Life history of Neoseiulus californicus ( McGregor , 1954 ) ( Acari : Phytoseiidae ) fed with castor bean ( Ricinus communis L . ) pollen in laboratory conditions

The predatory mite, Neoseiulus californicus (McGregor, 1954) (Acari: Phytoseiidae) is one of the principal natural enemies of tetranychid mites in several countries, promoting efficient control of those mites in several food and ornamental crops. Pest attacks such as that of the spider mite, Tetranychus urticae Koch, 1836 (Acari: Tetranychidae), is one of the problems faced by farmers, especially in the greenhouse, due to the difficulty of its control with the use of chemicals because of the development of fast resistance making it hard to control it. The objective of this work was to study the life history of the predatory mite N. californicus as a contribution to its mass laboratory rearing, having castor bean plant [Ricinus communis L. (Euphorbiaceae)] pollen as food, for its subsequent use as a natural enemy of T. urticae on a cultivation of greenhouse rosebushes. The studies were carried out in the laboratory, at 25 ± 2°C of temperature, 70 ± 10% RH and a 14 hour photophase. The biological aspects and the fertility life table were appraised. Longevity of 32.9 days was verified for adult females and 40.4 days for males. The intrinsic rate of increase (rm) was 0.2 and the mean generation time (T) was 17.2 days. The population doubled every 4.1 days. The results obtained were similar to those in which the predatory mite N. californicus fed on T. urticae.


Introduction
The predatory mites of the family Phytoseiidae constitute one of the principal natural enemies of phytophagous mites on the rosebush (Rosa spp.) culture, as well as in other ornamental and horticultural cultures produced in greenhouses, where they find favourable conditions which enable their possible use in biological control.Among the principal species of predatory mites used in the greenhouse there is the Neoseiulus californicus (McGregor, 1954) (Phytoseiidae) (REIS et al., 2005).
Biological control with the use of predatory mites is widely employed in North and South America, Asia and Europe.In Brazil, the species N. californicus and Phytoseiulus macropilis (Banks, 1904) are the most studied, therefore, besides being effective in the control of the spider mite in various cultures, they are already commercially produced, which allows their mass liberation in crops (SATO et al., 2002a;POLETTI et al., 2006).
The predation capacity of N. californicus is approximately fifteen to twenty spider mite eggs per day, feeding on all of the biological stages of the prey.As it is a generalist, it can also feed on other sources, such as pollen, other mites, thrips and aphids, thus surviving for days without the presence of the prey in the field (MORAES and FLECHTMANN, 2008).
Works conducted in Brazil on the use of predatory mites, especially N. californicus and P. macropilis, have been revealing high potential of those species in the control of Tetranychus urticae Koch, 1836 (Acari: Tetranychidae), mainly in protected cultivations systems (SATO et al., 2002b(SATO et al., , 2006;;POLETTI et al., 2006).
The two spotted spider mite, T. urticae, cosmopolitan and polyphagous, is considered one of the most important pest mite species.It is described as attacking more than 1,100 species of plants in 140 families of economic value (GRBIĆ et al., 2011;UNIVERSITY OF UTAH, 2011).
In the greenhouse, the maintenance of relatively stable environmental conditions for the development of plants usually favours the fast development of the pest, increasing the population before the producer notices.For dealing with a closed and artificial environment, it hinders the appearance of natural enemies and favours the fast evolution of pest mite resistance to the pesticides used (ZHANG, 2003).
The permanent study of management of pests that occur in protected cultivation systems is necessary in order to ensure efficient, economic, and ecologically sustainable control.
A common method to control the spider mite is the application of synthetic acaricides (SATO et al., 2007).
However, in many situations, the synthetic acaricides have selected resistant populations, generating the need for additional spraying and/or dosage increases (SATO et al., 2007(SATO et al., , 2009)).
Keeping in mind the need for efficient, less troublesome control, that is health friendly to the rose farmers, as well as contributing to environmental preservation, the study of the management of this culture regarding pest incidence, mainly the incidence of the spider mite, T. urticae, and its biological control with predatory mites, is necessary considering successful experiences that have been occurring throughout the world in several greenhouse cultures (OPIT et al., 2004;FERRERO et al., 2011;ALATAWI, et al., 2011).
In a greenhouse, the development cycle of the mite T. urticae is highly variable in function of the temperature, but under hot and dry weather conditions, it can complete its cycle in only seven days.High temperature and low relative humidity conditions favour the development of that mite.The egg to adult biological cycle has an average duration of ten days, and it is easily adaptable and possesses a high ability to acquire resistance to phytosanitary products (REIS et al., 2005).
This work was conducted with the aim of studying the biological parameters of the predatory mite N. californicus fed with pollen of castor bean plant (Ricinus communis L., Euphorbiaceae) as a contribution to its mass rearing and use in the biological control of T. urticae in the greenhouse.

Material and Methods
The experiments were conducted in the Acarology Laboratory of the Centro de Pesquisa em Manejo Ecológico de Pragas e Doenças de Plantas -EcoCentro, ofthe Empresa de Pesquisa Agropecuária de Minas Gerais -EPAMIG Sul de Minas, atthe Universidade Federal de Lavras -UFLA campus, in Lavras, MG, at 25 ± 2 °C of temperature, 70 ± 10% RH and a 14 hour photophase.

