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Control of the Clearwing Moth, Monopetalotaxis candescens (Lepidoptera: Sesiidae), on Cultivated ‘Rooibos’, Aspalathus linearis (Fabaceae), in South Africa

Hatting, J.L., Brand, J., Thiebaut, N.M.
African entomology 2013 v.21 no.2 pp. 294-303
Aspalathus linearis, Nomuraea rileyi, Sesiidae, active ingredients, beneficial insects, branches, chemical concentration, entomopathogenic fungi, esfenvalerate, harvest date, hatching, leaves, moths, neonates, pests, plantations, pollution, stomach, South Africa
The clearwing moth, Monopetalotaxis candescens, is a major root-boring pest of cultivated ‘rooibos’, Aspalathus linearis, in South Africa. Neonates penetrate the tap root at the base of the stem within a few hours of hatching, presenting a brief window for control of an otherwise highly cryptic pest. Several systemic and contact/stomach insecticides as well as the entomopathogenic fungus, Nomuraea rileyi, were evaluated from 2005–2012 on 6–8-month-old plantations of A. linearis. A strategy based on prophylactic applications of a contact/stomach insecticide (active ingredient: Esfenvalerate) during early to midNovember resulted in > 97 % control. This level of control was realized following delivery of 10 ml aliquots of a 0.4 % concentration of the chemical to the stem-base of individual plants. Attempts at biological suppression of M. candescens with N. rileyi proved unsuccessful. Commercial-scale application of the chemical was possible through the development of an automated measured-dose applicator (vehicle-mounted) consisting of multiple nozzle-lines carried/directed individually by operators. The stem-directed application strategy developed here implies reduced chances of the chemical coming into contact with leaves (and twigs) to be harvested early in the following year, minimum environmental pollution and/or little to no impact on beneficial insects residing on the plant.