Interspecific Interaction Between Phytoseiulus macropilis and Neoseiulus californicus (Acari: Phytoseiidae) Preying on Tetranychus urticae

The flower trade in Brazil is growing and emerging as a highly profitable business sector. In 2014, the sector gained approximately US$1.42 billion, and 8% growth is estimated for 2015 [1].

The state of Minas Gerais, Brazil, is a leader in this sector, particularly for the production of rosebushes (Rosa spp.) and other conventional cutting flowers. Although up-to-date data for this activity in Minas Gerais are not available, the primary municipalities for flower production in this state are Barbacena, Andradas, Araxá, and Munhoz [2].

The Asian rosebush grows well in Brazil and is cultivated in various Brazilian regions, with much of the production in greenhouses. Although the greenhouse environment provides better conditions for the control of pests and diseases, the environment is also more favorable for pests and diseases to develop. The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is a pest mite that deserves special attention as one of the major problems to affect rosebushes in protected cultivation systems [3].

Pest control is one of the challenges for the cultivation of flowers and ornamental plants, because any damage caused by insects and other arthropods to flowers and foliage makes them unacceptable to consumers, and therefore depreciates the final product to be marketed [4].

Although producers and consumers strongly demand reduced use of agrochemicals [5], the spraying of chemical pesticides remains the primary tactic for the control of pests and diseases. Spraying is often used for prevention [6], which causes ecological disequilibrium and environmental contamination in many cases [7], particularly when these products are misused, such as erroneous doses of plant protection products, unnecessary spraying beyond recommended, use of unregistered products for the crop etc.

The concerns of consumers for human health and environmental preservation have encouraged researchers to investigate the use of less aggressive agricultural practices that promote sustainability in agroecosystems [6]. Therefore, in the ecological management of pests, practices that preserve natural enemies in the environment are essential, and the use of selective products that minimize harmful effects to non-target fauna and maintain the ecological balance of the agroecosystem is indispensable [8].

Biological control is an important alternative for pest management. In addition to providing efficient control, biological control can add value to an agricultural product when well-planned and implemented, because an image can be established for consumers of a product that is produced ecologically [9].

The predatory mites Neoseiulus californicus (McGregor) and Phytoseiulus macropilis (Banks) (Acari: Phytoseiidae), among others, are used for the biological control of two-spotted spider mites on fruit trees, ornamental plants, and other crops. This method of biological control reduces the amount of chemical pesticides used for cultivation and includes the other benefits of reduced exposure of workers to chemicals and fewer residues in the environment [10].

The predatory mites can be classified into 4 types, and Type I were subdivided into subtypes to highlight the specificity in relation to the pest mite. In this group is P. macropilis being a mite of subtype I-a, that is, specialized in predating the genus Tetranychus. Type II mites are those that are selective of Tetranychidae mites but can also be fed from other genera or group of mites such as Tydeoidea, Eriophyidae, Tarsonemidae or even pollen. Although some authors question that N. californicus should be classified as Type III of predatory mites, they are maintained as Type II because they are associated with mites that produce large amounts of webs such as T. urticae. Type III of predatory mites does not get along with mites that produce webs because they can often get stuck in them. These Type III are those that are generalists and have also been subdivided into subtypes according to their habitat. Type IV of predatory mites are those for which pollen is an important part of the diet [11].

In Europe and the United States of North America, the cost of biological control methods may be similar to the cost of chemical control, particularly when the number of predators released is based on an estimation of the pest density, which makes biological control an attractive alternative for pest management [12] [13].

However, for biological control with predatory mites to be a viable solution in the productive sector, the biological characteristics and efficiency of these predaceous mites for pest control must be determined, and therefore investigations are required of the interactions between predatory mites.

Therefore, the objective of this study was to investigate the biological control of the two-spotted spider mite, T. urticae, on rosebushes growing in a greenhouse with the individual or joint release of the predatory mites, P. macropilis and N. californicus.