Early action as basis for averting threats of emerging diseases on crop production

Nigeria has just barely survived the “Tomota Ebola” plague, leading to over 720,000 MT in tomato loss that has left thousands of farmers counting their losses, and multi-billion naira losses in potential revenue.

If the fears now being expressed by experts are anything to go by, then the new strains of crop diseases that have been detected in other parts of Africa now constitute a threat to crop production in Nigeria as well, unless urgent actions are taken for effective surveillance and prompt reporting.

BusinessDay correspondent was first alerted on this by Vincent Isegbe, coordinating director, Nigerian Agricultural Quarantine Service who said, “changing trends, emerging diseases are coming up so we need to prepare. In the eastern part of Africa and central Africa, there is a disease called “maize necrotic lethal disease,” and there is another one called “cassava brown streak disease”. These two diseases are not in the country for now, but we have to watch out for them.”

As noted by the Food and Agricultural Organisation (FAO), while the Cassava Mosaic Disease (CMD) has been detected across the whole in Africa, survey evidence suggests that although CMD is still highly prevalent, the spread rate appears to be gradually reducing. The Cassava Brown Streak Disease (CBSD), on the other hand, is rapidly spreading.

Symptoms of Cassava brown streak disease appear as patches of yellow areas mixed with normal green colour. The yellow patches are more prominent on mature (bottom) leaves than younger ones. Experts have warned that it may be confused with other diseases especially cassava mosaic, thereby, urging prompt laboratory tests to confirm the actual diseases when detected on the farms.

Compared to cassava mosaic, “the negative impact is even more severe when cassava plants are infected by CBSD. The virus attacks the roots, making it often difficult for farmers to detect the disease before it is too late. Without adequate response mechanisms, CBSD may cause root production losses of up to 100 percent,” reports FAO.

Angela Eni, associate professor of virology and team lead at the Covenant University Hub, West Africa Virus Epidemiology (WAVE) project for root and tuber crop, during a farmers’ day it organised for members of the All farmers Association of Nigeria (AFAN) in Lagos, corroborates the fears earlier expressed by NAQS.

She said: “The cassava brown streak virus is a source of concern for West Africa because right now we are reporting that the virus is not currently in West Africa, but it is ravaging some countries in East and Central Africa, moving gradually west-wards because it has been reported in Democratic Republic of Congo (DRC), and Cameroun is very next to DRC.

“Cameroun borders Nigeria, so we are trying to create awareness. The crop we are talking about here is vegetative in cultivation. Primarily first of all, the transmission is through planting materials; infected cassava cuttings used for planting. Then it is also vector-borne; transmitted by the white fly- “Bemisia tabaci”. Unfortunately this white fly also transmits other diseases, but even though we have the white fly in Nigeria, the cassava brown streak disease isn’t present here (yet),” said Eni.

On the other hand, the Maize Lethal Necrosis Disease (MLND) is a result of a combination of two viruses, the Maize Chlorotic Mottle Virus (MCMoV) and any of the cereal viruses in the Potyviridae group, like the Sugarcane Mosaic Virus (SCMV), Wheat Streak Mosaic Virus (WSMV) or Maize Dwarf Mosaic Virus (MDMV). The double infection of the two viruses gives rise to what is known as MLND, also referred to as Corn Lethal Necrosis (CLN).

Maize is susceptible to this disease at all stages of development, specifically from seedling stage to near. The loss is due to infected maize plants with small ears, distorted and set little or no grains.

While Nigeria’s maize production at nearly 8 million tons makes it the largest African producer, the volume still falls short of local consumption needs. An outbreak of disease such as MLND can only make things worse.

Isegbe told BusinessDay that the agency had “put surveillance mechanisms in place in the last two years; asking people not to bring in any seed of maize, and no cassava cuttings. Of recent too in Cote d’ivoire, we have realised that there is this coconut yellow leather disease or so. You will see coconut standing like an electric pole; so that coconut is dead.”

