Stahlman, Phillip W.

Kansas State University

Kansas Agricultural Experiment Station Research Reports Volume 0 Issue 12 Keeping up with Research Article 11 1986 Competition and Control of Annual Bromes in Winter Wheat Phillip W. Stahlman This report is brought to you for free and open access by New Prairie Press. It has been accepted for inclusion in Kansas Agricultural Experiment Station Research Reports by an authorized administrator of New Prairie Press. Copyright 1986 Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. K-State Research and Extension is an equal opportunity provider and employer. Follow this and additional works at: https://newprairiepress.org/kaesrr Recommended Citation Stahlman, Phillip W. (1986) "Competition and Control of Annual Bromes in Winter Wheat," Kansas Agricultural Experiment Station Research Reports: Vol. 0: Iss. 12. https://doi.org/10.4148/2378-5977.7248 Competition and Control of Annual Bromes in Winter Wheat Keywords Keeping up with research; 90 (Oct. 1986); Kansas Agricultural Experiment Station contribution; no. 87-78-S; Winter wheat; Weeds; Cheatgrass; Annual bromes; Bromes Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License. This research report is available in Kansas Agricultural Experiment Station Research Reports: https://newprairiepress.org/kaesrr/vol0/iss12/11 , . ___ _ A!S September 1986 Competition and Control of Annual Bromes in Winter Wheat Phillip W. Stahlman Weed Control Research Agronomist Fort Hays Branch Station Downy brome (Bromus tectorum), Japanese brome (B. japonicus) , and cheat (B. secalinus) are win-1r annual grass weeds, which are referred to collec-•tvely as cheat or cheatgrass. The increase and spread of these weeds have been rapid in recent years, in re-sponse to favorable conditions created by conservation tillage practices and semi-dwarf wheat varieties. In-creased use of commercial fertilizers and selective, highly effective herbicides for broadleaved weeds in wheat also favors annual bromes. Cheat is most common in · the continuous vJheat region of Kansas, whereas downy brome predominates in the drier western part of the state. Japanese br,ome grows throughout Kansas, but becomes less abundant as soil moisture supply decreases. Most germination of annual bromes coincides with the seeding of winter wheat in the fall, when soil mois-ture is adequate. Additional seeds often germinate after fall rains and in early spring, so to be effective, soil-applied herbicides must remain active for several weeks and postemergent herbicides should be effective over a range of growth stages. This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.Competition Studies at the Fort Hays Branch Experiment Sta-tion near Hays indicated that downy brome and cheat . were highly competitive, when they emerged 1 to 7 days after wheat emerged in late September or early October. Crop losses increased linearly as downy brome and cheat density increased from low (20- 25/ yd2) to moderate (85-100/yd2) levels; yield losses for moderate densities of both species averaged 36 percent (Table 1) . Downy brome competition was less severe when wheat and weed establishment was delayed until early November in 1984; however, competition from cheat remained severe (Table 2). The competitiveness of both species was reduced when the weeds emerged 3 to 4 weeks after wheat emerged in late September, 1985 (Table 3). Control Metribuzin (Sencor and Lexone) is labeled for use in Kansas, Oklahoma, and Texas as a postemergent treatment to control annual bromes and other weeds in winter wheat. However, because of marginal crop safety, metrlbuzin should be applied only to certain tol-erant varieties after they have three or more tillers and Table 1. Percent crop loss from downy brome and cheat that emerged 1 to 7 days after wheat emerged in late September or early October, Fort Hays Experi-ment Station, Hays, KS. %Crop Loss 20-25 40-50 85-100 Year weeds/yd2 weeds/yd2 weeds/yd2 Downybrome 1983-84 17 21 45 1985-86 1 10 26 Mean 9 15 36 Cheat 1983-84 6 19 35 1985-86 16 22 38 Mean 11 20 36 Table 2. Percent crop loss from downy brome and cheat that emerged 1 to 7 days after wheat emerged in early November, 1984, Fort Hays Experiment Station, Hays, KS . Species Downybrome Cheat %Crop