Temporal and spatial dynamics of long‐distance Conyza canadensis seed dispersal

Abstract

Summary1. Glyphosate-resistant Conyza canadensis populations now infest more than 44 000 ha of arable land in eastern USA, only 5 years after the first resistant population was reported. Seed dispersal, the expansive use of glyphosate and the lack of tillage are all factors contributing to this high invasion speed. 2. Seed collected from deliberately established C. canadensis source populations were found at the furthest seed traps in our empirical studies, providing one of the most complete dispersal kernels for studying long-distance dispersal. The results indicate that seed regularly disperses at least 500 m from source populations. While a relatively small number of seeds moves long distances, 99% of the seed was found within 100 m of the source. 3. Empirical and mechanistic models were fitted to the data to predict the dispersal in the prevailing wind direction. Both models underestimated seed deposition beyond 200 m but the mechanistic model provided a better fit to the data (lower Akaike information criterion). A two-dimensional analysis examined the correlation between angular directions of wind and seed movement. All trials were anisotropic but only the cumulative wind and seed direction were significantly correlated ( P < 0·05). 4. The empirical model was used to explore the effect of increasing source strength, which would be expected as an infestation of glyphosate-resistant C. canadensis expands on a producer's farm. At infestation levels consistent with a heavy infestation in a 5-ha field, seed dispersed further than 1·5 km, easily affecting 10s to 100s of surrounding farms. 5. Synthesis and applications . Emigration of C. canadensis seed, from a source farm to adjacent farms, means that population dynamics and weed management are dependent on both intra-and interfield dispersal phenomena. Wind-dispersed plants challenge the common practice of single field management as a viable management option for herbicide-resistant weeds. Farms coupled by seed dispersal require proactive management practices by every producer to prevent and minimize the development of glyphosate-resistant infestations of undesirable and alien plants.

Manejo de Conyza bonariensis resistente ao herbicida glyphosate

“…Uma única planta pode produzir até 150.000 sementes, que são facilmente dispersadas pelo vento (Dauer et al, 2007), indicando que essa espécie possui alta capacidade para formar banco de sementes em curto espaço de tempo.…”

Herbicide-Resistant Weed Seeds Contaminate Grain Sown in the Western Australian Grainbelt

“…Palmer amaranth seed can spread via irrigation and other water flows, with the movement of animals, and through plowing, mowing, harvesting and spreading compost, manure, or cotton gin trash (Barber et al 2014;Norsworthy et al 2009). Weed scientists have also documented cases of resistant alleles transferred to susceptible populations through pollen movement, seed, or other propagules, in some cases at great distances (Beckie et al 2013(Beckie et al , 2015Borger et al 2007;Busi et al 2008;Dauer et al 2006Dauer et al , 2007Lu et al 2007;Rieger et al 2002;Shields et al 2006;Sosnoskie et al 2007Sosnoskie et al , 2012Watrud et al 2004).…”

A Multy-Year Study Reveals the Importance of Residual Herbicides on Weed Control in Glyphosate-Resistant Soybean

“…Plant characteristics such as self-pollination, seed production of approximately 200,000 and dispersion at distances greater than 500 m (Dauer et al, 2007), contribute to their good adaptation, survival and high rate of infestation in the agricultural system. Glyphosate-resistant Conyza bonariensis biotypes were selected due to the intense use of this herbicide (Vargas et al, 2007).…”