<i>Leptinotarsa texana Schaeffer</i> and <i>Gargaphia arizonica Drake &amp; Carvalho</i> as potential biocontrol agents for the noxious weed S <i>olanum elaeagnifolium Cav</i>

ABSTRACT Silverleaf nightshade ( Solanum elaeagnifolium Cav.; SLN) is a perennial forb native to the southern United States, Mexico and South America that has become a serious agricultural weed across the world. Biological control has emerged as a significant alternative for the management of (SLN) due to the challenges and high costs associated with chemical and mechanical controls. In this study, we used a combination of field and laboratory studies to (1) explore the fundamental and realized host ranges of two North American insects, Leptinotarsa texana Schaeffer and Gargaphia arizonica Drake &amp; Carvalho and (2) assess their suitability as potential biological control agents for SLN. Field trials over 2 years with SLN planted alongside close relatives, eggplant ( Solanum melongena L.) and potato ( Solanum tuberosum L.), showed that L. texana fed on both eggplant and SLN causing similar leaf damage to both, but no feeding damage was observed on potato. Over the same period, G. arizonica was found feeding only on SLN. In no‐choice laboratory experiments, G. arizonica fed on both eggplant and potato, but nymph survival and feeding damage were much lower on these nontarget plants, when compared to SLN. Collectively, these results suggest that biosecurity risks of G. arizonica are relatively low, and its biological control potential should be explored further, especially when compared to other candidate agents, such as L. texana .