Oakes Irrigation Research
Site
Carrington Research Extension Center * North Dakota State University
P.O. Box 531, Oakes, ND 58474-0531, Voice: (701) 742-2189, FAX: (701)
742-2700, email: rgreenla@ndsuext.nodak.edu
WEED CONTROL IN
PINTO BEAN
WITH REDUCED HERBICIDE RATES
Chad Ringdahl and Calvin Messersmith
NDSU Department of Plant Sciences
Table 38. Pigweed control, crop injury, and pinto bean yield.
An experiment was conducted to evaluate redroot pigweed and hairy nightshade control in pinto bean with five herbicides applied at reduced rates. 'Frontier' pinto bean was planted May 20, in 30-inch-wide rows at a seeding rate of 45 lb/acre. Pendimethalin was applied preemergence at 0.825 lb ai/acre on May 21 and incorporated with 1 inch of water. Experimental design was a randomized complete block with four replications and plot size was 10 by 20 ft. Treatments were applied to the center two rows of the plot with a bicycle-wheel-type plot sprayer equipped with a shield, delivering 8.5 gpa at 40 psi through 8001 flat fan nozzles.
First applications of the split treatments were applied on June 6 to pinto bean with one trifoliolate leaf, cotyledon to 4-leaf nightshade, and cotyledon to 4-leaf redroot pigweed. Visual evaluations were made 7 days after treatment to determine weed control and pinto bean injury. Sequential applications of split treatments were made when weeds were in the 4-leaf stage. Single application treatments were applied to 6- to 8-leaf nightshade and pigweed. Pinto bean was at the 7- to 8-trifoliolate leaf stage. All treatments were applied with methylated seed oil at 1.5% v/v.
Plots were harvested 23 September 1999, by pulling pinto beans from the center rows of each plot. Yield was calculated and data were analyzed using analysis of variance. Treatment differences were compared with a Fishers protected LSD.
Acifluorfen (Blazer), fomesafen (Reflex) and lactofen (Cobra), all are diphenylether herbicides and are contact cell-membrane-disrupter (PPO inhibitor) herbicides. The redroot pigweed control data suggests that a single application of these herbicides was not as effective as split applications. This may be due to several factors, (i) redroot pigweed canopy may have prevented adequate coverage of foliage resulting in reduced control, or (ii) redroot pigweed germinated after the single application of these herbicides resulting in the weeds escaping the herbicide treatment. Imazamox (Raptor) and imazethapyr (Pursuit) are imidazolinone herbicides, and are translocated, lipid synthesis inhibiting (ALS inhibitor) herbicides. Single treatments of these herbicides provided similar control of redroot pigweed as split treatments. This may be caused by several factors, (i) the translocation properties of these herbicides may overcome coverage problems associated with heavy canopies, or (ii) soil residual activity may provide control of redroot pigweed that had not emerged at the time of application.
All treatments provided 98% control of hairy nightshade. The nightshade density was low, perhaps due to the high pigweed density in the trial, but nightshade control was excellent when present. Pinto bean injury was highest with multiple applications of lactofen and acifluorfen, which was expected as these two herbicides can cause the most visible injury to soybean. Imazamox and imazethapyr did not cause increased injury with multiple applications.
Pinto bean yield appeared to follow the same pattern as crop injury. Pinto bean receiving multiple applications of acifluorfen and lactofen yielded less than other treatments. Treatments with combinations of imidazolinone and diphenylether herbicides resulted in yields similar to the handweeded check. Also, there was less pinto bean injury caused by imidazolinone plus diphenylether tank mixtures than diphenylether herbicides applied alone. This may be due to the lower rate of diphenylether herbicide applied to the pinto bean or possible protection of pinto bean from injury due to antagonism of the diphenylether herbicide by the imidazolinone herbicide.
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Table 38. Pigweed control, crop injury, and pinto bean yield in the 1999 edible dry bean weed control study at the Oakes Irrigation Research Site.
| Treatment | Rate | Number of applications | Pigweed control | Crop injury | Crop Yield |
| oz ai/acre | % | lbs/A | |||
| Imazamox | 0.5 | 1 | 97 | 5 | 1780 |
| Imazamox | 0.1875 | 2 | 98 | 4 | 1680 |
| Imazamox | 0.125 | 3 | 98 | 5 | 1790 |
| Imazethapyr | 0.5 | 1 | 96 | 4 | 1700 |
| Imazethapyr | 0.1875 | 2 | 95 | 5 | 1630 |
| Imazethapyr | 0.125 | 3 | 98 | 5 | 1930 |
| Lactofen | 1.5 | 1 | 80 | 5 | 1080 |
| Lactofen | 0.5 | 2 | 98 | 7 | 1130 |
| Lactofen | 0.375 | 3 | 95 | 11 | 1030 |
| Fomesafen | 3.0 | 1 | 80 | 5 | 1360 |
| Fomesafen | 1.2 | 2 | 96 | 5 | 1520 |
| Fomesafen | 0.8 | 3 | 98 | 5 | 1900 |
| Acifluorfen | 4.0 | 1 | 79 | 5 | 1510 |
| Acifluorfen | 1.6 | 2 | 94 | 6 | 1440 |
| Acifluorfen | 1.0 | 3 | 98 | 7 | 1300 |
| Imazamox + lactofen | 0.0625 + 0.375 | 2 | 98 | 8 | 1450 |
| Imazethapyr + lactofen | 0.125 + 0.375 | 2 | 98 | 7 | 1450 |
| Imazamox + fomesafen | 0.0625 + 1.0 | 2 | 98 | 4 | 1810 |
| Imazethapyr + fomesafen | 0.125 + 1.0 | 2 | 97 | 4 | 1720 |
| Imazamox + acifluorfen | 0.0625 + 1.0 | 2 | 98 | 8 | 1730 |
| Imazethapyr + acifluorfen | 0.125 + 1.0 | 2 | 94 | 5 | 1420 |
| Handweeded | NA | NA | 100 | 0 | 1890 |
| Untreated | NA | NA | 0 | 0 | 480 |
| C.V. % | 8.3 | 38 | 22 | ||
| LSD (0.05) | 11 | 3 | 460 | ||
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Go to Oakes Irrigation Research Site Weed Control Studies page
Go to Oakes Irrigation Research Site 1999 annual report