Assessing herbicide symptoms by using a logarithmic field sprayer

Abstract

BACKGROUND In field experiments, assessment of herbicide selectivity and efficacy rarely takes advantage of dose–response regressions. The objective is to demonstrate that logarithmic sprayers, which automatically make a logarithmic dilution of a herbicide rate, can extract biologically relevant parameters describing the efficacy of herbicides in crops, and compare localities and time of assessment. RESULTS In a conventional and an organic field, canola, white mustard, and no crop plots were sprayed with diflufenican and beflubutamid. A mixed effect log‐logistic dose–response regression, with autoregressive correlation structure, estimated ED50 and ED90 for visual and Excess Green Index symptoms at various days after treatment (DAT). For visual assessment, ED50 differed within no crop between locations for beflubutamid at 12 DAT and 26 DAT. For diflufenican, the ED50 was different within crops at the two fields at 12 DAT, but not at 26 DAT. The Excess Green Indices at ED50 were not different among herbicides, locations, and corps; ED90 differed for white mustard and canola for beflubutamid but not for diflufenican. CONCLUSION Suitable nonlinear regression models are now available for fitting dose–response data from a logarithmic sprayer in field experiments. The derived parameters (e.g. ED50) can compare selectivity and efficacy at numerous cropping systems. © 2018 Society of Chemical Industry

The perspective of the logarithmic field sprayer technology

“…4 Theoretically, the logarithmic sprayer can produce infinite numbers of rates. 17 The field rate is continuous, and you define the 'exact' dose by knowing the sprayer's speed, pressure, and dilution capacity. So, when grading the symptoms, we use distances from the initial spraying point.…”

“…1(B)), we would need several more well-chosen field rates than the number of parameters of the regression model (Eqn (2)). One can define infinite numbers of doses by a logarithmic spray (see Da Cunha et al 17 and data in the supplementary example).…”

“…Da Cunha et al 17 fitted a mixed model to logarithmic spraying responses. Only 2000 out of more than 3000 endpoint observations could be used because of computational limitations and problems with convergence.…”

“…The mixed nonlinear regression model was computer intensive and, in several instances, there were problems with convergences for some analyses. 17 Detailed information is provided in Supporting Information Data S1 and Data S2.…”

Unravelling Phytotoxicity and Mode of Action of Tripyrasulfone, a Novel Herbicide

“…Bleaching is a typical symptom of a wide range of herbicides that inhibit carotenoid biosynthesis . The majority of these herbicides target phytoene desaturase (PDS, EC 1.3.5.6), such as diflufenican and norflurazon, , or 4-hydroxyphenylpyruvate dioxygenase (HPPD, EC.1.13.11.27), such as tolpyralate, mesotrione, isoxaflutole, tembotrione, topramezone, and benzobicyclon. ,− PDS catalyzes the conversion of phytoene to ζ-carotene in the biosynthesis of carotenoids . HPPD converts 4-hydroxyphenylpyruvic acid (HPPA) to homogentisic acid (HGA), a key precursor of plastoquinone (PQ) and α-tocopherol.…”