Physiological Selectivity of Agrochemicals to Predatory Mites of Tetranychus urticae (Acari: Tetranychidae) on Rosebushes Growing in Greenhouse
Abstract
The growing of rose (Rosa spp.) in a greenhouse provides favorable conditions for both, the plant and the pest mite Tetranychus urticae Koch (Acari: Tetranychidae), for which chemical control is still used. Consumers' demand has encouraged researches to use less aggressive agricultural practices, making the biological control as a viable option. The objective of the present study was to investigate the physiological selectivity of plant protection products, used on rosebushes for the control of T. urticae and other pests or diseases, to Phytoseiulus macropilis (Banks) and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) both predatory mites of T. urticae on rosebush growing in a greenhouse. According to IOBC/WPRS, the residual method of spraying on a glass and leaf surface area was used for the physiological selectivity test of plant protection products for the predatory mites. The obtained results shown that with the exception of the acaricides-insecticide chlorfenapyr all other tested products - fungicides, acaricides and acaricides-insecticide - methiram + pyraclostrobin, thiofanate-methyl, boscalid + kresoxim-methyl, chlorothalonil, propargite, mandipropamid, mefenoxam, difenoconazol, bifenthrin and pyriproxifen, were innocuous (class 1) or only slightly harmful (class 2) to both species. Chlorfenapyr was highly toxic only for N. californicus (class 4), however after five days of its application no toxic residue of the product was detected on the glass surface and so the product has been classified as innocuous (class 1) as well for this predatory mite species after this period.
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Introduction
The flowers trade in Brazil is growing, so that it has been recognized as an emergent business sector of high profitability. In 2014, the sector gains were of approximately R$ 5.7 billion (US$ 1.42 billion, based on the exchange rate as R$4.00/dollar) and an 8% growth is estimated for the year of 2015.
The state of Minas Gerais stands out in this sector, especially, for the production of rosebushes (Rosa spp., Rosaceae) and of other conventional cutting flowers. Although there is not available up-to-date data of this activity in Minas Gerais, the flower production in this state occurs especially in the municipalities of Barbacena, Andradas, Araxá, and Munhoz.
The rosebush from Asia has developed well in Brazil and is cultivated in various Brazilian regions. A large part of the production occurs in greenhouses. Although this environment offers better conditions for the control of pests and diseases, it is also a more favorable environment to the occurrence of these two issues with a special highlight to the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), a pest mite that is one of the main problems that affect rosebushes in a protected cultivation system.
Conclusion
The following products, bifenthrin, boscalid + kresoxim-methyl, chlorothalonil, difenoconazole, metalaxyl-M + mancozeb, mandipropamid, methiram + pyraclostrobin, propargite, pyraclostrobin, and thiofanate-methyl are selective to N. californicus and P. macropilis and could be used as a strategy in the integrated management of insects, mites and diseases in rosebushes without affecting both predatory mite species.
The acaricide-insecticide chlorfenapyr is non-toxic to the predatory mite P. macropilis and, therefore, might be used as a tactic to the integrated management of the two-spotted spider mite in rosebushes. However, this product may not be used together the predatory mite N. californicus because this mite is sensitive to the product.
The predatory mite N. californicus, in integrated management program using the acaricides-insecticide chlorfenapyr, should only be released after five days of this product application.
