Citrus industry under threat in East Africa

Dar es Salaam. A destructive plant-feeding insect of Chinese origin is spreading across Africa and was recently traced in two East African countries: Tanzania and Kenya; where it is potentially jeopardising the citrus industry, a study published in PlosOne journal says.

The insect, known scientifically as Diaphorina citri, transmits a bacterium that is associated with a disease known as Citrus Greening Disease which has been notorious for ruining several citrus industries in Asia and America in the past decade.

Citrus is produced in most countries in Africa. In East Africa, Tanzania is the third ranking citrus producing country after Kenya and Madagascar, with a total production of about 45,084. mT annually, according to the United Nation’s Food and Agricultural Organisation(FAO).

Rural farmers in Tanzania rely on citrus fruit, one of the most important crops, to improve their income. Commercial citrus orchards are located in Tanga, Pwani region and Morogoro, often grown at altitudes below 600 metres.

Tanzanian researchers say, although the insect exists in the country as per the recent study, no destruction to citrus production caused by its Citrus Greening Disease, has been significantly documented so far.

Mohamed Mpina, a senior research scientist in plant protection from the Tropical Pesticide Research Institute (TPRI) says, “Plans are underway to establish any potential risk. We are currently raising awareness among farmers.”

But scientists who have been researching the insect Diaphorina citri, told The Citizen that if left unchecked, it may spread rapidly and further on the continent and ruin the citrus business; a sector that is already dodged by a myriad of challenges.

The lead author of the study, Dr Fathiya Khamis, a molecular biologist and a research scientist at the International Centre of Insect and Pest Ecology (ICIPE) said that citrus greening disease which is related to the insect is incurable, explaining why the study is advocating preventive measures.

She said the citrus industry in East Africa where production is already being hampered by many pests and diseases could be at stake if no concerted efforts are made to curtail the plat-feeding pest through workable interventions.

“[Prevention] will not only protect the citrus production and export capacity in Africa but also save the small-scale farmers who rely on citrus production for their livelihoods,’’ said Dr Khamis.

“Africa’s citrus industry is under imminent threat because the pest is spreading fast in the continent and with it, the devastating Citrus greening disease/HLB,’’ says Dr Khamis who is currently researching on invasive and non-invasive fruit flies and other pests of economic importance to the agricultural sector.

Currently, she says, the control of the pest has been heavily reliant on the use of contact and systemic insecticides such as phosmet, thiocylam and imidacloprid which are not human and environmentally friendly.

She recommends alternative ways of preventing the spread of the pest. “These pesticides are toxic and have deleterious effects on human health. Furthermore, these insecticides pose a threat to non-target insects especially the ecosystem service providers such as pollinators as well as natural enemies such as parasitoids and predators,’’ she told The Citizen.

The study, published in PlosOne on June 26 and titled: Microbiome diversity in Diaphorina citri populations from Kenya and Tanzania shows links to China, aimed at adding knowledge on the diversity of the population of the pest (D. citri) in Africa and the probable introduction source of the pest in the African countries.

The study also sought to evaluate the diversity of bacterial species found in the insect from Kenya, Tanzania and China and detect the antibiotic resistance genes which have been conferred by these bacteria to the insect.

The researchers say they relied on genetic screening and technologies to look into the possibility of the pest developing some antibiotic resistance, which if it happens, presents a challenge in the management of the disease which the vector spreads.

So far, according to the study, the Asian pest has been reported in Ethiopia, Kenya, Tanzania and Nigeria while a strain of the disease has been reported in Ethiopia and Kenya.

Speaking to The Citizen, the Tanzania Agricultural Research Institute (TARI) Director General Dr Geoffrey Mkamilo argued that much as the destructive insect may be existing in Tanzania, it would be too early to say the citrus industry is entirely under a significant threat.

“If the occurrence of the pests is sporadic, it doesn’t cause any significant damage. To establish that, we would have to first research on how many farmers have been affected, how has the pest impacted on agricultural output and so on. This needs a wider discussion and further research,’’ he said.

The researchers have urged Sub-Saharan African countries to ramp up surveillance for the pest and the disease, and implement stringent measures to contain its dispersal and spread.

They argue that there is a need to build capacity in using the findings from this study to develop sustainable integrated control strategies to effectively manage the pest and limit the spread of the disease.

In Tanzania, the Deputy Minister for Agriculture, Omari Mgumba says the government has so far come up with a number of initiatives to ensure the crops are adequately protected from potential danger.

He told The Citizen that the government has so far allocated Sh1.5billion for research on crops through the Tanzania Agricultural Research Institute (TARI). “They[TARI] are expected to come up with improved seeds for fruits and crops that can resist insects,” he said.

By 2003, the Tanzania National Sample Census of Agriculture, Tanga Region was regarded as the most significant producer of citrus fruits and as home to a variety of citrus fruits such as oranges, limes, lemon, mandarin and grapefruits.

But generally, studies show that citrus production in Tanzania is comparatively very low with reference to the world statistics. Back-yard citrus trees grow throughout Tanzania at different altitudes up to 2000 m, studies further show.