Influence of semilooper damage on cotton host-plant resistance to Helicoverpa armigera (Hub) S. Kranthi *, K.R. Kranthi, R.R. Wanjari Crop Protection Division, Central Institute for Cotton Research, Post Bag No. 2, Shankar Nagar P.O., Nagpur 440 010, India Received 7 June 2002; received in revised form 7 October 2002; accepted 7 October 2002 Abstract The semilooper, Anomis flava Fab is a foliage feeding lepidopteran insect, often found occurring in the cotton ecosystem during the first 60  /75 days of sowing. Its occurrence overlaps or just precedes the incidence of Helicoverpa armigera . This study reports the impact of mechanical wounding or of prior herbivory by semilooper larvae on cotton host-plant resistance to H. armigera. It is proposed that cotton plant damaged by semilooper or by mechanical means is less preferred for the growth of H. armigera. This is probably due to a reduction in the nutritive quality, induction of allelochemicals, such as chlorogenic acid and of oxidative enzymes, such as lipoxygenases and peroxidases in the damaged plants. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Semilooper; Helicoverpa armigera ; Induced; Host-plant resistance 1. Introduction Host-plant resistance is an important component of integrated pest management. It may be mediated through constitutive resistance and/or induced resis- tance mechanisms. Constitutive resistance is described as the phenomenon wherein the host-plant exhibits resistance to a biotic stress (generally insects, pathogens) irrespective of any external stimuli, such as insect injury, mechanical wounding etc. Induced resistance, on the other hand, is the mechanism by which the host-plant steps up its resistance in response to an external stimulus. Constitutive resistance has been characterized well in cotton. It is known that gossypol, hemigossypo- lone, H-1, H-2, [1], tannins [2], quercetin, rutin and many other flavonoids [3] contribute to bollworm tolerance. Numerous agricultural and wild plants ex- hibit induced responses to insect damage and studies have documented negative effects of induced responses on herbivore preference or performance [4]. However, induced responses in cotton have been studied only during the past decade [5  /7]. Plant chemical defense against insects is largely ascribed to plant secondary metabolites [5]. Published evidence indicates that induced responses to herbivory may include enhanced secondary metabolite production, a loss in the quantity and/or quality of essential nutrients and antioxidants or by the production of reactive oxygen species [6]. The importance of induced resistance can be realized from the following examples. Larval weights of Helicoverpa zea decreased by 61% when larvae were fed damaged foliage compared to the control foliage [7]. It was reported in a field trial that cotton plants damaged by mites Tetranychus sps at the cotyledonary stage were less likely to develop infestation of spider mites compared to control plants [8]. Cabbage looper moths preferred undamaged cotton and cabbage plants for egg laying [9]. For the study described herein, we have used two insect species, the cotton bollworm, H. armigera (Hub) and the cotton semilooper, Anomis flava (Fab). The cotton bollworm is a major pest of cotton in India and causes economic damage amounting to US$ 290  /350 million annually [10]. It feeds normally on the tender terminal leaves as neonates and subse- quently on the squares and bolls. A. flava , the cotton semilooper, is also a lepidopteran insect that feeds * Corresponding author. Tel.:  /91-7103-75549x302; fax:  /91- 7103-75529. E-mail address: krkranthi@satyam.net.in (S. Kranthi). Plant Science 164 (2003) 157  /163 www.elsevier.com/locate/plantsci 0168-9452/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII:S0168-9452(02)00345-X