Scientists at the National Agricultural Research Laboratories (NARL), have said they have established the cause of disease that started ravaging banana plantations in western Uganda last year.
The report of an investigation by scientists at NARL released on May 3 that Daily Monitor has seen says the disease is caused by insect pests called rust thrips.
Coupled with effects of lockdown that affected banana price, the identified pest is adding another layer of financial losses to farmers by rendering the affected bananas unmarketable.
The disease has so far been reported in 11 districts. Some farmers are, however, blaming the new breeds of bananas being introduced by the government as fuelling emergence of pests and diseases.
“They (rust thrips) are small yellow insects with narrow fringed wings. The insects attack by feeding on the green surface on the banana fingers,” the report read.
“The bananas appear brown, purplish to black. The discoloration is on the surface of the fruit peel. In extreme cases of severity, the whole bunch appears blemished,” the report further read.
The scientists said in the report that the pests cause more severe damage to younger fruits.
“Often the symptoms do not manifest until after two months as the fruits begin to mature. When the peel gets damaged as a result of feeding by thrips, the affected fruits first appear as grey and dusty, after turning rusty brown,” the scientists said in the report.
“As affected fruits continue to grow, sometimes the peel cracks causing scarring. The scars provide openings for opportunistic fungi including pathogenic ones like anthracnose that take advantage and enter the fingers making them start to shrivel and rot starting from the cracked points due to the fungal infection,” they revealed in the report.
Females can lay up to 150-300 eggs, depending on the species. Once the weather gets cold, some thrips can hibernate as eggs in leaf litter or soil outside or under benches in the greenhouse, according to available scientific information.
Dr Priver Namanya Bwesigye, the head of National Banana Research Programme at NARL, said the disease had subsided but that more cases are being reported.
She said they are working with extension workers in the communities to address the issue.
“Initially we had thought it was a disease different from what we knew but our deeper assessment showed it was the damages caused by thrips,” she told Daily Monitor.
Prof Wilberforce Tushemereirwe, the Director NARL at Kawanda, said the disease is majorly spread through poor farm hygiene practices.
“The major avenue for its spread is through planting materials which can be avoided by observing hygiene practices. The disease does not spread too fast if the planting materials are not moved to new places. The insects that cause do not fly long distances,” he said.
In already infected plantations management practices including cutting old leaves and detrashing within the same field aid the spread of thrips, according to the report.
The scientists say use of healthy planting materials from clean sources is a critical way to curb the disease.
“Avoid cultivating host plants near or within banana plantations.
Immediately at flowering, use commercial recommended clear polythene bags of 0.08mm thickness that are perforated at 76mm intervals with hole of 12.7mm to cover the bunch as it opens,” the scientists wrote in recommendation.
“Cut down the affected banana fruits and bury them to reduce the population of insects in the fields. Remove neglected plantations as these can serve as ground for thrips to multiply,” the scientists further wrote.