to prevent regrowth. The most direct approach is physical removal, known as grubbing, which requires digging up the entire corm and all attached root material. Since new shoots, or suckers, arise from buds on the corm, any fragments left can potentially sprout a new plant.
A more chemical method involves applying a systemic herbicide, such as glyphosate, directly to the plant’s vascular system. The pseudostem should be cut horizontally a few inches above the ground, and the herbicide is painted or poured onto the fresh cut surface within minutes. This allows the chemical to be absorbed and translocated down into the corm and connected root system, killing the plant from the inside out. Alternatively, holes can be drilled at an angle into the corm base and the herbicide injected.