60 Weed Control in Hybrid Cottonwood Plantations. Exp.# 93-600. An experiment was initiated near Boardman, OR. to evaluate preplant incorporated (PPI), preemergence (PRE) and postemergence (POST) treatments for general weed control during establishment of hybrid cottonwood trees for pulp. Plots were 10' x 220' in size, arranged in an RCD design with four replications. The treatments were repeated at four sites each with a different prior cropping history. The sites were: I. heavy wheat residue - Table 1. II. light wheat residue - Table 2. III. alfalfa - Table 3. IV. blue-grass for seed - Table 4. PPI treatments were applied on March 25 - April 6, 1993 and incorporated with a power driven rotovator. Hybrid cottonwood trees were planted in late April - early May and drip irrigated. PRE treatments were applied May 12, 1993. POST treatments were applied in late May, 1993. Evaluations of percent weed cover for individual species were made on June 14, July 13, and August 24. Estimates were made by placing a 0.5 m 2 quadrat across the row and visually estimating cover. Four quadrats per plot were evaluated. Results indicate that prior cropping history had a predominant effect on weed species composition. Volunteer crop species including volunteer potatoes in locations I and II, and volunteer alfalfa in location III were predominant. Glyphosate and 2,4-D provided consistently better weed control in all locations than other treatments. Trifluralin alone or in combination with metribuzin as a PPI treatment provided fairly good season long weed control. The Kerb /Goal split application provided fairly good early season control, but control diminished later in the season. Other treatments were fair to poor in season long weed control. Russian thistle and redroot pigweed were major weed problems late in the growing season in most plot areas. Watergrass (Echinochloa crus-galli) became a major problem in some plots at location IV. Treatment abbreviations in Tables: gly - glyphosate, pron - pronamide, oxy - oxyfluorfen, pend - pendimethalin, trif - trifluralin, metr - metribuzin. Weed references for Tables 1 through 4 are listed in Table 5.
61 Table 1. Weed Control in Hybrid Cottonwood Production - Location I Heavy Wheat. Exp.