Field evaluation of two systemic neonicotinoid insecticides against pink hibiscus mealybug (Maconellicoccus hirsutus (Green)) on mulberry trees

Infestations of the pink hibiscus mealybug, Maconellicoccus hirsutus (Green), in ornamental trees were already in an advanced state at the time of its discovery in the Imperial Valley of California (USA) in August 1999. Initial studies conducted in 2001–2003 provided encouraging results regarding the capacity of both insecticides to severely reduce, and in some cases completely eliminate infestations from individual trees. In 2004–2005, a total of 50 infested mulberry trees (Morus alba L.) were divided into two groups of 20 trees each treated with either imidacloprid or thiamethoxam, and a third group of ten trees retained as untreated controls. Branch samples collected from all 50 trees from early August through mid-October recorded a substantial reduction in M. hirsutus infestations in all trees treated with either insecticide, whereas infestations continued to rise in the untreated trees to a peak level in late September. By the end of the 2005 season, 10 of 20 imidacloprid-treated and 9 of 20 thiamethoxam-treated trees were completely free of M. hirsutus.