PEST AND DISEASE MANAGEMENT
Weevils
A black insect with clearly pronounced snout and hard fore wings. It lays eggs on the pseudostem area near the collar and eggs hatch into larvae which feed on the plant, tunnel into the corm causing damage.
Treatment:
- Use resistant plants
- Remove old corms, split them to dry to prevent breeding.
- Chop the old corms to prevent breeding ground.
- Trapping: Two types of traps, split pseudostem and disc-on-stump traps. Traps are made using 10 - 15 cm long pieces of banana stem, split in the centre and then laid upside down next to the infected plant. After 2-3 days, the traps will have attracted the weevils, then collect and kill them.
Nematodes
Nematodes are microscopic, which feed on banana roots. Nematodes burrow their way into the roots, feeding on them as they go thus reducing the uptake of water and nutrients in the roots causing the plant to eventually collapse.
Infection
The damage to roots is severe, it will cause toppling. If new fields become infested by using infected suckers, nearly all suckers will be infected with nematodes.
Symptoms
Infested plants will exhibit the following symptoms:
- Stunted root system or spots of stunted plants in larger plantations
- Root lesions
- Toppling: Plant falls & gets uprooted together with its roots.
- Wilting of plants even if there is adequate water supply
- Uniform yellowing or chlorosis of the lower leaves even if soil is adequately fertilized.
- Reduced number and size of leaves
- Brown-coloured rot on root surface. Brown lesions and tunnels within rhizomes.
- Low productivity.
Treatment
- Use resistant varieties such as Kabana6H, Kabana 7H, NAROBan 1,2,3,4&5.
- Always plant clean the suckers: Remove all roots and peel the corm. Destroy all peelings by burning them. Deep peeled suckers in boiling water for 30 seconds, shortly before planting.
- Apply manure at 2 ft from the base of the mat
- Ensure a clean field before planting
- Introduce a break crop e.g. cassava and sweet potato before replanting in devastated fields .
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Banana Rust Thrips (Chaetanaphothrips signipennis)
Thrips are small yellow insects with narrow fringed wings which cause damage by feeding on the tender green skin of young banana fruits. The bananas appear brown, purplish to black. The discolouration however is on the surface of the fruit peel. In extreme cases of severely affected fruits, the whole bunch appears blemish.
They cause more severe damage to younger fruits, often the symptoms do not manifest until after 2 months as the fruits begin to mature. When the peel gets damaged as a result of feeding by the thrips, the affected fruits first appear as grey and dusty, later turning rusty brown. As affected fruits continue to grow, sometimes the peel cracks causing scarring.
Treatment:
- Use healthy planting materials from clean source.
- Avoid cultivating host plants near or within banana plantations.
- Immediately at flowering, use commercial recommended clear polythene bags of 0.08mm thickness that is perforated at 76mm interval with hole of 12. 7mm to cover the bunch as it opens.
- Cut down the affected banana fruits and burry them to reduce the population of insects in the fields
- Remove neglected plantations as these can serve as ground for thrips to multiply
Banana Bacterial Wilt (BBW)
(Local names: “Kiwotoka” (Luganda), “Kajunde” (Runyakole))
This is disease is caused by a bacteria called xanthomonas campestris Pv. Musacearum which enters the plant via natural openings, fissures and wounds and makes the fruit unpalatable and eventually kills the plant.
How it spreads
It spreads through rough tools such as pangas, hoes, pruning knives and any other agent that injures the plant when contained. Transmission by insects that visit banana male buds to feed on sap that oozes out when banana flowers fall off.
Treatment
- Avoid transfer of infected plant parts
- Break off male bud after formation of last cluster using a forked stick to prevent spread of disease.
- Cut affected stem off ground
- After working on each stool, disinfect contaminated tools (pangas, hoes, knives) with jik, soap & water. Dip them in 20% solution of Jik (1 volume of Jik to 4 volumes of water) before moving to the next stool or flame the cutting tools to disinfect
- Adopt good crop management practices (ABCD approach)
Fusarium Wilt
Fusarium Wilt (also known as Panama Disease) is a destructive fungal disease that enters the plant through the roots, disrupting the plant’s ability to transport water and nutrients. It commonly affects apple bananas/dessert bananas and juice making bananas such as kayinja, Sukari Ndizi or Kabalagala.
How it spreads
Use of infected planting materials, water, soil particles, tools, footwear and machinery can spread the fungus from plantation to plantation.
Symptoms
Infected plants will exhibit the following symptoms:
- Yellowing and drying of leaves
- Wilting
- Splitting of the stem base
- Vascular discolouration
Treatment
Once a plantation is infected with Fusarium Wilt, the only option for continued long-term banana production is to replace susceptible cultivars with resistant ones e.g FHIAs
The fungus cannot be controlled using fungicides and cannot be eradicated from the soil using fumigants. All infected plant material should be destroyed by drying and burning to reduce disease inoculum.
Do not plant susceptible cultivars (dessert types; Bogoya, sukali ndizi and Pisang Awak also known as Kayinja and Bluggoe) in fields with a previous history of fusarium wilt to avoid build-up of pathogen.
Black Sigatoka (Black leaf streak disease)
This is a foliar fungal disease that affects leaves of plants leaving them unable to function properly. It slowly kills the plant by affecting its photosynthesis.
Infection
Black Sigatoka doesn’t enter the plant via the roots. Instead, fungal spores, which are scattered when the fruit of the fungi burst, land on the leaves of the plant and begin to germinate.
Most infections start on the underside of the leaves. As the spores mature, they form blackish-brown streaks. The streaks get bigger and blacker, until they form large spots (or lesions) which restrict the plant’s ability to photosynthesize.
(Image of infected plant)
Symptoms:
- Blackish-brown streaks on leaves
- Speckling on underside of leaves
- Reduced bunch weight
- Drying of leaves.
- Speckling on underside of leaves
Treatment
- Use resistant varieties e.g Kabana6H, NAROBans 1,2,3,4,5
- Remove & burn diseases leaves
- Black Sigatoka usually develops on the 3rd or fourth leaf to have opened, so encourage the plant to produce plenty of new functional leaves by enhancing the plant’s nutrition.
- Enhance nutrition through use of manure,
- Carry out timely pruning when leaves are dry
- Good field sanitation: Reduce the humidity in the field by maintaining the correct spacing, good field sanitation (removing infected leaves and weeds) and proper drainage.
VIRAL INFECTIONS
Viral infections are caused by viruses. A virus is a microscopic organism that requires a host (the plant) to reproduce. Once a virus infects a plant, it starts to take over its functions.
Plant viruses are usually transferred from plant to plant by insects. Viral diseases that commonly affect banana include Banana Streak Virus (BSV) and Banana Bract Mosaic Virus (BBRMV).
Banana Streak Virus (BSV)
Banana Streak Virus causes reduced leaf size, leaf streaking and leaf mottling. In severe cases, it can cause the pseudostem to split and collapse. It also reduces the productivity of plants.
Infection
Banana Streak Virus is spread by infected planting materials and mealbugs.
Symptoms
- Infected plants will exhibit the following symptoms:
- Reduced leaf size
- Yellow streaking of leaves (which then becomes black)
- Mottling of leaves
- Splitting and collapse of pseudostem
- Low productivity
Treatment
There is no way to treat or control Banana Streak Virus because it enters the genes of the plant. Therefore, infected plants must be removed and destroyed.
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