Sensor‐based assessment of herbicide effects

Abstract

SummaryNon-destructive assessment of herbicide effects may be able to support integrated weed management. To test whether effects of herbicides on canopy variables could be detected by sensors, two crops were used as models and treated with herbicides at BBCH 20 using a logarithmic sprayer. Twelve days after spraying at BBCH 25 and 42 days after sowing, nine sensor systems scanned a spring barley and an oilseed rape field experiment sown at different densities and sprayed with increasing field rates of glyphosate and tribenuron-methyl. The objective was to compare ED 50 s for crops and weeds derived by the different sensors in relation to crop density and herbicides. Although sensors were not directly developed to detect herbicide symptoms, they all detected changes in canopy colours or height and crop density. Generally ED 50 s showed the same pattern in response to crop density within herbicide, but there were marked differences between barley and oilseed rape. We suggest that the results of comparing the various sensor outputs could become a stepping stone to future standardisation for the benefit of the research and development of sensors that will detect herbicide effect on crops and weeds, particularly at the most vulnerable stages of development of the canopy.

Influence of Density and Development Stage of Ryegrass on Glyphosate Effectiveness

“…In greenhouse experiments with both species (L. multiflorum and L. rigidum), high-density plants with thinning after application or without thinning demonstrated that a higher herbicide dose was required to obtain the same level of control of low-density plants. This can be verified by Several studies from the literature have shown that increasing the plant density affects herbicide effectiveness (Lati et al, 2012;Moon et al, 2014;Streibig et al, 2014). The increase in the density of Echinochloa crus-galli from 12 to 48 plants m -2 required an increase in the flucetosulfuron dose from 8.7 to 20.1 g ha -1 to obtain the same degree of control (Moon et al, 2014).…”

Assessing herbicide symptoms by using a logarithmic field sprayer

“…At 23 DAT a DJI‐Phantom 3 professional UAV flew at an altitude of 40 m to capture RGB images of the whole experiment at each location. Each subplot was cropped from the images, and the Excess Green Index (2 x G–B–R) assessed for each of approximately 1850 pixel columns per sprayed plot . At the conventional field, we excluded the sprayed no‐crop plots as they did not show any better dose–response relationship.…”

“…We used the Excess Green Index for herbicides other than carotenoid inhibitors where the symptoms resulted in color changes. 5 Numerous image analyses tools have been published and made available (approximately 150) on the Internet, most of them gratis, but as Lobet 16 puts it ' … there is a lack of wileyonlinelibrary.com/journal/ps robust validation practices or the absence of longtime support'. Consequently, we do not claim that the Excess Green Index is superior to other indices 5 , but it is simple and seems rather robust.…”

“…demonstrated how logarithmic spraying assessed the potencies ( ED 50 ) and selectivity indices of various herbicides in grass seed crops. We used logarithmic spraying to analyze images taken by an unmanned aerial vehicle (UAV) …”

“…We used logarithmic spraying to analyze images taken by an unmanned aerial vehicle (UAV). 4,5 Logarithmic spray experiments are currently not accepted as documentation in the registration of pesticides; they are considered mere demonstration tools. Logarithmic sprayers can be a valuable screening tool by replicating experiments at numerous locations, in the same way as in the crop breeding industry.…”