DISTRIBUSI DAN IDENTIFIKASI POPULASI SINTRONG (Crossocephalum crepidiodes.Benth) RESISTEN PARAKUAT PADA LAHAN JAGUNG (Zea mays) DI KABUPATEN DAIRI

Abstract

Crassocephalum crepidioides on Cornfields in Dairi Regency had been reported to
become more difficult to control using paraquat. The objective of the research was to
determine the characteristics and the distribution of C.crepidioides resistant to paraquat
in cornfields. The experiment was carried out in two steps, the first step was screening
the population of C. crepidioides with paraquat at the recommended dose, and the second
step, dose-response experiment for the resistance level of C. crepidioides population with
dose 0, 76, 152, 304,5, 609, 1218, and 2436 g.ai /ha. In the first step experiment, paraquat
dichloride was applied at 280 g.ai/ha. The treatments were arranged in a randomized block
design with 3 replication. The second step experiment was that the resistant populations
confirmed in the first experiment were sprayed for their dose-response. The treatments
were arranged in a randomized complete block design (CRBD). The results showed that
of 30 populations of C. crepidiodes, 19 populations (63.3%) were categorized to be
resistant with the mortality ranging from 10.84% to 52.08%, and 11 populations (36.7%),
was categorized as high resistance with mortality of 0% to 9.21%. The level of
resistance (R/S) of R-C25, R-C27, and R-C30 populations of C. crepidioides were 12,3,
14,86, and 24,83 times consecutively, compared with the susceptible population. The
number of C. crepidioides chlorophyl leaves in susceptible populations was significantly
lower than that of a resistant populations.