Effect of glyphosate doses applied through different methods on the control of Congo grass (Imperata cylindrica L.) growing in newly planted pomegranate (Punica granatum L.) orchards in Iraq

Abstract

Congo grass, Imperata cylindrica L. is one of the most harmful invasive perennial grasses in Iraq, infesting newly planted pomegranate orchards. Therefore, the field experiment was conducted to control Congo grass by spraying different concentrations of glyphosate (0.36 kg a. i./l). The complete randomized block design (CRBD) was used for the experiment with three replications. Total eight treatments of glyphosate were used in this study. In first control treatment (T1), only water was used i. e. without glyphosate. The second treatment (T2) contained 1 litre glyphosate in 1 litre of water. The third treatment (T3) contained 1 litre glyphosate in 2 litres of water. Likewise, 4th, 5th, 6th and 7th treatments contained 1 litre glyphosate in 3, 4, 5 and 6 litres of water, respectively. In eighth treatment (T8), herbicide glyphosate @ 1.8 kg a. i./hawas sprayed with a Knap Sack pressure sprayer on Congo grass. The results indicated the superiority of T2 treatment for the control of Congo grass as compared to other treatments. It showed the highest control rate which reached to 62.40% in the scale of 1 to 100. Whereas T2 and T3 treatments indicated the lowest average regrowth rates of Congo grass to the tune of 6.03 and 6.98%, respectively, in the scale of 1 to 10. It appeared that the effectiveness of the glyphosate continued beyond 360 days after treatment. Significant differences were found in the reduction of the plant height to 74.3 cm under T5 as compared to other treatments. Significantly lowest foliage dry weight (125.67 g/m2) of Congo grass was recorded under Tas compared to T4 T1 and T7 treatments. The other treatments (T8, T2, T3, T4 and T5) were at par in respect to production of foliage dry weight. Significantly lowest rhizome dry weight was observed under T5 (141.33 g/m2) as compared to T1, T3, T6, T7 and T8), whereas rest of the treatments (T2 and T4) were at par with T5 in respect to rhizome dry weight production. The Rope-wick sprayer gave greater control of Congo grass compared with Knap Sack sprayer and that too without affecting pomegranate plants.