Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2006
Publication Date: 1/10/2007
Citation: Lovelace, M.L., Talbert, R.E., Scherder, E.F., Hoagland, R.E. 2007. Effects of multiple applications of simulated quinclorac drift rates on tomato. Weed Science 55:167-169.
Interpretive Summary: Various factors can cause herbicide drift from the intended application site. Injury or total crop loss to non-target plants or crops may ensue after drift occurs, depending on the plant sensitivity. Tomatoes (Lycopersicon esculentum) and rice (Oryza sativa) are commercially grown in close proximity in areas of Arkansas, and tomato growers suspect that drift of the herbicide, quinclorac (applied to rice several times per season) has caused injury and crop loss in some instances. Research on simulated-drift of quinclorac showed that tomato plants were very sensitive, with injury (various growth abnormalities) occurring at rates of 0.42 g per hectare (0.001 times the normal rate for rice). Tomato yield also was lowered at rates above 0.42 g per hectare. Overall, tomato plant injury and yield reductions increased as the drift rate or number of drift applications increased.
Technical Abstract: Quinclorac (Facet) drift has been speculated as the cause of injury to tomato crops throughout Northeast Arkansas. In this study we set out to determine if tomato plant injury and yield reduction were correlated with simulated drift rates of quinclorac. Experiments s were carried out at Fayetteville, AR, in 1999 and 2000. Maximum plant injury (visual ratings) was about 20% when plants were treated with either, one, two, or three applications (weekly intervals beginning at first flower bloom) of quinclorac at 0.42 g ai ha-1 (0.001 times the normal use rate to simulate drift). Maximum plant injury ranged from 48 to 68% with quinclorac treatment of 42 g ha-1. Overall, increasing quinclorac rate and number of applications increased tomato injury. In both years, tomato plant fresh weight accumulation was not influenced by one, two, or three applications of quinclorac at 0.42 g ha-1 compared to the untreated control. In 1999, increasing the rate of quinclorac from 0.42 g ha-1 to 4.2 g ha-1 reduced plant fresh weight accumulation. In 2000, there was no significant difference in plant fresh weight when plants were treated with quinclorac at 2.1 to 4.2 g ha-1. Evaluation of the herbicide rate effect indicated that quinclorac at 0.42 g ha-1 did not reduce tomato fruit yield (total weight of edible fruit) compared to the untreated control, but yield decreased as rate increased above 0.42 g ha-1. Increasing application number generally decreased tomato yield, and overall as maximum visual plant injury increased, tomato yield reduction also increased linearly. We conclude that quinclorac at simulated drift rates can adversely affect tomato plant growth and yield.