Biological Performance of Tetranychus bastosi (Acari: Tetranychidae) on different hosts

Tetranychus bastosi Tuttle, Baker & Sales (Acari: Tetranychidae) has been observed in more than 36 host species and it is considered a potential pest mite for several crops, however its occurrence is still restricted to Brazil. The present study determined the biological, reproductive parameters and host preference of T. bastosi in three plant species: Morus rubra L. (Moraceae); Ipomoea batatas L. (Convolvulaceae); and Psidium guajava L. (Myrtaceae). The incubation period of T. bastosi eggs was longer in M. rubra (5.9 days), followed by I. batatas and P. guajava (4.0 days for both). The longest larval period was observed in P. guajava (5.7 days). The longest durations of the protonymph and deutonymph stages were recorded in P. guajava (3 days) and M. rubra (2.3 days). However, T. bastosi could not complete its life cicle on P. guajava. The longest period from egg to adult of T. bastosi was observed in I. batatas (30 days). The highest longevity of T. bastosi was observed in the hosts I. batatas and M. rubra (39.8 and 30.2 days, respectively). The longest average duration of a generation (T) was observed on M. rubra 21.3 days. Nevertheless, for the intrinsic capacity for population increase (rm) and finite rate of increase (λ) no differences were observed on I. batatas and M. rubra. In this sense, T. bastosi presents a high biological performance in I. batatas and M. rubra, however P. guajava was not considered a suitable host for the red spider mite.

The oviposition of T. bastosi on its hosts begins after the females have produced a significant amount of web, usually establishing colonies on the abaxial surface of the leaves, causing chlorotic spots and damaging plant growth (Santos et al. 2010; Lima et al. 2017; Barros 2013. Nevertheless, the biological performance of T. bastosi can be influenced by the host plant species, including intraspecific variations of different genotypes (Barros 2013; Lima et al. 2017. Overall, there are few studies regarding ecological aspects and the development of T. bastosi on different hosts of economic crops, as papaya, Carica papaya L. (Caricaceae) and common bean, Phaseolus vulgaris L. (Fabaceae) (Lima et al. 2017) in addition to Jatropha curcas L. (Euphorbiaceae) (Barros et al. 2013; Marçal et al. 2013) and cassava, Manihot esculenta Crantz (Euphorbiaceae) (Lima et al. 2017).
Thus, the objective of the present study was to evaluate the biological performance of T. bastosi on M. rubra, I. batatas and P. guajava to identify the potential for colonization and infestation of T. bastosi on diferente host species.

Tetranhychus bastosi rearing
Stock rearing was maintained in jack bean plants Canavalia ensiformis* L. (Fabaceae), grown in plastic pots (2 L) containing a mixture of soil and Basaplant®^substrate (1:1). Healthy plants were infested through direct contact with leaves of plants infested with the mite. The stock of T. bastosi was maintained at the Laboratory of Agricultural and Forestry Entomology (LEAF/CECA/UFAL) with a temperature of 25±1°C, 70±5% RH and 12h photophase.

Biological features of T. bastosi
To obtain eggs, 50 females of T. bastosi were removed from the stock breeding and placed in an experimental unit for oviposition. The experimental unit consisted of a Petri dish (Ø 9cm) containing a polyethylene foam (1 cm thick), moistened with distilled water. On the set, discs of leaves (Ø 5.0 cm) of the selected host species were placed, surrounded by strips of hydrophilic cotton. Eggs were observed every 12 hours to determine the viability and duration of egg phase. After hatching, the larvae were individualized in experimental units formed inside arenas, which consists of a plastic container (26 cm long, 16 cm wide and 4 cm high) containing inside a polyethylene foam rectangle (20 cm long, 11 cm wide and 1 cm high). In each arena, eight experimental units were formed. Each experimental unit consisted of a 5.0 cm (Ø) leaf disc of the selected host species, surrounded by strips of cotton wool moistened with distilled water, to prevent mites from escaping and maintain leaf turgidity. The mites were observed every 12h, determining the viability and duration of the larva, protonymph and deutonymph stages. After the emergence of adults, males and females were observed separately every 24 hours to determine longevity. Chrysalis phases were not observed. It was not possible to calculate the duration of immature phases considering males and females.
The experiment design was completely randomized, with three treatments consisting of the plant species M. rubra, I. batatas and P. guajava and 100 replications per treatment, where each experimental unit represented a replication. Data were analyzed using the Two-sex life table statistical package (Chi 1988) and the TWOSEX-MSChart program (Chi 2017).

Tetranhychus bastosi fertility life table
Fertility life table parameters were obtained regarding the net reproduction rate (Ro), intrinsic growth rate (r m ), duration of one generation (T), finite rate of increase (λ), stage-age specific survival (sxj), survival rate (lx) and specific fecundity (mx). Data were analyzed based on stage and age, using the Two-sex life table statistical package (Chi 1988) and the TWOSEX-MSChart program (Chi 2017).
Population standard errors were estimated using the bootstrap method. A number equivalent to 100,000 bootstraps was used to obtain stable estimates of standard error. The paired bootstrap test was used to compare statistical differences (Efron and Tibshirani 1993). The computer program TWOSEX-MSChart (Chi 2017) was used for the analysis and calculation of population parameters.

