Phytoseiulus persimilis

Phytoseiulus persimilis belongs to the family Phytoseiidae, the order Parasitiformes. In natural conditions Phytoseiulus occurs in the countries of tropical climate only. It is successfully introduced in many countries of Europe and America. In Ukraine this predatory mite is widely applied for the defense of vegetable crops in glass-covered ground.

The size of an acariphage body is about 0.5 mm. Its coloration varies from orange-red to dark-red, sometimes cherry. The egg is oval, lactescent-white with a yellow-orange tint. Its size is 0.18–0.21 mm. The egg is well differs from the smaller (0.14 mm) and sphere-shaped egg of the spider mite. The egg of the acariphage requires more stable hydrothermal conditions than the larva, the nymph and the adult individual. The larva is hexapod (six-legged), yellow-orange, 0.17–0.2 mm in length. The larvae are not very motile and don't feed. Under usual conditions the cycle of Phytoseiulus ontogenesis is shorter than the spider mite development and takes about 5 days at 30°C, 9 days at a temperature of 20°C and 25 days at a temperature of 15°C. The female lays 2–6 eggs per day and during life cycle does 106–108 eggs. The life span of the acariphage is 20–25 days. Because of tropical origin P. persimilis has no the stage of diapause and operates during the whole year in glass-covered habitations. Sex ratio is generally 1:4 in favour of female individuals.

Concerning food specialization Phytoseiulus is a typical oligophage. It feeds on representatives of the family spider mites: the two-spotted spider mite (Tetranychus urticae), the garden spider mite (Eotetranychus pruni), the hawthorm red spider mite (Tetranychus viennensis) and etc. There are data about the ability of the predator to suppress species Bryobia lagodechiana (early stages) and Panonychus citri. The prey is sucked out entirely. The predator develops 1.5–1.9 times as faster than the prey (the spider mite). Phytoseiulus is able to feed on the mites of active stages and their eggs. Every day the female of Phytoseiulus eliminates about 30 eggs or 24 individuals of the later stages of the pest. But it prefers to feed on fresh-laid eggs of the prey. Feeding on diapause females of the spider mite the predator kills 4–5 females of the pest, but this food source reduce the fertility of the predator. Without food the female of the predator perishes in 4 days. Under the excess of preys the adult predator kills mainly adult pests and bigger nymphs leaving some number of spider mite nymphs, larvae and eggs for feeding of its larva stage. Having eliminated the main part of pest colony adult predators migrate onto other leaves inhabited by spider mites where again lay eggs and continue their activity. The nymphs of the acariphage almost entirely liquidate the remains of pest colonies and also migrate onto other leaves for the search of food. Phytoseiulus is a very aggressive predator which is well adapted to dwell in the webby colonies of spider mites. Owing to morphological adaptation (long dorsal setae (hairs)) and the specially constituted pre-tarsi (pre-paws) of legs the predatory mite is able to slip between web threads without tangling in it. The cannibalism of Phytoseiulus is slightly expressed.

Phytoseiulus persimilis Phytoseiulus persimilis Phytoseiulus persimilis

Application

The effectiveness of the acariphage in the suppression of spider mites can change dependently on the species of a host-plant. Phytoseiulus can be applied for vegetable crops and ornamental plants in glass-covered ground: the sweet pepper, the cucumber, the tomato, the melon, the eggplant, the strawberry, the gerbera and the rose. It is important to note that its effectiveness is considerably reduced on very fuzzy crops (for example some kinds of tomatoes).

For successful biological control it is important the duly revealing of pest presence in order to respond immediately. The systematical conducting of monitoring allows the presence of pests to be determined in time and the degree of its development to be estimated for the elaboration of the effective system of crop protection. The rate of acariphage invasion depends on the following indexes: the density of crop colonization by the pest, the species of a crop and hydrothermal conditions. In industrial conditions the optimum decision is prophylactic invasions in amounts of 5–10 individuals per 1 m2 every 2 weeks (in dependence on a crop, climate conditions, the level of pest presence). The intensive development of spider mites requires mass invasions: 20–50 individuals per 1 m2 (if necessary invasions are repeated). The terms of the suppression of pest population depends on the initial ratio of predator-prey.

Hydrothermal conditions exert considerable influence on the development of the acariphage. The most favourable temperature for development of the predator is 25–30°C with a relative air humidity of more than 70%. The sum of effective temperatures for the completion of development cycle in dependence on conditions of air humidity fluctuates within 110–130 degree-days (on an average 120). The essential deflections of hydrothermal conditions cause the deterioration of predator activity. In the conditions of low relative air humidity and high temperature it is possible the maintenance of predator activity by means of artificial making of high relative air humidity. It achieves by way of water spraying under high pressure (the systems of humidification, tank sprayers and etc.).

It is effective application of the complex (blend) of acariphages in the system of crop defense against spider mites. Additionally for the suppression of the pest it is possible to use Amblyseius (Neoseiulus) califiornicus, Ambliseius andersoni.

Remark:
Some synthetic pesticides exert negative influence on Phytoseiulus persimilis (the deterioration of activity, part or full mortality). It is possible the treatments with chemicals that are loyal (selective) for the predator.

Advantages

  • application for many crops (vegetable and ornamental);
  • the control of all the pest stages;
  • the high level of activity under the optimum conditions;
  • easy to apply;
  • the ability to suppress to 95% of pest population;
  • the long-term effect of acariphage application.

Transportation and storage

  • keep out of direct sunlight;
  • transport and store at 5–10°C;
  • apply within 18 hours since the moment of reception.