Potential of generalist predators for biological control of the key invasive tomato pest, Tuta absoluta, in Senegal

The tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has recently invaded sub-Saharan countries and is a major pest in tomato crops. Predators have shown promising potential for controlling the pest in tomato fields. Mirid predators are commonly used for biological control of whiteflies and they also prey on T. absoluta. The aim of this study was to evaluate the potential of generalist predators to control the tomato leaf miner in tomato crops. The effect of predators on tomato leaf miner populations was determined by contrasting T. absoluta population abundance and the generalist predators biocontrol in each field, using biocontrol services index method (BSI). Predators were excluded using cages erected in 25 tomato fields from March to June in 2015 and 2016. Predators collected from tomato fields were identified as Nesidiocoris tenuis (93.1%) the most abundant generalist in tomato crops, Orius sp. (2.2%), coccinellid (4.7%) and spiders (3.1%). We observed higher control efficiency of T. absoluta population by the existing predator populations in both years. BSI values in 2015 ranged from 0 to 1, with an average value of 0.43. BSI values in 2016 ranged from 0 to 1, with an average value of 0.7. Predators provided high levels of biological control of leafminer in all sites. The biological control variability to the tomato leafminer suppression between fields and years showed that the landscape factors and fields management could be the keys drivers of predator abundance.