Tetranychus urticae, Koch, 1836

Santana, Mauricéa Fidelis de, Câmara, Cláudio A. G., Monteiro, Vaneska Barbosa, Melo, João Paulo Ramos de & Moraes, Marcilio Martins de, 2021, Bioactivity of essential oils for the management ofTetranychus urticae Koch and selectivity on its natural enemy Neoseiulus californicus (McGregor): A promising combination for agroecological systems, Acarologia 61 (3), pp. 564-576 : 566-567

Rearing of Tetranychus urticae and Neoseiulus californicus

Specimens of T. urticae were originally collected in 2008 from grapevine Vitis (vinifera L.) in the municipality of Petrolina in the state of Pernambuco, Brazil (09°12 ′ 43.9 ″ S, 40°29 ′ 12.7 ″ W)

and then maintained in the laboratory on jack bean Canavalia (ensiformes L.) at 25 ± 1 °C, 65 ±

5% relative humidity and a 12-h photoperiod without any exposure to acaricides. The predator mite N. californicus was collected from the municipality of Bonito in the state of Pernambuco, Brazil (08°28 ′ 13 ″ S, 35°43 ′ 43 ″ W) on chrysanthemum ( Dendranthema grandiflora Tzvelev. )

and bred in the laboratory since 2010 with no exposure to acaricides. The breeding method of T. urticae and N. californicus was according to methodology used by Born et al. (2018).

The predator mite was reared in plastic arenas (25 cm diameter) maintained in B.O.D. at a mean temperature of 27 °C and a 12-h photoperiod. Jack bean leaf was placed with the margin surrounded by moistened hydrophilic cotton to avoid the escape of the mites. Cotton fibers were placed on the jack bean leaves to stimulate oviposition. As a food source, T. urticae and castor bean pollen ( Ricinus communis L.) were offered every 2 days.

Residual contact assay

The leaf disc painting method described by Araújo et al. (2020) was used to test the action of C. aurantiifolia , C. limon , C. sinensis var. mimo , L. sidoides , C. rhamnifolioides , P. divaricatum , C. grewioides and positive control (Azamax) by contact toxicity. The experiments were performed with open Petri dishes (10 cm diameter). Leaf discs (5 cm diameter) were cut from leaves of greenhouse-grown jack bean C (. ensiformes). Test solutions were prepared by diluting the EO in water and DMSO (Dimethylsulfoxide) (0.5%) (negative control). The concentration used in the bioassays ranged from 0.009 to 5.40 μL mL−1 for the EO. The concentration of the botanical and conventional insecticides used as positive control ranged from 0.009 to 10 μL mL−1 for Azamax. Leaf discs (5 cm diameter) were immersed in solutions for 30s. Control mites were held on leaf discs immersed in the water and DMSO. Each leaf disc was infested with 15 adult females of T. urticae . Five replicates were used in each bioassay and repeated 2×

on different dates using a completely randomized design, totaling 150 mites per concentration. Mortality was determined under a dissecting microscope 24 h after the onset of treatment. Mites were considered dead if the appendages did not move when prodded with a fine paintbrush. The residual contact assays were performed at 25 ± 1 °C, 65 ± 5% RH and a 12-h photoperiod. Fifty adult females of T. urticae were placed on leaf discs (8cm diameter) for 24 hours to effect oviposition. After that period, T. urticae were removed. The leaf discs with T. urticae eggs were immersed in the concentrations of EO, Azamax and control (water and DMSO) (adaptated from Esteves-filho et al. 2013). Subsequently were placed to dry for 30 minutes at room temperature. Each leaf disc 300 eggs were left, which served as contaminated food for N. californicus . Each leaf disc was infested with 15 adult females of N. californicus . Five replicates were used in each bioassay and repeated 2× on different dates using a completely randomized design, totaling 150 mites per concentration. Mortality was determined under a dissecting microscope 48 h after the onset of treatment. Mites were considered dead if the appendages did not move when prodded with a fine paintbrush. The residual contact assays were performed at 25 ± 1 °C, 65 ± 5% RH and a 12-h photoperiod.

Ovicide assay

The methodology used in this test was adapted from Esteves-Filho et al. (2013). Leaf discs

(5 cm diameter) were cut from leaves of greenhouse-grown jack bean C (. ensiformes). Leaf discs were infested with 15 adult females of T. urticae , which were maintained for 24 hours for oviposition. Then leaf discs with eggs of T. urticae were immersed in the concentration of each oil, azamax and control, as bioassays described above. Subsequently were placed to dry for 30 minutes at room temperature. Each leaf disc 50 eggs were left. Each bioassay and repeated 3× on different dates using a completely randomized design, totaling 150 mites per concentration. Evaluation was performed after 96 hours of application of oil, azamax and control, which is recorded the number of emerged larvae.

Statistical analysis

For the determination of the lethal concentration necessary for a 50% mortality rate (LC 50)

and 90% (LC 90) of the mite population in the residual contact tests, the mortality data were analyzed using the Probit model implemented in the POLO-Plus 2.0 (LeOra Software 2005) program, with the calculation of 95% confidence levels. Toxicity ratios (TR) and RS (Relative Selectivity) were determined based on the method described by Robertson and Preisler (2017).