Mealybug control in Flemish greenhouses with Cryptolaemus montrouzieri and Chrysoperla carnea

Abstract: Mealybugs are economically important pests in many crops worldwide. In temperate climate regions, they are mainly a problem in greenhouse crops. In Flemish greenhouse ornamentals, four mealybug species are responsible for over 90 % of the mealybug infestations: Planococcus citri (C), Pseudococcus longispinus (L), Pseudococcus viburni (V) and Trionymus bambusae (B). To validate the efficiency of two commercially available beneficials, Cryptolaemus montrouzieri and Chrysoperla carnea, against hotspots of the four mealybug species, a greenhouse experiment was conducted in plant cages. Plots consisted of either 8 Ficus benjamina plants, which were infested with C, L or V or 4 Fargesia-bamboo plants which were infested with B. Mealybugs were counted on each plant before the start of the experiment. For treatment, 1 commercial sachet containing around 1000 larvae of either Cryptolaemus montrouzieri or Chrysoperla carnea were released in each cage and all mealybugs on the plants were counted again 4 weeks later. Compared to the control treatments, both predators gave high levels of control of C, L and V. Control of B was however insufficient by both predators. These results show the potential of hot spot treatment as an IPM strategy in greenhouses to prevent further spread of mealybugs. They also highlight the importance of correct identification of mealybug species in IPM.