Development and evaluation of attract-and-kill to control the tomato leafminer Tuta absoluta (Meyrick)
The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a pest of economically important cash and food crops, especially of tomato (Solanum esculentum L.), potato (Solanum tuberosum L.) and various other solanaceous crops (URL 1). The species originates from South America and was unintentionally introduced as an invasive species to Southern Europe, including the Mediterranean Basin, North Africa and the Middle East (Desneux et al. 2010, 2011). Still more regions with similar environmental conditions of South American regions are highly threatened by the high invasion potential of T. absoluta (URL 1). Where field conditions do not match the environmental demands, T. absoluta may establish in protected crops with adequate climatic conditions and a year-round availability of food plants (Desneux et al., 2010). The preference for tomato as host plant is reflected by tremendous yield loss of 80-100% in greenhouse and field tomatoes in newly invaded areas with lacking control measures (Desneux et al. 2010). The economic impact of T. absoluta in tomato production in South America is immense, since it is the main factor limiting tomato yields (Ferrara et al. 2001). Under favorable conditions, T. absoluta can produce up to 12 generations per year (EPPO 2005). After mating the females preferentially oviposit on leaves as well as on the remaining aerial plant surface (Torres et al. 2001). When the larvae hatch, they penetrate the surface to feed on the mesophyll. Hence they damage the whole tomato plant (leaves, stems and fruits) by mine- and gallery formations, resulting in a loss of photosynthetic active leaf area, reduced plant growth and major fruit damages and losses (Vargas et. al 1970, Urbaneja et al. 2013). Although secondary infections by pathogens, causing fruit rot, might be induced by the feeding activity of T. absoluta in the fruit (EPPO 2005). In potato it infests leaves, stems and tubers and might become a serious pest under favorable environmental conditions (Pereyra and Sánchez 2006). Several control strategies, aiming to decrease the risk of yield reduction, were developed and continuously improved (Desneux et al. 2010, Urbaneja et al. 2012)The use of chemical insecticides is a common management practice in South America (Lietti et al. 2005), which induced insecticide resistance (Siqueira et al. 2000, 2001, Lietti et al. 2005). Additionally, the abundance of natural enemies of T. absoluta might be reduced by insecticide applications (Vacas et al. 2013) and thus interfere with their role as biological control agents. To overcome these problems, integrated pest management (IPM) strategies could be a more sustainable and effective alternative, in the long term. The attract-and-kill strategy has proven to be a promising control method to control lepidopteran pest species, such as the potato tuber moths Phthorimaea operculella (Zeller) and Symmetrischema tangolias (Gyen) (Kroschel and Zegarra 2010, 2013). An insecticide-pheromone coformulation is the basis of this strategy. The species-specific sexual pheromone acts as attractant for the male moths, which are killed, after coming into contact with the insecticide compound. Thus, successful reproduction and consequently plant damage is effectively prevented. Showing a high efficiency and a protective effect on non-target organisms, the attract-and-kill strategy could be a cost effective solution for small scale farmers, especially in developing countries of the tropics and subtropics (Kroschel and Zegarra 2013).