Biology and control of sugar beet significant weeds redroot pigweed (Amaranthus retroflexus L.)

Reproductive ability of redroot pigweed (Amaranthus retroflexus) in sugar beet stands is strongly influenced by crop sowing time. Redroot pigweed produce lower amount of seeds if sugar beet is sowed right in time (till half of the April) than in late sowed stands, which are more infested by this weed and so the seed production of redroot pigweed is there higher. This species emerges from soil surface at most (at the temperature above 20 degreesC) or from the depth of 20 mm. Maximum depth for redroot pigweed emergence is 40 mm but only on sandy soils. Under field condition, it starts to emerge during April with maximum emergence rate during May. This is followed by rapid decrease of emergence and during summer (July - August) it does not emerge at all. In some years it is possible to detect second wave of emergence during August.