These concerns have seen 15 potential agents rejected or shelved, and only two released to date include the sap-sucking lace-bug, Gargaphia decoris<\/em> (released in 1999), and the flowerbud-feeding weevil, Anthonomus santacruzi<\/em> (released in 2008).<\/p>\n In their first study, the authors examined the idea that light (full-sun or shade) could affect lace-bug feeding and plant responses. Experiments on leaf physiology, showed that lace-bug feeding was effective by reducing photosynthesis of bugweed under both full-sun and shade conditions. However, interestingly, plants in the sun experienced additional damage due to water loss, which caused them to suffer the effects of overheating. \u201cThis research suggests that the lace-bug has the potential to damage bugweed severely. Future research is needed to identify and address the biotic factors, such as predators, that currently constrain the agent\u2019s performance in the field<\/em>,\u201d explains Cowie.<\/p>\n In a second study, the authors focussed on the more promising of the two agents, the flowerbud-feeding weevil, Anthonomus santacruzi<\/em>. This weevil has not become as widespread as expected, but its establishment has been confirmed along the KwaZulu-Natal South Coast and in the Sabie region of Mpumalanga.<\/p>\n The authors combined climate modelling, thermal-physiology and humidity assessments to predict which climatic factors are most likely to restrict the establishment and spread of the weevils in South Africa. They found that low temperatures and low relative humidity, particularly during winter months, constrain the establishment of the flowerbud-feeding weevil in South Africa. \u201cThese results suggest that future releases of this agent should be focused in areas that are better suited to the species\u2019 climatic requirements<\/em>,\u201d explains Cowie.<\/p>\n \u201cThis research highlights that the sap-sucking lace-bug and the flowerbud-feeding weevil maintain the potential to be effective agents against bugweed. These agents deserve renewed attention and investment in terms of their release strategies. The incorporation of plant ecophysiology and climate modelling offers additional techniques for the assessment of biocontrol agents\u2019 efficacy<\/em>\u201d, says Cowie, lead author of the two papers published in Biological Control<\/em>.<\/p><\/blockquote>\n Cowie, B.W., Byrne, M.J., Witkowski, E.T.F., and Venter, N. 2016 Exacerbation of photosynthetic damage through increased heat-light stress resulting from Gargaphia decoris<\/em> sap-feeding. Biological Control<\/em> 94: 82-89. http:\/\/dx.doi.org\/10.1016\/j.biocontrol.2015.12.008<\/a><\/p>\n Cowie, B.W., Venturi, G., Witkowski, E.T.F., and Byrne, M.J. 2016. Does climate constrain the spread of Anthonomus santacruzi<\/em>, a biological control agent of Solanum mauritianum<\/em>, in South Africa? Biological Control<\/em> 101: 1-8. http:\/\/dx.doi.org\/10.1016\/j.biocontrol.2016.06.005<\/a><\/p>\nRead each of the papers in Biological Control<\/em><\/h4>\n
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