engleski

Resistant populations of Johnsongrass (Sorghum halepense L.) and common ragweed (Ambrosia artemisiifolia L.) in Croatia to ALS herbicides

The objective of this study was to confirm the resistance of Sorghum halapense and Ambrosia artemisiifolia to acetolactate synthase herbicides (ALS). Seeds of plants that had survived a ALS herbicide application (R) were collected from soybean and corn fields in fall 2018. A susceptible population of both species that had never been treated with ALS herbicides (S) was also included in the experiment. Bioassays on whole plants were conducted with linearly increasing (R) and linearly decreasing (S) herbicide doses at BBCH 13 and 12, respectively, for S. halapense and A. artemisiifolia. The bioassays included 9 doses ranging from ½ to 64 times the recommended field dose (x). The experimental design was a completely randomised design with 4 replicates and 5 plants per pot. The logistic curve was used to estimate the herbicide dose required to reduce 50% of the aboveground mass, and then the resistance index (GR50 R/GR50S) was determined. The results indicate that all herbicides were very effective on the S populations of both species. However, a high level of resistance was found to all herbicides tested: 81.86 for nicosulfuron, 370.78 for foramsulfuron, and 155.47 for imazamox in S. halapense and 293.15 for foramsulforn and 31.7 for tifensulfuron in A. artemisiifolia. The detected resistant populations urgently require the long-term incorporation of other weed control methods due to the long viability of the resistant dormant seeds of both species in the soil seed bank.

foramsulfuron, tifensulfuron, imazamox, nicosulfuron, maize, soybean

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