In field studies trifluralin and pendimethalin at 1.7 kg ai ha-1 applied PPI controlled itchgrass 87 and 78%, respectively, in late season when averaged over a 2-yr period. Clomazone at 1.1 kg ai ha-1 applied PRE to the soil surface in one year controlled 80% of itchgrass compared with 51% when applied PPI. POST application of 0.15 kg ai ha-1 fluazifop-P, 0.21 kg ai ha-1 haloxyfop, 0.10 kg ai ha-1 quizalofop, and 1.1 kg ai ha-1 diclofop controlled at least 90%. Itchgrass control was less effective with 0.43 kg ai ha-1 sethoxydim and 0.07 kg ai ha-1 clethodim POST and poor with 0.15 kg ai ha-1 imazaquin and 0.07 kg ai ha-1 imazethapyr.

Field studies were conducted in the northern and southern cane belt areas of Louisiana to determine the effect of itchgrass on sugarcane growth and yield. Itchgrass was allowed to interfere with sugarcane season-long, early-season from emergence in the spring until layby (last cultivation) in mid-June, and late-season from layby until harvest. Itchgrass germination occurred throughout the growing season. Populations of millable sugarcane stalks and yields of cane and sugar were similar for no interference, early-, and late-season interference. Season-long itchgrass interference reduced sugarcane stalk populations and cane and sugar yields an average of 34, 42, and 43%, respectively, compared with no interference.

Interference between itchgrass and soybean was evaluated over two years using area-of-influence procedures. Soybean seed weight within 20 cm of the weed was reduced 15 to 21%. In the first year, seed weight reduction of 9% was detected at a distance of 40 to 60 cm from the weed. Weight reductions were attributed to decreases in seed number of 12 to 22% within 40 cm of the weed compared with the 140 to 160 cm control area. Itchgrass interference increased soybean height within 40 cm of the weed, but soybean canopy width was generally unaffected. Soybean interference did not affect height of itchgrass plants, but did reduce weed stem numbers 89 to 94% when compared with weeds growing alone. With interference of 8 wk or less, both itchgrass green and dry weights were similar when weeds were growing alone or within the soybean row. Green and dry weights were reduced approximately 80% when itchgrass was in competition with soybean for 10 wk.