P. persimilis preys exclusively on spider mites such as Tetranychus spp. which feed on plants. Therefore, the most common method for rearing P. persimilis is on ...
Rearing and mass production of the predatory mite P h y t o s e i u l u s p e r s i m i l i s D. Fournier, P. Millot & M. Pralavorio
LN.R.A., Station de Zoologie et de Lutte Biologique 37, boulevard du Cap, 06 602 Antibes, France
Keywords: Acari, Phytoseiulus persimilis, predator, rearing, conservation, release
Abstract A method for mass rearing Phytoseiulus persimilis Athias-Henriot is proposed. This predacious mite is maintained in rearing units composed of cylinders which contain leaves heavily infested with Tetranychus urticae Koch. The bottom of the cylinders is made of gauze. Fresh cylinders with prey are placed at regular intervals on tops of older ones and predators will migrate upward. Empty cylinders at the undermost position are removed. Production takes place in a controlled-environment room under optimal temperature and humidity. Harvesting of predators in bran which can be easily disseminated over the crops is also described. A method of estimating the conserved populations is proposed.
Introduction The use of Phytoseiuluspersimilis for controlling Tetranychus urticae has considerably increased since the first trials by Bravenboer & Dosse (1968). Laboratory rearing methods have been designed for studying this predatory mite. Some of these methods have been applied for larger scale production of predators for biological purposes. The following paper describes a method of laboratory rearing, originally designed for genetic studies, which has been tested for its feasibility for mass rearing. It has yielded better results than the methods currently used. P. persimilis preys exclusively on spider mites such as Tetranychus spp. which feed on plants. Therefore, the most common method for rearing P. persimilis is on plants infested with tetranychids (Bravenboer, 1975). The disadvantage of this method is that three levels of trophism (plant, prey, predator) must be simultaneously controlled to get maximal predator numbers at harvest without heterogeneity throughout the production unit. Rearing on cut leaves infested with tetranychids is Entornol. exp. appl. 38, 97-100 (1985). 9 Dr W. Junk Publishers, The Hague. Printed in the Netherlands.
frequently used in the laboratory (Bakasova, 1978) and this approach avoids the synchronization problems encountered in the previous method. In other methods prey is collected from heavily infested leaves by brushing the spider mites off the leaves (Theaker & Tonks, 1977) or by applying other techniques (Plotnikov & Kloptseva, 1969; Scopes, 1968; Bakasova, 1976). However, these techniques are usually too laborious for mass rearing. Finally, some rearing tests on artificial medium were carried out by Shehata & Weismann (1972) and Kennett & Hamai (1980), but they resulted only in larval development. We describe here a method of rearing on cut leaves which avoids leaf rotting and allows the easy recovery of P. pers#hilis populations.
Rearing method Biology and behaviour. P. persimilis requires a temperature of 10-30 ~ with an optimum at 25 ~ and over 70-80% humidity (Fournier et al., 1985). T. urticae exhibits a negative geotropism and shows
98 an increased tendency to migrate upward when the plant gets dry, food becomes scarce and humidity decreases (Hussey & Parr, 1963). P. p e r s i m i l i s follows this migration and moves more actively as the food is scarce or, conversely, it remains at sites with high prey density (Sabelis, 1981).
