This research clearly showed the effect of temperature on development time of all stages of A. swirskii by way of Lee and Gillespie (2011) and Farazmand et al. (2020) demonstrated that development time of A. swirskii is seriously related to temperature. The results obtained from the present research showed that the egg incubation period of A. swirskii at different temperatures had significant differences and varied from 1.24 to 3.84 d. At 15°C, the length of this period was 3.84 ± 0.19 days and at 30°C, the length of this period was 1.24 ± 0.06 days. Development time recorded in the present research was different from that reported by Farazmand et al. (2020) who noted that the egg incubation period of A. swirskii at 15°C was 7.29 d, in contrast, they estimated this value to be 1.51 d at 30°C, which is almost the same as the result of the current research (Table 2). Lee and Gillespie (2011) stated that the egg incubation period of A. swirskii at a temperature of 25°C is 1.7 d that slightly different from that estimated by the current study (Table 2). This discrepancy may be a repercussion of the rearing methods, experimental conditions, and diets along with differences in data analysis. In the present study, A. swirskii (fed on TSSM) had the shortest larval stage among all biological stages. Our results indicated that durations of the larval (~ 1 day) which was similar to or slightly higher than the populations obtained from the same species. This is a natural mechanism because the larvae are non-feeding and defenseless. But one of the good features of an effective and efficient biological control agent is the short maturation period, which causes the length of one generation to decrease and the efficiency of these agents to increase (Yazdanpanah et al. 2022).We observed the pre-adult duration in both sex (female and male) have significant differences. These figures are similar to those formerly performed on this predatory mite reported by Lee and Gillespie (2011) and Farazmand et al. (2020) who noted a 7-d pre-adult duration at 25°C. Furthermore, Yousef et al. (1982) estimated that this value at 30°C is 5.6 d that was similar the durations that obtained in the current study. The pre-adult duration of this predator mite that feeds on Thrips tabaci Lindeman at 25ºC (7.8 days) reported by Wimmer et al. (2008) are different from those estimated in our study at the same temperature. Since the rate of development and success of predator mites largely depends on the quality and quantity of preys provided (Gotoh and Gomi, 2003), the difference between our results and the literature may be related to this issue. One of the main factors in the success of biological control agents against pests is their development rate, and any natural enemy that has a faster development rate is more likely to be successful in pest control.
The development rate reaches its maximum at the fastest development temperature (Tfast) and in which the population fitness may not be maximum due to high mortality. Based on the results of this research, considering that the maximum development rate was recorded at 32°C among all temperatures tested, it can be considered as the fastest development temperature (Tfast). Using the Janisch/Kontodimonas model, as ranked second fitted model in the preadult stage, the fastest temperature has been seen at 34°C. Similar results have been reported for other phytoseiids mites: Neoseiulus cucumeris (Oudemans) (32°C) (Yazdanpanah et al. 2022), Typhlodromus bagdasarjani Wainstein and Arutunjan (Acari: Phytoseiidae) (34°C) (Ganjisaffar et al. 2011), Neoseiulus womersleyi (Schicha) (Acari: Phytoseiidae) (33°C) (Lee and Ahn 2000), and Phytoseius plumifer (Canestrini and Fanzago) (Acari: Phytoseiidae) (34°C) (Gorji et al. 2008). Amarasekare and Savage (2012) believe that the optimal temperature (Topt), is the temperature at which the value of intrinsic increase (r) reaches its maximum. Accordingly, the optimal temperature of this predator is 27°C (Rahimi et al. 2022). Meanwhile, some researchers demonstrated that the optimal temperature is which the development time and the mortality are the lowest (Aghdam et al. 2009; Shi et al. 2013). In the case of this mite, it seems that 27°C is a more suitable temperature for mass rearing of this predator due to the short development period and total longevity of adults. However, in order to make a comprehensive and correct decision in this matter, more studies are needed on the optimal rearing conditions such as temperature, humidity and also different food sources. There are many reports that the temperature of 35°C and above reduces development rate of phytoseiid mites (Broufas and Koveos, 2001; Broufas et al. 2007; Ganjisaffar et al. 2011; Jafari et al. 2012; Yazdanpanah et al. 2022). Based on the results of the current research, the upper temperature threshold (TU) for immature stages was estimated by the Beta model (45°C).
