Grass weed control and herbicide tolerance in cereals

Abstract

Field trials were undertaken over three years to determine herbicide options for grass weed control in cereal crops (wheat and barley) The susceptibility of phalaris perennial ryegrass Italian ryegrass prairie grass and soft brome to a range of herbicides were evaluated at fixed rates and with a logarithmic sprayer Wheat and barley damage and grain yield were also assessed and in general good tolerance was found in the 11 cultivars evaluated The trials identified a number of control options for grass weeds in wheat and barley in particular preemergence mixtures of cyanazine terbuthylazine; chlorsulfuron terbuthylazine; or metribuzin alone Brome species were the most difficult to control and further research is required

A herbicide resistance risk assessment for weeds in wheat and barley crops in New Zealand

“…We expanded the weed species list to include species known to occur in wheat and barley fields in the wider New Zealand context. Grasses and some broadleaf genera were not identified to species by Bourdôt et al [22], hence we took steps to address this gap and other omissions by using other literature [23,24], expert knowledge and field observations made in January (late summer) of 2019 and 2020. Species nomenclature follows the New Zealand Flora and taxonomic authorities are listed in S1 [26], with risk scores of 1, 2 or 3 given for low, medium or high risk respectively.…”

“…Our weed list contained 69 species from the original Bourdôt et al article [22]. An additional 32 species were added based on field observation, expert opinion and relevant literature [23,24], resulting in a total of 101 weed species for consideration. Digitaria sanguinalis, Echinochloa crus-galli, Erigeron spp.…”

Chemical control of brome grasses (<i>Bromus spp</i>) in cereals

“…There was some early damage to wheat, but this was transitory and did not affect wheat biomass at harvest. This study and another report in this volume (Rolston et al 2003) indicate that barley maybe more sensitive to herbicide treatments, and variation between cultivars needs to be considered when selecting a chemical option.…”

Using a selectivity index to evaluate logarithmic spraying in grass seed crops

“…The logarithmic sprayer delivers an exponential decrease in the dose in response to time and was first described in 1955 3. It is used for screening for selectivity of herbicide leads 6. As the doses are exponentially declining from an arbitrary initial value, the reading of the response can be distributed along the distance of the spray strip in order to describe dose–response curves.…”

“…As the doses are exponentially declining from an arbitrary initial value, the reading of the response can be distributed along the distance of the spray strip in order to describe dose–response curves. The logarithmic sprayer has been used in herbicide research to find selective herbicides both in horticultural7 and in agricultural crops,6 and for control of specific weeds 8. The logarithmic sprayer would be useful for assessing selectivity indices, for example comparing the tolerance of a crop in relation to the sensitivity of a weed 9.…”