Emergence and viability of teosinte seeds (Zea mays ssp. mexicana ad int.) subjected to sheep digestion

Abstract

Summary A few years ago, a new invasive weed was found in Spanish maize fields grazed by sheep after harvest and identified as a subform of teosinte (Zea mays ssp. mexicana ad int). If teosinte seeds survive digestion, then the weed could spread via sheep manure. The aim of this study was to assess the effect of this process on the emergence and viability of teosinte seeds. In an in sacco study, seeds were introduced into the rumen of fistulised wethers and extracted after 24, 48, 72 and 96 h. Then, seed emergence was recorded and the viability of non‐germinated seeds was analysed. In an ‘intake and in vivo’ study, lambs were kept in metabolic cages and fed for 6 days with 200 g teosinte seeds and ears. The daily faecal production was individually collected, seeds were recovered and viability was tested (15 days). In the in sacco trials, a decrease in teosinte viability was observed after remaining for 48 h or more in the rumen. In the ‘intake and in vivo’ trial, between 0.1% and 3% of the ingested seeds that were excreted were viable. Uncoated seeds that lost their exocarp during the mastication and digestion processes were less viable (18%) than intact excreted seeds (74%). The last viable and intact seeds appeared 4 and 6 days after intake respectively. In areas with teosinte infestation, sheep grazing on maize stubble should be avoided and, in case of ingestion, sheep should be kept isolated for 4–6 days to avoid the spread of this invasive weed.

Update of environmental risk assessment conclusions and risk management recommendations of EFSA (2016) on EU teosinte

“…In infested agricultural areas in Arag on and Catalu ña, a set of measures across many fields have been implemented since 2014 and 2015 to monitor, control and/or eradicate teosinte. These measures include (see also Pardo et al, 2016;Cirujeda et al, 2019):…”

“…In infested agricultural areas in Aragón and Cataluña, a set of measures across many fields have been implemented since 2014 and 2015 to monitor, control and/or eradicate teosinte. These measures include (see also Pardo et al, 2016; Cirujeda et al, 2019): Conduct of systematic field inspection surveys at different crop development stages, to identify, map and monitor the presence and evolution of teosinte, and assess the level of infestation at a field level; ○In Aragón, two infestation levels are considered: ‘low’ (= scattered, isolated teosinte plants) and ‘high’ (= teosinte plants occurring in patches or being spread out throughout the entire field); ○In Cataluña, three infestation levels are considered: ‘low’ (= scattered, isolated teosinte plants), ‘medium’ (= and few teosinte plants occurring in patches) and ‘high’ (= teosinte plants being spread out throughout the entire field); Implement control and/or eradication measures that are proportionate to the level of infestation. Depending on the level of infestation, such measures may include: ○Removal of teosinte plants close to sprinklers, pivots and other structures as soon as they are detected and always prior to seed ripening; ○Removal of teosinte plants potentially appearing in field margins; ○Clean field machinery to avoid dispersal of teosinte seed between agricultural fields; ○Prohibit/avoid the growing of maize or sorghum on severely infested agricultural fields during the next two to three spring/summer sowing seasons; ○Use stale or false seedbeds to promote teosinte seed germination and their control prior to planting of a crop through chemical and/or mechanical means; ○Use shallow tilling practices to control teosinte that emerged between maize rows; ○Rotate crops by growing a summer, broadleaf crop (such as sunflower, alfalfa and beans) and winter cereals (e.g.…”

Aspectos de la dispersión y viabilidad de las semillas de teosinte (Zea mays ssp.) en el Valle del Ebro

“…Un aspecto importante para contener la infestación de cualquier mala hierba es conocer y cuantificar las vías de dispersión entre parcelas. En el caso del teosinte, al tratarse de una semilla de gran tamaño, mayor de 5 mm, con un peso de mil granos relativamente elevado de 120 ± 0,2 g (Cirujeda et al, 2019) y sin vilanos ni estructuras laminares que permitan planear, se considera difícil que pueda dispersarse de forma anemócora (Greene y Johnson, 1993). Sin embargo, hay que tener en cuenta el posible efecto de las máquinas que intervienen en el proceso de cultivo, sobre todo las cosechadoras y remolques que transportan la cosecha, en la dispersión de las semillas de esta especie, tal y como se ha citado para otras malas hierbas como Avena spp.…”

“…Otra posible vía de dispersión de una mala hierba podría ser a través del ganado, bien directamente en el caso del pastoreo o indirectamente con el esparcido de los estiércoles y purines en el caso de estabulación total. En ese sentido, Cirujeda et al (2019) mues-(Zea mays ssp.) firstly detected in the Ebro valley (NE Spain) in 2014.…”

Potential for endozoochorous seed dispersal by sheep and goats: Risk of weed seed transport via animal faeces

“…There are great differences among animal species, but also among individuals of the same species, in seed fate through their guts (Cirujeda et al., 2019). One animal may have numerous viable seeds in the pellets, while, another has none (Heady, 1954).…”