24 research outputs found
Hairy fleabane (Conyza bonarienis) response to saflufenacil in association with different formulations of glyphosate subjected to simulated rainfall
Saflufenacil has been used to control glyphosate resistant weeds, including hairy
fleabane. There are several glyphosate formulations, which are related to different salts and
adjuvants. Differences between these formulations may result in variations in efficacy, especially
in the face of unfavorable environmental conditions, such as the occurrence of unexpected rainfall
after application. The objective of this study was to evaluate the control of hairy fleabane with
saflufenacil in tank mix with different formulations of glyphosate subjected to simulated rainfall
after application. The treatments evaluated were salts of glyphosate (isopropylamine, potassium
and ammonium salt), different periods of simulated rainfall after herbicide application (30, 120
and 240 min, and no rainfall), and the presence or absence of saflufenacil and a non-ionic
adjuvant. Absorption of saflufenacil by hairy fleabane is rapid, since simulated rainfall after 30
min after application did not result in loss of efficiency when the herbicide is applied with
adjuvant. The association of isopropylamine and ammonium salts of glyphosate with saflufenacil
increases the control of hairy fleabane and prevents the occurrence of regrowth when rainfall
occurs at 30 min after the application. The occurrence of simulated rainfall after 240 min reduces
the glyphosate efficiency by 30%, 15% and 60% for the isopropylamine, potassium and
ammonium salt formulations, respectively. The addition of adjuvant improves the efficiency of
glyphosate salt of potassium by 40%. The response of the mixture of glyphosate and saflufenacil
is variable, mainly in situations of rainfall after application
Interactions of Saflufenacil with Other Herbicides Promoters of Oxidative Stress to Control Joyweed1
Low temperature reverses the resistance to glyphosate in hairy fleabane (Conyza bonariensis)
Environmental factors and the addition of adjuvants to the spray tank mix may interfere with
glyphosate efficiency in hairy fleabane control. The objective of this study was to evaluate
the effect of air temperature and the addition of ammonium sulfate (NH4)2SO4 to glyphosate in the control of glyphosate-resistant (GR) and -susceptible (GS) hairy fleabane. Treatments consisted of air temperatures of 12°C and 25°C, six doses of glyphosate from zero to
2,880 g · haâ1, the presence or absence of (NH4)2SO4 in the spray solution, and one GS and
another GR biotype. At the lowest tested dose (180 g · haâ1), control of the GR biotype was
91% and 20% when the plants were kept at 12°C and 25°C, respectively, reducing the resistance factor (RF) by 9.30 times and was associated to the reduction of temperature. The addition of (NH4)2SO4 increased the control by 10â20% at high glyphosate doses and at 25°C.
The resistance of hairy fleabane to glyphosate was completely reversed when the plants were
maintained at 12°C. At this temperature, resistant plants were controlled even at doses well
below that recommended for the control of this species. At 25°C, a dose four times higher
than that recommended was required for satisfactory control. At the field level, under situations of low temperatures, it was possible to improve the efficacy of glyphosate applications
in hairy fleabane control, if there were no other mechanisms of resistance involved