RESEARCH PAPER Distribution of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) in tomato fields and its relationship to weather factors Waqas WAKIL 1 , M. Usman GHAZANFAR 2 , Yong Jung KWON 3 , Mirza A. QAYYUM 1 and Fozia NASIR 1 1 Department of Agri-Entomology, University of Agriculture, Faisalabad, Pakistan 2 University College of Agriculture, Sargodha, University of Sargodha, Pakistan 3 School of Applied Biology and Chemistry, Kyungpook National University, Sankyuk-dong, Daegu, 701-710, South Korea Correspondence Waqas Wakil, Department of Agri- Entomology, University of Agriculture, Faisalabad 38000, Pakistan. Email: arid1972@yahoo.com; waqaswakeel@hotmail.com Received 10 January 2010; accepted 24 August 2010. doi: 10.1111/j.1748-5967.2010.00301.x Abstract A survey was conducted in tomato fields at different localities to assess the distri- bution of tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctu- idae) in Punjab Province, Pakistan. The effect of weather factors on its population was also investigated. Eleven tomato-growing districts were selected and data for larval population and fruit infestation were recorded. The maximum larval popu- lation (5.2 larvae/plant) of H. armigera was recorded in Bahawalpur district with 32.6% fruit infestation. However, the minimum larval population (1.4 larvae/plant) inflicted 14.7% fruit infestation in Rawalpindi district. The temperature was posi- tively correlated while relative humidity showed negative interaction with the larval population and fruit infestation. Key words: distribution, population, relative humidity, temperature, tomato fruitworm. Introduction The tomato Lycopersicon esculentum Miller crop covers 46 000 ha with total production of 470 000 tonnes in Paki- stan (FAO 2007). This crop generally suffers from different foliage and fruit feeders such as tomato fruitworm Helicov- erpa spp.; various armyworms Spodoptera spp.; russet mites Aculops lycopersici; stink bugs Euschistus conspersus, Thyanta pallidovirens, Chlorochroa spp. and Nezara viri- dula; and aphids Macrosiphum euphorbiae (Hartz et al. 2008). In Pakistan, the tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is known as the key pest attacking many crops including chickpea, cotton, tomato, potato, tobacco, okra, sunflower, cabbage and pigeon pea in the field (Callahan et al. 1972; Zalucki et al. 1986; Ahmed 1994; Torres-Vila et al. 2003; Talekar et al. 2006; Wakil et al. 2009a,b). There are a number of reasons it is the key pest, including high polyphagy, wide geographical range, mobility, migratory potential, facultative diapause, high fecundity, propensity to develop resistance to insecti- cides and larval feeding behavior (Zalucki et al. 1986; Fitt 1989; Zalucki 1991; Anonymous 2000; Torres-Vila et al. 2002a,b). The young larvae burrow deep into tomatoes and are overlooked even in the peeled fruits (Garcia 2006), which results in contamination of tomatoes and adversely affects yield (Hoffmann et al. 1991). In Tamil Nadu, losses of fruit range 40–50% (Srinivasan 1959). Similarly, in Northern India, 30% loss of the fruit was observed due to tomato fruitworm (Singh & Singh 1975). Selvanarayanan and Narayanasamy (2006) reported 5–55% losses from this insect pest in the tomato growing areas of India. Tomato fruitworm has also caused 35% yield loss in tomato (Latif et al. 1997) and 37.79% specifically in Karnataka, India (Dhandapani et al. 2003). Considering the extent of damage caused by this devas- tating insect pest, a detailed survey was initiated to study the distribution of H. armigera and to evaluate the effects of temperature and relative humidity on the population fluctuations and fruit infestation in the tomato-growing areas. Entomological Research 40 (2010) 290–297 © 2010 The Authors Entomological Research © 2010 The Entomological Society of Korea and Blackwell Publishing Asia Pty Ltd