Field emergence of weeds during the growing season of sugar beet.
Monitoring of field emergence of selected weeds important in sugar beet stands was carried out in 2001-2011 during the growing season (from March to November) in two locations in the Czech Republic. High level of field emergence of Avena fatua, Chenopodium album, Mercurialis annua, and Abutilon theophrasti was recorded during March and April. In years with high April temperatures, the following weeds also emerged at the end of the month: Amaranthus retroflexus, Amaranthus powelii, Echinochloa crus-galli, Datura stramonium, and Solanum physalifolium. Highest field emergence of most of the monitored summer weeds was recorded in May, but during years with low precipitation, Echinochloa crus-galli, Galinsoga ciliata, Datura stramonium, and Solanum physalifolium did not emerge intensively until June. In the second half of growing season of sugar beet, field emergence of most of monitored weeds decreased. Highest level of emergence was recorded during the summer for Galinsoga ciliata, Mercurialis annua, and Datura stramonium. On the contrary, emergence of Echinochloa crus-galli, Amaranthus powelii, and Abutilon theophrasti reduced during the summer, although in some years these weeds emerged with higher intensity during this period. Emergence of Avena fatua during the summer was sporadic.