I t
M e t h o d . Prey is reared on healthy bean plants. On-
ly the most severely attacked leaves are harvested by the time the tetranychid population reaches its highest level, viz. just before individuals migrate to fresh leaves. The other leaves are left on the plant: they will be harvested later or serve to infest new plants. The cut leaves are placed in a 30 cm high plastic cylinder as big in diameter as in height, with a large-mesh screen at the bottom (Fig. I). A number of nylon threads are stretched through the inside of the container to prevent leaves from sticking together when fading. When starting the rearing process, a small quantity of predators is placed into the cylinder. Two sealing lids are attached to the top and the bottom of the cylinder. A haemolysis tube inserted into the opening of the top lid indicates at any time the size of the two populations. When predators can be seen in the haemolysis tube, searching food, deficiency of prey in the cylinder is evident. A second cylinder filled with heavily infested leaves is then superposed on top of the first one. All the hungry P. p e r s i m i l i s individuals capable of moving migrate into the upper cylinder through the large meshes of the screen which separates them from food. When the last eggs have hatched, the lower cylinder is empty of preys and predators. Then the predators can continue to breed until food becomes scarce. At that point, a third cylinder is added to the cage, etc. When the cage becomes too high, the lower units, which are free of mites, are removed without affecting the rearing process. The rearing units are installed in a controlled-environment room at a temperature which may vary from 15 ~ to 25 ~ depending on the urgency of the need of predators. The relative humidity in the cage should be close to 80-90%, with some openings on the sides or with air blowing through it. Harvesting,
storing and releasing the predators.
Once the predator population has reached its highest level, the animals can be collected. As the population has concentrated in a small number of leaves,
f
F
aI
C
13
li
t Fig. 1. P. persimilis rearing cage. A: dry bean leaves without
mites (time1). B: bean leaves+ tetranychids+ predators (time 2). C: fresh bean leaves+ tetranychids (time 3). t: haemolysis tube (opening). a: clamp. F: nylon thread network, ae: aeration. Cage d'blevage de P. persimilis.A :feuilles sbches sans acariens. B: feuilles de haricot + tbtranyques + prbdateurs. C:feuilles de haricot frafches + tbtranyques, t: tube ?t h~molyse, a: blastique. F: rbseau de fils de nylon, ae: abration.
99
e
!
The bran used for harvesting and storing the phytoseiid mites may also be used for disseminating them over the field (Jones et al., 1977; Ables et al., 1979; B. K. Koppert, pers. comm.). The mites plus bran are packed in small carton containers and populations are simply homogenized by rotating them round their axis. They are distributed over the crop with emphasis to the places where the infestation by spider mites is largest.
A
Discussion and conclusion
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Fig. 2. Method of recoveringmites in bran. A: rearingcylinder. B: bottom Lid(bran + predators). Mbthode de rbcupbration des acariens dans le son. A: cylindre d'blevage. B: couvercle (son + prbdateurs).
the insects can be removed by using an aspiratory. However for field trials, it is advisable to trap the predators in bran which has been initially sieved and wetted to 90-95% moisture by means of a draft passing first through water and then through a potassium nitrate solution. The bran is directly poured at a rate of 100-200 cc per liter of cylinder. The cylinder containing a population ready to harvest is stirred, the bran passing between the leaves will trap most of the mites which will fall onto the bottom lid (Fig. 2). The cylinder is then put back into the rearing unit and the mites that still remain in it are used for further breeding. The bran which contains the predators may be held at 10 ~ in a 95% wet air draft to prevent drying. The efficacy and length of conservation depend on the amount of prey put initially or added subsequently after extraction using the same technique. At this point it is easy to determine the number of predators: an aliquot part of bran is taken and placed in dry atmosphere in an open container placed in a tray with water to which a few drops of detergent are added. The number of phytoseiid mites is then estimated by counting the individuals that escaped out of the dry bran and will drown in the water.
