Selectivity of Four Preemergence Herbicides on Weed Groups Associated with Cotton (Gossypium barbadense; cv. Giza 80) and Their Joint Impact with Hand Weeding

Four preemergence herbicides; Amex EC-48% (butralin) at 2.5 L (1.2 kg a. i.) per feddan (0.42hectar); Stomp extra SC-45.5% (pendimethalin) at 1.7 L (0.7735 kg. a. i.); Lumax SC-15% (mesotrione) at 1L. (0.15 kg. a. i.) /feddan and Gardo EC-96% (s-metolachlor) at 0.6L (0.576 kg. a. i.) /feddan, were evaluated.  Amex, stomp extra and Gardo, as single treatments at the recommended field rate were ineffective against annual broad leaved weeds; however, their integration with one hand hoeing increased their performance and this enrichment may be a sole effect of hand hoeing once.  Dissimilarly, Lumax moderately controlled annual herbs and its effect increased when one hoeing was integrated to reach the same magnitude of weeded control treatment (hand hoeing twice at 30 and 60 days after sowing.).  Amex, Stomp extra and Gardo performed well against annual grasses; the excellent performance was with Stomp extra, offering more than 90% reduction in this weed group.  Amex and Gardo offered moderate effect with 77.71 and 66.83% compared to 64.29% in weeded control treatment.  Hand hoeing once enhanced the performance of Amex and Gardo to 91.07 and 97.26%, respectively. Contrary, Lumax was ineffective on annual grasses as a single treatment and its performance enhanced by 37.65% when integrated with hoeing once.  It seems that Amex, Stomp extra and Gardo are selective on annual narrow leaved weeds and Lumax was selective on annual broad leaved weeds.  Tested herbicides were not effective against perennial broad leaved weeds neither when used alone or in combination with one hand hoeing.  With the exception of Lumax, tested herbicides performed well as single treatments against perennial narrow leaved weeds.  However, their integration with one hand hoeing antagonized the performance of Amex, stomp extra and Gardo.