Amaranthus palmeri shows adaptation in different cropping systems
Amaranthus palmeri (Amaranthaceae - EPPO A2 pest) is a dioecious summer annual species native to North America. In its native range, it is a weed in agricultural fields and disturbed habitats. It has a high fecundity and a long-lived seed bank, which make management of the species difficult. In the EPPO region, it is established in a few countries and transient in several others. In the USA, A. palmeri is one of the most economically detrimental weed species in cropping systems. It has been recorded to reduce yield loss by 91, 68 and 54 % in maize, soybean and cotton respectively. An experiment was conducted in 2018 and 2019 in five locations in the Mid-West, USA. Forty-eight A. palmeri seedlings were transplanted between rows of soybean and maize and in bare ground in June and again in July. The plants were monitored until the end of July. Results showed that A. palmeri planted in June produced 42% more biomass than plants planted in July. Early planted A. palmeri produced 75.5 g per plant in bare ground, 28.3 g per plant in soybean, and 16.3 g per plant in maize, whereas the later planted cohort produced 62.6, 6.3, and 1.4 g per plant in bare ground, soybean, and maize, respectively. A. palmeri height was most impacted when growing in maize and averaged 85.2 cm tall in the early planted cohort, and 38.2 cm tall in the second cohort in maize. The timing of flowering differed between crops and planting time. A. palmeri plants growing in intense competition, such as under low light in maize, resulted in the longest flowering period. The results show that A. palmeri shows a high level of plasticity which can promote its adaption to different habitats and expansion into different cropping systems.
Sources
Oliveira MC, Jhala AJ, Bernards ML, Proctor A, Stepaovic S, Werle R (2022) Palmer amaranth (Amaranthus palmeri) adaptation to US Midwest agroecosystems. Frontiers in Agronomy 4, 887629. https://doi.org/10.3389/fagro.2022.887629