This method has many obvious advantages: the area for rearing tetranychids can be reduced, and environmental conditions can be perfectly controlled. Problems due to variation in climate, space and time as encountered in standing crop production are thus avoided. Production can be easily modified by varying the temperature of the rearing room and the number of occupied cylinders. This rapid and easy-to-use method requires little technical skill and allows a reliable estimation of the populations released in the field, and (5) may be useful for genetical studies. By using a smaller cylinder, it allows independent rearing of several strains. After experimenting during 5 years on a small scale, it appears that the main problems encountered are inherent to any rearing of P. persimilis. Problems are related to the continuous production of healthy bean plants or to the production oftetranychids. The rearing units should be frequently monitored to avoid any excessive increase in humidity causing leaf rotting and to avoid the starving of some individuals: P. persimilis is very susceptible to the lack of food (Fournier et al., 1985). According to our first estimates, rearing in a cylinder 30 cm high X 30 cm in diameter can supply 500-2 000 adults daily. This amount would be two to five times higher than that obtained with the glasshouse method, but the results of glasshouse production are, in fact, too variable to be used for comparison purposes. R6sum6 Une nouvelle mbthode d'blevage et de p r o d u c t i o n de masse de l'acarien prkdateur, Phytoseiulus per-
similis
100 Une m6thode d'61evage de Phytoseiuluspersirnilis permettant une production continue est propos6e. La multiplication des auxiliaires a lieu dans des unit6s d'6levage form6es de cylindres contenant des feuilles fortement charg6es en Tetranychus urticae et renouvel6es r~guli~rement par juxtaposition d'un nouveau cylindre. La production a lieu dans une salle climatis~e ce qui permet de maintenir des conditions de temp6rature et d'hygrom~trie optimum pour le d6veloppement de P. persimilis. La r6colte des pr6dateurs dans du son, support facile h diss~miner dans les cultures est 6galement d~crite, une m6thode d'estimation des populations de conservation est 6galement propos6e.
References Ables, J. R. et al., 1979. Methods for the field release of insect parasites and predators. Trans. Am. Soc. Agr. Engineers USDA 22:59 62. Bakasova, N. F., 1976. 'Elevage de Phytoseiuluspersimilis A. H. durant rautomne et l'hiver' (in Russian). Zashch. Rast. 38: 3-5. Bakasova, N. F., 1978. 'Instructions provisoires concernant les m6thodes d'~levage et de conservation des femelles de Phytoseiulus persirnilis A.H.' (in Russian). Ed. VIZR Leningrad, 2-8. Bravenboer, L., 1975. Biological control in protected cultivation. Semaine d'~tude agriculture et hygiene des plantes, 8-12 sept. 1975, Gembloux, 289-296.
Bravenboer, L. & G. Dosse, 1962. Phytoseiulus riegeli Dosse als Pr~idator einiger Schadmilben aus der Tetranychus urticae Gruppe. Entomol. exp. appl. 5: 291-304. Fournier, D., M. Pralavorio & O. Pouri~re, 1985. Etude du phytos~iide Cydnodrodromus chilenensis Dosse en vue de son utilisation contre Tetranychus urticae Koch sur fraisier. Entornophaga (in press). Hussey, N. W. & W. J. Parr, 1963. Dispersal of the glasshouse red spider mite Tetranychus urticae Koch. Entomol. exp. appl. 6:207 214. Jones, S. L. et al., 1977. A new and improved technique for the field release of Trichogramma pretiosum. The southwestern Entomologist 2:210 215. Kennett, C. E. & J. Hamai, 1980. Oviposition and development in predacious mites fed with artificial and natural diet (Acari, Phytoseiidae). Entomol. exp. appl. 28:109-115. Plotnikov, V. F. & R, 1. Kloptseva, 1969. 'Conservation de Phytoseiulus persimilis" (in Russian). Zashch. Rast. 4: 38. Sabelis, M. W,, 1981. Biological control of two-spotted spider mites using phytoseiid predators. Part. 1: Modelling the predator-prey interaction at the individual level. Agric. Res. Rep., Wageningen, Netherl. 910:242 pp. Scopes, N. E. A., 1968. Mass rearing of Phytoseiulus riegeli Dosse for use in commercial horticulture. PI. Path. 17: 123-126. Shehata, K. K. & L. Weissmann, 1972. Rearing the predacious mite Phytoseiuluspersimilis Athias-Henriot on artificial diet (Aearina:Phytoseiidae). Biologica (Bratislava) 27: 609-615. Theaker, J. L. & N. V. Tonks, 1977. A method for rearing the predacious mite, Phytoseiulus persimilis (Acarina:Phytoseiidae). J. Entomol. Soc. Brit. Columbia 74: 8-9.
Accepted: December 6, 1984.
