Russian thistle (Salsola spp.) biology and management

摘要

One of the major weed species of the dryland cropping region of the Pacific Northwest (PNW) in the USA is Russian thistle (Salsola spp.). Sixty percent of the wheat-producing area of the PNW is an arid to semi-arid region characterised by severe winderosion because of intensive tillage during the dust-mulch fallow period between winter wheat crops. Attempts to reduce the number of erosive fallow hectares by growing no-till spring crops have been impeded by Russian thistle. This weed thrives in thisenvironment because it is capable of season-long germination and seedling establishment, even with very short periods of moisture after light rains (2.5 mm). Russian thistle is a shallow germinating weed and therefore flourishes in trashy, no-till environments. It reduces farm income by reducing crop yield and quality and increasing production costs. Russian thistle is very competitive because of its high water use efficiency and its rapid and extensive root growth in early spring. After crop harvest, Russian thistle produces an abundance of biomass and seed. It also extracts soil moisture to a point that soil recharge by winter and spring precipitation may not be sufficient to produce a crop the following year. Russian thistle management strategies must focus on preventing seed production throughout the crop rotation cycle. This includes in the crop, after crop harvest, and during the fallow period. If spring crops are planted, growers must use management practices that optimise crop competitivenesswith Russian thistle. Furthermore, neighbours must also control their Russian thistle so that reinfestation does not occur by seed dispersal from the wind-driven tumbling weeds.