Weeds represent one of the most significant challenges to agricultural productivity in Malaysia. This chapter offers insights into the biology of key problematic weeds in major field crops such as oil palm, rice, and pineapple, together with the management of the problematic weeds through integrated approaches. In oil palm plantations, herbicide-resistant weeds such as Eleusine indica (goosegrass) and Clidemia hirta (soapbush) pose serious threats, demanding strategies like legume cover crops, mulching, and precision herbicide applications. Rice production suffers substantial yield losses (5–85%) due to invasive Oryza spp. (weedy rice) and Echinochloa crus-galli (barnyardgrass), necessitating interventions such as stale seedbed techniques integrated with pre-emergence herbicides, optimized water management, and herbicide-tolerant varieties like Clearfield® rice. Meanwhile, pineapple cultivation faces 25–35% yield reductions from aggressive weeds like Ageratum conyzoides (billy goat weed) and Digitaria ciliaris (southern crabgrass), with soil-specific solutions including plastic mulch in peat soils and targeted herbicides in mineral soils. The chapter explains the critical role of integrated weed management in sustaining agricultural productivity, emphasizing strategies tailored to crop life cycle from planting to harvest to minimize weed competition while preserving environmental and economic viability.