# 93-600. Rate --------------------------Broadleaves---------------------------- ------Grasses------- TMT (lb ai/a) Timing Dead LQ PW PL RT NS BR HB VOP OBL WG VOW OGR ---------------------------------------% cover------------------------------------------ control -- 6 22 1 -- 7 4 5 12 3 7 1 9 1 gly+2,4-d 1.125+0.5 POST 30 0 0 -- 0 0 0 1 0 0 0 0 0 oxy+pron 1.6+1.0 POST 4 1 0 -- 0 0 2 0 6 0 0 8 0 oxy/pron 1.6/1.0 PPI/POST 10 0 0 -- 0 0 1 0 3 0 1 1 0 trif+oxy 2.0+1.6 PPI 10 1 1 -- 0 1 1 1 17 1 1 1 0 pend+diuron 3.3+1.0 PPI 10 0 1 -- 2 1 0 1 13 1 1 1 0 trif+metr 2.0+0.5 PPI 10 0 1 -- 1 8 0 1 17 1 0 1 0 metribuzin 0.5 PRE 9 2 1 -- 4 6 1 5 8 4 1 12 1 metr+diuron 0.5+1.0 POST 2 0 1 -- 0 2 2 1 10 2 4 15 0 trifluralin 2.0 PPI 10 1 1 -- 0 11 1 4 11 3 1 1 0 metr/metr 0.5/0.5 PRE/POST 3 0 1 -- 0 5 0 1 15 1 3 12 1 terbacil 1.6 POST 22 0 1 -- 2 1 0 1 5 1 1 24 0 control -- 20 35 3 10 12 4 3 1 2 6 1 -- 3 gly+2,4-d 1.125+0.5 POST 24 0 1 0 1 1 0 1 0 2 1 -- 0 oxy+pron 1.6+1.0 POST 18 5 1 0 2 1 5 1 6 2 6 -- 0 oxy/pron 1.6+1.0 PPI/POST 10 2 1 0 4 3 0 0 7 0 6 -- 1 trif+oxy 2.0+1.6 PPI 12 1 1 0 1 10 0 3 10 1 0 -- 0 pend+diuron 3.3+1.0 PPI 10 1 4 0 6 2 0 2 16 2 1 -- 1 trif+metr 2.0+0.5 PPI 10 1 1 0 2 26 0 1 13 2 0 -- 0 metribuzin 0.5 PRE 23 5 3 5 17 10 1 3 8 4 1 -- 2 metr+diuron 0.5+1.0 POST 20 0 4 0 0 4 1 1 11 3 5 -- 3 trifluralin 2.0 PPI 13 2 1 3 2 33 1 2 9 6 1 -- 1 metr/metr 0.5/0.5 PRE/POST 18 0 3 0 4 11 0 1 10 3 7 -- 3 terbacil 1.6 POST 34 0 5 3 9 0 0 3 19 2 0 -- 1 control -- 21 53 9 18 16 0 1 1 -- 7 2 -- 0 gly+2,4-d 1.125+0.5 POST 22 2 2 1 0 0 1 1 -- 1 5 -- 0 oxy+pron 1.6+1.0 POST 28 2 3 2 6 0 0 1 -- 5 14 -- 0 oxy/pron 1.6/1.0 PPI/POST 18 8 1 0 5 0 2 0 -- 1 9 -- 1 trif+oxy 2.0+1.6 PPI 24 7 5 5 7 1 1 1 -- 1 0 -- 0 pend+diuron 3.3+1.0 PPI 16 9 9 1 29 0 1 1 -- 1 0 -- 0 trif+metr 2.0+0.5 PPI 28 5 4 1 9 4 0 2 -- 2 1 -- 1 metribuzin 0.5 PRE 26 17 3 6 42 0 3 1 -- 15 6 -- 2 metr+diuron 0.5+1.0 POST 37 1 17 1 7 0 2 0 -- 5 10 -- 3 trifluralin 2.0 PPI 43 9 7 4 3 3 3 1 -- 4 1 -- 0 metr/metr 0.5/0.5 PRE/POST 36 1 9 1 16 0 3 3 -- 9 13 -- 1
62 terbacil 1.6 POST 45 0 7 8 26 0 3 4 -- 6 8 -- 0
63 Table 2. Weed Control in Hybrid Cottonwood Production - Location II Light Wheat. Exp.# 93-600. Rate -------------------Broadleaves------------------- -------Grasses-------- TMT (lb ai/a) Timing Dead LQ VOLP PW RSF OBL GF WG VOLW OGR ---------------------------------% cover---------------------------------- control -- 0 4 9 1 1 2 0 1 27 0 gly+2,4-d 1.125+0.5 POST 44 1 0 0 0 0 0 0 0 0 oxy+pron 1.6+1.0 POST 0 4 12 7 1 0 2 8 9 0 oxy/pron 1.6/1.0 PPI/POST 0 5 17 4 0 1 1 8 0 0 trif+oxy 2.0+1.6 PPI 0 1 17 1 0 0 0 1 1 0 pend+diuron 3.3+1.0 PPI 0 1 22 3 0 1 0 2 0 0 trif+metr 2.0+0.5 PPI 0 1 22 1 1 1 1 1 0 0 metribuzin 0.5 PRE 1 1 14 0 1 2 0 1 22 0 metr+diuron 0.5+1.0 POST 0 1 13 3 1 1 1 10 12 0 trifluralin 2.0 PPI 0 1 15 2 1 0 1 1 1 0 metr/metr 0.5/0.5 