Common coffee pests and diseases and their control

Coffee production is increasing at a fast rate in Uganda as more people take up coffee growing since its market is assured and the prices are quite attractive. 
For a long time in the past, the country’s annual average coffee production stagnated at three million 60-kg-bags but last year Uganda produced an unprecedented seven million 60-kg bags, according to the Uganda Coffee Development Authority (UCDA). 
We are however, struggling to increase production against the odds and challenges of climate change whose footmarks are right before our eyes.

Pests and diseases 
The big challenges for the coffee farmer today include pests and diseases, many of which are new in the history of coffee farming. 
Robert Ssentamu, UCDA regional coffee extension officer in Sembabule and Bukomansimbi districts believes that the best way to go about the challenges lies in farmers turning to good agricultural practices, soil nutrient management, and pests and disease management and control. 
“Here in the central region we grow Robusta coffee which has its own diseases while in eastern Uganda and some parts of western Uganda they grow Arabica coffee which too has its own pest and disease problems,” he says. “Some of the issues, such as extreme weather conditions and soil nutrition deficiency, of course cut across all regions.”

Coffee wilt disease 
He says the coffee wilt disease (CWD) which wiped out 56 percent of the crop in 2005 is one of the most devastating diseases for Robusta coffee. “It was first noticed in Bundibugyo in 1993 but it is amazing how fast it spread to the rest of the country,” he told Seeds of Gold. “In 2006 Uganda hardly produced even two million bags,” he adds.
He says CWD is a fungal disease which kills coffee trees by blocking water and nutrients passage within the branches. “The branches wilt one after another until the entire tree dries up,” he says.

How to control wilt  
The dead tree remains infectious for years and it must be uprooted and burnt right in the place where it has been. Ssentamu warns that the virus survives in the soil for a long time and it can be spread by running water, wind, and sharp tools. “When the virus gets into contact with a bruised part of another tree infection takes place,” he says. He further recommends fertiliser application since strong plant vigour increases tolerance to the disease.
He advises farmers to exercise a lot of hygiene by disinfecting their tools every time they use them to work on a diseased tree before going ahead to work on another.

 “Unfortunately, the infected tree does not always manifest infection symptoms and some healthy looking trees could already be infected. So the best practice would be to disinfect tools after working on each tree,” he says.
  Disinfection involves dipping the tools in a container of a disinfectant such as JIK or passing the tool over fire. He also advises farmers to observe good spacing regulations to avoid situations of branches of diseased trees brushing against those of healthy ones.
“All new farmers joining Robusta coffee growing and everybody else struggling to restock their gardens should go for CWD resistant varieties now available in all coffee nurseries registered by UCDA,” says Ssentamu. 

“In fact the arrival of CWD resistant lines has taken away the threat of the disease to coffee farmers.” He says the coffee varieties are also selected and bred to resist or tolerate many other coffee pests and diseases apart from being high yielding and producing big coffee beans.
Black Coffee Twig Borer (BCTB)
Ssentamu goes on to reveal that perhaps the worst Robusta coffee pest today is the Black Coffee Twig Borer (BCTB).
According to some studies the pest has caused nine percent of national annual total loss and is in 69 percent of the farms in 26 districts surveyed and in each one of which 40 percent of the plants are under attack. 

Ssentamu says BCTB was also first noticed in Bundibugyo District in 1992. The pest which is visible to the naked eye spreads very fast especially during dry periods. He says it can fly a distance of up to 200 metres in a few minutes. It lays its eggs in the coffee tree twig after boring a hole in it. Between 25 and 30 days the eggs are hatched but the twig dies in the process. Heavy tree shade conditions are the best environment for the BCTB and Ssentamu advises farmers to trim all shade trees in their gardens and to ensure that the trees are planted according to the correct spacing, like 60 feet from each other.
 
Control 
He says some trees are particularly good hosts for the pests and should not be placed in or near coffee plantations. These trees include lusambya, musizi, and avocado. 
“Any shade trees planted in the coffee plantation should be well pruned to discourage possible hosting of the BCTB since it abhors high altitudes. The pest attacks more than 200 different plants in the world and here in Uganda it attacks some 45 plants,” he says. “It is a dangerous pest and can also attack the CWD-r lines,” he adds.
He encourages farmers to work more closely with agricultural services extension officers about control measures which include the use of pesticides sold in farmers’ shops. Some of the helpful pesticides he mentioned are kohinor, confidor, imax, immidacloprid and Tebuconazole. 

Another way of fighting BCTB is the use of alcohol traps placed here and there within the plantation. Ssentamu also warned farmers to be cautious when purchasing coffee seedlings. 
Often the pest attacks coffee nurseries as well, which is why intending farmers should go to only UCDA registered nurseries for planting materials. 

Deus Nuwagaba, deputy executive director, National Union of Coffee Agribusinesses and Farm Enterprises (NUCAFE), attributes most coffee pests and diseases to poor management practices and failure by farmers to do soil analysis before planting the crop. “Most coffee crop pests and diseases are soil born and there is general nutrient imbalance and water stress wherever CWD is reported to exist. So it is important for farmers to have the soil in their plantations thoroughly tested and analysed to find out which nutrients are missing and if there are pests in the soil,” he says.

Coffee berry borer
Nuwagaba mentions coffee berry borer as a serious problem mainly in Arabica coffee causing significant damage with perhaps as high as 50 percent yield loss. It makes holes in coffee cherries causing them to drop off the tree when they are still green while the others that do not fall off get defective beans. The dead or damaged cherries must be destroyed as they are a source of further infection. 
Nuwagaba says the stem borer is a big problem mainly in Arabica coffee areas. It is a beetle which drills holes into the coffee tree stem and kills it. It may kill a cluster of trees and reduce yields on the farm. 

Larvae remain inside the tree and continue to develop if the branches are not destroyed in good time. The use of chemicals such as Fenitrothion is advised but it is important to strictly follow manufacturer’s instructions.
There are many other coffee crop pests and diseases. Farmers must always consult trained agriculturists for advice and guidance about how to go about them.