D3428: Management of Madeira mealybug, Phenacoccus madeirensis (Green) (Hemiptera: Pseudococcidae), on ornamental coleus with new insecticides

Madeira mealybug, Phenacoccus madeirensis (Green) (Hemiptera: Pseudococcidae) is a difficult greenhouse pest to manage in the production and maintenance of ornamental plants. Some of the most effective controls for P. madeirensis and other mealybugs include neonicotinoid and broad-spectrum pyrethroid insecticides that can disrupt biological controls or may be prohibited in some cases. We assessed the efficacy and plant safety of seven new insecticides as possible alternative management tools for P. madeirensis, compared with a standard commercial insecticide and unsprayed plants. Foliar applications at various rates were made to pre-bloom ornamental coleus, Coleus scutellarioides var. ‘Wizard Velvet Red’ (Lamiaceae), heavily infested with P. madeirensis. Following application, counts of P. madeirensis were taken at 3, 7, 14, 28, and 42 DAT and plants were also evaluated for phytotoxicity symptoms. Five out eleven insecticide treatments significantly reduced numbers of P. madeirensis adults and nymphs. The industry standard, Safari®, provided the highest overall control of P. madeirensis reducing mealybug populations about 99% 42 DAT. Several products, including TetraCURB MAX®, a rosemary oil-based biopesticide, provided comparable levels of control to the industry standard 28 DAT. After 42 d, significantly fewer egg masses were found on plants treated with ISM-555, Safari®, SP3014, and TetraCURB MAX® than on unsprayed controls. There were no or only minor symptoms of phytotoxicity in any treatment. Given the heavy initial infestation levels, earlier intervention may have provided an even higher level of control. These products may offer IPM-compatible alternative management tools for P. madeirensis in greenhouse production of ornamentals.