PRE/POST 0 1 11 1 0 0 1 1 17 0 terbacil 1.6 POST 0 1 7 1 1 0 1 0 24 0 control -- 22 13 -- 1 2 5 1 2 -- 0 gly+2,4-d 1.125+0.5 POST 33 1 -- 2 1 0 0 4 -- 0 oxy+pron 1.6+1.0 POST 14 14 -- 11 1 1 14 22 -- 0 oxy/pron 1.6/1.0 PPI/POST 10 15 -- 13 4 1 4 29 -- 0 trif+oxy 2.0+1.6 PPI 11 3 -- 2 3 0 1 4 -- 0 pend+diuron 3.3+1.0 PPI 11 8 -- 11 2 1 1 5 -- 0 trif+metr 2.0+0.5 PPI 13 4 -- 3 3 0 3 2 -- 0 metribuzin 0.5 PRE 25 1 -- 2 1 4 1 6 -- 0 metr+diuron 0.5+1.0 POST 15 8 -- 9 2 1 9 22 -- 0 trifluralin 2.0 PPI 11 9 -- 6 7 1 1 2 -- 0 metr/metr 0.5/0.5 PRE/POST 18 2 -- 7 1 1 3 13 -- 0 terbacil 1.6 POST 29 1 -- 1 1 2 1 4 -- 0 control -- 19 40 -- 12 1 7 4 13 -- 0 gly+2,4-d 1.125+0.5 POST 24 3 -- 11 3 1 0 15 -- 0 oxy+pron 1.6+1.0 POST 10 33 -- 21 0 2 11 39 -- 2 oxy/pron 1.6/1.0 PPI/POST 4 37 -- 21 2 3 3 29 -- 2 trif+oxy 2.0+1.6 PPI 9 26 -- 8 2 2 0 8 -- 0 pend+diuron 3.3+1.0 PPI 11 21 -- 27 0 5 4 18 -- 0 trif+metr 2.0+0.5 PPI 13 26 -- 4 5 2 1 5 -- 0 metribuzin 0.5 PRE 25 8 -- 11 1 7 3 24 -- 0 metr+diuron 0.5+1.0 POST 15 11 -- 18 1 4 18 38 -- 0 trifluralin 2.0 PPI 14 21 -- 13 7 2 2 12 -- 0 metr/metr 0.5/0.5 PRE/POST 18 8 -- 21 0 0 8 40 -- 0 terbacil 1.6 POST 22 3 -- 6 1 4 1 42 -- 0
64 Table 3. Weed Control in Hybrid Cottonwood Production - Location III Alfalfa. Exp.# 93-600. Rate -------------------Broadleaves------------------- -------Grasses-------- TMT (lb ai/a) Timing Dead LQ PW BR HB ALF OBL WG GF OGR ---------------------------------% cover---------------------------------- control -- 9 8 0 10 7 64 1 0 3 0 gly+2,4-d 1.125+0.5 POST 45 2 0 1 10 11 3 0 2 0 oxy+pron 1.6+1.0 POST 1 0 0 0 0 71 2 0 1 0 oxy/pron 1.6/1.0 PPI/POST 10 0 0 0 0 15 0 1 1 0 trif+oxy 2.0+1.6 PPI 10 0 0 0 1 28 1 0 1 0 pend+diuron 3.3+1.0 PPI 10 0 0 0 1 28 1 0 0 0 trif+metr 2.0+0.5 PPI 8 1 0 1 1 23 0 0 1 0 metribuzin 0.5 PRE 11 0 0 6 2 65 4 1 4 1 metr+diuron 0.5+1.0 POST 2 2 0 1 9 65 1 1 3 1 trifluralin 2.0 PPI 10 1 0 2 1 28 2 0 1 0 metr/metr 0.5/0.5 PRE/POST 0 0 0 1 1 71 1 0 2 0 terbacil 1.6 POST 18 0 0 0 0 65 1 1 1 0 control -- 21 14 0 1 0 66 3 0 7 0 gly+2,4-d 1.125+0.5 POST 53 3 0 0 1 18 6 1 6 0 oxy+pron 1.6+1.0 POST 10 0 0 0 0 80 1 1 2 0 oxy/pron 1.6/1.0 PPI/POST 10 1 0 0 0 52 1 4 1 0 trif+oxy 2.0+1.6 PPI 10 0 0 0 0 58 5 0 1 0 pend+diuron 3.3+1.0 PPI 11 1 0 0 1 55 1 0 1 0 trif+metr 2.0+0.5 PPI 10 1 0 0 1 60 2 0 1 0 metribuzin 0.5 PRE 14 1 0 1 1 72 5 0 9 0 metr+diuron 0.5+1.0 POST 13 5 0 0 0 76 1 1 2 0 trifluralin 2.0 PPI 11 0 0 0 0 61 3 0 0 0 metr/metr 0.5/0.5 PRE/POST 10 0 0 0 0 78 0 0 5 0 terbacil 1.6 POST 12 0 0 0 0 75 1 0 3 0 control -- 5 8 0 0 0 76 7 1 