At present, in Romania, chemical weed control strategies in maize suppose the application of two treatments: the first pre-emergent crop (before or right after sowing, in order to control mono- and some annual dicot species) and a second post-emergent crop (during vegetation in order to control mono- and some perennial dicot species). Taking into account the excessive sensitivity of maize to weeding, particularly during the first 4-6 weeks of vegetation, applying combined herbicides pre-emergently (that contain two to three active substances) is of particular importance. In this paper, we study the effect of simple or combined herbicides (Adengo, Akris, Merlin Duo, Merlin Expert, Successor T, Wing P, compared to the herbicide Guardian), applied at two times: pre-emergently and early post-emergently on annual weed control in maize. Research was carried out at the Didactic Station in Timişoara in 2009, on a cambic, fertile chernozem with high weeding risk. The most frequent weed species were annual monocots (63.0%), followed by annual dicots (21.5%). Compared to the standard treatment (Guardian CE), maximum efficiency in controlling annual weeds upon pre-emergent application was in the variant treated with Adengo over 91%.  In general, the efficiency of combined herbicides applied early post-emergently was determined by the optimal phase of the weeds at the time of treatment, by the ratio of the two weed groups and by the amounts of rainfall after treatment application. Among herbicides, the best efficiency was again that of the herbicide Adengo (0.30-0.35 l/ha) with 96%, followed by the herbicide Merlin Duo (2 l/ha) with 89%. The species not controlled were perennial (mono- and di-cots), the annual dicot species Hibiscus trionum, as well as all the annual weed species in advanced treatment (above the optimal phase of maximum 4 leaves). Taking into account that neither of the tested herbicides controlled perennial mono- or di-cot weeds: on lands strongly infested by these weeds, we also need to apply a proper post-emergent treatment. All herbicides applied, pre-emergently and early post-emergently, were very selective for the cultivated maize hybrid DKC 5143.

corn crop; weeds control; herbicides; preemergent and postemergent early apply

Presentation: oral