Can effective weed management be obtained by grouping species by life cycle? Case studies from the cotton industry II.
Individual weed species have different life cycle characteristics and these differences often require specific management strategies. Despite this, identification of commonality in key life cycle parameters between different species may increase the effectiveness of weed management strategies. This growth cabinet study examined the development of 19 weed taxa and two cotton cultivars. Phenological development was assessed using a day degree relationship that had previously been validated for cotton. The trial was conducted under a 12 h light regime at 35°C and 12 h dark regime at 25°C until 690 day degrees after cotton emergence. In general, the weeds examined had rapid seedling leaf development and a shorter vegetative period than cotton. Some taxa emerged earlier than cotton, while others produced seeds before flowering in cotton. The results indicated that while early season post-emergence weed control in cotton crops will be important in managing the weeds examined, more attention should be paid to pre-emergent cotton weed control. To reduce seed set, targeted management of certain weed species such as Amaranthus macrocarpus Benth., Echinochloa colona (L.) Link, Ipomoea lonchophylla J.M.Black, Trianthema portulacastrum L. and Urochloa panicoides P.Beauv. during their early growth is needed.