A low cost pest control method against the voracious coffee thrip has worked for thousands of farmers who have lost tons of coffee berries translating into a 10 percent dip in the country’s coffee output. The method involving mulching and irrigating the crop experts say requires farmers to be aware of the soil moisture levels.
Though thrips attack berries, they are largely concentrated under the leaves. The leaves turn irregularly grey, with silvery patches and black spots. They then fall leaving a stunted coffee plant.
Thrips are brown in colour with feathers that look like birds wings.
With rains having failed thanks to the change in weather patterns scientists are sounding the alarm that an increase in thrips is imminent which could further spur the use of pesticides..
Nearly half of all coffee farms in Kenya have thrips on their crops, but the pest is most prevalent in the main coffee growing zones in the Upper Midlands. However, the pest is only considered a threat if it rises above the stipulated Economic Injury Level (EIL) of 2 to 3 thrips per leaf. In well tended coffee plantations most fall under the EIL threshold.
Indeed, coffee researchers don’t normally rate thrip as a major coffee pest, but following the surge in numbers in recent years they have moved to outline measures farmers can implement to control or eradicate them. The Coffee Research Foundation is advising farmers to mulch their coffee trees to conserve moisture and if they have irrigation kit, to irrigate their plantations in dry spells.
As a long term measure, CRF is also encouraging farmers to plant the Cordia tree and intercrop it with coffee to provide shade in dry spells. The tree matures in 2 to 3 years if the rains are good and is spaced 30 by 30 metres. Once its leaves fall, it provides organic matter that helps conserve moisture in the soil.
The mulch from fallen Cordia leaves also encourages the multiplication of predator mites that feed on thrips. The predator mites are inherent in coffee farms but organic matter ups their numbers. Introducing Cordia “is a bio pest control measure,” said Mugo.
Coffee plants are additionally more immune to thrips attack when they getting extra nutrients from the organic matter. “The same as when a person is healthy, he is less likely to fall sick,” said Dr Mugo.
Nonetheless, where the thrips reach or surpass the stipulated EIL of 2 to 3 thrips per leaf, spraying with pesticides is mandatory.
When the level of infestation becomes high, thrips can cause total crop loss in the following season. This is likely where leaves fall and coffee plants are left bare by the pests. The plants then fail to flower the following year leading to a barren coffee season.