Pre-empting a horticultural and food security disaster in eastern Africa

Scientists from the Nairobi-headquartered icipe, African Insect Science for Food and Health, the Kenya Agricultural Research Institute (KARI) and the International Potato Centre (CIP), Peru, with funding from BMZ, Germany, have joined forces to control the invasive horticultural pests of the genus Liriomyza, in eastern Africa.

Leafminer flies, as these pests are commonly known, cause crop damage in their adult and larval stages. The females puncture the plant leaves and in some instances the fruits with their ovipositors. The flies mainly use these punctures for feeding, but 10% of the time, they lay eggs in them, which then develop into larvae. A heavy attack of leafminers leads to large-scale destruction of leaf tissue, shrivelling of the leaves and eventually, the complete defoliation of the entire plant. More importantly, the presence of leafminer larvae on export produce is of quarantine relevance in the European Union markets.

Liriomyza leafminers were restricted to the New World until the 1970s but have since then been spreading to other parts of the world. In eastern Africa, three polyphagous species, L. huidobrensis, L. sativae and L. trifoli, have been recorded on French and runner beans, snow and sugar snap peas, okra, aubergine, passion fruit and various species of cut flowers.

A significant area of concern is that in South America and Southeast Asia, L. huidobrensis has been known to attack and damage potato crops to crisis levels. Even though no attacks have been noted on this crop in eastern Africa, it is important to pre-empt such a possibility, which would be catastrophic as potatoes provide a fallback in bad maize years, preventing serious famines.

Overall, if not contained, the leafminer problem in East Africa would threaten the livelihoods of the region’s small-scale farmers, who produce 80% of vegetables for the local and export markets. Leafminers easily develop resistance to synthetic pesticides, thus necessitating the use of the newest plant protection materials, which are often out of the reach of such farmers. Synthetic chemicals also have an adverse effect on the natural enemies, which are important in controlling the leafminers. Moreover, while only L. huidobrensis is a listed quarantine pest in the EU, there is currently no practicable method for inspectors to distinguish between leafminer larvae on import produce. As a result, whole consignments are usually rejected when any leafminers are detected.

The work by icipe, KARI and CIP will build on the extensive studies on leafminers already done in the developed countries. Further, it will address existing research gaps towards environmentally-friendly, affordable and sustainable management of leaf miners in eastern Africa.

One of the priority areas will be to improve biocontrol of leafminers. The researchers will also look at other control techniques, which would be harmless to the natural enemies such as trap crops and biopesticides.

The technologies generated through this study will be of benefit to small, medium to large-scale farming units. In addition, national research and extension services, non-governmental organisations and the private sector enterprises could use the results for producing and marketing biopes.