Euseius scutalis

K, Zahra Gorji, K, Parviz Shishehbor, K, Farhan Kocheili & K, Elham Riahi, 2024, Quality control of the predatory mite Euseius scutalis (Acari: Phytoseiidae) againstTetranychus turkestani (Acari: Tetranychidae) over 30 generations of rearing on cattail pollen, Acarologia 64 (3), pp. 819-832 : 821-822

How Euseius scutalis performs before and after long-term rearing on cattail pollen

A random selection of around 150 E. scutalis females was taken from the stock colony and then moved to an experimental unit for oviposition. When the oviposited eggs hatched, defrost cattail pollen ( Typha latifolia L.) collected from Dorud County, Lorestan Province, Iran, was offered to mites until they reached adulthood (G1). The diet of female progeny from the first generation was kept unchanged for as long as 30 generations (G30). After 10 (G10), 20 (G20),

and 30 (G30) generations, the life table parameters of E. scutalis were estimated when switched to T. turkestani . The trial was set-up with four treatments: individuals from the stock colony

(G0), individuals reared on cattail pollen for 10 generations (G10), individuals reared on cattail pollen for 20 generations (G20), and those raised on cattail pollen for 30 generations (G30)

were compared. About 100 females were first randomly chosen from the related cultures and put in experimental arenas for 24 hours. The newly laid eggs were transferred individually to the experimental units. After the eggs hatched, T. turkestani was added to the units and the number of consumed prey was replaced daily by new ones. The number of prey provided to each experimental unit was increased by changing the predator stage. Specifically, 20, 25,

30, and 50 immature stages of T. turkestani were offered as food at the larval, protonymphal, deutonymphal, and adult stages, respectively. Each day, experimental arenas were checked and the duration and survival of each life stage were documented. The males and females of each treatment were paired immediately after the adults appeared. When there were more females than males or if a male who was paired with a female died, additional males of the same age from the laboratory colony were paired with them; however, the longevity and number of consumed prey were not documented. There were 51, 41, 43, and 45 replicate experimental arenas used, respectively for the treatments mentioned earlier. The daily data recording was conducted to determine the pre-oviposition period, oviposition days, adult longevity, survival, and fertility. The observations were carried on until all adults had died. The daily sex ratio was estimated by collecting eggs during the oviposition period daily and kept in the same conditions as their female parents until adulthood.

The predation ability of E. scutalis was assessed in G0, G10, G20, and G30 populations in life table experiments as well. Daily recording of the number of dead T. turkestani was done until all predators died. To distinguish between the number T. turkestani of preyed by male and female of E. scutalis , the predation rate of 20 males was examined under the same conditions. The female daily consumption rate was determined by subtracting the average male consumption from the consumption of pairs (Farhadi et al. 2011). All the experimental units were placed in a growth chamber at 25 ± 1 °C, 60 ± 10% RH, and a photoperiod of 16L:8D h.

Statistical analysis

Using TWOSEX-MSChart, the age-stage, two-sex life table method was applied to analyze the life history data of E. scutalis ( Chi & Liu 1985 ; Chi 1988 ; Chi 2023a). The TWOSEX-MS

Chart program was used to estimate age-stage-specific survival rate s (xj), age-stage-specific fecundity f (xj), age-specific fecundity m (x), age-specific survival rate (l x), and age-specific fecundity m (x), as well as population growth parameters for each treatment ( Chi 2023a). By using this program, the bootstrap method with 100000 re-sampling was used to estimate the means and standard errors of different stage durations, total pre-oviposition period (TPOP), adult pre-oviposition period (APOP), fecundity, oviposition days, and adult longevity, and the life table parameters [intrinsic rate of increase (r), finite rate of increase (λ), gross reproductive rate (GRR), net reproductive rate (R 0), and mean generation time T ()] ( Chi 2023a). The mean of all parameters was compared between different treatments using the paired bootstrap test.

The computer program CONSUME-MS Chart ( Chi 2023b) was used to analyze the daily consumption of all individuals. To compute the age-stage predation rate c xj (), the daily consumption of each individual was taken into account. The mean number of T. turkestani preyed by an individual E. scutalis during its life span C (0), the number of T. turkestani required for the production of an offspring from a E. scutalis (Qp) , the entire consumption capacity of a stable population whose maximum value is one (ψ), and the predation potential of E. scutalis population by combining its growth rate (λ), age-stage predation rate c xj (), and stable age-stage structure (a xj) (ω) were computed based on Chi and Yang (2003). The bootstrap resampling method was used to estimate the variations and standard errors of predation parameters. Different stages’ predation rates were compared using the Tukey test P (<0.05) (SPSS 21.0).

Using the TWOSEX-MS Chart program, the comparison of C 0, Qp, ψ, and ω was made based on the paired bootstrap test (with 100,000 resampling) ( Chi 2023a).