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Annual bluegrass ( Poa annua ) resistance to indaziflam applied early‐postemergence
Author(s) -
Brosnan James T,
Vargas José J,
Spesard Bruce,
Netzband Derek,
Zobel John M,
Chen Jinyi,
Patterson Eric L
Publication year - 2020
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.5740
Subject(s) - poa annua , simazine , metribuzin , glufosinate , glyphosate , biology , tebuconazole , herbicide resistance , agronomy , pesticide resistance , semiochemical , atrazine , malathion , pesticide , weed control , horticulture , weed , pest analysis
BACKGROUND Indaziflam is an alkylazine herbicide used to control annual bluegrass ( Poa annua L.). Several locations in the southeastern USA reported poor annual bluegrass control following treatment with indaziflam during autumn 2015. A series of controlled environment experiments were conducted to confirm putative resistance to indaziflam in annual bluegrass collected from these field locations. RESULTS Indaziflam (25 g ha −1 ) effectively controlled all putative‐resistant annual bluegrass collections when applied preemergence (PRE), but was ineffective when applied early‐postemergence (< 2.5 cm plant height; BBCH scale = 1; EPOST). In agarose‐based plate assays, EPOST I 50 values for putative‐resistant collections ranged from 2424 to 4305 p m compared with 633 p m for the herbicide‐susceptible control; therefore, resistance indexes (R/S) ranged from 3.8 to 6.8. Resistant collections were not controlled by foramsulfuron, flumioxazin, glyphosate, glufosinate, metribuzin, pronamide, or simazine applied EPOST. Indaziflam content in herbicide‐susceptible annual bluegrass was greater than a resistant collection from 0 to 10 days after treatment (DAT). Susceptibility was not restored when resistant collections were treated with indaziflam plus 1‐aminobenzotriazole (10 mg L −1 ), tebuconazole (1510 g ha −1 ), or malathion (400 g ha −1 ). CONCLUSIONS This is a first report of resistance to indaziflam in any plant. Additionally, we confirm that these annual bluegrass collections are resistant to several other herbicidal modes‐of‐action. It is unclear if this multi‐herbicide resistance is due to a single resistance gene, multiple resistance genes, non‐target site mechanisms, or a combination thereof. Additional research to better understand resistance mechanisms in these annual bluegrass collections is warranted. © 2020 Society of Chemical Industry