Nelly Bassily | February 1, 2010
John Mwangi was not happy with his coffee harvest this year. His trees produced only 350 kilograms of berries. Normally, he harvests more than ten times that amount. But this year, his crop was attacked by pests known as green scales.
Many coffee farms in Kenya’s Nyeri District have been attacked by green scales. Local agronomists say crops were particularly vulnerable after the recent drought.
Robert Thuo is an agronomist with the Kenya Heartland Coffee project. He explains how green scales damage trees. The insects attack during the dry season, sucking fluid from the trees. They then excrete onto the leaves, leaving them black. The trees become stressed and may die.
Green scales are an unwelcome arrival in Nyeri. But they are not a new pest.
Dr. Chrispine Omondi is a former researcher with the Coffee Research Foundation. He says green scales are manageable and no cause for alarm. He suggests solutions for the short- and long-term.
In the short term, ladybird beetles (sometimes called ladybirds or lady beetles) can be introduced to coffee plantations. The ladybirds eat green scales, controlling the pest in an environmentally-friendly manner.
To protect future crops, Dr. Omondi recommends intercropping coffee with shade trees. The intercropped trees should be taller, providing shade for the coffee. When coffee bushes are protected from the hot sun, they are less vulnerable to pest attack. They also mature more slowly, producing a better berry.
Dr. Omondi explains that intercropping has other benefits. It prevents soil erosion, improves soil quality, and offers crop diversification.
Several agro-chemical companies are trying to find a chemical pesticide that will control green scales. To date, they have had no success.
You may also be interested in this related FRW article on intercropping coffee and bananas:
-“Uganda: Coffee and bananas make good neighbours” (FRW #90, November 2009)
-For links to Farm Radio International’s scripts on pest management, go to: http://www.farmradio.org/english/radio-scripts/pest.asp.