Mesotrione control and pigment concentration of large crabgrass (Digitaria sanguinalis) under varying environmental conditions.
BACKGROUND
Mesotrione is a carotenoid biosynthesis-inhibiting herbicide currently labeled for crabgrass (Digitaria spp.) control. Mesotrione control of large crabgrass has been reported to vary with temperature and relative humidity; however, the effect of irradiance on mesotrione efficacy has not previously been reported. Likewise, little is known about pigment concentrations of Digitaria spp. The present research investigated the effects of mesotrione on large crabgrass, Digitaria sanguinalis (L.) Scop., control and pigment concentrations under varying irradiance at three temperatures.


RESULTS
Mesotrione (0.28 kg ha(-1)) control of large crabgrass did not differ between temperature levels (18, 26 and 32 degrees C). Control was similar at tested irradiance levels (600, 1100 and 1600 micromol m(-2) s(-1)). Mesotrione reduced large crabgrass chlorophyll a, chlorophyll b and total carotenoid concentrations, as well as chlorophyll a to b ratios. Treated plant bleaching was highest 7 days after treatment (DAT) but decreased by 21 DAT. Treated plants were less than 10% necrotic 3 and 7 DAT but nearly 35% necrotic 21 DAT. Treated large crabgrass bleaching was highest and photochemical efficiency was lowest 7 DAT. These results indicate that some plant recovery occurs prior to 21 DAT.


CONCLUSIONS
Although mesotrione efficacy has previously been reported to vary according to environmental factors, mesotrione control of large crabgrass did not vary with measured temperature and irradiance levels in this study. On account of crabgrass convalescence, secondary applications of mesotrione may control large crabgrass more effectively when applied prior to 21 DAT.
McCurdy
James D
JD
Plant Sciences Department, The University of Tennessee, Knoxville, TN 37996, USA.
McElroy
J Scott
JS
Kopsell
Dean A
DA
Sams
Carl E
CE
D002338:Carotenoids / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism*; D003512:Cyclohexanones / Q000494:pharmacology*; D031746:Digitaria / Q000187:drug effects* / Q000378:metabolism; D017753:Ecosystem; D006540:Herbicides / Q000494:pharmacology*; D010858:Pigmentation / Q000187:drug effects
D003512:Cyclohexanones; D006540:Herbicides; D002734:Chlorophyll; D002338:Carotenoids; C432907:mesotrione