Evaluation of the efficacy of some foliar herbicides on control of purple nutsedge (Cyperus rotundus L.) in sugarcane (Saccharum officinarum L.)

Abstract

Two experiments were undertaken at the research Farm of Sugarcane Research Center at Guneid during the seasons of 2004/05 and 2005/06. One field and one pot experiment were executed during each season to evaluate the effect of new foliar herbicides versus other chemical and manual methods on the control of purple nutsedge in sugarcane. The objectives of the trials were: 1) to compare the effectiveness of two traditional methods (hand weeding and hoeing) in controlling purple nutsedge 2) to evaluate the efficacy and selectivity of two new herbicides in controlling the growth of the purple nutsedge as compared to the standard sugarcane herbicide (Gesapax +Gesaprim) and to evaluate the impact of that on yield and 3) to assess the effect of the treatments used on production and viability of purple nutsedge tubers. The products used were a tank mixture of ametryne + atrazine known commercially as Gesapax 50 FW + Gesaprim 50 FW, used as standard herbicide at its recommended rate 3.81 L + 3.81 L product/ha, the ready made mixture of Trifloxysulfuron-sodium + ametryne known commercially as Krismat 75 WG at three levels 1.79, 2.38 and 2.98 kg product/ha and the herbicide Trifloxysulfuron-sodium known commercially as Envoke 75 WG at three doses 0.025 kg, 0.030 kg and 0.035 kg product/ha. The study revealed that, very good control of the purple nutsedge was attained by all chemical treatments compared to untreated check. The newly used herbicide (Envoke) at its highest rate and Gesapax +Gesaprim at its recommended rate significantly reduced the number of purple nutsedge compared to the untreated check. Also Gesapax +Gesaprim gave the lowest number of green leaves per weed. Results in the two seasons of both the field and the pot experiments indicated that, eight weeks from the application of the herbicides non of the herbicides led to any significant difference in the growth of purple nutsedge. The herbicides Envoke and Krismat showed consistent reduction in tubers production and germination ability of Cyperus rotundus. Therefore, their successive application may lead to persistence and continuous reduction in number of the purple nutsedge weed. The traditional method of controlling the weed by hand hoeing in both the field and the pot experiment, gave the tallest sugarcane plants and the greatest number of sugarcane tillers as compared to the herbicide treatments. The study showed that, the standard herbicide (Gesapax + Gesaprim) was phytotoxic to sugarcane plant early in the season and this was reflected in the reduction of some sugarcane growth parameters. However, this effect disappeared by time starting from eight weeks from application. Envoke herbicide did not show any phytotoxic effect on the crop, but Krismat showed severe phytotoxicity which disappeared after eight weeks from application. Non of the weed control measures significantly affected the sugarcane yield (tones/ha) nor the juice quality.