IITA IPM project 16: The ecology of the African root and tuber scale, Stictococcus vayssierei Richard and its attendant ant Anoplolepis tenella (Santchi).

Duration: 3 years (2004 to 2006)

Purpose: To develop sustainable practices for the control of this emerging major cassava pest in Central Africa.

Background/descriptions: The African root and tuber scale (ARTS), a subterranean scale insect indigenous to the humid forest of Central Africa, has increasingly become a major pest of cassava since the mid-1970s. Preliminary yield loss trials from the Democratic Republic of Congo showed that high scale densities could lead to losses of over 60% of cassava root yield. Present evidence partially supports the hypothesis that increased pressure on forest resources (caused by logging and increasing rural populations) has led to shortening of fallow periods and general degradation of forest soils, resulting in an environment in which ARTS has thrived, aided by the native ant Anoplolepis tenella (Santchi). This ant thrives in disturbed forest environments and is likely the single most important factor leading to the rise in the pest status of ARTS. The ant helps the scale to avoid drowning in its own secretion, carries the mobile stage of the scale to new plants and infestation sites, and probably protects the scale from predators and parasites. A direct outcome of the characterization of the environments in which the scale has thrived is the formulation of cultural and habitat management strategies such as vegetation management strategies to reduce reservoir scale populations, particularly in fallows, and disrupt ant-tending of the scale. Other potential management strategies, such as the use of pathogens, predators and parasites also require investigation as alternative options or as complementary components of an integrated pest management programme to minimize scale infestations and cassava crop losses.

Agroecozone(s) and location(s): Humid Forest in Cameroon and the Democratic Republic of the Congo

Expected outputs: a) Ant-ARTS interactions characterized and at least one method that interfere with ant foraging developed; b) At least one natural enemy identified, characterized and deployed for ARTS control in at least one affected country

Potential Impact(s) (Beneficiary/ies): To be stated

Partners: a) IRAD - Cameroon; INERA – DRC; b) University of Douala – Cameroon; c) University of Massachusetts – USA; d) Wageningen University – the Netherlands

Development investor(s): Dutch Ministry of Foreign Affairs

IITA contact person(s)/principal investigator(s): Rachid Hanna R.Hanna@cgiar.org website http://www.iita.org