Forecasting pests and disease attack to the food chain in Africa
Thirty-three plant and forest pests and diseases and animal and aquatic diseases were forecasted by FAO experts for the period April to June 2018.
The Food Chain Crisis Early Warning Bulletin indicate that the transboundary threats to animal and plant health and food safety have a potential high impact on food and nutrition security for the three months ahead. A total of 257 forecasts were conducted in 115 countries.
Rwanda is expected to battle with three pests and diseases; Fall armyworm (FAW) in maize, Bronze bug and Red gum lerp psyllid in eucalyptus plantations during the period of April-June 2018.
FAW has infested all of the 30 districts in the country. Many male FAW moths have been caught in pheromone traps. During the last season (A), FAW infested maize in all districts. Throughout agricultural season B (from March to June), maize is grown in limited parts of the country; nevertheless, during the forecast period, there will still be sufficient maize to sustain high FAW populations. Considering the amount of moths caught and eggs observed on the maize plant, its presence is expected.
In the Forest pests and diseases category, Bronze bug (aumastocoris peregrinus) is highly likely to spread in eucalyptus plantations. Severe infestations of this pest result in leaf senescence, leaf loss, thinning three canopies, and branch dieback. Red gum lerp psyllid (Glycaspis brimblecombei) outbreaks are highly likely to continue occurring in eucalyptus plantations. The survey conducted in November 2017 shows that the spread is likely to be high in 2018.
The pest has continued to damage eucalyptus plantations, since 2015 in Rwanda. Red gum lerp psyllid nymphs and adults feed on sugar rich phloem. Excessive feeding pressure causes premature leaf drop. Extensive and repeated defoliation events, caused by psyllid, weaken trees and cause premature deaths of highly susceptible eucalyptus species.
Eastern Africa on the alert
Animal diseases in Eastern Africa, precipitation forecasts for April-June predict above-normal rainfall. FAO, therefore, advises that the veterinary services and livestock farmers’ communities remain vigilant to the potential occurrence of Rift Valley fever (RVF) outbreaks in human and/or animal populations. In this sub-region, RVF infections are likely to occur. RVF infestations were reported in cattle and humans in Uganda (November 2017) and South Sudan (December 2017).
In Uganda, these outbreaks occurred in the cattle corridor between Kenya and Uganda in areas of low suitability for vector amplification but in medium/high suitability areas for RVF spread, based on climate and expert opinion models. In South Sudan, they occurred in a swampy area following a period of suitable climatic conditions for vector amplification.
Given the density of domestic animals in the area, uncontrolled cross-border movements of livestock, conflicts, and lack of veterinary services, the disease is likely to spread within the affected countries. In some countries, H5N1 and H5N8 Highly pathogenic avian influenza (HPAI) viruses may cause new outbreaks.
Plant pests and diseases
Fall armyworm (FAW) - Spodoptera frugiperda, is a pest that can cause significant damage and crop yield losses, if not well managed. The insect continues to be of high concern for Africa, particularly, because its impact on maize can be very detrimental. Maize is its preferred host and a major staple crop for smallholders. In addition to maize, the pest has also been detected on an increasing number of other crops (e.g., sorghum and sugarcane).
FAW, therefore, can affect the food security and livelihoods of many people. In Western, Central, and Eastern Africa, it will be the maize-cropping season; FAW is expected to continue its spread across new areas, and damage will be high. In Eastern Africa, FAW presence is now confirmed in all countries except for in Djibouti and Eritrea.
In most Eastern African countries, the forecast period coincides with the major maize growing season. Unless appropriate action is taken, the likelihood of spread and damage will be high because the pest will have access to significant amounts of maize, which is its preferred host.
In Eastern Africa,Cassava brown streak and mosaic diseases continue to affect many countries and might amplify in areas where weather conditions are favorable. Tomato leaf miner (Tuta absoluta) infestations vary with the seasons. Insect pest populations and infestation levels are likely to be relatively low across countries in this sub-region during this forecast period, because it generally coincides with the main rainy season during which there is limited tomato production.
Tomato is mainly produced under irrigation during the warm dry season, and these conditions also happen to be favorable for the pest to flourish. If left uncontrolled under these conditions, leaf miner infestations are typically high and can lead to yield losses of 80 - 100%.
Aquatic diseases
Countries in Eastern and Southern Africa such as Angola, Botswana, Malawi, Namibia, the United Republic of Tanzania, and Zimbabwe are at risk of the fish disease Epizootic ulcerative syndrome (EUS). Except for the United Republic of Tanzania, these countries border the Chobe Zambezi River where the first EUS case was reported in this region, in Botswana. In most of these countries, water temperatures during the period April to June 2018 will range from 18 to 25 °C, which are optimal temperatures for the development of the oomycete fungus that causes the disease.
Tilapia Lake virus (TiLV) may have a wider distribution than is currently known, and it is likely to be a significant threat to the global tilapia industry. High awareness and vigilance for TiLV are required in tilapia producing countries in Northern, Eastern, and Southern Africa.
TiLV, already present in Egypt (scientific literature), is likely to have a wider distribution than currently known and may become a threat to the tilapia industry in Africa (Ghana, Kenya, Nigeria, Uganda, Zambia, and Zimbabwe).