Phenology of Five Palmer amaranth (Amaranthus palmeri) Populations Grown in Northern Indiana and Arkansas

Abstract

Palmer amaranth (Amaranthus palmeriS. Watson) is a problematic weed encountered in U.S. cotton (Gossypium hirsutumL.) and soybean [Glycine max(L.) Merr.] production, with infestations spreading northward. This research investigated the influence of planting date (early, mid-, and late season) and population (AR, IN, MO, MS, NE, and TN) onA. palmerigrowth and reproduction at two locations. All populations planted early or midseason at Throckmorton Purdue Agricultural Center (TPAC) and Arkansas Agriculture Research and Extension Center (AAREC) measured 196 and 141 cm or more, respectively. Amaranthus palmeriheight did not exceed 168 and 134 cm when planted late season at TPAC and AAREC, respectively. Early season plantedA. palmerifrom NE grew to 50% of maximum height 8 to 13 d earlier than all other populations under TPAC conditions. In addition, the NE population planted early, mid-, and late season achieved 50% inflorescence emergence 5, 4, and 6 d earlier than all other populations, respectively. All populations established at TPAC produced fewer than 100,000 seeds plant−1. No population planted at TPAC and AAREC produced more than 740 and 1,520 g plant−1of biomass at 17 and 19 wk after planting, respectively. Planting date influenced the distribution of male and female plants at TPAC, but not at AAREC. Amaranthus palmerifrom IN and MS planted late season had male-to-female plant ratios of 1.3:1 and 1.7:1, respectively. Amaranthus palmeriintroduced to TPAC from NE can produce up to 7,500 seeds plant−1if emergence occurs in mid-July. An NEA. palmeripopulation exhibited biological characteristics allowing it to be highly competitive if introduced to TPAC due to a similar latitudinal range, but was least competitive when introduced to AAREC. AlthoughA. palmerioriginating from different locations can vary biologically, plants exhibited environmental plasticity and could complete their life cycle and contribute to spreading populations.

Effect of emergence time on growth and fecundity of Rapistrum rugosum and Brassica tournefortii in the northern region of Australia

“…No significant differences were observed between populations of both weeds in plant height, number of leaves and biomass. In contrast, Spaunhorst et al 30 observed different growth and seed production between Amaranthus palmeri S. Watson populations in response to different planting www.nature.com/scientificreports/ dates. Different responses in weed populations to environmental factors can be attributed to genetic diversity and maternal conditions over the course of maturation 44,45 .…”

“…It could be concluded that, that, despite the reduction in the number of seeds in late-emerged weeds, the control of these weeds (even in boundary areas) should not be neglected in order to achieve sustainable and long-term weed management. In the current study, the viability and dormancy of produced seeds-which play an important role in the proliferation of weeds-from different planting dates were not evaluated 30,39,50 . Furthermore, it has been reported that the interaction effects of flowering time and growth period length could result in different emergence responses to environmental conditions as observed in the collected seeds of Ipomoea hederacea (L.) Jacq.…”

“…In many studies, it has been reported that the emergence, vegetative growth, seed production and phenological behavior of different weed populations could vary according to environmental conditions 30,31 . This study was conducted to evaluate the effect of weed emergence time on growth, flowering and seed production of two populations of R. rugosum and B. tournefortii from high and medium rainfall areas.…”

Effect of PPO-Inhibiting Herbicides on the Growth and Sex Ratio of a Dioecious Weed Species Amaranthus palmeri (Palmer Amaranth)

“…The differential effect of fomesafen may be due to the presence of the adjuvant system in the Flexstar ® herbicide, which increases herbicide absorption and translocation. A priority for early season control of A. palmeri could also be beneficial as late emerging populations have been observed to be more male-biased than early season populations [64]. Populations with a female-biased sex ratio may need more effective management practices than populations having more male-biased sex ratios where fewer seeds will be produced.…”

Grand Challenges in Weed Management

“…Similarly, information on weed phenology would allow more specific control methods to be developed by accurately estimating the timing and effects of weed competition on crop yield (Ghersa and Holt, 1995). A recent study on Amaranthus palmeri S. Watson phenology concluded that while species originating from different regions of the USA can vary biologically, it was the plant's environmental plasticity which contributed to population spread (Spaunhorst et al, 2018).…”