Biotic and abiotic factors influence horseweed emergence

Abstract

Factors affecting horseweed emergence are important for management of this weed species, particularly because of the presence of herbicide-resistant biotypes. Horseweed emergence was highly variable and not strongly correlated to soil temperature (r 2 = 0.21), air temperature (r 2 = 0.45) or rainfall (r 2 = 0.32). Horseweed emerged mainly during April and September in Tennessee when average daytime temperatures fluctuate between 10 and 15.5 C. However, some horseweed plants emerged during almost any month when temperatures ranged from 10 to 25 C and adequate moisture was available at the soil surface. Horseweed densities ranged from a low of 30 to 50 plants m−2 to a high of > 1,500 plants−2 at one location. These extremely high densities illustrate the ability of horseweed to be an effective ruderal plant that can produce stands that approach monoculture densities if not controlled. The amount of crop residue remaining after harvest from the previous field season was in the order of corn > cotton > soybean > fallow. Residue from a previous corn crop reduced horseweed emergence compared with soybean and cotton residues in a no-tillage situation. Decreased horseweed density due to crop residue presence indicates that a systems approach may help reduce horseweed populations.

Functional Traits and Reproductive Allocation Strategy of Conyza canadensis as they Vary by Invasion Degree Along a Latitude Gradient

“…The possible reason for this is that eastern China and northern China, in which C. canadensis vigorous occurs [11,12], have the same or similar climate with their natural habitat in the original distribution region. Meanwhile, C. canadensis emerged when average daytime temperatures fluctuate between 10 and 15.5ºC [13]. The mean annual temperature of Jinan and Zhenjiang were also in the range basically.…”

“…At present, the species has become naturalized in China and is one of the most detrimental and widespread invasive species in most regions of China [11,12]. This species thrives in many habitats, especially in areas subject to human disturbance [13]. The results of this study can provide a platform to better understand the mechanism of successful invasion of C. canadensis and then lay an important theoretical foundation and practical significance for effective invasion prevention and control.…”

Longevity of Horseweed Seed Bank Depending on the Burial Depth

“…This decrease occurred until August (fourth collection period), after that it remained constant, at values close to 40%. The seed bank in the soil can undergo dramatic changes, modifying its dynamics and the proportion and quantity of seeds (Main et al, 2006). Seed bank losses are due to germination, migration and degradation/predation by microorganisms and invertebrates (Chee-Sanford et al, 2006).…”

“…In Brazil, the occurrence of the species Conyza canadensis, C. bonarensis and C. sumatrensis (Lazaroto et al, 2008;Sansom et al, 2013) is frequent; they are associated with conservation systems, such as no-tillage and minimum soil cultivation (Main et al, 2006). Thus, in conventional cropping systems, horseweed management is relatively simple, and soil preparation can significantly reduce the population of these plants (Davis et al, 2009).…”

Spatial and temporal distribution of weeds in no-tillage system

“…The horseweed plants that germinated in areas with suppressing species had difficulty to develop, facilitating the control with herbicides (Main et al, 2006). In this context, the association of glyphosate with herbicides that have alternative action mechanism, such as 2,4-D or chlorimuron-ethyl, complemented with an application close to crop sowing of a contact herbicide, such as paraquat+diuron, can reduce the incidence of horseweed resistant to glyphosate (Lamego et al, 2013).…”