Development of the immature stage
The viability of the immature stages of egg, larva and protonymph of T. bastosi was observed for the three hosts under study, however postembryonic development was completed only in M. rubra and I. batatas (Table 1). The incubation period of T. bastosi eggs showed a statistical difference between M. rubra (5.6 days) and the other plant species involved in the bioassay, I. batatas and P. guajava (4.0 days for both). The longest larval period was observed when T. bastosi was fed with P. guajava (5.7 days), differing from M. rubra and I. batatas (4.0 days). The protonymph stage lasted longer in P. guajava (3.0 days), differing from M. rubra (2.1 days) and I. batatas (1.6 days). The deutonymph stage was not observed on P. guajava, however, when compared to the other hosts, on M. rubra had a longer duration (2.3 days), statistically differing from I. batatas (1.5 days). When the development from egg to adult was evaluated, significant differences between the treatments M. rubra (12.8 days) and I. batatas (9.8 days) were observed. T. bastosi did not complete the cycle (egg-adult) when the host was P. guajava (Table 1).

Stage
Means (± standard error) followed by the same letter in the column do not differ from each other by paired Bootstrap test at 5% significance.

Life table parameters
The larval, protonymph and detonymph stages of T. bastosi overlapped in the two hosts, however the adult stage of T. bastosi achieved a higher survival rate when the mite was fed on I. batatas (Figure 1).
The specific fertility curves (mx) fluctuated throughout the oviposition period, reaching values of 0.0 after 35 days for M. rubra and I. batatas (Figure 2). However, it is evident the expressive growth at the beginning of the oviposition period, around the 10 th day, for both hosts. The maximum increase in specific fertility (mx) of T. bastosi occurs approximately on the 25th day for M. rubra, remaining oscillating and decreasing sharply from the 30th day onwards. For I. batatas, the maximum values of specific fertility (mx) were observed on the 15th day after the beginning of development, decreasing from this period onwards, as observed by the interaction between specific fertility (mx) and survival (lx) (Figure 2).

Discussion
Tetranychus bastosi was able to survive, reproduce and complete its development on M. rubra and I. batatas, however, it could not complete its life cycle on P. guajava. For that, it is suggested that the development of T. bastosi on P. guajava could be inhibited by chemical compounds of the secondary metabolism or limiting morphological factors (presence of trichomes, hairs, viscous substances, etc.) in the immature phase. In this sense, it is possible that new reports of the ocuurence of T. bastosi on P. guajava may be at random, since this host was not a suitable for the red spider mite.
Mites have shown different parameters of development, fecundity and life table, according to the host species, being affected not only by the species but also by the nutritional quality of the host (Helle and Sabelis 1985; Razmjou et al. 2009; Najafabadi 2012. The fecundity of T. bastosi in I. batatas and M. rubra was 15.5 and 18.9 eggs/female, respectively. These values are considered high when compared to the average fecundity of T. bastosi in J. curcas around 10.4 eggs/female (Marçal et al. 2013) and 7.08 to 10.88 eggs/female (Barros 2013). Our results indicate a high reproductive performance of T. bastosi on the hosts, with possibility to achieve major pest status on field, as observerd previously for I. batatas (Lima and Breda 2021). Lower longevity results than those of the present study were reported for females of T. bastosi on J. curcas, ranging from 9.16 to 13.88 days according to Barros (2013) and 16.0 days (Marçal et al. 2013). Females of T. bastosi on P. vulgaris and M. esculenta showed average longevity of 16.9 and 13.0 days, respectively (Lima et al. 2017). Information about the longevity period under controlled conditions may suggest a pre-availability and adaptation between T. bastosi and the host species.
For I. batatas, T. bastosi presented a sex ratio of 1, indicating that all eggs produced by females feeding on this host, origin only females. According to Young et al. (1986) female mites are able to control sex ratio according to several factors, including the oviposition environment and resource quality, however, further investigation is needed to fully understand this parameter. The intrinsic rate of increase adequately summarizes the physiological qualities of a species and can also be assimilated to mites evaluating the ability to increase population (Golizadeh et al. 2017; Southwood andHenderson 2000). In the present study, high net development rates were observed for I. batatas and M. rubra, likewise, the innate capacity for population increase and the finite rate of population increase. Similar results of rm for T. bastosi were observed in J. curcas, P. vulgaris and M. esculenta (0.05, 0.18 and 0.12, respectively) and λ (1.02, 1.20 and 1.13 respectively) (Marçal et al. 2013; Pedro Neto et al. 2013; Lima et al. 2017. Thus, T. bastosi presents a significant biological performance on the hosts I. batatas and M. rubra.

Conclusion
The biological performance of T. bastosi varied among the hosts, revealing that I. batatas and M. rubra are adequated hosts to T. bastosi while P. guajava was not suitable for T. bastosi development. Studies towards differences of biological traits in T. bastosi are scarces but may indicate its potential to achieve major pest status in the field. However, futher studies are needed to fully understand the interactions among T. bastosi and its host plants.