Femi Oke, chairman of the Lagos State Chapter, All Farmers Association of Nigeria (AFAN) remarked that many farmers across the country have been complaining of virus, pests, and other diseases, which have been unknown before.

Oke lamented inability of farmers to surmount these challenges, as many of them are even unable to identify the new strains of plagues on their farms, calling on the government to come to their rescue.

Adeola Elliot, chairman of the Agric group at Lagos Chamber of Commerce and Industry on his part, bemoaned the failure of research in Nigeria, especially tertiary institutions, describing them as implicit in the present condition of agriculture that is in a hapless state, and farmers also becoming susceptible to almost any form of attacks on their commodities.

The cassava value chain alone has over N10trillion in potential revenue. The Nigeria Cassava Growers Association (NCGA) had exclusively disclosed its plans to BusinessDay, revealing that “if from the over 84 million hectares arable land available in Nigeria, 5million is devoted to the production of Industrial Cassava and we are able to reap 40 MT of Cassava from an hectare of farmland, it implies that we shall have 200,000,000 MT per year.

“The above 200 million MT of raw Cassava can be milled into 50million MT of Industrial Starch. At present, Industrial Starch sells for over N200, 000 per ton which means we can generate 10 trillion naira yearly from Cassava.”

Also, the market of ethanol in food grade and biofuel is limitless. In fact, Nigeria according to NCGA imports over 97% of her ethanol. With the low starch content of our cassava (which can be doubled), we are presently able to obtain 166 litres of ethanol from a ton of cassava. 200 million MT of cassava will therefore give us 33,200,000,000 litres of ethanol. Ethanol is sold at about N300 per litre and that means 9.9 trillion naira. If starch content is doubled, we shall have almost double the ethanol value and double the income, says NCGA.

The West Africa Virus Epidemiology (WAVE) for root and tuber crop project seems to be the only response at the moment in preparing against an eventual outbreak of cassava brown streak (and other diseases in Nigeria). The project presently entails visits to farms for crop analysis, talking to farmers and creating awareness. Where there is report of a sighting, samples are taken into the laboratory. The virus is an RNA type virus, so there are standard molecular techniques, which will screen samples with specific primers to find and amplify only RNAs related to the cassava brown streak virus in order for further actions to be taken.

Nigerian authorities may not be adequately prepared to guard against these looming diseases as the quarantine service lacks personnel and other resources needed to effectively check influx of infected commodities (or seedlings).

Isegbe of NAQS had also said that “We have a lot of challenges of emerging diseases and we need very strong diagnostic labs to be able to continuously take samples to prevent any of such things from coming in. So for people bringing in samples of food materials, we have to constantly check. You know it is expensive to run a lab, some of the reagents could expire in three months, some in one month, some in six months, once they expire, it is waste, but you cannot say you will not prepare because the day you choose not to prepare, the disease may choose to come in, what are you going to do?”

The NAQS boss explained that it has been difficult for quarantine to man Nigeria’s 4047 kilometres stretch of borders effectively. Immigration opened 33 stations in 2013, and till date, the quarantine service is yet to send its staff to complement activities in those new stations.

As recommended by FAO, strict quarantine procedures during international exchange of cassava germplasm and the use of resistant/tolerant varieties and virus-free planting material are key for the control of both CMD and CBSD in Africa.

Farmers living along borders between countries should be targeted for awareness raising on importance of avoiding moving cassava plant materials across borders without following quarantine procedures. It is also recommended that movement of cassava germplasm between countries should only be done through virus-indexed tissue culture form. In other words, only virus-tested tissue culture materials should be used for inter-country germplasm movements.

Presently, experts are speaking of threats in cassava, maize, and even coconut, but other crops may be at risk, and this implies the need for more concerted efforts in identifying emerging diseases as they occur. Beyond identifying diseases however, it is imperative for researchers (and other entities charged with such responsibilities) to now find more solutions than simply reporting.

CALEB OJEWALE