Maintenance rearing of Neoseiulus californicus and Tetranychus urticae
The rearing of N. californicus was initiated with mites from a pre-existent rearing on Jack-bean leaves, Canavalia ensiformes (L.), free from pesticide application and infested with T. urticae, located in the Acarology Laboratory do Instituto Federal de Educação, Ciência e Tecnologia do Sul de Minas Gerais, campus de Inconfidentes, MG.The mites were taken to the Laboratory of EcoCentro in Lavras and were maintained in 3 cm diameter arenas of flexible PVC plastic, floating in distilled water in 15 cm diameter Petri dishes, according to the methodology of Reis and Alves (1997).The predators were fed with castor bean pollen.

Biological aspects of Neoseiulus californicus
All the biological characteristics of N. californicus were obtained with castor bean plant pollen as food.
The studies were conducted in 3 cm diameter arenas, made with black flexible plastic PVC sheets, floating in water in 15 cm diameter Petri dishes 2 cm deep, as mentioned previously.
For the observation of the embryonic stage, eggs of the predator with less than 12 hours of age were individualised and maintained on disks, totalling 5 five arenas per 15 cm diameter Petri dish, in a total of 20 dishes, which resulted in the study of 100 eggs of the predator.The eggs were observed daily at 8:00 a.m. and 4:00 p.m. to determine the moment of larval eclosion.
After the eclosion of the larvae, the duration (in days) was observed of each developmental stage (larva, protonymph, deutonymph) and the egg-adult stage duration was calculated.
In the post-embryonic development, observations of the immature forms were also conducted twice per day, at 8:00 a.m. and 4:00 p.m..A hundred specimens were used for evaluation of the predatory immature stage.In the adult phase only one observation per day was made, at 8:00 a.m., in couples formed with the females still in the deutonymph stage.The males that died were substituted by others from the laboratory rearing.

Fertility life table of Neoseiulus californicus
Starting from the formation of the couples, with surviving females of the post-embryonic development study, the pre-oviposition periods, oviposition, post-oviposition and the longevity of the female and male were observed, using the methodology described by Reis et al. (2007) in the life history study of Amblyseius herbicolus (Chant, 1959) (Phytoseiidae).
To construct the fertility life table, each couple was confined in black flexible plastic PVC disk arenas of 3 cm in diameter, floating on distilled water, totalling 5 arenas per 15 cm diameter Petri dish, for a total of 20 dishes or 100 couples.
Each predator couple was evaluated every 24 hours, with the supply of castor bean pollen as food and the removal of the eggs.
For the calculations, the methodology of Andrewartha and Birch (1954) 1 apud Silveira Neto et al. (1976) was used.With the values obtained of age intervals (x), specific fertility (Mx) and survival probability (Lx) the following were calculated: the net reproduction rate (R o ), the mean generation time (T), the intrinsic rate of increase (r m ), the finite rate of increase (λ) and the time required for the population to double in the number (TD), which, according to Tanigoshi et al. (1975) is equal to ln 2 /r m .

Results and Discussion
The results obtained of the biological aspects and fertility life table having castor bean pollen as food will be presented and discussed.
L. (Typhaceae), as food and did not observe statistical differences when comparing the results obtained with the T. urticae and pollen diets.According to the author, the results with the other foods, than that with T. urticae and pollen diets, were not satisfactory for the development of the predator.

Fertility life table of Neoseiulus californicus
The results of the fertility life table showed that the estimate of the innate capacity for predator population growth (r m ) was 0.17 females/female/day.This results were close to that observed by Canlas et al., (2006), Vasconcelos, (2006) (Tables 3 and 4).
In studies of the biology of N. californicus fed with holm oak pollen, Quercus ilex L. (Fagaceae), Preverieri et al. (2006) observed a higher value for the intrinsic rate of increase (r m = 0.28), suggesting that the pollen of that plant can be used satisfactorily for rearing of N. californicus.
The mean generation time (T) was 17.2 days, the net reproduction rate (R o ) was 18.7 females and the finite rate of increase (λ) was 1.2 females/day.The mean generation time and the finite rate of increase were similar to the values found by Canlas et al. (2006) with the predator feeding on T. urticae, there not being large differences when compared with castor bean pollen in this study.The population is estimated to double (TD) every 4.07 days (Table 4).Rahmani et al. (2009) verified that the finite rate of increase (λ) was 0.04 when N. californicus fed on T. tabaci and in the present study with castor bean pollen it was 1.2.It is known that the higher the finite rate of increase, the higher the daily population growth.However, it should be taken into account that the ideal laboratory conditions are considered for the reproduction and development of the predatory mite.In the greenhouse and mainly in the field, it is expected that the predatory mite is subjected to various ecological factors that can alter its reproductive and developmental capacity.

Table 1 .
Duration in days of immature stages of Neoseiulus californicus, at 25 ± 2° C of temperature, 70 ± 10% RH and a 14 h photophase, fed on castor bean plant (Ricinus communis) pollen, compared with three works where the food was Tetranychus urticae.

Table 2 .
Duration in days of the of pre-oviposition, oviposition, post-oviposition periods and number of eggs laid per day by females of Neoseiulus californicus at 25 ± 2° C, 70 ± 10% RH and a 14 h photophase, fed on castor bean plant (Ricinus communis) pollen, compared with four works where the food was Tetranychus urticae.