Influence of Pyrithiobac Application Rate and Timing on Weed Control and Cotton Yield in Greece¹

Abstract

Field experiments were conducted at four locations (Larissa, Halkidona, Thessaloniki, and Halastra) in Greece to evaluate weed and cotton response to various pyrithiobac rates applied preplant incorporated (PPI), preemergence (PRE), or postemergence (POST). Pyrithiobac applied PPI or PRE at 0.068, 0.102, or 0.136 kg ai/ha controlled black nightshade, pigweeds, and common purslane at Larissa. However, pyrithiobac applied PRE at Thessaloniki and Halkidona was more effective against black nightshade and pigweeds than pyrithiobac applied PPI. Pyrithiobac applied PPI or PRE at 0.068 or 0.102 kg/ha did not control common lambsquarters at Thessaloniki. Weed control with trifluralin plus fluometuron applied PPI and alachlor plus fluometuron applied PRE at Larissa was slightly lower than that obtained with pyrithiobac. At Halkidona, trifluralin plus fluometuron applied PPI and alachlor plus fluometuron applied PRE provided weed control similar to that obtained with pyrithiobac. But at Thessaloniki, these treatments provided better weed control than pyrithiobac. Furthermore, pyrithiobac applied early postemergence (EPOST), midpostemergence, or in sequential systems controlled black nightshade and pigweeds, but it resulted in fair to good control of common purslane, velvetleaf, and common cocklebur. None of the POST treatments controlled common lambsquarters. Fluometuron EPOST controlled black nightshade, common lambsquarters, and common purslane ≥70, 86, and 67%, respectively. Fluometuron EPOST did not control pigweeds, velvetleaf, and common cocklebur. Cotton treated with pyrithiobac, regardless of method of application, yielded similar to the weed-free control. Cotton treated with pyrithiobac PPI at the highest rate (0.136 kg/ ha) yielded less at Halkidona, although adverse effects after its application were not visually apparent. Yield of cotton treated with herbicides was similar, with no difference among treatments.

Residual phytotoxic activity of pethoxamid in soil and its concentration in soil water under different soil moisture conditions

“…Several studies have reported that the residual phytotoxic activity of soil‐applied herbicides primarily coincided well with the amount of herbicides in the soil, such as atrazine (6‐chloro‐ N ‐ethyl‐ N′ ‐[1‐methylethyl]‐1,3,5‐triazine‐2,4‐diamine; Aladesanwa 2005), imazamox (2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1 H ‐ imidazol‐2‐yl]‐5‐[methoxymethyl]‐3‐pyridinecarboxylic acid; Bresnahan et al . 2002), isoxaben ( N ‐[3‐(1‐ethyl‐1‐methylpropyl)‐5‐isoxazolyl]‐2,6‐dimethoxybenzamide; Chandran & Derr 1998) and pyrithiobac (2‐chloro‐6‐[(4,6‐dimethoxy‐2‐pyrimidinyl) thio] benzoic acid; Kaloumenos et al . 2005), and imazethapyr (2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1 H ‐imidazol‐2‐yl]‐5‐ethyl‐3‐pyridinecarboxylic acid; Ayeni et al .…”

Tillage implement effects on herbicide efficacy and the yield of cotton grown under a sprinkler or drip irrigation system

“…2006). Also, Kaloumenos et al . (2005) found that pyrithiobac provided excellent control of black nightshade and redroot pigweed.…”

“…2005). However, pyrithiobac provides poor control of some economically important broad‐leaved weeds, like common lambsquarters ( Chenopodium album L.) and tall morningglory ( Ipomoea purpurea L. Roth) (Culpepper & York 1998; Kaloumenos et al . 2005), while trifloxysulfuron‐sodium provides poor control of velvetleaf ( Abutilon theophrasti Medik.…”

Problems and achievements of cotton (Gossypium Hirsutum L.) weeds control

“…Cotton plants show signs of damage after application of the herbicide, but they recover after 30 -40 days. In Greece the effect of different doses of pyrithiobac-sodium on weeds and cotton was studied (Kaloumenos, 2005). Ryrithiobacsodium was applied at different periods: before sowing by incorporation, after sowing before emergence, and during the growing season of cotton.…”