Specific Activity of Four Preemergence Herbicides on the Most Popular Weed Species in Cotton (Gossypium barbadense; cv. Giza 80) Cultivated in Minia University Farm

Of twelve weed species that were surveyed in 2014 cotton growing season, only five species (Euphorbia helioscopia; Corchorus olitorius; Brachiaria repans; Echinochloa colonum and Convolvulus arvensis var. arvensis) were dominant.  In 2015, 16 weed species were surveyed (ten from those surveyed in 2014 and six extra species); however, the sole dominant species was Echinochloa colonum.  Four preemergence herbicides were applied after sowing cotton and just before the first irrigation.  Those herbicides are:  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.  For controlling Echinochloa colonum; Amex and Stomp extra performed very well either when used as single treatments or in integration with one hand hoeing; Gardo moderately controlled this species, however one hoeing significantly enhanced its performance; Lumax was ineffective in controlling Echinochloa colonum.  For controlling Brachiaria repans; Amex and Stomp extra were effective; Gardo was ineffective, however its performance moderately enhanced when followed by one hand hoeing.  Lumax was ineffective in controlling this weed species.  The efficiency of the four herbicides on Corchorus olitoriusis ranged from weak to moderate; however, their joint performance with one hoeing was excellent.  Hand weeding twice was better than the four herbicides as single treatments in controlling Corchorus olitoriusis. The four herbicides were ineffective on Euphorbia helioscopia; however their integration with one hand hoeing enhanced their performance to great extent.  Based on the reduction in the population density, none of the four herbicide treatments offered good control against Convolvulus arvensis var. arvensis even when these treatments were followed by one hoeing.  Weeded control treatment was ineffective on Convolvulus arvensis var. arvensis.