Arne van Aalst is soon to take up his position at Koppert Biological Systems. Van Aalst, who is now general director at the growers' association...
SPIDEX plus SPICAL: A Winning Combination
11 February 2009
The combined use of both SPIDEX (Phytoseiulus persimilis) and SPICAL (Amblyseius californicus) to control the two-spotted spider mite (Tetranychus urticae) in roses continues to give superior results. This is because, unlike in the past where only P. persimilis was used singly, growers can now benefit from a complimentary effect when these two predators are used together.
The reason why these two natural enemies work well simultaneously is that they have inherently different characteristics. For instance, Phytoseiulus is an effective predator of spider mite in moderate temperature and high relative humidity. It is an avid feeder, hence is ideal for rapidly bringing down spider mite populations. The challenge with Phytoseiulus however is that it struggles in extremes of temperature and low humidity. Further, Phytoseiulus is not able to survive for long in the absence of food.
Amblyseius californicus (SPICAL) on the other hand, whereas not such an avid feeder, is able to withstand higher temperatures than Phytoseiulus. In addition, both research as well as practical field experiences show that A. californicus is more resistant to chemical applications.
In the midst of varying temperature and relative humidity through the year, this two-pronged approach gives stability to the bio-control program. Hence inspite of high summer temperatures, the spider mite remain under control and growers do not experience sudden upsurges of the pest.
The Koppert program for spider mite control in roses therefore typically entails the introduction of inundative quantities of P. persimilis and A. californicus during the clean-up phase. Consequent applications constitute regular introduction of SPICAL throughout the crop, while limiting SPIDEX application in response to any new pest hot spots.
Successful bio-control in roses almost always comes with other fringe benefits. These include better control of the pest and higher yields in terms of stem numbers harvested. Growers also achieve better quality flowers, that is longer stem length, glossier healthy leaves and sometimes, bigger bud size. All this at a comparable and sometimes lower pricing than chemical control of spider mite.
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