Infestation of Spanish moss (Tillandsia usneoides L.) by the ensign scale Orthezia tillandsiae Morrison (Homoptera, Coccina: Ortheziidae) and possibilities of their biological control at the Botanical Garden of the Technical University of Dresden.
In the Botanical Garden of the Technical University of Dresden, ensign scales (Ortheziidae) appeared on Tillandsia usneoides L. 1997 for the first time in Saxony. In 1999 the species could be identified as Orthezia tillandsiae. In the context of a dissertation at the University of applied sciences of Dresden the insects were investigated and ways of biological treatments were tested. The tests showed an impaired growth and weakening of the host plants as well as a higher susceptibility to secondary parasites. The efficiency of biological control of O. tillandsiae was tested using different predators: Cryptolaemus montrouzieri (larvae and adults), Chrysoperla carnea (larvae) and Rhyzobius lophantae (larvae). C. montrouzieri achieved the best results. Furthermore, C. montrouzieri was tested for reproduction using the prey O. tillandsiae. The ladybirds did not reproduce after consuming O. tillandsiae nor did they lay any eggs. Their growth was inhibited and they did not pupate. One experiment showed that a small amount of a feed-mixture consisting of O. tillandsiae and Planococcus citri at a ratio 3:1 was enough to stimulate the ladybirds into laying eggs. A further experiment with the same feed-mixture showed that they pupated and continued to develop. Following this investigation NeemAzal-T/S was then applied, which resulted in a decrease of approximately 50% compared to the population of the control group. The tested methods did not allow a complete control but only a consecutive regulation - which in the sense of biological control - still has to be improved.