Field evaluation of selected botanicals and commercial synthetic insecticides against Thrips tabaci Lindeman (Thysanoptera: Thripidae) populations and predators in onion field plots Abdul Khaliq a, b , Azhar Abbas Khan a, * , Muhammad Afzal a , Hafiz Muhammad Tahir c , Abubakar M. Raza a , Arif Muhammad Khan d a Department of Agricultural Entomology, University of Sargodha, Sargodha, Pakistan b Fodder Research Institute, Agriculture Department (Research Wing), Sargodha, Pakistan c Department of Biological Sciences, University of Sargodha, Sargodha, Pakistan d Department of Biotechnology, University of Sargodha, Sargodha, Pakistan article info Article history: Received 11 January 2014 Received in revised form 25 March 2014 Accepted 30 March 2014 Keywords: Chemical insecticides Biopesticides Eco-friendly IPM onion thrips abstract The effectiveness of three botanical insecticides (neem, datura and bitter apple), and three new chem- istry synthetic insecticides (acephate, spirotetramat and spinetoram) against onion thrips (Thrips tabaci) was evaluated in experimental field plots at university of Sargodha, Pakistan. The influence of these botanical and chemical insecticides on natural predators and crop yield was simultaneously investigated. All the botanicals and chemical insecticides tested caused significant reductions (45e70%) in thrips populations; the botanicals gave more than 60% control of thrips, while among chemical insecticides, acephate was found to be the most effective followed by spirotetramat and spinetoram, respectively, and these insecticides gave better control than the botanicals. The adverse effects of the botanicals on predator populations were negligible compared to the chemical insecticides. All chemical treatments resulted in a significantly higher yield compared to the untreated control. The botanicals and chemical insecticides became less effective by 7 days after treatment. Therefore, it is recommended that treatment with botanical or chemical insecticides should be repeated weekly consecutively at least three times to keep thrips populations below economic injury levels until crop maturity. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), is a key foliage-feeding pest of onion worldwide (Lewis, 1997; Smith et al., 2011). Immature stages of T. tabaci prefer living in the central leaves of the plant, reducing their photosynthetic ability (Jensen et al., 2003). The infested leaves become wrinkled and silvery in appearance; yield losses due to thrips may range from 18 to 60% (Waiganjo, 2004). This pest also causes significant reduction (28e73%) in the bulb size (Fournier et al., 1995; Childers, 1997; Jensen et al., 2002). If the crop is attacked by T. tabaci in its early growth stages, the yield loss may reach 90% (Anonymous, 1984). T. tabaci has a wide range of hosts and its populations switch from one crop to another in search of suitable hosts (Ibrahim and Adesiyun, 2010a). Therefore, attacks by onion thrips are relatively unpredictable (Gangaloff, 1999). T. tabaci can directly damage the crop by sucking cell sap, or indirectly serve as a vector of many serious plant viruses (Jenser et al., 2003; Thungrabeab et al., 2006; Whitfield et al., 2005). In Pakistan, onion is an important vegetable crop grown in agricultural land areas amounting to nearly 110 thousand hectares (Malik et al., 2003). To improve crop yield and profitability, it is desirable to introduce sustainable control measures. In this regard, numerous control measures have been practiced for population management of thrips; however use of chemical insecticides re- mains the major control strategy. The frequent use of synthetic chemical insecticides against thrips can cause development of resistance in the target pop- ulations as well as ecosystem disturbances. It may also lead to insecticidal residues in onion bulb and mortality or escape of bio- control agents (Shah et al., 2000). The most severe constraint to realizing the potential of natural enemies in field crops is their disruption through widespread use of insecticides that have a broad range of toxicity to both pests and their natural enemies * Corresponding author. Tel.: þ92 483703661. E-mail address: azhar512@gmail.com (A.A. Khan). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2014.03.019 0261-2194/Ó 2014 Elsevier Ltd. All rights reserved. Crop Protection 62 (2014) 10e15