6 0 gly+2,4-d 1.125+0.5 POST 48 7 11 0 0 12 0 3 5 0 oxy+pron 1.6+1.0 POST 3 0 1 0 0 83 5 2 2 0 oxy/pron 1.6/1.0 PPI/POST 1 0 1 0 0 70 3 8 1 1 trif+oxy 2.0+1.6 PPI 1 1 0 0 0 74 7 0 0 0 pend+diuron 3.3+1.0 PPI 2 0 1 0 0 78 4 0 2 0 trif+metr 2.0+0.5 PPI 1 1 1 0 0 73 1 0 1 0 metribuzin 0.5 PRE 5 0 0 0 0 74 10 0 17 0 metr+diuron 0.5+1.0 POST 3 3 1 0 0 78 0 1 6 0 trifluralin 2.0 PPI 2 1 1 0 0 68 7 0 0 0 metr/metr 0.5/0.5 PRE/POST 4 0 0 0 0 80 3 1 7 0 terbacil 1.6 POST 4 1 1 0 0 78 5 0 9 1
65 Table 4. Weed Control in Hybrid Cottonwood Production - Location IV Grass. Exp.# 93-600. Rate ----------------------Broadleaves---------------------- -------Grasses-------- TMT (lb ai/a) Timing Dead LQ PW RT NS HB OBL GF WG VOLG OGR ------------------------------------% cover------------------------------------- control -- 20 1 -- 0 -- 1 1 -- 0 41 0 gly+2,4-d 1.125+0.5 POST 41 1 -- 1 -- 9 1 -- 1 9 0 oxy+pron 1.6+1.0 POST 28 2 -- 0 -- 3 1 -- 1 19 1 oxy/pron 1.6/1.0 PPI/POST 9 1 -- 0 -- 0 0 -- 1 1 0 trif+oxy 2.0+1.6 PPI 10 1 -- 0 -- 1 1 -- 0 1 1 pend+diuron 3.3+1.0 PPI 10 1 -- 1 -- 2 1 -- 1 2 1 trif+metr 2.0+0.5 PPI 10 0 -- 0 -- 1 1 -- 0 1 0 metribuzin 0.5 PRE 52 0 -- 1 -- 0 1 -- 1 17 0 metr+diuron 0.5+1.0 POST 29 1 -- 0 -- 3 1 -- 5 14 1 trifluralin 2.0 PPI 10 1 -- 0 -- 4 1 -- 1 2 1 metr/metr 0.5/0.5 PRE/POST 32 0 -- 0 -- 1 1 -- 1 19 0 terbacil 1.6 POST 74 0 -- 1 -- 0 1 -- 1 0 0 control -- 32 1 2 1 0 2 9 1 1 43 3 gly+2,4-d 1.125+0.5 POST 74 1 0 0 2 5 0 1 3 1 0 oxy+pron 1.6+1.0 POST 26 7 5 1 1 3 5 4 11 24 1 oxy/pron 1.6/1.0 PPI/POST 10 3 0 0 2 1 0 4 28 2 1 trif+oxy 2.0+1.6 PPI 11 1 0 0 3 6 1 1 1 1 0 pend+diuron 3.3+1.0 PPI 11 5 1 2 3 9 1 1 4 2 1 trif+metr 2.0+0.5 PPI 11 4 1 0 5 5 2 1 0 2 0 metribuzin 0.5 PRE 45 2 0 5 2 4 3 3 4 30 0 metr+diuron 0.5+1.0 POST 27 3 2 1 1 4 1 7 10 27 1 trifluralin 2.0 PPI 16 3 1 0 3 7 3 3 2 3 0 metr/metr 0.5/0.5 PRE/POST 23 0 1 1 4 3 3 4 8 38 0 terbacil 1.6 POST 79 0 1 1 1 4 0 1 3 5 2 control -- 22 5 3 1 0 1 13 1 6 48 0 gly+2,4-d 1.125+0.5 POST 73 0 1 0 1 10 1 0 11 1 0 oxy+pron 1.6+1.0 POST 16 13 5 0 2 0 11 10 25 30 3 oxy/pron 1.6/1.0 PPI/POST 10 11 0 4 0 0 4 9 53 5 0 trif+oxy 2.0+1.6 PPI 16 5 0 0 15 2 3 0 3 3 0 pend+diuron 3.3+1.0 PPI 16 17 4 12 8 0 2 1 6 6 0 trif+metr 2.0+0.5 PPI 16 13 2 4 19 2 4 1 1 2 0 metribuzin 0.5 PRE 28 6 1 2 2 1 15 8 13 35 0 metr+diuron 0.5+1.0 POST 22 2 8 7 3 1 0 15 24 34 0 trifluralin 2.0 PPI 18 32 0 0 14 1 6 3 7 5 0 metr/metr 0.5/0.5 PRE/POST 13 3 8 3 13 0 7 14 9 42 0 terbacil 1.6 POST 33 3 13 13 7 1 4 3 28 19 3 Table 5. Weed Reference for Tables 1 through 4. Exp.# 93-600.