Loss 20-25 45- 50 85-100 180-190 weeds/ yd2 weeds/ yd2 weeds/ yd2 weeds/ yd2 0 3 5 30 1 35 11 51 Table 3. Percent crop loss from downy brome and cheat that emerged 21 to 28 days after wheat emerged in late September, 1985, Fort Hays Experiment Sta-tion, Hays, KS. Species Downybrome Cheat %Crop Loss 20-25 45-50 85- 100 180-190 weeds/ yd2 weeds/yd2 weeds/yd2 weeds/yd2 1 9 2 16 5 16 4 14 Table 4. Control of downy brome in winter wheat with metribuzin (Sencor or Lexone) applied postemer-gence at 0 .375 and 0.50 lb ai/acre, Fort Hays Experi-ment Station, Hays, KS. Time of Application Fall Spring Years Tested 4 7 Control, % Avg. Range 73 58 to 96 42 23 to 100 This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.l secondary roots 2 inches or longer. Metribuzin is most effective when applied to actively growing weeds in the fall, but wheat in western Kansas often is not sufficiently well developed to withstand fall-applied metribuzin be-fore weeds go dormant. At Hays, postemergent appli-cations of metribuzin in the fall (when possible) have given fair to good control of downy brome, but control with spring applications has been poor in most years (Table 4). Diclofop (Hoelon), which was labeled in 1986 for control of downy brome, applied preplant and incorpo-rated at 0.75 lb ai/acre, has given good control of downy brome at Hays (Table 5), but has been less effec-tive on cheat and Japanese brome (data not shown), for which it is not labeled. The granularformulation oftrial-late (Granular Far-go) at 1.5lb ai/acre was also labeled in 1986 for control of annual bromes as a preplant or preemergent treatment that does not require mechani-cal incorporation; however, rainfall is required to acti-vate granular triallate not incorproated mechanically. Liquid-formulated triallate applied preplant at 1.0 lb ai/ acre and incorporated has given good control of downy brome at Hays (Table 5). Granular triallate applied pre-plant at l.Sib ai/acre controlled 90 percent of downy brome on a 15-acre plot at Hays in 1985- 86. Table 5. Control of downy brome in winter wheat with preplant and incorporated applications of diclofop (Hoelon) and triallate (Far-go), Fort Hays Experiment Station, Hays, KS. Herbicide Years Control, % and Rate Tested Avg. Range . Diclofop 0.75lb ai/A 6 84 64 to 99 Trial! ate 1.00 lb ai/A 4 85 60 to 96 This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.Recommendations Yearly infestations of annual bromes often vary de-pending on the time and amount of fall rains. When possible, wheat seeding should be delayed until after one or two flushes of emerging bromes following Au-gust and September rains have been killed with tillage or non-selective herbicides (Roundup, Landmaster, or Paraquat). Because diclofop and triallate must be applied be-fore the severity of the brome infestation is known, ap-ply these herbicides only to fields having a history of an-nual brome presence. Herbicide application to the outer 100 to 200ft of other fields will slow the migration of annual bromes into fields frorh road ditches. Annual bromes that emerge soon after wheat has been seeded should be sprayed with metribuzin in the fall, only after wheat has developed several tillers and has well-developed secondary roots. If metribuzin ap-plication must be delayed until spring, apply as early as possible, but only after weeds have resumed growth and when rainfall is predicted. Application of metribu-zin to varieties other than those listed on the herbicide labels may result in crop injury. NOTE: Trade names are used to identify herbicides. No endorsement is intended, nor is any criticism implied of similar products not mentioned. KAES Contribut ion 87-69-S Agricultural Experiment Station, Manhattan 66506 Keeping Up With Research 89 September 1986 Publications and public meetings by the Kansas Agricultural Experiment Station are available and open to the public regardless of race, color, na· lienal origin, sex, or handicap. 9·86-3M This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.

Competition and Control of Annual Bromes in Winter Wheat (1986)

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Competition and Control of Annual Bromes in Winter Wheat (1986)

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