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Maize is the third main cereal crop after wheat and rice in Pakistan, and second after wheat in Khyber Pukhtunkhwa. Horse purslane (Trianthema portulacastrum L) a member of family Aizoaceae, is a common weed of maize, cotton and vegetables all over Pakistan (Hashim and Marwat, 2002). Due to indeterminate habit, vegetative and reproductive growth continues for the entire life span (Nayyar et al., 2001). Out of 69 weed species T. portulacastrum was realized as the most aggressive weed of maize crop (Kumar and Singh, 1983). At a density of 12 plants m-2 of T. portulacastrum gave lower maize yield of 3.54 t ha-1 than weed-free plots 3.89 t ha-1 (Ansar et al., 1996), and infestation can lead to 32.3% losses in maize crop (Balyan and Bhan, 1989). Horse purlane caused 25 million dollars loss to maize production each year in Pakistan (PhD Thesis of Muhammad Saeed).

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