Single herbicide treatments for control of broadleaved weeds in onion (Allium cepa)

Interactions among genotype, environment and agronomic practices on production and quality of storage onion (Allium cepa L.) - A review

“…Although early growing season is generally regarded the critical period for weed control (Ashton, Monaco 1991; Radosevich et al 1997), it is also deemed that the optimum weeding time ranges from 21 to 56 days after the emergence of onion seedlings (Bond, Burston 1996) and the weed control in late season also plays a significant role in weed management (Ghosheh 2004). Indeed, the long growing season of storage onion allows for periodic flushes of weeds, therefore the crop must be kept weed-free for a relatively long term after planting to avoid yield loss (Dunan et al 1996;Sivesind et al 2012).…”

“…and oxadiazon at 3 kg/ha a.i., both of them applied two weeks to two months after crop emergence. Oxadiazon activity shows a shorter effect than the oxyfluorfen one, but the latter may result in leaf necrosis caused by phytotoxicity (Ghosheh 2004), even in the early phenological phases under rates as low as 68 g/ha (Warholic 1982). Crop injuries may also occur later in the season, probably due to active herbicide residues that are absorbed by the roots from deeper layers of soil (Ghosheh 2004).…”

“…Oxadiazon activity shows a shorter effect than the oxyfluorfen one, but the latter may result in leaf necrosis caused by phytotoxicity (Ghosheh 2004), even in the early phenological phases under rates as low as 68 g/ha (Warholic 1982). Crop injuries may also occur later in the season, probably due to active herbicide residues that are absorbed by the roots from deeper layers of soil (Ghosheh 2004). However, onion plants show a positive vegetative reaction (Warholic 1982;Ghosheh 2004) and therefore, post-emergence treatments result in higher yield of bulbs than the pre-emergence applications (Ghosheh 2004).…”

“…Notably, onion plants are poor competitors with weeds because of their slow growth, small stature, shallow roots, and thin cylindrical upright leaves not able to suppress weed growth by shading. Therefore, weeds cause a reduction of soil moisture, nutrients, sunlight and growing space to onion plants, which may result in the reduction of plant growth, yield and quality of bulbs (Ghosheh 2004), up to 62% and 71% in terms of seedlings number and production of bulbs, respectively (Qasem 2006). According to Ghosheh and Al-Shannag (2000) weed occurrence is even more devastating to yield of onion bulbs than the Thrips tabaci insect infestation.…”

“…In direct-seeded onion, effective pre-emergence weeding can be performed with herbicides, such as glyphosate for non-specific weed control, oxyfluorfen for broadleaved weeds and fluazifop-butyl for wild oat (Ghosheh 2004).…”