Effective use of the predatory species, Phytoseiulus persimilis and Stethorus punctillum in controlling the two-spotted mite Tetranychus urticae in croton greenhouse

Abstract

Abstract The croton, Codiaeum variegatum is a beautiful tropical plant. The two-spotted mite, Tetranychus urticae Koch, causes economic damage to the croton. The present study aimed to control T. urticae by releasing two predatory species, Phytoseiulus persimilis Athias Henriot and Stethorus punctillum Weise, depending on the suitable temperature and humidity of each predator. The experiments were carried out at commercial plastic greenhouses for two seasons. Once the mite T. urticae infestation was detected, the predators were released. The predator, P. persimilis was released three times, with a rate of 9/m2. It increased when the temperature and humidity ranged from 25.5–29°C and 72.8–86.4% RH, respectively, while it disappeared when the temperature increased above 30°C. There was a negative correlation between P. persimilis and temperature, but a positive correlation with relative humidity. The predator, S. punctillum, was released twice, at a rate of 0.5/m2. It increased when the temperature and humidity ranged from 31.8–35°C and 65–77% RH, respectively. There was a positive correlation between S. punctillum and temperature, but a negative correlation with relative humidity. In the two seasons, the population numbers of the mite T. urticae decreased gradually to nil/cm2/croton leaf in the biological greenhouse. In the control greenhouse, the population of T. urticae increased to 59.47 ± 6.34 and 85.63 ± 10.45/cm2/croton leaf in 2019 and 2020, respectively, at the end of the season. Integration of the two predators, P. persimilis and S. punctillum was able to achieve effective control of T. urticae when used according to the suitable temperature for each predator in croton greenhouses.