In the present study, the lower temperature threshold and thermal constant were obtained using both ordinary and Ikemoto linear models. The lower temperature threshold of the egg stage was 17.53°C as estimated by the Ikemoto linear model (Table 3). Our laboratory observations confirm this estimation because at a temperature of 17°C, all larvae of the predatory mite continued to grow, while at a lower temperature, i.e. 15°C, very few eggs hatched and no development was observed. The lower temperature threshold for the development of the egg stage of A. swirskii was 8.09°C, which was estimated by linear models. The lower temperature threshold value is different from that estimated by Frazmand et al. (2020) (11.45°C). Because the T0 estimated by Ikemoto linear was closer to the observed results than ordinary model, the former was accepted for estimating the mentioned parameter. Based on Honek and Kocourek (1988, 1990) T0 decreased if K increased therefore, the thermal constant estimated by the ordinary and Ikemoto model was 133.22 and 86.51 degree-day, respectively. The estimated thermal constant values of A. swirskii (86.51 DD) are different from those estimated for Phytoseiulus longipes Evans (Acari: Phytoseiidae) (28.7 DD) (Ferrero et al. 2007), Neoseiulus cucumeris (Acari: Phytoseiidae) (112.8 and 123.5 DD) (Yazdanpanah et al. 2022), N. californicus McGregor (Acari: Phytoseiidae) (90 DD) (Castagnoli and Simoni, 1999), N. womersleyi (69.36 DD), N. longispinosus (Evans) (Acari: Phytoseiidae) (61.5 DD) (Sugawara et al. 2017), and Euseius finlandicus (93.5 DD) (Broufas and Koveos, 2001). The thermal characteristics may be affected by population (Lee and Elliott, 1998), stage of development (Honek, 1996), and food source (Golizadeh et al. 2007) and the difference may be due to one or a set of the above factors. The R2adj coefficients were higher for the Ikemoto model. This coefficient is used to fit the regression between temperature and growth rate. Although linear models only estimate the lower temperature threshold, this temperature is suitable for analyzing insect population phenology due to the simplification of the analysis (Ikemoto and Kiritani, 2019).
26 nonlinear models were fitted to describe the relationship between A. swirskii development rate and temperature. AIC is used in many studies related to the ranking of models (Zamani et al. 200; Aghdam et al. 2009; Zahiri et al. 2010; Pakyari et al. 2011), because it has the ability to adjust for the quantity of parameters of a model by giving a reprimand to models with many parameters (Akaike, 1974). Our observations showed that the development rate of the egg stage at 32°C was the lowest, i.e. 1.3 days. Based on the results of Table 5, the Beta model is ranked second in describing the temperature-dependent development rate of the egg stage and estimated − 1.041, 38.39 and 31.91°C for lower and upper temperature thresholds and optimum temperature, respectively (Table 5). Similarly, the upper temperature thresholds and optimum temperature for protonymph development were 34.59 and 34°C as estimated by Janisch/Kontodimonas model, which is the third best model based on the AIC. Among the 26 non-linear models fitted, the Ratkowsky model is ranked the first for all stages of egg, larva, protonemph and deutonemph, these results are similar to the results of Shi et al. (2016) who mentioned the Ratkowski model was the best model to describe the development rate for 10 other insect data. In contrast, Mirhosseini et al. (2018( claimed that this criterion is not biologically reliable. Mirhosseini et al. (2018) state that based on their results, more appropriate temperature for Nesidiocoris tenuis (Hemiptera: Miridae) is 28°C, while the Beta model, which ranked second in describing the temperature-dependent development rate of the egg stage, has estimated this temperature to be 34°C. Similar results are seen for y Analytis-1/Allahyari, Hilbert and Logan and Analytis-1 models. Considering that in some researches, the AIC has lacked validity in estimating the minimum temperature (Mirhosseini et al. 2018), it seems that the biological validity in the laboratory and the field as a function of temperature to choose the best model describing the development rate in addition statistical validation is needed. Some researchers have stated that among all the models that describe the development rate of arthropods, the most reliable and beneficial models are those that are designed based on physiological and biochemical mechanism (Shi et al. 2017). These contrasts indicate model selection is critical because of the significant differences between model predictions. Rebaudo and Rabhi (2018) pointed out each of the criteria for model selection has its advantages and disadvantages therefore, a combination of different methods should be used in model selection. The results of the present study provided essential information about the biology of A. swirskii which will lead to better performance of this predator as an impressive biological control agent against pests in greenhouse.
One of the key factors in pest control is knowing the interactions between temperature and development rate of pests on which predators prey are also important for pest control studies. Based on unpublished data (Farazmand et al. 2020) the lower temperature threshold and the thermal constant for the total immature stages of females of T. urticae was 8.71ºC (linear model) and 204.08 DD respectively, and the thermal constant for the total immature stages of Bemisia tabaci (Gennadius) was 390 DD (Muniz and Nombela, 2001). The lower temperature threshold and the thermal constant for total immature stages of A. swirskii females are lower than those above-mentioned. Therefore, it can be assumed that this predator is able to control both of these pests with a higher generation rate. In this study, we demonstrated that A. swirskii appears to be better adapted to higher temperatures, and has the potential to be used as biological control agent against Tetranychus species in greenhouse crops where temperatures are typically high in the summer.