Chemical control of the mealybug Phenacoccus solenopsis (Hemiptera: Pseudococcidae) in Australian cotton–Glasshouse assessments of insecticide efficacy

Abstract

Abstract The efficacy of commercially available chemical insecticides and biopesticides on the cotton mealybug (CMB), Phenacoccus solenopsis, was evaluated in the glasshouse. Spirotetramat, sulfoxaflor and buprofezin were identified as key insecticides for use in integrated pest management (IPM) strategies aimed at controlling CMB without flaring other co-occurring pests. When used as a single application, spirotetramat and sulfoxaflor at the rate of 96 g (active ingredient, ha−1) provided variable control of CMB. Spirotetramat used in a double spray tactic (two sequential sprays, 14–15 days apart) without crop oil provided ≥80% control of adult CMB while the addition of oil (5% v/v) increased control to ≥90%. Clothianidin synergised the spirotetramat + oil combination and was identified as a potentially useful tank mix option for use in situations where a quick knockdown of high density and/or large infestation of CMB is required, or to treat high risk infestations in squaring or younger cotton when the abundance of beneficial insects is typically low. Sulfoxaflor used in a double spray tactic provided ≥90% control of adult CMB. The addition of Pulse® penetrant (0.5% v/v) to both options improved overall efficacy. Addition of crop oil to sulfoxaflor did not yield any tangible benefits. Spirotetramat and buprofezin were identified as important tools in managing situations where whitefly (Bemisia tabaci) is the primary pest management target, but CMB is also present in the crop. Buprofezin was effective on early instar mealybugs; this makes it an option for arresting CMB population growth while allowing the beneficial insect populations to increase. Sulfoxaflor was shown to be a useful option in situations where CMB is present along with key pests such as mirids (Creontiades spp.). Mealybugs are typically well controlled by naturally occurring beneficial insects without the need for insecticide use. Chemical insecticides for CMB control should be considered only as a last resort and deployed within the bounds of an IPM strategy.