Relative natural resistance of Populus deltoides clones against defoliator Clostera cupreata (Lepidoptera: Notodontidae) in northern India A. P. SINGH Division of Forest Entomology, Forest Research Institute, P.O. New Forest, Dehra Dun, U.P., India. 248 006; E-mail: singhap@icfre.up.nic.in Key words: feeding potential, pest, poplar, susceptibility Abstract. Populus deltoides (poplar) that is extensively being planted commercially in agro- forestry combinations in northern India is prone to attack by a defoliating insect, Clostera cupreata. In order to evaluate the relative susceptibility/resistance of different clones and to identify the resistant ones, 80 clones of American origin were evaluated in Dehra Dun, India. The feeding potential of the pest on different clones varied significantly. The clones were grouped into six categories depending on their susceptibility as most resistant or R1 (12 clones), moderately resistant or R2 (14 clones), marginally resistant or R3 (10 clones), marginally susceptible or S1 (17 clones), moderately susceptible or S2 (18 clones) and most susceptible or S3 (nine clones). Clone ‘110120’ of Tennessee was most resistant where as Oklahoma clone ‘104’ was most susceptible to this pest. Amongst the most resistant clones (R1), only three clones, WSL-4, WSL-12 and WSL-18 (source: WIMCO Seedlings Ltd, India) were found to be superior, in terms of growth increment, as compared to the standard and most widely planted clones in northern India i.e. G-3 and G-48, and are promising clones for plantation in defoliator prone areas. Introduction Enhancing wood production is an urgent necessity today especially in developing and over-populated countries like India. To achieve this goal hundreds of clones/hybrids of Populus deltoides Bartr. Ex. Marsh. have been introduced in northern India (above 28° N latitude) from USA, Australia and Europe, since 1965. The performance of these clones in terms of survival and growth is being monitored in nurseries as well as in the field plantations throughout north Indian states (Kumar et al., 1999). Several promising clones [G-3, G-48 (Australian), S7C15, S7C8, S7C14, ST-67, ST-121 (American), L-34, L-82, L-83, L-84 (Indian) etc.] of P. deltoides have also been identi- fied and planted extensively under different agroforestry systems (bund, block and row plantations) on a commercial scale (Kumar et al., 1999 and Sharma, 1999). During the period 1984–92 alone, under a collaborative agro-farm- forestry project carried out by WIMCO (Western India Match Company Ltd) – NABARD (National Bank for Agriculture and Rural Development, India), 15,837 farmers planted 1.32 million poplars over an area of 26,446 ha in northern states of Uttar Pradesh, Punjab and Haryana (Jones and Lal, 1989). Agroforestry Systems 49: 319–326, 2000.  2000 Kluwer Academic Publishers. Printed in the Netherlands.