Leafmining caterpillars

It is a common pest of groundnuts in South and South-East Asia and a major pest in India, and it has recently invaded Africa. It was first found in Uganda in 1998 and is now recorded in Mozambique, Malawi, Democratic Republic of Congo and South Africa. In all African countries where this leafminer has been found, the pest has reached epidemic densities and severe yield losses have been observed on groundnut (The New Vision. 2004; Kenis and Cugala, 2006). The adult is a mottled moth, with a full wing span of up to 18mm. The moth lays eggs on the underside of the groundnut leaf and petioles. Yellowish green caterpillars hatch, tunnel into the leaves and feed between the upper and lower epidermis of the leaf. Mined leaves become distorted within a few days. Caterpillars are grey-green with a shiny black head. There are five larval instars. The first instar has an average length of 0.56 mm. At pupation, they rarely exceed 8 mm in length.

Three or four mines per groundnut leaflet can cause so much distortion that a leaf exposes as little as 30% of the potential photosynthetic area to the sun. Later, when the caterpillar becomes too large to occupy the mine, they emerge to the leaf surface and either fold over a single leaf and hold it down with silk, or web together two or more leaflets. They live and feed in the shelter they have constructed. Pupation takes place inside the webbed leaflets. Damaged leaves become brownish, rolled and dry, which results in early defoliation and affects the growth and yield of the plants.