n African Entomology - Control of the clearwing moth, Monopetalotaxis candescens (Lepidoptera: Sesiidae), on cultivated 'rooibos', Aspalathus linearis (Fabaceae), in South Africa
|Article Title||Control of the clearwing moth, Monopetalotaxis candescens (Lepidoptera: Sesiidae), on cultivated 'rooibos', Aspalathus linearis (Fabaceae), in South Africa|
|© Publisher:||Entomological Society of South Africa (ESSA)|
|Affiliations||1 Agricultural Research Council, 2 Agricultural Research Council and 3 Rooibos Ltd|
|Publication Date||Sep 2013|
|Pages||294 - 303|
|Keyword(s)||Agricultural insect pests, Clearwing borer, Control and Red bush tea|
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 mid-November 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.
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