Infestation of groundnut by the groundnut leafminer, Aproaerema modicella (Deventer) (Lepidoptera: Gelechiidae) and rates of parasitization of this pest in South Africa

Abstract

The groundnut leafminer (GLM), Aproaerema modicella (Deventer) (Lepidoptera: Gelechiidae), is an important pest of groundnut in India and some parts of Africa. This is the first study examining the levels of infestation and rates of parasitization of this pest on groundnut in South Africa. A general survey was done of GLM parasitoids at several sites in the groundnut production areas together with a 2-year study of GLM infestation and parasitism levels at the Tshiombo irrigation scheme. GLM larvae or pupae on infested groundnut leaves were collected and held for emergence of moths or parasitoids. Nine species of parasitic Hymenoptera parasitized GLM immatures, which was low in comparison to the large number of parasitoids known to attack the pest in Asia, the origin of the pest. Hypomicrogaster sp. (Braconidae) and Baryscapus sp. (Eulophidae) were recorded for the first time on GLM. Larval parasitization rates ranged between 3.7 and 54.2% and pupal parasitization rates ranged between 4.8 and 43.7%. Mean infestation levels of GLM (larvae and pupae) were between 1.2 and 1.9 (SE ±0.6) per plant during 2006 and 1.0 and 26.9 (SE ±2.8) per plant during 2007. In the second year of the study, the economic threshold for this pest, between 2 and 10 larvae per plant, was surpassed indicating that GLM is an important economic pest on groundnut in South Africa.